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S R2 R1


IA − 
at solar noon, it evidently becomes a meridian instrument. It has the advantage
also of reflecting the sun when it is just too cloudy for a shadow to
be distinct, and in fact you can only see it through darkened glass when
the sun is bright.
The instrument consists of three small plates of glass put together at
their edges in a brass box about 2 inches wide and high, so as to form a
hollow prism of any convenient angle, no precision being necessary in this.
ABC in this figure is the section of it at right angles to the axis of the
prism. The front glass BC is plain; the other two are blackened behind to
form reflectors. But though the front glass is transparent, it also reflects,
because there are dark ones behind it. SI and IR1 are sections of the planes
of incidence and reflection of the sun’s rays from the glass BC, those planes
being all parallel to the axis of the prism, which should be approximately
parallel to the earth’s axis. Part of the rays passes through that glass,
WATER CLOCKS. 11
and is reflected by glass AC to AB, and again reflected there and sent
through BC to R2. Now let the angle of incidence, and therefore of first
reflection at I, be called A− (A being the angle between the two reflecting
glasses), and let the other angles be designated as in the figure. It requires
no mathematics beyond the knowledge that the three angles of every triangle
= 180, commonly called  to see that the angle  =  − (C + A − ) in
the small triangle near C; and in the one near A, 
 =  − (A + ) = C − ;
and in the triangle near B,  =  − (B + 
) =  − (B + C − ) = A + .
That is to say, the angle , made by the plane of emergence of the twice
reflected rays with the front glass, differs from that of the once reflected by
2. Therefore, if the prism is so placed as to make  = 0, which it will be if
the angle of incidence = A, the twice reflected rays will come out parallel to
the once reflected, and the two images of the sun will coincide. In fixing the
instrument however, we have nothing to do with the angles; but simply to
adjust it by trial with a chronometer (for it cannot be done without), so that
the images do coincide at solar noon. They were at first made so as to be
fixtures on the stone where they were set, and so they were always exposed
to the weather, and besides, if cemented in wrongly, they were wrong for
ever. To avoid both these evils, I suggested the making of a brass plate to
be fixed on the stone, with a raised slip adjustable by screws, against which
the instrument is to be laid closely when used, but at other times it may
be kept in the house. Some of them are made to turn on an axis parallel to
the earth’s axis, and then they can be presented to the sun at other hours
besides noon, but only for the given latitude like a sun-dial. Some are made
adjustable for latitude also. They are moreover made for star observations
with the reflectors silvered instead of blackened, on account of the greater
feebleness of star light. A table was published to be used with them, showing
the time of first and last contact of the two images of the sun for every day
in the year, as that observable perhaps more accurately than the time of
coincidence; at any rate it gives three chances of observation instead of one.
But many people prefer my meridian slit.
WATER AND SAND-CLOCKS.
The earliest time-keeping machine is the clepsydra or water clock of the
Greeks and Romans, which was no doubt made in various ways. Vitruvius
mentions one made as a water wheel, which would probably be very irregular.
This simplest in construction is a graduated cylindrical vessel with a hole in
the bottom, and this appears to have been the most commonly used: but
they must surely have discovered that the water in that case by no means
runs out with uniform velocity, though they did not know, and some of
the modern writers on antiquities apparently do not either that the velocity
varies as the square root of the height of the water above the hole. But if a
SAND CLOCKS. 12
trough is kept full by a stream, and a hole made anywhere in it, the water
will then run uniformly into, and rise uniformly in, another cylindrical vessel
in which its height may be marked on the sides, if it is of glass, or else by a
floating index, and that will make a very fair clock. I do not however find
any notice of such a one in books on Greek and Roman antiquities. Various
other forms of clepsydra are described in them, which it is not worth while
to copy here.
The case is different with sand. If a column of dry sand ever so high
stands over a small hole, the sand will run out no faster than if it is a very
moderate height, for the same reason that a pile or cone of sand on a given
base will stand up to a certain height and angle only, which depends on
the amount of friction between the particles. The angles of the waist of
an hour-glass ought to agree with that natural angle of the sand in order
that it may run out uniformly to the end—if that is of any consequence,
which it hardly is for the boiling of eggs, or even for the old use of limiting
the length of sermons; which object might sometimes be advantageously
accomplished now by a descending sounding-board, or as sounding-boards
are gone out of fashion, by a pulpit bottom or ‘drop’ let down by clock work
after 25 minutes.
The burning of graduated candles was another mode of marking time,
and if the candles were of wax, as they probably were, and sheltered from
wind, and the wicks uniform throughout, the measure would be accurate
enough for any purpose for which it was likely to be used. The consumption
of oil in a lamp might also be marked and used in the same way.
This seems the proper place to notice a genuine water clock, invented
and used by Lord Rosse for the important purpose of driving an equatorial
telescope so as to keep it pointed to a star, against the earth’s rotation, for
which there are various contrivances. It is described in the R.A.S. Monthly
Notices, vol. xxvi., and the principle of it is that the water is let out slowly
from a box by an india rubber tube carried by a float, so that its mouth is
always at the same small depth below the surface of the water; and as the
pressure depends only on that depth the outflow is uniform and the descent
of the float with it, and that has a cord attached to it, and at the other end
attached to the wheel which drives the telescope. The great equatorial at
Greenwich is driven by another kind of water clock, which will be notified
farther on, as it is combined with a revolving pendulum, and we will now
proceed to what are properly called
CLOCKS.
The invention of clocks driven by a weight has been generally attributed to
Pacificus, Archdeacon of Verona, in the ninth century; and also to Gerbert,
afterwards Pope Silvester II., who made a clock at Magdeburg in 996, when
OLD CLOCKS. 13
he was an Archbishop. But there does not seem to be any contemporary
proof that either of these were weight clocks; nor is it certain that Gerbert’s
was a clock at all; for it is described by an old writer quoted in Beckmann’s
‘History of Inventions’ (4th ed. 1846) thus:—‘Magdeburg horological fecit,
illud recte constituens considerate per fistulam stella nautarum duce’—i.e.
‘he made a time-piece at Magdeburg, setting it by looking at the pole-star
through a tube.’ Beckmann thought William, Abbot of Hirshaw in the
eleventh century, had the best claim to the invention; of whom it was said,
‘Naturale horologium ad exemplum coelestis hemisphoerii excogitavit;’ and
soon after, certain monks had the duty ‘horologium dirigere et temperare,
et signa pulsare;’ which however looks rather like their directing the clock
than the clock them, or as they say at sea, ‘making it ten o’clock,’ rather
than learning from the clock that it is so.
But he also says that in those times the day and the night were each
divided into twelve hours, between sunset and sunrise; and if so, such hours
could not be shown by any clocks; for we may be sure that no clocks of those
days were able to adapt themselves to hours of such varying length. And all
this seems to me very insufficient evidence of the existence of clocks, as we
now understand the word; which, by the way, appears not to have driven
out the older word ‘horologe,’ until the time of Henry VIII., having been
long used for a bell (cloche).
But it may be safely concluded from the various allusions to horologia,
and to their striking spontaneously, in the twelfth century, that genuine
clocks had been invented before then, though there is no surviving description
of the construction of any clock until the thirteenth century, when it
appears that a certain ‘horologium’ was sent by the Sultan of Egypt in
1232 to the Emperor Frederic II. ‘It resembled internally a celestial globe
in which the sun, moon, and planets moved, being impelled by weights and
wheels, so that they pointed out the hour, day and night, with certainty.’
The oldest clock mentioned in England is that which was put up in a former
clock-tower of Westminster, with some great bells, in 1288, out of a fine
imposed on a corrupt Lord Chief Justice, of which a memorial survived near
the same spot in a sun-dial which stood on a house in Palace Yard, pulled
down within my time, with the inscription ‘Discite justitiam moniti.’ In
1292 a clock is mentioned in Canterbury Cathedral, costing £30; and the
old striking part of the original one in Exeter Cathedral was at work not
long ago, and perhaps is still, though the going part had been replaced;
and the same at Peterborough, probably of about the same date. That of
Glastonbury Abbey, afterwards at Wells Cathedral, dated 1325, is now in
the South Kensington Museum, going. One by Richard Wallingford, Abbot
of St. Albans, made in 1326, is said to have been such as there was not in
all Europe, showing various astronomical phenomena. There was also one
at Dover Castle, with the date 1348 on it. That also was exhibited going in
1876.
CLOCK TRAIN. 14
A description and picture of the clock made by Henry de Vick for
Charles V. of France in 1370 may be seen in old editions of the Encyclopædia
Britannica, whether authentic or made up from some other I do not know.
I did not think it worth repeating in the eighth edition, for which I wrote
the article on clocks. It was very like our common clocks now, except that
it had only an hour hand, and a vibrating balance (but no balance spring)
instead of a pendulum. It is impossible that such a clock could go well,
and it seems strange that the apparently simpler contrivance of a pendulum
should not have come till four centuries after clocks were first invented; and
yet that is the general tradition. I suppose therefore that the pendulum in
the old Peterborough, and Exeter, and other church clocks were added long
after their original construction. Those clocks were wound up by long spikes
or handles sticking out of the wooden barrel over which the rope goes which
carries the weight. In many old church clocks the weight is only a large
stone. It is not until quite modern times that church clocks had minute
hands besides the hour ones, but in other respects there is surprisingly little
difference in principle between the oldest of these machines and most turret
clocks of the present day.
The going part of a clock is, and always has been, nothing but a train
of some number of wheels and pinions, of which one turns in 12 hours, and
another in 1 hour, if there is a minute hand. The first, or slowest, or ‘great’
wheel, is turned by a weight hanging by a rope wound round a barrel on
that wheel’s axis, or arbor, as it is called in clock-making; and the last or
quickest wheel drives a fan-fly, or a fly-wheel, or a pair of vibrating arms,
called a ‘balance,’ or a pendulum, to regulate the velocity of the train. A
spring clock is merely a compound of a large watch and a common clock.
Fig. 3: Pinions
Any one who has looked at the inside of a clock—and it is useless to read
this book until you have—knows it consists of a few large wheels with a good
many teeth, and that the teeth of every large wheel, except the highest, are
engaged in or drive some much smaller wheels fixed on the axes or arbors of
all the large ones except the largest. These small wheels are called pinions,
and their teeth are called ‘leaves’ for distinction. This figure 3 shows a set
of pinions of from 6 to 16 leaves, the lowest and the highest numbers used.
It also shows the kind of steel plate which is used for drawing pinion wire.
CLOCK TRAIN. 15
For it is cheaper to make the arbors of such wire, turning off the projections
all along the arbor except where they form the pinion itself, than to cut the
pinions out of the solid. But they are not so good as cut ones, and I believe
are not used in the best clocks.
Fig. 4: Common Clock Train
The largest wheel in the train, which is called ‘the great wheel,’ appears
to be stuck on the end of the barrel which carries the string and the weight
attached to it—whether with a moving pulley or not, does not signify as
a matter of principle, which is all we are considering at present. The only
effect of the pulley in to take a double string of twice the length of a single
one in the same clock case, which enables a larger barrel to be used and also
prevents the string from untwisting.
CLOCK TRAIN. 16
But if the great wheel were really fixed to the barrel there could be no
winding up, except by an endless chain contrivance, which we need not now
consider. Accordingly the real arrangement is that the great wheel rides
freely on the arbor of the barrel, and is connected with it by a ratchet and
click; the ratchet being a saw-toothed wheel on the end of the barrel, and
the click being on the great wheel with a spring to keep it in the ratchet
teeth, which pass under it in winding, but cannot return, except with the
great wheel itself. You will see a picture of it under ‘Maintaining Powers,’
farther on in the book. And it is all the same whether the barrel is turned
in the old way by spokes, or in the modern way by a key or ‘winder’ put
on the squared end of the arbor; only in the former case the barrel rides
loose on the arbor, and in the latter is fixed to it and the wheel rides loose.
Consequently the weight is always acting on the train, except at the time of
winding; and in all good clocks there are contrivances for keeping the force
on even then, called maintaining powers.
Now suppose the great wheel has 120 teeth, and the pinion which it
drives has 10; then if that pinion and its arbor and the wheel stuck on to
it turn in one hour, the great wheel will evidently turn in 12 hours. The
wheel which turns in an hour is called the centre wheel in house clocks,
because that arbor comes through to the centre of the dial and carries the
minute hand. Suppose that wheel has 64 teeth and drives a pinion of 8;
then that pinion and the wheel on its arbor will turn in 8 minutes; and if
that has 60 teeth and drives another pinion of 8, that pinion and arbor will
turn in a minute, and the wheel on that arbor is the scape-wheel, which
drives the pendulum vibrating in a second, as we shall see presently. Not
that there is any virtue in these particular numbers of teeth and leaves,
or that the pendulum need vibrate seconds; most church clock pendulums
are slower, and all short spring clock pendulums are faster. All that is
requisite theoretically is, that the numbers of the teeth of all the wheels
multiplied together, and divided by the numbers of the leaves of all the
pinions multiplied together, should give the proper velocity-ratio between
the slowest wheel and the quickest. Thus, if the scape wheel has to turn
60 times as fast as the centre wheel, and there is one between them, which
may turn in any time, the product of the teeth divided by that of the leaves
must = 60, and subject to that, you may distribute the numbers as you
please—theoretically; but practically other considerations come in, such as
that the slower wheels must be larger than the quicker ones, or they could
not clear the arbors below them; that if the leaves of the pinions are very
few they do not drive easily, and if they are many the teeth must be many
and small, and more expensive to cut, and so forth; and the result is that,
in the common long house clocks the numbers are usually what I gave just
now; but in astronomical clocks or regulators they are higher, sometimes
twice as much; in turret clocks they vary more, according to circumstances,
as will be seen hereafter.
FLIES AND FLY WHEELS. 17
The simplest of all the methods of regulating the velocity of the train,
and one which certainly existed before De Vick’s time, is the fan fly, or a
pair of arms with vanes which are resisted by the air. I think it by no means
improbable, though it is never likely to be ascertained now, that some of
those earlier clocks were trains of wheels with a fly to regulate their velocity,
instead of a balance, which De Vick used in his going part, though he had a
fly in the striking part, as the earlier English clocks have, and exactly as it
is used to this day. So long as the force and friction of the train are uniform
the velocity of the fly will be uniform, as the variation of density of the air
is too small to affect it materially; and it should be observed, that a long
fly with a rather slow motion is less affected by variations of force than a
short and quick one; but as far more accurate methods are now used, it is
unnecessary to go further into this.
A fly wheel, which is either a wheel with a heavy rim or a pair of weighted
arms at right angles to the axis which carries them, is another method; but
not so good, because, not being resisted by the air nearly so much as fans,
it is much more affected by a change of force, which in clock work nearly
always means a change of friction in the train. It acts simply by its moment
of inertia, which is constant, and therefore the velocity cannot be constant
if the force varies. In fact there is theoretically no limit to the velocity of a
fly wheel driven by a weight, so long as the weight can go on falling, though
practically a terminal velocity is soon reached, when the friction and the
increasing resistance of the air balance the force; but of course this balance
is disturbed and the velocity changes as soon as the force varies.
Conical Pendulum. A pair of weighted arms attached to a revolving
vertical axis by horizontal hinges, so that they can fly farther out as they go,
will regulate the velocity more completely than a fly wheel or arms rigidly
fixed, and still better if it has fans attached to it, but not completely enough
to keep it uniform if the force varies much. They are like the ‘governor’ of
a steam engine in appearance, but no further; for the governor arms work
a lever which opens more or less of the throttle valve of the steam pipe,
according as the engine is going too slow or too fast. A single ball or pair
of balls hung in this way and driven by a clock train form what is called a
conical pendulum, because each arm describes a cone, and the time of its
revolution may easily be determined as follows, except so far as it is affected
by friction and resistance of air:—
Let l be the length of each arm, and  the angle at which it happens to be
inclined to the vertical axis, which of course depends on the rate of revolution
or angular velocity, which is usually called !; then the centrifugal force of
each ball = !2l sin ; and as that is the force which keeps the balls away
from the vertical, it must balance the force which draws them to it, which is
g tan  (g being the usual symbol for the force of gravity, or twice the number
of feet which a body falls in the first second of time, and g in this latitude
is 32.2); therefore ! or the angular space moved over by the arms in one
CONICAL PENDULUM. 18
Fig. 5: Revolving
Pendulum
second = p g
l cos , and the time of a complete revolution
through 360 or 2, is 2
! = 2pl cos 
g . If
you wish to know what that means in figures, you
must express l in feet, as g is, and write the numerical
value 3.14159 for , and take the numerical
value of cos  from a table of sines and cosines;
and the result, after extracting the square root
and dividing, is the number of seconds in which
the revolution is performed. We shall see hereafter
that it is just so much less than the time of
a common vibrating pendulum of the same length
as pcos  is less than 1. And as the cosine varies
least when an angle is small, a clock of this kind
will go better when the length of the arms and the
weight of the balls are such that they make only a
small angle with the axis when the clock weight is
driving them. But again it must be remembered
that these results are very much modified in actual
working by the resistance of the air, which
acts more strongly on the balls as they fly farther
out, and thereby tends to regulate the velocity, as
it does with a fan fly.
A clock of this kind is often used to turn the reflectors
or coloured lenses of revolving lighthouses,
and also for the more accurate purpose of driving
large equatorial telescopes, to keep them pointed
to a star notwithstanding the revolution of the
earth. For the earth does not move by jerks, as a
clock with a vibrating pendulum and escapement
necessarily does. A revolving pendulum alone will
not do without some contrivance to equalise the
force upon it, or to check the pendulum itself by
friction.
The simplest form of it is setting the revolving
balls within a conical ring, which they can graze
slightly, and it is better if they are furnished with
slight grazing springs. And if the cone is also made
raisable by a handle within reach of the observer,
so that he can regulate the friction, probably this
is enough in all ordinary cases.
But for telescopes of great importance superior
contrivances are used. The chronograph at Greenwich,
which drives a barrel covered with paper, on which the times of various
BALANCE-WHEEL ESCAPEMENTS. 19
observations are pricked by galvanic communication from the observers, is
an ordinary clock with a revolving pendulum, driven by an arm which also
carries round a kind of spade, dipped a little into an annular trough of water;
and the farther out the pendulum swings the deeper it pushes the spade
into the water, by a simple lever arrangement which can easily be imagined.
The great equatorial telescope there has a similar pendulum and trough;
but besides that, the clock is itself driven by a ‘Barker’s mill,’ or a pair of
revolving horizontal arms on a vertical axis, all hollow and receiving water
at the top of the axis. The arms have holes near their ends, on opposite
sides, and the water flowing out there drives the arms the other way. The
pendulum also works a throttle valve as the governor of a steam engine does,
and so regulates the flow of water through the mill.
A revolving pendulum may be hung by a single wire, as there is no
tendency to twist, and they are so made in bedroom clocks, which have the
advantage of being silent. But it is difficult to get a wire strong enough
for a heavy pendulum which would not also be too stiff. The Greenwich
ones are hung by a kind of universal joint, made of two pairs of suspension
springs in stirrups, set across each other, one turned upwards and the other
downwards, with a cross between.
We shall have to notice afterwards some other clocks for this purpose,
in which a revolving continuous movement is combined with a vibrating
pendulum and escapement; but I must describe escapements first.
It is perhaps worth mentioning that any point in a wheel revolving uniformly
has always the same velocity in a horizontal direction as some point
in a pendulum which makes a double vibration in the same time as the
wheel revolves; and therefore, theoretically, a constant motion of a clocktrain
might be got by connecting some point in a 1 sec. pendulum with a
pin in a small disc revolving in 2 seconds, by a rod so long as to be practically
horizontal. But it would probably be impracticable to keep the force
constant enough to give just proper impulse to the pendulum; and if too
much was given, there would be a jerk at the end of every beat, and if too
little, the pendulum and the clock would stop.
BALANCE-WHEEL ESCAPEMENTS.
Before we go into the theory of pendulums we should notice the one other
mode of regulating the motion of a clock-train which existed long before
pendulums were applied. The earliest escapement of which there is any
known description is that which De Vick’s clock had, and which is called the
crown-wheel escapement. The object of that, as of all the later escapements,
was to let a tooth of the quickest wheel in the train escape past some stops
called pallets at every vibration of the balance, and that wheel is thence
called the scape-wheel, and a crown-wheel from its shape. The pallets A,
BALANCE-WHEEL ESCAPEMENTS. 20
B, in fig. 6, are pieces of steel fixed to the axis or arbor of the balance C
Fig. 6: Balance Wheel Escapement
in planes at right angles to each other, one of them set so as to be pushed
one way by the front teeth D of the wheel, and the other the other way by
the back teeth. As one tooth escapes past its pallet, the other pallet is in
a position to receive and stop the opposite tooth. But as the balance has
then acquired a swing in the direction in which it has been pushed by the
escaping tooth, it does not stop immediately, but swings a little farther and
so drives the wheel back again a little, producing what is called the recoil.
This is just the same as the old ‘vertical’ watch escapement, which remained
in use until a few years ago, with this important exception, that the time
BOTTLE-JACK ESCAPEMENT. 21
of vibration of a watch balance is regulated by a thin spiral spring fixed
to it and to the frame, whereas this had none, and so its regulating power
over the train depended solely on its moment of inertia, and on its swinging
farther for any increase of force, which by no means makes it isochronous.
The same thing is still to be found in bottle-jacks; the piece of meat to
be roasted forms the balance, and the noise at each change of its motion
is the ‘ticking’ of the escapement. It is true the meat makes several turns
for one tick, while De Vick’s balance made only half a turn, but that is
because there is a wheel on the pallet arbor in the jack, worked by a pinion
on the meat arbor, as in the rack lever watch escapement; but otherwise the
bottle-jack escapement is precisely the same as in De Vick’s clock, in which
the axis of the balance was vertical, and not horizontal as in fig. 6.
PENDULUMS.
Pendulums, like many other things, may have been invented several times
over in different ages, or even in the same. In an old edition of the Encyclopædia
Britannica it is said that ‘the ancient astronomers of the east
employed pendulums in measuring the times of their observations, patiently
counting their vibrations during the phases of an eclipse or the transit
of the stars, and renewing them by a little push of the finger when they
languished. Gassendi, Riccioli, and others, in more recent times followed
their example.’ If so, it is plain that this knowledge had itself languished
and died, before the making of what has long been called Galileo’s discovery
in the church at Florence, that a chandelier, and therefore any other pendulum,
vibrated different arcs in the same time, provided they were none of
them large ones. When we consider the vast number of pendulums of various
kinds that there are swinging about the world, it certainly is difficult to
imagine that nobody ever made that observation before the sixteenth century.
The application of it to the regulating of clocks however is a different
thing, as that required invention as well as observation. To be sure, all that
was needed was to omit one of the weights in De Vick’s balance, and set it
in a vertical instead of a horizontal plane, and it is strange enough that this
slight but valuable alteration should have waited three centuries to be made.
It would then assume this form (fig. 7), which is the same as the other in
all but the position of the parts and the omission of one arm and weight of
the balance. The bent end of the arm (called the fork) is substituted for a
weight in this drawing, because it was afterwards found better to hang the
pendulum independently, and connect it with that arm, called the crutch,
by means of the fork. But I have seen small clocks of the last century, and
even some modern French ones, with the crutch itself made into a pendulum
by merely putting a ball at the end of it.
There seems no doubt however that the first person who investigated
PENDULUMS. 22
and established the mathematical theory and properties of the pendulum
was Huyghens, the Dutch philosopher, in the seventeenth century; but it
seems equally certain that the first pendulum clock was made for St. Paul’s
Church in Covent Garden, by Harris, a London clock-maker in 1621, though
the credit of the invention was claimed also by Huyghens himself, and by
Galileo’s son, and Avicenna, and the celebrated Dr. Hooke, the undoubted
inventor of the balance spring of watches, and the discoverer of its theory.
The main point of Huyghens’s discovery seems at first sight a long way off
Fig. 7: Crown-Wheel Escapement
any connection with what we now understand by a pendulum, viz., a weight
or bob at the bottom of a long rod, which is hung by a string or a thin spring
at the top, and the bob therefore swinging in a circular arc, or something
CYCLOIDAL CHEEKS. 23
very near it. For he proved that the curve in which a bob hung by a string
of insensible weight must move in order to be isochronous in its vibrations,
is not a circle, but a cycloid, or the curve traced out by a point in the rim
of a circle rolling upon a straight line, e.g., a nail in the tire of a carriage
wheel rolling on a smooth road, or P in circle DEP rolling on BGC in fig. 8;
and he showed how a certain other property of the cycloid might be made
use of to enable a pendulum bob to describe a cycloidal instead of a circular
arc. It is not worth while to fill these pages with demonstrations which may
be found in any mathematical treatise on mechanics, especially as I must
assume the reader to have some of the knowledge which is only to be got
from such books, in order to understand the demonstrations if I gave them.
Therefore we may as well begin at this point, that a body moving by gravity
in a cycloid (with the curve downwards, as BPFC in fig. 8) does describe
both large and small arcs in the same time; the reason of which is that the
Fig. 8: Cycloidal Theory
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G
force may be proved to be always in proportion to the distance along the
curve from its lowest point point, F.
But how is a pendulum bob, hung by a string or wire from a fixed point,
to be persuaded to describe a cycloid? It so happens that if a cycloid BFC
is cut in two, and one half BF removed as a solid with a convex edge to
AC (making AG = FG = DE), and the other half to AB, the end P of a
string = AF, fixed at A, and moving between those ‘cycloidal cheeks’ will
redescribe the old cycloid BFC. This is mathematically expressed by saying
that the involute of a cycloid is another equal cycloid, and therefore also the
evolute is; the evolute being the cheeks, and the involute the curve described
from them: the proof of this belongs of course to geometry, not mechanics,
and is of no consequence to us at present. Huyghens therefore proposed to
hang clock pendulums by a string or a thin spring between cycloidal cheeks,
CIRCULAR ERROR. 24
and that was for some time thought a very superior method of making clocks.
I have no doubt there are some still in existence, as I have seen them.
But after a time it was found that clocks went rather worse with these
cheeks than without them; and then it occurred to somebody that the cycloidal
theory is only true for what is called in mathematics a simple pendulum,
or one in which not only the bob, but the centre of the bob, is alone
supposed to have any weight; and of course there is no such thing possible,
for the rod must have some thickness, or it is not stiff enough to work, or
to be driven by the clock, and if you make the bob very heavy, with the
view of rendering the weight of the rod insignificant, then the bob itself
must be large, and differs considerably in its mechanical effect from a single
imaginary heavy point at its centre. And besides that, the spring or string
cannot be made to act against the cheeks without friction and other disturbing
causes; all which things are said to have been proved to produce greater
deviations from isochronism than a variation of several degrees in the arc.
Indeed we shall see hereafter that the common clock escapements tend to
produce an error of their own, which the deviation from cycloidal vibration
(commonly called the circular error) is actually useful in counteracting.
Nevertheless the cycloidal theory is valuable to this extent: it shows why
a common pendulum is very nearly isochronous for different small arcs; for
the string AP will evidently describe very nearly the same curve near the
bottom F, whether the cheeks are there or not: in other words, a bob
vibrating in a small circular arc is almost identical with one in a cycloidal
arc described by a string of the same length. The actual time of a circular
vibration cannot be calculated without the aid of the higher branches of the
integral calculus, and even then it can only be exhibited in the form of a
rather awkward series, which would be little better than useless, except for
small arcs; and for them it is quite sufficient to take only the two first terms
of it. The whole calculation may be found in Pratt’s Mechanics, or in the
8th edition of the Encyclopædia Britannica, under article Pendulum. The
first term is simply the expression for a cycloidal vibration, t = pl
g the
letters of which I have already explained at p. 17, for the conical pendulum,
whose time of vibration you now see is less than that of a plane pendulum of
the same length in the proportion of pcosine of the angle which the conical
one makes with the vertical axis.
Circular error.—The next term in the series (omitting all the later
ones which are still smaller) constitutes the circular error K, or the excess
of the time of vibration in a circular arc over that in the cycloidal one
belonging to the same length of pendulum; and it is accurate enough for all
practical purposes to say that K =  a2
16pl
g ; and therefore for a whole day,
K = 5400a2 in seconds, whatever the length of the pendulum is; the amount
of which you may easily calculate from the fact that if a = 2, as usual in
clocks its numerical value is .035, and therefore K = about 6 seconds. But
CIRCULAR ERROR. 25
this is more than what is called the circular error in a clock pendulum; for
we need not care what is the difference between the time of a cycloidal arc
and the actual circular arc which the pendulum describes, but only between
two small circular arcs, a and a1, as the pendulum is likely to describe in
different states of the clock. This quantity, which we may call 
K, is only
5400(a2  a21
); and if we assume the larger of the two arcs to be as much 21
2

and the smaller 2, the circular error between them will be rather less than
4 seconds a day. This is a very large variation of arc for a tolerably good
clock, and when it is as small as it generally is, the circular error may be
expressed by differentiating the expression 5400a2, and we may say (so long
as both the arc and its variations are small, remember) that 
K = 10800a da
(da being the variation of the arc). Thus if a = 2 and da = 100, 
K will
be very nearly 1 second: i.e. the clock will lose a second a day for such an
increase of the arc, independently of any other increase or counteraction of
the circular error, which may be produced by the escapement at the same
time.
For the common purpose of finding the length of a pendulum to beat
seconds, or any other required time, we need not trouble ourselves with
anything beyond the equation t = pl
g in which t is the number or fraction
of seconds, and l is expressed in feet, because g means 32.2 feet (in this
latitude), and  is 3.1416 or the numerical value of 180. Therefore in
order that t may be 1 second, you will easily find by a little calculation
that l must be 39.1393 inches; and having got that fixed, you may find the
length of pendulum for any other time of vibration very easily by multiplying
39.14 inches by the square of the ratio of the intended time to 1 second. But
to save trouble I will put down a few of the lengths, omitting small fractions.
seconds ft. in. seconds. inches.
4 52 2 11
4 61
3 29 4 1 39.14
21
2 20 5 3
4 22
2 13 01
2
2
3 17.4
11
2 7 4 1
2 9.78
These seconds, and the second used as the unit of time in all mathematical
formulas, are seconds of mean time; and as a sidereal day is shorter
than a mean one in the ratio of .99727 to 1, a sidereal pendulum must be
shorter than a mean one in the square of that ratio, which makes the sidereal
seconds pendulum at Greenwich 38.87 inches. I have met with persons
who could not understand how an increasing gravity can make pendulums
go faster; and others, with a little mathematical knowledge, think that the
force varying as the distance from zero (in small arcs) is opposite to the fundamental
law of gravity varying inversely as the square of the distance. The
RADIUS OF OSCILLATION. 26
answer to the second of these is, that the zero, or middle, or lowest position
of a pendulum is not an attracting body like the earth (which attracts as
if it were all condensed into its centre); and the tendency towards zero is
only a mathematical consequence of that law of gravity. The stronger the
tendency to zero, or the stronger gravity is, the faster the pendulum will
evidently fall; and the sooner gravity will bring it again to rest in rising.
The time of rising always = the time of falling, under any force which is
equal at equal heights during the rise and fall.
Centre of oscillation.—It must be remembered that these are only the
theoretical lengths of simple pendulums with all the weight concentrated in
the centre of the bob, and that this theoretical length by no means coincides
with the actual length down to the centre of gravity of the pendulum, but is
always longer. This length may properly be called the radius of oscillation,
as the lower end of it is always called the centre of oscillation; which is
not a fixed point in the body, like the centre of gravity, but a relative one,
every axis of suspension having a radius and centre of oscillation of its own.
It is not always a simple process to calculate this length (which we may
as well call l) for any given pendulum as it requires either the integral
calculus or some rules deduced from it; but it will be easy to explain the
nature and meaning of the quantities on which it depends. Let m be the
mass of each particle of the pendulum, which in these calculations must not
be confounded with the weight, which is written mg (g being the force of
gravity), r the distance of m from the axis of suspension, and M the mass
of the whole pendulum; then the radius of oscillation = the sum of each
particle multiplied into the square of its distance from the axis, divided by
the sum of each particle multiplied into its distance simply; that is to say,
l = Pmr2
Pmr
(P being used to indicate this kind of summation, which can
only be performed by integration).
The numerator in this fraction is called the moment of inertia of the
body with reference to that axis of suspension. Of course there is some
quantity k2 which = Pmr2
M , and k is then called the radius of gyration
for that axis, and Mk2 is obviously the moment of inertia again. In like
manner some quantity h = Pmr
M , and h is then the distance of the centre of
gravity of the whole pendulum (not of the bob, remember) from the same
axis, which is easy enough to find in bodies of the shape commonly used
for pendulums. It appears then that the effective length l of a pendulum
always = k2
h ; and it is only when the rod is very thin and the bob itself
small but heavy, that k and h can be assumed to be even approximately
identical, and therefore both = l, as they are in a simple pendulum. But it
does conveniently happen that the centre of oscillation in small pendulums
of the usual forms is generally near the centre of gravity of the bob, and
sometimes coincides with it, as we shall see.
This quantity Mk2, the moment of inertia, always appears in mathematPENDULUMS.
27
ical formulae as the resister of forces of rotation or vibration on an axis, and
of all disturbances of such forces after they have set the body in motion,
and therefore we see at once why long and heavy pendulums are better than
short and light ones. There are a few other simple propositions relating
to the centre of oscillation and the theory of pendulums, which it will be
appropriate to notice here.
Draw a pendulum of any shape you like, supposed to be vibrating in
the plane of the paper, and call its centre of suspension S, and its centre of
gravity G, and the distance between them h. All bodies have this property,
that their moment of inertia round any axis through G (which we call Mk2
1)
is less than round any other axis parallel to that, and we are not concerned
with any but parallel axes; and further, if the other axis is distant h from
the centre of gravity, the k2 round that new axis = k2
1 + h2. Therefore if
O, somewhere below G, is the centre of oscillation corresponding to S, l
or SO = k2
1+h2
h ; and l − h, or GO = k2
1
SG; or the centres of suspension and
of oscillation are reciprocal. In fact, if the pendulum is wide enough, you
may draw two circles round G with radii GS and GO, and if you stick an
axis through the pendulum, at right angles to the same plane of vibration,
anywhere in either of those two circles, it will vibrate in the same time as
on the original S. Consequently, if you construct a pendulum (symmetrical
on both sides of its middle plane of vibration, to prevent it swinging with
a twist) with one fixed axis S, and another adjustable one for O, and a
movable weight to adjust the time by, you can make it vibrate in the same
time on both axes; and by adjusting the movable weight also, the pendulum
can be made to agree with the vibrations of a clock pendulum which is
beating seconds; and then the distance between S and O, or the two knife
edges which represent them, being measured, we shall know that that is
the length of the simple seconds pendulum. It has also been proved that if
round axes are used instead of knife edges, the distance between them (not
their centres) equally represents the radius of oscillation, provided the axes
roll on a plane.
If all the standard yard measures in the kingdom should ever be lost,
they could only be restored by this process, according to an Act of Parliament,
5 Geo. IV. c. 74, which declared that a yard is 36
39.1393 of the length
of the pendulum which vibrates mean seconds in London at the level of
the sea, in a vacuum. The force of gravity decreases so much towards
the equator that an English pendulum would lose 21
4 minutes a day there.
The following rule for the length of the seconds pendulum in any latitude
has been deduced from observation, near enough for all practical purposes:
l = (1 − .0027 cos 2 lat.) 39.1156 inches; that number of inches being the
length of the pendulum at lat. 45. When the latitude is more than 45,
cos 2 lat. becomes −, and so l exceeds its length at 45, as of course it ought
to do. Another still simpler formula is l = 39.017 [the length of a seconds
BADNESS OF THE FRENCH METRE. 28
pendulum at the equator] +.2 sin2 of latitude.
That Act however has been repealed, and some standard weights and
measures are deposited in various public places under an Act of 18 & 19
Vic. c. 72. The late Astronomer Royal provided a set, open to anybody,
at the Observatory gate. But if they all happened to be destroyed, new
ones could be made from the old pendulum ratio. Indeed Mr. Johnson of
Wilmington Square had one ready for that calamity. A simple pendulum
36 in. long would vibrate in a time which is to 1s. as 362 to 39.142, or
.846 of a second, or 70.92 times in a minute; and he has made a clock with
a reversible pendulum vibrating in that time, and consequently 36 inches
between the two knife edges.
The length of a seconds pendulum so nearly resembles the French metre
of 39.371 in., that some persons may fancy that that most ridiculous and
mischievous revolutionary measure had an origin even as rational as being
the length of a seconds pendulum in some latitude. But it has not. It was
intended to be the 40 millionth part of a meridian of the earth—about as
rational a standard as if we enacted that the yard should be the 420 millionth
of the mean distance of the moon, which it is very nearly; and astronomers
know the moon’s distance within a less fraction than the difference of the
metre from what it pretends to be, but is not.2 Yet there are people who
want to force on all the world this absurd, inconvenient, and useless measure,
invented by a nation whose language is declining over all the world; while the
English language, with that standard of measures which every man carries
in his arms, his legs, and in his head, is spreading over all the world, so
that it will soon be the only universal language to be found everywhere, if
it is not so already. Doctrinaires of this kind may cram penny-school girls
with French metres, and centimetres, and kilograms; but our yard grew
and will remain as the natural standard of length until the stature of the
human race alters. For it is the length of a good stride of a man of what
is generally considered the best height, and that height is two such lengths,
and so is the stretch of his arms, and a yard is the natural length of his
walking-stick. A metre would be the yard of a nation of giants. With the
yard too goes the equally natural and still older measure of a foot, which
all nations had, with such small variations as would occur in times when
they had no scientific provisions for preserving exact standards. Some great
authorities believe inches to have been the oldest measure of all; and the
Egyptian cubit, which was unquestionably used in building the Pyramids,
from the many simple multiples of it which occur there, confirmed by the
discovery of one accidentally built up in a wall at Thebes, was probably 20
of their inches, being a little more than 20 of ours; and the ‘sacred cubit’ of
the Jews was 25, according to Sir Isaac Newton. Probably the authors of
2See the essay ‘On Celestial Weights and Measures,’ in Sir J. Herschel’s Familiar Lectures,
condemning the metre strongly.
SHORT AND SLOW PENDULUMS. 29
the new 25 inch to a mile Ordnance survey of England little thought that
they were reverting to that ancient standard. At the same time, I do not
accept the theory of the Scotch Astronomer Royal,3 that the 25 inch cubit
was embodied in the Pyramid dimensions, besides the one of 20.7 inches,
or 20 of some of the old continental inches. A variation of one thousandth
is practically nothing in unscientific ages, and is less than the variation of
many foot-rules now, and it is singular that if our inch were a 1000th longer,
the earth’s polar axis would be just 500 million inches.
Short and slow pendulums.—There is a kind of pendulum which is
properly enough used in the instrument called a metronome, for counting
the time in music lessons in a way that requires no particular accuracy, and
occasionally, but very improperly, used for small clocks. It follows from the
propositions I have been explaining, that if a pendulum with a heavy rod is
set vibrating on an axis very little above its c.g. it will vibrate slowly, like
a scalebeam; and consequently you may have a 2 seconds pendulum in the
compass of a few inches. But even if the weight of it were equal to that of a
large pendulum, its regulating power, or power to resist disturbance, would
be very much less, because that is measured by the moment of inertia Mk2,
which is the sum of the weight of each particle × its distance2 from the axis,
and that of course must be small in a short pendulum, though its time may
be long if h is very small. The time of a metronome pendulum is adjusted
by a small sliding weight on the rod above the axis of vibration, the bob
being of course below it. Moving the weight up brings the c.g. of the whole
nearer to the axis, and also increases the Ml2 of the whole, and so in both
ways makes it go slower, and vice versˆa. It is kept going by a roughly made
watch movement and a common recoil escapement, such as I shall describe
presently for clocks.
Shape of pendulums.—Whatever the shape of a pendulum is in other
respects, it is essential that the back and front should be alike both in weight
and shape; or to speak mathematically, that it should be symmetrical on
each side of the middle plane of its vibration, or it will wobble, and vary
its time in some irregular and incalculable way. It does not significantly
however, if one side of the bob is larger than the other in the direction of
vibration; but as that would look ugly and the other does not, one never sees
the ugly but innocent deviation, but frequently the other; for the pendulums
of common clocks are often unsymmetrical in the back and front, and are
therefore bad ones, though perhaps as good as the clocks they belong to. For
this reason the old fashioned lens-shaped bob, or the flat cheese shape which
some clockmakers use for church pendulums, are not good ones, because it
requires great care to fix them with their own middle plane coinciding with
the middle of the rod. It is true that a lens moves through the air with
3See an amusing pamphlet on it by Mr. F. D. Wackerbarth, and the remarks on the
Pyramid in my ‘Book on Building.’ (Lockwood & Co.)
SUSPENSION OF PENDULUMS. 30
less resistance than any other shape; but then it must be very large to be
of the same weight as a sphere or a thick cylinder with the axis vertical,
and we shall see afterwards that nearly all clock errors are inversely as the
weight (and length) of the pendulum. But there is a shape which would
probably be found to combine some of the advantages of both though Baily’s
experiments (in Phil. Trans. for 1932) showed some results which no one
could have foreseen; I mean a cylinder of elliptic section, or one having the
same horizontal section as a lens, but thicker; or of the section formed by
two arcs of a circle of 120, which would make the horizontal length and
thickness as 121
8 to 7 inches—a very convenient size for a large bob 13 in.
high; which would weigh about 188 lbs. in cast iron and 288 in lead, and is
equal to a round cylinder of 81
4 inches diameter. But such figures are only
approximate, the weight depending on the density of the casting; and I have
neglected the hole for the rod, as that would be compensated and more by
the rod’s own weight. A spherical bob is not so good as this shape, because
a slight error or looseness in the hole would throw much more of the weight
on one side and increase the tendency to wobble, a very serious defect. For
all practical purposes a cylinder is probably the best shape, and is used now
in all the best large clocks. I also introduced the plan of making the top
slightly domical, to prevent bits of dirt resting on it, which would accelerate
the pendulum, as we shall see presently under ‘regulation.’
Bobs for large clocks are generally made of cast iron, partly because it
is cheaper than lead, and also because very heavy lead bobs are liable to
be bruised out of shape in moving about before the pendulum is hung. But
there can be no doubt that lead is best, as its specific gravity is half as much
again as iron, and therefore it is less resisted by the air, which we shall see
afterwards affects pendulums by no means insensibly. For the same reason it
is a mistake to put lead bobs in brass cases, as is usually done in ‘regulators’
or astronomical clocks, as it increases the bulk much more than the weight.
The lead looks very well japanned. It is equally absurd to case lead weights
in brass, though it does no actual harm as it does in the bob.
Suspension of pendulums.—Pendulums are generally suspended by
a spring, for the obvious reason that they then swing without any friction—
except of the air. Some French pendulums are still hung by a string,
but that has some friction. The spring is not designed to act with any
force as a spring, though it does very slightly, and therefore is not at
all analogous to the balance spring of a watch, which is thus the substitute
for gravity. The spring is enclosed in a slit, or between two pieces
called chops at the top of the pendulum, which also carry the rod, except
in the American clocks, where the wire itself is flattened out into a
spring. The top of the spring is also riveted between two smaller pieces
in common clocks, so as to make a lump which holds up the spring in
the cock, which is a fixed piece with a slit in it just wide enough to hold
the spring. In clocks of the higher class the two upper chops are much
SUSPENSION OF PENDULUMS. 31
thicker and firmly screwed together, and a large pin put through them,
Fig. 9: Suspension of
Pendulums
and the chops themselves go through the cock
tightly and are held up by the pin which lies in Vs.
This will be better understood by this picture of
a heavy pendulum and its suspension. We are not
concerned with the lower part just yet. The nearly
square plate is a cast iron plate bolted to the wall,
out of which project the two thick pieces on which
the pin lies. The pin itself is like a bolt with a
tail projecting backwards through the head, and
the piece corresponding to the head, on the right
side in the figure, is the nut. The chops of the
pendulum itself are shown a little below, and the
way I introduced of making them for ‘regulator’
or astronomical clock pendulums which have the
steel rod screwed into a solid piece, is to file out a
slit wide enough to hold the spring and a piece of
brass on each side of it, and the whole is pinched
together by a screw. You cannot cut a slit thin
enough for the spring alone. This will be shown
in the figure of the four-legged gravity escapement
hereafter.
A perfectly firm suspension is essential to good
performance of any clock, and the heavier the pendulum
the firmer its support must be. It is well
known that clocks will influence each other when
fixed against a wooden wall, however firm it may
appear, and that one pendulum will thus actually
set another of equal length vibrating. Consequently
a free pendulum can be kept swinging
from an apparently immovable support which has
an invisible vibration or twist imparted to it by a
clock below beating in the same time. All good
regulators have the pendulum cock screwed to the
back of the case, and that firmly screwed to a
strong wall; or, better still, the cock is cast with
a cast iron back or bracket which also carries the
movement, and that is screwed directly to the wall,
the whole front of the case lifting off. In the Westminster
clock the pendulum cock is a large iron
frame built in right through the wall with a flange
behind, and the cocks of many other large clocks
are fixed with bolts through the wall. With a firm
suspension the pendulum swings farther than with
CONNECTION WITH CRUTCH. 32
a weak one, and we shall see afterwards that (other things being equal) the
errors of clocks vary inversely as the square and sometimes as the cube of
the arc.
It is hardly necessary to say that the whole of the pendulum suspension
should be so adjusted that the bend of the spring may be exactly opposite
the pivot of the pallet arbor, in order that the fork which embraces the
pendulum, as described at page 21, may have as little friction as possible. It
must not however be tight, for the reason just now given, viz. that no point in
the pendulum describes quite a circle, and the difference is sensible enough
generally to stop the clock if the fork fits the pendulum rod too tightly.
It is equally necessary that the plane of vibration of the pendulum should
be exactly at right angles to the pallet arbor, or else there will be a sliding
motion of the pendulum backwards and forwards in the fork. But obvious as
these things are, they are all constantly neglected, especially in large clocks,
where the friction of all the parts is also the greatest. The fork indeed is
seldom left too tight, because that mistake tells its own story directly; but,
by way of making up for it, it is very often so loose that you hear the shake
of it from one side to the other at every beat. There ought to be a drop of
oil there, as that is just enough to keep a steady hold without either shake
or tightness, since oiled surfaces are not really in metallic contact.
In old church clocks a long pendulum was often put for convenience a
good way off the clock, but so as to swing in the same plane as the crutch,
which is connected with it by a light horizontal wooden bar, no heavier than
an organ ‘tracker.’ The pendulum top too was often higher than the pallet
arbor, so that the pallets moved through a larger arc than the pendulum.
There is no advantage in that; but if the pivots at the ends of the horizontal
bar fit closely, there may be less loss of power by ‘shake’ than there generally
is between the fork and the pendulum. Indeed I have seen old regulators
made in that way, even with the pendulum in the usual place, by using two
short horizontal arms thus, D<C
P
, C being the pivot in the crutch, P the
pivot in the pendulum, and D the one at the junction of the two arms DC,
DP. But this is decidedly inferior to the other plan of putting the pendulum
on one side of the clock, since that requires only two pivots instead of three,
and there is no twisting action on the pendulum. If the horizontal bar
were attached by slight springs it would be better still, for there would then
be neither shake nor friction, and the springs would no more impede the
action than the pendulum spring does, for any moderate arc. There is yet
in existence one great London clock of the last century with fans on the
pendulum just above the bob (like the wings on the ankles of Mercury) to
prevent it swinging too far, and they are actually placed obliquely, of which
the effect of course is to make it swing with a twist. The late Mr. Vulliamy
told me he removed fans from the pendulum of the Horse Guards clock.
Sometimes heavy pendulums are hung by two narrow springs instead of one
PENDULUM SPRINGS. 33
broad and thin one, to secure the vibration in the proper plane; but it is a
bad plan, because it is difficult to get the two springs equal in all respects.
The springs of ‘regulator’ pendulums of 14 or 15 lbs. are generally about 1
2
an inch broad and 2 inches long; I mean clear of the chops of course; that
of the 6 cwt. pendulum at Westminster is 3 in. by 5 and 1
60 in. thick.
There should always be a degree plate, with a pointer to it on the pendulum
wherever it can be most conveniently seen. The length of 4 on the
plate is always .07× its distance from the top of the pendulum; and as the
only use of the degree plate is to see that the pendulum keeps the same arc,
or to see how it varies, no very great accuracy is required in the degrees.
Pendulum springs.—Various opinions have been propounded on the
proper strength for them, but none on any solid grounds, and some on
altogether mistaken ideas of the duty of the spring. Probably the thinner it is
the better, provided it is thick enough not to be bent too sharply or strained
by the weight of the pendulum. Every now and then a clock is troubled with
the disease of spring-breaking over and over again. Sometimes this proceeds
from the lower edges of the upper chops being left sharp, which in time cut
the spring; and perhaps more frequently from some unseen inequality in the
fixing; and it is better to let the pendulum hang at first with the lower chops
a little loose, and only to screw them up after the pendulum has got a square
bearing, and to take care not to put it out in doing so. It is wonderful how
much more trouble people will take to do things wrong than would serve to
do them right, and it is almost incredible that some clock-makers send out
their best clocks with the lower edges of the upper chops not horizontal but
rounded into a circular arc. The slightest reflection would show anybody
that springs so fixed must tend to ‘buckle,’ or bend not in a straight line, at
every vibration. And others make the upper chops, which have the strain
of vibration, thinner and weaker than the lower ones which have no strain.
There should always be a block of wood close under the bob of a heavy
pendulum, to prevent the top from breaking the crutch and pallets if it falls
from the spring breaking.
A spring does not bend only at one point as a string does; and therefore
a pendulum bob hung by a spring does not move exactly in a circle, but
in something more like a cycloid described with that radius of curvature,
as in fig. 8, p. 23; and it has often been attempted to make springs which
would render the pendulum absolutely isochronous for all such arcs as it is
likely to swing. Possibly the thing could be done, if it was worth doing;
but both I and some other persons who have spent a great deal of time
on experiments have come to the conclusion that it is not, for reasons will
appear when we come to consider the effect of the escapement on the time of
vibration. Indeed I may say at once, with respect to the only escapement I
have yet described and all others on the recoiling principle, that the circular
error, which it is the object of these spring contrivances to correct, is already
more than corrected by those escapements: for the clocks never lose, but
PENDULUM REGULATION. 34
gain, when the arc of the pendulum increases; so that the circular error is
actually useful for counteracting the escapement error, and the clock goes
better than it would with a perfect cycloidal pendulum, or any equivalent
contrivance.
Pendulum regulation.—Though pendulums can be made by calculation
and experience very nearly of the proper length, they always require
some adjustment afterwards, besides regulating from time to time, according
to the state of the clock. The usual way of doing this is by a screw
cut at the lower end of the rod, with a nut on which the bob rests, and by
which it can be raised or lowered to make the pendulum go faster or slower.
The lower part of the rod is always made into a square or some shape on
which the bob cannot turn, except in certain compensated pendulums, as
we shall see; for otherwise the bob would twist round with the nut. By that
means you can hold the bob and the rod steady while you turn the nut. It
is convenient to have the thread of the screw such that one complete turn of
the nut will make a minute a day difference in time; and the better class of
pendulums have a large round nut divided by marks which mean a second
a day, with an index fixed to the bob.
It is easy to find what should be the width of the thread for one turn
to do a minute a day. Let l be the length of the pendulum, and dl a small
increase of l, and dt of t. Then we know that
t + dt
t
=
pl + dl
pl
; or, 1 + dt
t
= s1 + dl
l
There is a result of the binomial theorem which we shall often have
occasion to use in pendulum problems, which may be stated thus:—When a
quantity is of the form 1+m, m being a small fraction, (1+m)n practically,
or as astronomers say, sensibly = 1+nm whether n is + or −, a fraction or
an integer; and it may be as well to mention for those who do not know it
that (1 + m)−n means 1
(1+m)n . Consequently here dt
t = dl
2l ; and multiplying
by all the seconds in a day, 86400, and calling dT the daily increase, dT =
43200dl
l sec. So if we want dT to be a minute for one turn of the nut, dl or
the width of the thread must = l
720 , or about 1
18 inch, a very convenient size
for a fine screw.
But this mode of regulating is inconvenient for large clocks with very
heavy bobs, and it is better to fix a collar on the rod at some convenient
height, on which small weights can be laid to accelerate the clock, and taken
off to retard it. The place where a given weight is most effective is at the
middle of the length, but it does practically as well to put it somewhat
higher, and the higher it is the less risk there is of shaking the pendulum
in putting the weight on or off, by which any accurately going clock is
seriously disturbed. The proportion and position of these regulating weights
are determined as follows:—Let m be a little weight added to the pendulum
TEMPORARY REGULATION. 35
at a distance d below the top, and l above O the centre of oscillation; then—
t + dt
t
=
1p
l ·
pMl2 + md2
pMl + md
= q1 + md2
Ml2
q1 + md
Ml
and since m
M is very small this practically
=  1 + md2
2Ml2! 1 −
md2
2Ml2!
which again for the same reason = 1− m
2M d
l − d2
l2 . From which you see at
once, that if d = l
2 , −dT or the daily acceleration = 10800m
M ; or the 10800th
part of M laid on the pendulum half way from the top will accelerate it a
second a day; and if d = either l
3 or 2l
3 , m must = M
7200 to do a second a day.
We shall get exactly the same result for b if we reckon from o; for if
you substitute l − b for d in this last equation, the result is that dt
t =
− m
2M b
l − b2
l2 ; as might have been foreseen from the fact that the centres
of suspension and oscillation are reciprocal (p. 27). You will easily see too
that the worst mode of regulating is by a sliding weight near the middle of
the pendulum; for the acceleration by moving the weight upwards from b to
d is measured by dl−bl+b2−d2
l2 , which is o when d = b, and very little while
they are anything near equal. In short the middle of the pendulum is the
place of maximum effect for the weight, and of minimum effect for moving
it.
Temporary regulation is also sometimes required in the best clocks:
i.e. they want putting on or back a few seconds or less, though the pendulum
may not want permanently altering. Stopping the pendulum and setting it
off again so disturbs it for some time that it must be always avoided if
possible. One way of altering the clock a very little is to put on or take off
a small regulating weight for a certain number of hours. Another mode now
resorted to in very fine clocks is to apply a temporary magnet, which can
be made and unmade for any required time, so as to act on the pendulum
either with or against gravity, and so to accelerate or retard the clock, until
it shows the proper time. Other methods have been tried which all disturbed
the pendulum too much. The first is used at Westminster, where it is easy
to put on small weights without disturbing that slow and heavy pendulum.
I regulate my best regulator with a gravity escapement by bits of card laid
on the bob of about 40 lbs.: that is, for permanent regulation.
Some common clocks are regulated by a nut at the top, above the cock,
which pulls up the spring through the slit in the cock; but this is thought
unfit for fine work, because the spring ought to be tighter in the cock than
is possible if it is to be capable of being pulled down by the weight of the
pendulum. But I rather doubt that, if it is made carefully.
COMPENSATION OF PENDULUMS. 36
Compensation of pendulums.—All substances of which pendulums
can be made expand by heat, and consequently every pendulum naturally
goes slower in hot weather than in cold; and though the lengthening of the
rod is far too small to measure, except by most delicate experiments, it is
enough to make a difference of a minute a week between moderate winter and
summer heat (40 and 70) with a common iron wire pendulum, and in five
days with a brass one, and a minute in three weeks even with a wooden rod,
which varies the least of all materials, but is subject to a little uncertainty
from absorption of damp. The following is a table of the expansion of such
materials as can be used for pendulums, i.e. of dl
l for 1000 (F) of heat,
which I use to get rid of unnecessary decimals, as we are only concerned
with the proportions:—
White deal, and perhaps other woods, have .0023 expansion and specific
gravity from .5 up to .9.
lbs
Flint glass expands .0048: a cubic inch = .1166
Platinum. . . . . . . . . . .0056 ,, .76
Steel rod, tempered .0064 ,, .28
Cast iron . . . . . . . . . . .0066 ,, .26
Iron rod . . . . . . . . . . . .0070 ,, .28
Brass. . . . . . . . . . . . . . .0100 ,, .30
Copper . . . . . . . . . . . . .0106 ,, .32
Silver. . . . . . . . . . . . . . .0115 ,, .38
Lead . . . . . . . . . . . . . . .0165 ,, .41
Zinc . . . . . . . . . . . . . . . .0160 ,, .253
Mercury, in bulk. . . .1000 ,, .49
its expansion in length depending on the vessel.
These differences make it easy to devise a pendulum which will always
keep the bob at the same height. To take the most simple example, suppose
we set a brass tube 6.4 ft. long on a nut at the bottom of a steel rod of 10 ft.;
it is evident that the top of the tube, or a bob resting on it, will stay at the
same height in all temperatures. This would be a very inconvenient sort of
pendulum, but we can do the same thing by breaking up the long lengths
into pieces, none of which must be more than 3 ft. for a 39 inch pendulum,
and consequently a steel and brass pendulum must have three lengths of
steel and two of brass. Accordingly the old gridiron pendulum, invented
by Harrison, who became the first chronometer maker of his time from a
carpenter, had a central steel rod with a cross at the bottom carrying two
upright brass rods as columns, on the top of which was another cross piece
from which hung two steel wires, again carrying a cross at the bottom, on
which two more brass columns stood, and from the top of them hung two
more steel wires carrying the bob.
ZINC COMPENSATION OF PENDULUMS. 37
Another form of it, invented by Troughton, was to substitute alternate
brass and steel tubes for each pair of rods. If iron were used instead of steel,
another pair of each would be required, making thirteen rods altogether.
But since the introduction of zinc-working brass pendulums have gone
out, because zinc expands enough to do the compensation with only one
zinc tube, and is stiff enough, which lead is not. It might also be done with
platinum and brass, but that is too expensive, and zinc with steel or iron
does just as well. The figure at p. 31 shows the best construction of large
pendulums of this kind, and that of small ones is substantially the same,
only short zinc tubes may be much thinner in proportion than long tubes,
which have to carry heavy weights, acting as a column which must run no
risk of bending. For small pendulums the zinc need not be more than .1 inch
thick, but for 2-sec. pendulums, with bobs of suitable weight, the zinc tubes
are made three-fold, all drawn tight upon each other, and altogether 3
8 in.
thick. The tubes for somewhat lighter bobs and shorter pendulums may be
half that thickness, or even less. No rule can be given for such things. For
1-sec. pendulums a steel rod 1
4 in. thick is enough, but for a heavy bob I
prefer 3
8 in., as it has to be tapped for screws at each end. I will give some
further directions about construction presently.
The calculations for the proper length of zinc are not quite so simple as
you may imagine, except as a first approximation: in fact, if you attempt it
all at once it is much too complicated to be practicable. We have seen at
p. 35 in effect that the transfer of a very small weight from the lower part
of a pendulum to the upper produces a great acceleration, and this happens
in the rising of the weight of both tubes under expansion, yet it cannot be
taken into account in any simple calculation. I suppose it is from this cause
that the expansion of zinc, given in all other tables as .017 for 1000 of
heat, gives wrong results for these calculations, as is proved by experience.
I find .016 is the nearest value to produce right practical results. You must
remember, too, that the point which we have to keep at the same level is
no measurable one, such as the centre, or the bottom, or the top of the
bob, but the c.o. of the whole pendulum, and we know nothing a priori of
its relation to the top of the tubes of the total length of the pendulum, by
which I always mean down to the bottom of the bob; for all these have to be
found by trial. In the usual astronomical, or 1-sec. pendulum of this kind,
it happens that the c.o. of the whole nearly coincides with the c.g. of a bob
of 9×3 or 31
3 or 4 inches; but in large ones with heavy tubes it comes much
nearer to the top.
Again, an iron bob may be considered as attached to the iron tube
anywhere, as they both expand equally; and therefore, as fixed at the c.o.
And a lead bob may in fact be fixed at the c.o., and now generally is in the
best pendulums, in order to avoid the slower changes of temperature in a
thick bob than in tubes. But in commoner ones it is hung on a flange or
collar at the bottom, and then you get the benefit of the expansion upwards
ZINC AND STEEL COMPENSATION. 38
of about 41
4 in. of lead (up to the c.g. or c.o.) in addition to the zinc tube,
which therefore has to be shorter than in the two other cases. And further,
if the rod is steel its expansion is at a less rate than of the iron tube.
Bearing in mind, then, that any practicable calculation is only approximate,
we may proceed with them as follows: Let l (as usual) be the length
from the top of the spring to the c.o.; r the length to the bottom of the zinc
tube, which rests on the nut at the bottom of the rod; z the zinc tube to be
found; s the iron tube, which may or may not = z, as just now explained; c
the height from the bottom to the c.o. Then for a steel rod, and a lead bob
resting on the bottom, we must have—
.016z + .0165c = .0064r + .007s . . .A
But now s = z, assuming all the bottoms to coincide, as they always do
nearly; and we know by experience c to be about 4–5 in. for a 9-in. bob,
and r about 44 in a 1-sec. pendulum, and we may introduce them at once,
bearing in mind that the moment you translate one algebraical letter into
inches all the rest become numbers of inches only. Then transposing all the
unknown and known terms to opposite sides, equation A becomes—
(.016 − .007)z = .2816 − .0742 = .2074,
which gives z = 23; but it is safer to begin with the tubes a little longer,
in case the compensation is not found quite enough, as they are easy to
shorten, but impossible to lengthen.
When the bob is fixed, or may be considered fixed, at its c.o., the equations
will be, first, for a steel rod and lead bob fixed at its middle,
.016z = .0064r + .007s = .0064r + .007(s − c), . . .B
and for iron rod and bob,
.016z = .007(r + 2 + c). . . .C
Taking the same values as before for r, &c., B will give 28.3 in. for z; which,
however, is more than the length of zinc in the Greenwich sidereal pendulum,
adjusted to mean solar time in order to compare it with others. I had my
own made full 28 in., and I have no reason to think it is over compensated,
but I cannot say I have tried it specially for compensation. The Greenwich
one, with z = 26 more agrees with the tabular expansion .017 of zinc, but
not quite.
The Westminster pendulum, I know by its weekly rate for a year, is
exactly compensated. It was made at first for the .017 expansion, and was
soon found to be under-compensated, and we had to make new tubes. If you
insert in equation C the lengths given for that pendulum in the table below,
you will see that .016 almost exactly agrees with the ascertained results, c
THE HEAVIEST PENDULUMS. 39
being of course = r −l. All the heights of bobs in this table are reckoned to
the top of the dome, and my own, the third in the table, at Batch Wood,
St. Albans, is slightly domed at the bottom also, and the weights are those
of the whole pendulum approximately, as nothing respecting compensation
turns on them. All the measures are inches.
sec l r z bob
Weight of
pendulum.
11
4 61 68.5 48.5 14×8 200 lbs.
11
2 88 98 68 15×9 300 ”
11
2 88 96.5 61 14×8 lead 300 ”
2 156.5 173 125 20×12 700 ”
The tube should have some holes or long slots (which look better) on
each side, to allow the air to reach the zinc, so that both tubes may change
their temperature simultaneously. At Westminster the zinc weighs 67 lbs.,
and the iron tube 40 lbs., and the rod 62 lbs., out of the 700 lbs. total weight.
That is no longer the heaviest pendulum in England, for Mr. Godman,
a clockmaker, organ-builder, and bicycle-maker at St. Albans, has put a
21
2 -sec. pendulum to the clock which he made for St. Peter’s church there
with a bob of 9 cwt., which he made in pieces called ‘shifters’ in clock
weights, piled on each other like cheeses, to make it manageable without
machinery, which is practically as good as one piece. And that has lately
been exceeded by a 2-sec. pendulum of 12 cwt. in St. Nicolas’s Church at
Bristol, by Mr. Langford there. It is an odd coincidence that both those
makers had the boldness also to put the gravity escapement a long way off
the clock, because for local reasons it could not be near the best place for
the pendulum, and with a gravity escapement that may be done very well.
I need hardly say that thin iron rods on each side of the zinc tube may be
used instead of the iron tube if you like.
In one or both those places there was this good reason for so separating
the escapement from the clock—and there may be the same in others,
especially where new gravity escapements are put to old clocks—that the
clock itself could not be fixed firmly enough to carry the pendulum without
yielding; the importance of which has been noticed at p. 29, and will be
proved farther on. But there was no difficulty in fixing the escapement with
the pendulum on iron brackets bolted to the wall.
Some persons appear to be misled by the well-known necessity for a secondary
or auxiliary compensation in chronometer balances, which will be
explained afterwards, into supposing that no single compensation of a pendulum
can be complete.4 But they depend on different principles, and the
errors of an uncompensated balance are twenty times those of the commonest
iron wire pendulum for the same variations of heat, being 6 sec. a day for
4See Horological Journal, April 1882
PENDULUMS DIFFER FROM BALANCES. 40
1 of heat, according to experiments. I may as well however explain a little
more about the matter. The complete mathematical calculation for compensated
pendulums does exhibit a very small and insignificant error, which
is never taken account of in the ordinary calculations, and I only mention it
to say that it is so small, and is not the defect which the persons I refer to
have imagined. It is the effect on the moment of inertia, and therefore on
the time of the pendulum, of the increase of length of all the rods and tubes,
which of course have all some weight of their own. The moment of inertia
of every such piece, say of length z inches and mass Z (which is z times
the mass of one inch long of such rod or tube), of which the c.g. is h from
the suspension, must then be Z h2 + z2
3×4; and the moment of inertia of
the whole is the sum of all those quantities in the numerator of the fraction Pmr2
Pmr
or l. And to each of them has to be added its own increment for
heat, viz. for the rod and the two tubes, and strictly even for the increase of
length of the bob, and the resulting one for h in each case; and the squares
of all these appear in the numerator, and their first powers in the denominator.
This is much too complicated for calculation except by successive
approximations.
It is quite true that if a pendulum is not compensated at all its errors
increase more slowly than the temperature, because the time varies only as
the square root of the length, while the length varies as the temperature.
But that does not the least affect the question of how it behaves when it is
compensated, so as to keep some point in the bob which practically agrees
with the centre of oscillation, or is at l from the top at the same level. I
say ‘practically agrees,’ because it need not be very exact. For if the c.o.,
which is at least approximately known, in the bob is kept at the proper
level, it is clear that every other point pretty near it will be so too, since
all the motions are absolutely very small, and of course their differences are
smaller still. And that is the answer to this imaginary difficulty. I may
anticipate the balance compensation so much as to say that besides the 20
times greater effect of a given change of temperature thereon, the rate of a
balance depends on an external cause, viz. the varying strength of the spring,
enormously more than on the mere variation of the moment of inertia, on
which a pendulum rate depends, where also it is partly corrected by gravity
acting farther from the vertical as the pendulum lengthens; i.e. both the
numerator and denominator increase, but the numerator increases most, as
it contains squares. Gravity has nothing at all to do with a balance, if it is
balanced, as of course it should be.
Wood and Lead.—The same is the principle of the simplest of all the
compensation pendulums. According to the tabular rates of expansion of
lead and of a deal rod, it is easily calculated that a bob 14 in. high on a rod
46 in. long ought to make a compensated 39 in. pendulum; for c.o. is about
.4 in. below c.g. of the bob when it is 14 in. long, so that the rod must be
WOOD, ZINC, AND LEAD COMPENSATION. 41
39.14+6.6, or nearly 46 in., and then we shall have 6.6×.0016 = 46×.0023,
which is right. Such a pendulum however was found to be overcompensated,
and at first one is inclined to conclude that the expansion of deal has been
overrated; but this was with a dead escapement, and I am satisfied, for
reasons which will appear farther on, that such escapements contain a sort
of irregular compensation of their own; and I advise no one to rely on a
shorter proportion of lead bob than the above for a wooden rod for other
kinds of escapements such as I shall describe.
Wooden rods are generally and rightly used for large clocks where compensated
pendulums cannot be afforded: but such clocks are exposed to
great changes of temperature—often as much as 40 between winter and
summer, and to 30 on the average of each; which would make a difference
of 20 sec. a week with an uncompensated wooden pendulum; whereas good
public clocks ought to be guaranteed to vary not more than 5 or 6 sec. a
week at the utmost—a much easier condition than 1 sec. a day, because one
day may partially correct another. The Westminster clock only varies 1 sec.
a week on the average, omitting casual disturbances by men and thunderstorms.
Wooden rods should be as thin as will bear proper fastening at the
ends, which may be thicker for that purpose. Any thickness which could be
practically used and worked will bear ten times the weight of any bob that
would be used. They should also be thoroughly dried and saturated with oil
or some antiseptic fluid, and varnished to keep them from absorbing damp.
Small ones are sometimes gilt; but even then they are not to be relied on,
and I believe all the best makers agree that they are unfit for the highest
class of clocks, though they will do for all but the highest. The late Mr. Vulliamy
used to use mahogany and teak instead of deal, but I do not know
whether it was from experience, which alone can determine such a question.
I should think that the creosoting process would be a good one for wood
pendulums; but that also wants trying.
Wood, zinc, and lead compensation.—There are places which invite
the use of longer pendulums than can well be made of iron and zinc only,
because a very long zinc tube requires to be very thick to be safe against
bending. If wood can be made trustworthy by creosoting it in vacuum (as
they do railway sleepers), or in any other way a very good long compensation
pendulum may be made, with a zinc tube only about a third as long as
an iron rod requires, and only a fifth of the whole length of the pendulum.
Suppose we want a 21
2 sec. pendulum, of which the simple length is 244.6 in.,
with a cylindrical lead bob, say 13 × 10 in., which will weigh 400 lbs. The
lead itself will give us a little compensation due to the height of the c.o.
above the bottom of the bob. The problem can only be solved by successive
approximations, and they are too long to go through here; but if you try the
following figures you will find them come as near as any pendulum can be
made without adjustment, especially as there is some uncertainty about the
expansion rate of wood, which I have taken according to the above table,
COMPOUND BAR COMPENSATION. 42
and also taken its specific gravity at .1 of iron for simplicity or a cubic inch
= .028 lb., for a heavyish wood, such as teak or mahogany. Take the total
length to bottom of bob 253 in., of which about 240 in. will be wood rod,
with a section of 11
4 in. diameter, and it will weigh about 71
2 lbs. First let
us see what length of zinc tube this will require, supposing the bob to be
hung by a pair of thin steel rods from a cross head resting on the top of
the zinc tube. There should however be a smaller collar fitting the top of
the tube, with a slightly rounded top for the cross head to lie on, as there
would otherwise be a risk of its not bearing square on the tube, but all on
one edge. The expansion of so much of the bob as lies below the c.o. of the
pendulum will give us some compensation; and as we have assumed that to
be the difference between 244.6 and 253, we have 8.4×.0165 = .138, for the
expansion of the lead upwards; and 240×.0023 = .5552 for that of the wood
downwards. Calling the zinc tube z we have .0172z upwards. The steel rods
will be quite 2 in. longer than the tube, and there are 13 in. of fastenings and
spring; so that we must add at least (z+15).0064 downwards. Equating the
downward and upward expansions, you will find that z must be 50 inches.
Smeaton’s pendulum.—I have a clock with an old 1-sec. pendulum
by Holmes, a celebrated clockmaker of the last century, with the following
compensation, which was invented by Smeaton, the great engineer. The rod
is of brass, 43 inches long + 2 inches of steel spring, and on a collar screwed
to the bottom of it rests a thin zinc tube 122
3 inches long, from the top of
which is hung an iron tube of the same length, by the end being merely
turned over, and on the bottom of that tube turned outwards rests a lead
bob also of the same length, enclosing the tubes, so that the pendulum looks
simply like a glass rod with a lead bob. The c.o. of the pendulum is 6 inches
from the bottom of the bob, and therefore the expansion of 6 inches of lead
+ that of the zinc tube upwards has to balance that of the glass rod and
the iron tube downwards, as you may calculate from the table that it will
very nearly.
Another form of steel, zinc, and glass pendulum has been proposed, with
a glass tube instead of the iron one, which would require a shorter length of
zinc; but I see no advantage in it over the common one.
Compound Bar compensation.—Before going to the mercurial pendulum,
which requires more detailed examination, we will dispose of a few
others which require shorter notice. This one (fig. 10) is founded on the
principle of the compensated balance in watches. WCW is a compound
bar of brass and iron brazed together with the brass side downwards. As
brass expands more than iron, the bar will bend upwards as it gets warmer
and carry the weights WW with it, and they may be so adjusted both by
magnitude and position as to raise the centre of oscillation as much as the
elongation of the pendulum rod lets it down. I cannot give any details of
the proportions, as this plan does not appear to have been used in England
except in experiments, and old Mr. Dent told me it was found inferior to
HOMOGENEOUS COMPENSATION. 43
Fig. 10: Compound Bar Compensation
the other methods, over which I do not see that it has any advantage except
the facility of adjustment. It is said in Kater’s treatise to have answered in
France, but the French seem to prefer complicated compensations to simple
ones. It might however be used to complete the adjustment of another compensation
left imperfect for that purpose, in which case the weights would
only need to be very small.
Homogeneous compensation.—All the compensations I have yet mentioned
require the use of at least two substances of different expansibility;
but there is one which does not; and though it is practically of little or no
value, in any form in which it has yet been made or suggested, it is worth
while to describe the principle of it. If the pendulum spring is drawn up
through a close slit in the cock as much as the pendulum lengthens by heat,
its effective length will remain the same; and this may be done by various
arrangements, of which the simplest is hanging the spring to another cock
above the slit one, set on the top of a stiff bar long enough to expand upwards
as much as the pendulum rod expands downwards. This bar may
ELLICOTT’S COMPENSATION PENDULUM. 44
be either of the same or of a different metal from the pendulum rod and
its length will of course depend on its material; or the slit cock may be on
one end of a lever, of which the other is pulled down by a wire of the same
length and metal as the pendulum rod. But there is a serious objection to
this plan in every form; if the slit is loose enough to let the spring slide up
and down through it, it is too loose for the proper action of the pendulum
in a clock good enough to require a compensation for temperature. There
is no other kind practically worth describing.
Fig. 11: Ellicott’s Compensation Pendulum
Ellicott’s pendulum.—There is another bad one which is still used in
small French clocks, though it has long ago been abandoned in England,
where it was invented by Ellicott a clockmaker in the last century. AC the
main rod is of iron or steel and it has a pair of levers set on a cross pin at
MERCURIAL COMPENSATION. 45
the bottom, of which only one BCD is shown here: at A there is a strong
collar fixed to the rod, and between that collar and the short arm of each
lever stands a stiff brass rod. The bob hangs by two pins, of which D is one,
on the long arms of the levers; and it is evident that by a proper adjustment
of the levers the bob may be made to rise under the expansion of the brass
rods just as much as the expansion of the iron rod lets down C, the axis
of the levers. But this action involves considerable friction at D, and the
pressure on the ends of the brass rods must very much exceed the weight
of the pendulum, and it is said to move by jerks, and is altogether inferior
even to the old gridiron, and much more to the zinc or mercurial pendulum,
besides being much more difficult to make properly. I suppose they are only
made because they have a kind of scientific look to ignorant people, in clocks
made to show and to sell.
Mercurial compensation.—The principle of this, which is used in all
the best astronomical clocks (subject to a remark to be made afterwards),
is the same as of the wood and lead; only, mercury being fluid requires a
different mode of calculation. For it must be in a jar which has some sideway
expansion of its own, and the rise of the mercury is only the excess of its
expansion in bulk over that which the increased width of the jar allows it.
The jars can only be made of either glass or iron, as mercury amalgamates
with and so destroys any other metal that could be used. Although iron is
the best, glass is the most commonly used, either from old habit or ignorance,
and so we must consider both of them, and we will take the glass first, and
in both cases neglect at first the weight of the jar itself: which by a strange
oversight was forgotten altogether by Francis Baily, P.R.A.S., in a far more
elaborate paper on this subject (in vol. i. of their Memoirs) than there is
any need of, seeing that after all a compensated pendulum can only be
accurately adjusted by trial, of itself or one exactly like it. It is almost
equally strange that this mistake was never discovered for forty-four years,
though the best clockmakers and the late Mr. Bloxam, who most thoroughly
investigated the theory of escapements in two papers in the 22nd and 27th
vols. of the R.A.S. Memoirs, had practically found that the received height
of mercury was insufficient. But they all attributed it to the pendulum
spring being stiffer in cold than heat; which always appeared to me a most
inadequate explanation, considering the weakness of the spring in proportion
to the weight of a pendulum. In 1863 I had to calculate the height for the
iron jar of a pendulum intended to weigh 40 lbs., and finding the result far
beyond Baily’s proportions, I looked carefully through his paper and then
found out the mistake, and published the correction of it in the Mechanics’
Magazine, of 5 Feb. 1864. Another reason why it had escaped discovery was
that dead escapements, which nearly all astronomical clocks had, contain
(as I said before) an irregular kind of compensation of their own, from the
greater fluidity of the oil in warm weather. It is remarkable that Hardy,
the inventor of another kind of escapement which I shall notice afterwards,
BAILY’S MISTAKE ABOUT MERCURIAL COMPENSATION. 46
had calculated the height of his mercury rightly before Baily’s paper which
everybody accepted.
Fig. 12: A new kind of jar
Mercury expands .1 in bulk while the
glass jar increases .0048 in diameter, and ...
the sectional area increases as (1.0048)2 or
1.0096 to 1; ... the mercury will rise .1–.01
(say) or .09 of its own height. And since the
c.g. of the bob is very nearly at O, let x be
half the height of mercury; then .09x must
be = .0066(l+x) for the steel rod, which is
usually carried down to the bottom of the
jar in the form of a long ‘stirrup,’ on which
the jar stands. That makes x = 3.1 in.
or the height of the mercury 6.2 in., which
has to be increased .1, or rather more for
a reason which will appear afterwards, and
that is Baily’s result—without considering
the weight of the jar.
The weight of the glass jar and rod
may be a 6th of the ultimate or corrected
weight of the mercury; and about much
more height must be added for it, as it is
evidently much the same as if all the bob of
pendulum were mercury, but its rise only 5
6
of its real amount. And approximately this
is near enough, seeing that pendulums vary
in their proportions and must be finally adjusted
by trial; and glass jars are going out
of use for the best pendulums, which it is
now agreed ought to be much heavier than
the old two-inch wide cylinder allows.
The late Captain Kater used for his experiments
entirely glass pendulums, which
of course require a less height of mercury
than steel ones. There is however no advantage
in that, but rather the contrary,
as the jar must be inconveniently wide to
hold any considerable weight, besides the
difficulty of handling a heavy glass pendulum
safely. Others have made the steel rod
go through the bottom of the jar; but that
is a bad plan, as it involves stuffing to make
the hole mercury-tight, and allows no subsequent
adjustment without risk of destroyCAST
IRON JARS. 47
ing that tightness. It is desirable however that the rod should plunge into
the mercury, that they may take the same temperature, and the best way of
doing this with a glass jar would be that shown in this drawing. The shape
of the jar speaks for itself. The black ring round the neck is in two pieces
of brass, put on with a piece of thin leather to improve the fitting, before
the cap is dropped over it and screwed to them with two or three screws to
each half of the ring. All other plans with the same object that I have seen
involved some cementing to the glass or stuffing, which is not to be trusted.
The small hole in the cap is for adjusting the quantity of mercury according
to experience.
Cast iron jars are superior to glass, first because they are safer, and
firmer on the rod, and the construction simpler when done properly; secondly,
because the mercury can be heated in them to drive off any moisture
or air bubbles between the mercury and the jar, as is done with barometers;
thirdly, because (contrary to the common notion) the extra height required
for the weight of the jar is an advantage, especially when you want a very
heavy bob. Calling the jar about a third of the mercury in weight, a 40 lbs.
pendulum will have a jar only 31
2 in. wide outside; and one holding 40 lbs.
of mercury will be 31
2 in. inside, for we shall find the mercury to be nearly
9 in. high, and a cubic in. of pure mercury weighs half a pound, and common
mercury weighs slightly less. The best construction, and much cheaper than
that generally used till lately, is to cast the jar 1
4 in. thick, and twice as
long as it need be, in order to secure sound casting, as they do for cannon,
cutting off the ‘dead head;’ turn the outside if you like for appearance, or
else japan it, and ‘enamel’ the inside, i.e. coat it with glass, which stops up
all the pores. The cap is partially dropped into the top of the jar just turned
out to fit it and held by 4 or 5 screws through the jar. The rim is marked
out into divisions of 1 sec. a day as described at p. 34, an index being fixed
to the steel rod, which is tapped and screwed through the cap exactly as
in the last figure, while the cross-head is to hold it steady when you turn
the jar for regulating. A 40 lbs. pendulum made thus costs less than old
Mr. Dent used to pay for the pendulum alone without the mercury, on the
old construction. This is the construction now used by Mr. Brock of 64,
George Street, Portman Square, who used to be with Dent, and has done
all except church clock work for me for some years. Enamelling the jars was
his idea.
For an approximate calculation like the last, we have only to use the
expansion .0066 of cast iron instead of glass for the jar, and that makes the
rise of the mercury .1 − .0132 or .087 nearly. And assuming the mercury to
weigh 3 times the jar and rod, the rise must be 4
3 times as much as if they
had no weight, or we may treat the rise of the mercury relatively as .065, or
3
4 of its real amount. We know that the height must be something over 8 in.,
and the total length of the pendulum nearly 431
2 , allowing the c.g. of the bob
to be a very little above O. It is not worth while to distinguish between the
MERCURIAL V. ZINC COMPENSATIONS. 48
expansion of cast iron and steel for the short length of the cylinder, and we
may say that the rise of the c.g. of the mercury, or the increase of x, or .065x,
must = 43.5 × .0064 = .2784, and ... x = 4.3 nearly. The assumption that
x is something over 4 in., for the mere purpose of finding the total length
of the rod, does not affect the result sensibly, as you will see if you try it as
an inch more or less. But this is not quite enough, because it is not the c.g.
but the c.o. that has to be kept at the same height, and we must find how
much less h really is than l for we have only yet stated it approximately. If
b is the radius of the cylinder when the weight of the rod is insignificant,
lh = k2 or = k2 + x2
3 + l2
4 . but b is so small compared with h that that
term produces no sensible effect. Then putting 39.14 for l and either 4.3
or 4.4 for x you will find by solving the quadratic equation that h = 38.98
or l − h = .16 in. = .036x: ... we must say .964 × .065x or .0626x = .2784
as before, and ... x = 4.44, which makes the height of mercury just under
9 in. in a jar which weighs 1
3 of the mercury. I found mine not quite enough
compensated with 81
2 in., and it is perhaps a little over done with 9—a
widely different result from Baily’s 6.6 for an iron jar. The calculation of
compensation otherwise than by this method of approximation runs into
equations of a high order and becomes unmanageable, and after all it is
better to adjust the height of the mercury finally by trial. The longer the
bob is, or the heavier the rod and compensation tubes, the more the c.g. of
the bob (not of the whole pendulum) is below c.o. A very long bob is not
desirable on account of the increased resistance of the air, and therefore it
is not expedient to make the jar more than about a third of the weight of
the mercury, which is in every way a convenient size.
It is now thought at Greenwich that zinc and steel pendulums are as good
as mercurial ones. The normal sidereal clock there has a zinc pendulum,
and I am told that its daily variation of rate is reckoned by hundredths of
a second. If this is so, it will be a considerable saving in expense, inasmuch
as there is no doubt that pendulums ought to be much heavier than used to
be the fashion. I must say that the performance of the great Westminster
clock goes far to confirm the Greenwich opinion, for it has no discoverable
error of temperature.
Barometric compensation.—It is evident that the larger the bob is
for its weight, i.e. the less its specific gravity, the more it will be resisted by
the air, and the smaller arc it will swing under a given force. We shall see
afterwards that all the escapement errors involve Wh
Ml divided by either a2
or a3, Wh being the force that actually drives the pendulum for a day, or
weight × daily fall, after deducting the friction, and Ml the same as before,
and the arc from zero as usual. Therefore the larger a is for a given weight
the better a great deal. Moreover, the greater the density of the air is, the
more it diminishes the effective specific gravity of the pendulum, viz., by
an amount = sp. g. of the air, which is variously estimated at something
near the 840th of that of water, and therefore about a 9000th of an ordinary
VALUE OF LARGE ARCS. 49
lead pendulum with deal rod, or a mercurial one with a glass jar and the
usual appendages, which make its mean sp. g. about 11, water being 1. And
this reduction is considerably increased in a swinging pendulum by the air
which it drags along with it. Baily found, by comparing the times of free
pendulums of various kinds in vacuo and in air (see Phil. Trans. of 1832),
that the stationary loss of sp. g. is sometimes doubled by vibration. One
specially curious result should be noted, that a thin flat rod with a very
elliptical section was more affected in this way than a round one three times
as thick, although a lens-shaped bob was less affected than a sphere of the
same diameter and of course much heavier in proportion to its surface, which
so far gives it an advantage. But we have no information whether the air
affects a lens more or less than a sphere of the same weight.
Bloxam said in a note to his paper in the R.A.S. Memoirs of 1853 that
Baily overlooked the fact that the current produced in the descent of the
pendulum prevents it from being retarded in the ascent as much as it would
have been if the air had been at rest. He also always found the circular error
to be less than its theoretical value, and the resistance of the air doubtless
tends to produce this effect.
Without going through Baily’s various results it is enough to say that
he found pendulums of sp. g. about 11 gain nearly 13 sec. a day by being
put into a vacuum; as that was the daily increase of time (+
T or − ‘rate’)
for an inch rise of barometer, which is shortly called the barometric error,
apart from any circular or escapement error which may accompany it. A
small platinum ball hung by a wire gained 5 sec. in vacuo, against 91
2 for a
lead one of the same size (for a sphere is less affected than a cylinder); the
gain was nearly 14 for a brass and 56 for an ivory ball, and 19 for a round
copper rod .41 in. thick and 5 ft. long; which last was 3 times as much as
its stationary loss of specific gravity. But this effect on the rod as a whole
pendulum is insignificant when it carries a bob much heavier than itself, as
it usually does.
Baily found also by calculation that with an arc of 2 450 the barometric
error ought to be neutralized by the circular error, i.e. by the diminution of
arc produced by the increased density of the air. That result differs from
the one arrived at by Bloxam, but was verified by the performance of the
Westminster clock during the year 1872, in which I ascertained that the
barometric error does not exist, i.e. is exactly neutralized, by the fact that
applying any correction, either + or −, bearing a constant proportion to the
actual variations of the barometer, would have increased the small average
variation of the clock. I mention as a fact, without professing to account
for it, that Bloxam found the barometric error of his clock less with an arc
of 90 than with a considerably larger one. But I am decidedly in favour of
large arcs, especially for large clocks exposed to greater variations of force
than small ones, and I adopted one at Westminster before I knew that it
agreed with Baily’s calculation, which it has so remarkably verified.
BAROMETRIC COMPENSATION. 50
In order to avoid the barometric error, Mr. Carrington adopted the plan
of a perfectly air-tight clock case, the winder going through a ‘stuffing-box,’
and then he exhausts the air down to some given pressure a few inches below
the usual height of the barometer (see R.A.S. Notices of Nov. 1872). But
this is much too troublesome for common use. Dr. Robinson, of the Armagh
Observatory, long ago adopted the much simpler plan of compensating the
error by attaching a pair of very thin barometers on the right and left sides
of the pendulum rod, above the bob (R.A.S. memoirs vol. 5). This evidently
has the effect of raising a small weight of mercury from near the bottom of
the pendulum to near the top when the density of the air increases, and vice
versˆa. But I shall presently point out an inconvenience of this mode of doing
it, and Dr. Robinson expressly says that the adjustments were troublesome.
The barometric error also varies considerably even between clocks of nominally
the same kind; so much that it is not safe to assume any given amount
beforehand, but it must be ascertained from observation of that particular
clock before the calculations are made for correcting it. In the best kind of
astronomical clocks, with detached, or with gravity escapements, but not
dead ones, we may take the daily loss (+
T) for the present at 0.3 sec. a
day for an inch rise of barometer, or that is the barometric error so far as it
is unconnected by others which attend it.
In a paper on this subject in the R.A.S. Monthly Notices of 1873 I remarked
that two barometers are unnecessary, because a slight want of symmetry
in (not across) the plane of vibration cannot affect the pendulum.
Moreover, with a bob of the length required for an iron jar mercurial pendulum
there is not room to put the barometer tube entirely above the jar.
What we have to do is to find the position and the diameter 2x of the
barometer which fixed at some given height will thus compensate a 39 inch
pendulum of given weight, say 40 lbs. It is tempting at first sight to make
the great mercury jar serve as a basin for the barometer; but there are various
practical objections to it, and it is much better to use a syphon tube
bent over the side of the jar, in which therefore a ‘rise of barometer’ of r in.
will be only an absolute rise r of 1
2 in. in the longer leg, with a fall of 1
2 in.
in the shorter. Let the mercury in the long leg reach to d below the top of
the pendulum, and in the short one to b above the centre of oscillation: ,
the specific gravity of mercury, is such that a cubic inch of mercury is very
nearly half a pound. Then, by the same mode of calculation as at p. 34, the
little weight transferred from b to d being x2r,
−
T =
43200x2r
M
ld − d2 + b2 − lb
l2 sec.,
or putting 1
4 for r and 40 for M we must have (nearly)
850x2 ld − d2 + b2 − lb
l2 = .3.
GREENWICH BAROMETRIC COMPENSATION. 51
Now d must be substantially > b for this to keep its sign, and also to keep
tolerably constant for different degrees of rise. For simplicity let b = 0,
and ... d = 9 in.: this gives 2x or the diameter of the tube .03 in. If the
barometric error is 3 times as much, 2x must be p3 times as much or about
.05; in either case rather a thermometer tube than a barometer one. The
tube, after being bent over and down either the right or left side of the jar,
had better be brought up to the rod again, and the two branches joined
there by heat for strength, and tied to the rod by waxed thread rather than
any metal fastening. If the compensation is found to be overdone the tube
has only to be untied and raised, and if insufficient it may be lowered, if
room enough has been left for it in the bend.
As the barometric error never lasts long in one direction it will very seldom
be thought necessary to apply the compensation to large clocks; and
we have seen that it can be otherwise materially reduced, if not absolutely
corrected, as it is in the Westminster pendulum, by making it swing a large
arc. If it were necessary to apply the barometric compensation to a long
pendulum the best way would be to put an annular basin for the mercury
on the top of the bob, round the compensation tubes, and have a straight
barometer dipping into it. It may easily be calculated that the same barometric
error of .3 sec. a day with a 11
4 sec. pendulum of 200 lbs., and also
with a 11
2 sec. pendulum of 300 lbs. would be corrected by a barometer
tube of about a sixth of an inch diameter. The reason why the same tube is
enough for the heavier pendulum is that the rise of the mercury is in a more
effective place, i.e. near the middle of the pendulum. A 13 ft. pendulum of
700 lbs. with the lower surface of the mercury 6 in. above c.o. requires a tube
of .3 diameter for the barometric error of .3 sec: another odd coincidence of
figures. If the barometric error in any particular clock is found to be 2 or
3 times as much as this, 2x or the diameter of the tube must be p2 or p3
as much as the above figures, and it must vary in the same way with the
pweight of the pendulum. We shall have to consider this further when we
come to escapements.
The normal sidereal clock at Greenwich has a barometric compensation
of a more complicated kind. An independent fixed barometer raises and
lowers a magnet which attracts the pendulum more or less according to
its position. I must say that seems to me a roundabout way of doing the
business, and I should have been inclined first to try a large arc of 2 450
like that of the Westminster clock, and if that is not sufficient, then the
simple barometric tube compensation, with the bottom of the tube near the
bottom of the bob.
ANCHOR PALLETS. 52
RECOIL ANCHOR PALLETS.
The next important invention which followed that of pendulums, and that
very soon, was a pair of anchor-like pallets moving in the plane of the scapewheel,
instead of the ‘vertical escapement’ with pallets set across a crown
wheel, which pallets being very short required a long swing of the pendulum
to let the wheel escape. It is not indeed absolutely necessary that crown
wheel pallets should be very short, and they would go with less friction if
they were long and the teeth of the wheel few; but the recoil would be more
violent, and they would require more careful adjustment, and as a matter of
fact they always were short. Anchor pallets in the form in which they were
first invented either by Dr. Hooke, whom I have already mentioned as one
of the claimants of the pendulum, or by Clements, a London clockmaker of
his time, had a recoil, no less than the crown wheel pallets, but they could
be made to escape at as small an arc as you please. Fig. 13 is a drawing
of the recoil escapement, as it is always called, which is still used in all the
common clocks in the world, though it has long been abandoned in all that
make any pretension to great accuracy.
In this figure the tooth a has just escaped from the left pallet A, and
b has dropped on to pallet B; the pendulum is therefore moving to the
left, and it will not stop immediately but will go on a little farther and so
make the wheel recoil a little, as you may see clearly enough in any oldfashioned
house clock with a seconds hand: as it returns, the wheel urges
the pendulum again to the right and so gives the impulse which is necessary
to maintain its motion against the resistance of the air and the friction of the
escapement itself; and then tooth b escapes, and the tooth below a falls on
A and the same action takes place there. You observe that I have drawn the
acting faces convex. For some theoretical reasons they ought to be concave;
but, as very often happens in clockwork, the one practical reason of friction
preponderates the other way. Even if they are made flat, the teeth always
wear holes in them, though the teeth are of brass and the pallets of steel,
made as hard as possible, and it is evident that the friction at the recoil is
much greater if the pallets are concave than convex. Moreover it is always
found that as the pendulum arc decreases from any decrease of force in the
clock, it loses and vice versˆa; and concave pallets would not diminish this
error, but increase it. Some considerable persons stuck to this escapement
for some time after the dead escapement was invented, being apparently
misled by the fact that variations of force produce less variation of the arc
in this than in the dead escapement, because the friction of the recoil checks
the arc; but it does not follow that the variations of time are less: in fact it
has been proved both by experience and calculation that they are not.
I may as well mention here that a ‘steady rate’ means, not necessarily
that the clock is going right, but that it is going uniformly, or regularly
gaining or losing exactly the same number of seconds a day or a week. The
ANCHOR PALLETS. 53
Fig. 13: Anchor Pallets
RECOIL ESCAPEMENTS. 54
rate is always written + when the clock gains, and − when it loses; which you
must remember is just the opposite of the signs appended to the expressions
for the various errors of the time in the mathematical formulae; for when t
the time of vibration of the pendulum increases, dt is +, and the clock loses
and the rate is too little or −.
Harrison’s recoil escapement had scarcely any friction. It was invented
by him when he was a working carpenter in Lincolnshire. Any one
who wants to see a description of it will find one in the 7th edition of the
Encyclopædia Britannica; but I did not think it worth while to repeat it in
the 8th; nor here, as it is a mere obsolete curiosity, and nobody else ever
made it to answer, even before better things were invented. If such a thing
were worth doing, it might be done much more simply by a three-legged
scapewheel, such as I shall describe as one form of the dead escapement
(at p. 70), but without the horizontal or dead pallets there, and with the
impulse pallets set deeper and not in the same line, though parallel to the
pendulum. The impulse would be given with nearly as little friction as it
is there, and the recoil would also have very little; and if the force on the
scapewheel were made uniform, as it may be by a contrivance which I shall
describe for turret clocks, there is no reason why such an escapement should
not go very well, though the dead one would go better.
Clock out of beat.—Most people seem to know that the beats of a
clock ought to sound equal in time, but most people have a very erroneous
notion that this depends on the clock being set on a perfectly level surface,
or standing vertically; whereas that has nothing at all to do with it, unless
the crutch has been so adjusted that the pallets do escape at equal angles
when the clock case stands upright. No doubt they ought to be so adjusted,
because a clock looks better standing straight than crooked. In the best
clocks the beat is made adjustable by beat-screws at the bottom of the
crutch or fork. In common ones it is simply bent by hand till the beats
sound equal. Mr. Dent made the fork pins in turret-clock escapements to
open with a spring, to prevent the teeth being damaged in case they should
be caught by the escaping corner of the pallets when the clock is put back, or
the pendulum set going without the clock being wound up. Each ‘prong’ of
the fork must have a separate spring, both set against a stop between them.
The crutch and everything attached to the pallets ought to be kept as light
as possible, because they are in fact a pendulum, moving on pivots instead
of a spring, and therefore with much more friction than the real pendulum.
But a long crutch is better than a short one, because less angular motion
and force is lost in the looseness or ‘shake,’ which, as I explained at p. 32,
must be left between the fork and the pendulum. The proper way to try
whether a clock is in beat is to let the pendulum swing only just far enough
for the escape, and then you will easily hear if the beats are unequal.
When a clock with any kind of anchor escapement (which all clocks may
be assumed to have, unless the contrary is known) sounds ‘out of beat,’ it
THEORY OF THE COMMON DEAD ESCAPEMENT. 55
wants either one side lifting or the crutch bending—which you please. If the
right-hand beat of the pendulum (i.e. the blow on the left-hand pallet) comes
too quick, the right pallet escapes too soon or does not go deep enough.
Therefore the right side of the clock wants lifting; for that is equivalent to
moving the pendulum and pallets to the left. Or it wants the fork or bottom
of the crutch bending to the right, which, remember, is making a bend in
the crutch to the left, for that carries the pallets to the left. Or if there is a
beat screw in the fork, it wants turning to the right or ‘setting up,’ so as to
move the crutch to the left. And vice versˆa, if the left beat comes too quick,
the left side of the clock wants raising, or the fork tending to the left, or the
beat screw turning to the left.
I shall notice afterwards, under French clocks, a contrivance which some
of them have to make the beats gradually adjust themselves. Recoil pallets—
and dead ones too—should only just clear the teeth, and when the points
get worn so as to allow more clearance the pallets should be renewed.
DEAD ESCAPEMENTS.
These are also of the anchor kind; but in fig. 14, as in fig. 13, a tooth of
the scapewheel has just escaped from pallet A and another has just fallen
on to pallet B; but the face on which it falls is very different, as the shape
of the teeth also is, but that is only to give room for clearance, and in both
cases it is only the point of the tooth that acts. Here, you see the face of
the pallet is divided into two, and one part is an arc of a circle of radius CB
while the other part is much the same as it was in the recoil pallets. The
consequence evidently is that there is no recoil here, and the tooth lies dead
on the circular face BE (which is therefore called the dead face) however far
the pendulum may swing, until it returns to B, and then the tooth begins
to act on the impulse face and gives the impulse to the pendulum exactly
as in the other escapement. In the same way the dead face DG of the other
pallet is part of a circle with radius CD: the dotted line being the old recoil
shape.
This is the dead escapement, which was invented early in the last century
by Graham, who invented also the mercurial pendulum and the horizontal
watch escapement; and the great advantage of it is that although a slight
increase of force on the scapewheel increases the arc of the pendulum, it does
not sensibly increase the time, if the escapement is properly made. This
was first demonstrated mathematically by Sir G. Airy, in the Cambridge
Philosophical Transactions in 1827 (Vol. III. p. 105), and it may be made
tolerably clear without any mathematics, as follows. If each tooth could
drop exactly on the corner dividing the dead and impulse faces of the pallet,
as at B, it is clear that the impulse on each pallet would begin and end
when the pendulum is at the same distance on each side of zero or the
THEORY OF THE COMMON DEAD ESCAPEMENT. 56
Fig. 14: Dead Escapements
THEORY OF DEAD ESCAPEMENTS. 57
vertical. In other words, as much of the impulse would be given while the
pendulum is falling as while it is rising, and therefore its gravity would be
increased on one side and diminished on the other through equal arcs and
during equal times, and therefore on the whole the accelerating force on the
pendulum, and therefore its time of vibration, not altered. Neither would
the friction on the dead faces, if it were constant throughout, and if it acted
through the same arcs before and after zero, affect the time directly; for
while the pendulum is falling the friction acts contrary to gravity, and with
gravity while it is rising after the escape has taken place. As it is always
resisting the motion of the pendulum it tends to diminish the arc; and on the
other hand, the impulse always tends to increase it; so that here also there is
counteraction to some extent; but as the friction on the pallets does not vary
in any definite proportion to the force of the train, but sometimes one way
and sometimes the other, no useful relation of this kind can be established.
All we can say about the arc is that it increases under an increased force
or a diminished friction, until the remaining friction on the pallets and the
resistance of the air stops the increase.
Mr. Bloxam came to the conclusion, in his elaborate papers on escapements
in vols. 22 and 27 of the Astronomical Society’s Memoirs, that so
far from the dead friction being a thing to be disregarded as constant and
not materially affecting the rate of the clock, as Mr. Airy had assumed, it
probably affects it more than all the other escapement errors together in an
astronomical clock with even a moderately good train, and in a way which
it is impossible to calculate on account of the different circumstances under
which it varies. It is evidently very improbable that the friction can be made
the same while the point of the tooth is (as we may say) ploughing its way
up the pallet during the ascent of the pendulum and sliding down it in the
descent. Having said this I shall not attempt to deal any farther with the
dead friction, but its existence must be borne in mind as capable of either
mitigating or increasing the other errors, as the case may be; and some idea
of the magnitude of its effects may be formed from this, that I remember the
arc of a new church clock of Mr. Vulliamy’s increasing from 2300 to 30300
in the first year, from no other visible cause than the self-polishing of pallets.
And it afterwards fell off again from the pins of the heavy scapewheel
wearing hollows in the pallets where they dropped.
Now let us apply the same reasoning to the recoil escapement, and we
shall find that the result is just the opposite from that in the dead. That part
of the impulse which is within the points where the teeth fall on the pallets
is the same as in the dead escapement, and therefore may be taken not to
affect the time; but in the ascending portion of the recoil the force is acting
with gravity, and so it is in the descending portion. Whenever the force of
gravity is increased the time of a falling or swinging body is diminished; and
therefore on the whole any increase of the force of the clock in the recoil
escapement tends to make the pendulum go faster. But the recoil resists
EFFECTS OF FRICTION IN DEAD ESCAPEMENTS. 58
the pendulum in rising as much as it impels it in falling, and by means of
the friction resists it much more; and as the force through the other portion
of the arc, corresponding to the impulse in the dead escapement, tends to
increase the arc, they may so nearly balance each other that an increase of
clock weight may produce no visible alteration in the arc at the very same
time that it is, as we may say, knocking the pendulum backwards and forwards
more rapidly between the same limits; whereas the dead escapement
just sends it so much faster as to make the whole vibration take very nearly
the same time while it has to pass through a longer space—subject to the
following modifications.
The first of them is this: the teeth cannot safely be made to drop exactly
on the corners of the pallets, but must have a little of the dead face to fall
upon; and therefore the angle or arc of impulse before zero must be rather
less than that after zero, and therefore the tendency to increase the time
preponderates. For the same reason there is necessarily rather more of the
dead friction in the descent of the pendulum, where it acts against gravity,
than in the ascent, and so that also tends to slowness. The greater this
difference is, or the higher up the dead faces the teeth drop, the greater
these causes of error are; and yet it is very seldom that one sees a dead
escapement whose maker appears to have had the least idea of this fact; for
I suppose if they had, they would not make them as if they thought the
right thing was for the tooth to fall as far over the dead face of the pallets
as possible, instead of falling as near the corner as possible.
Another modification is the circular error, which I have already explained,
and which acts in the same direction as the one last mentioned,
increasing the time with the increase of the force and therefore of the arc.
But there is another of the opposite kind; for when the whole arc increases,
that portion of the arc and of the time during which the impulse
or disturbance of the natural time of vibration takes place becomes less in
proportion to the whole, and that diminishes the increase of time which
would otherwise be caused.
And yet further, we have hitherto assumed that nothing varies except
the force of the scapewheel teeth on the pallets, and the friction which is
due thereto. But the friction on the pallets may and constantly does vary
even more than the force of the clock, and generally in just the opposite
direction; for as the clock and pallets get dirty together, the force on the
pallets decreases, which accelerates the time, while the friction increases,
which retards it; and so on the whole it is by no means certain which result
will preponderate in the natural state of the clock, or by how much; and the
only certain way to get a steady rate out of a dead escapement clock is to
take as much care as possible to keep the force and the friction constant;
which is only to be done, and can be done in small clocks with light wheels,
by very accurate workmanship, highly finished and hard acting surfaces,
and keeping them clean and just sufficiently oiled, and above all a good
MATHEMATICAL THEORY OF DEAD ESCAPEMENTS. 59
pendulum, properly fixed. It is necessary for this also that the two pivots
of the great wheel should be as nearly equal as possible, even at the cost
of making the back one larger than it otherwise need be. I have frequently
observed the arc to be sensibly greater at that end of the week at which
the string is at the back end of the barrel, and therefore the weight acting
principally on the thin pivot. When a pivot has to be used for winding, it
must be made much thicker than is required for a mere pivot, and I find
it an improvement to let both the pivots rest on friction wheels as large as
there is room for. They may both be on one arbor, but the front one must
ride loose, as they will not have quite the same velocity under the differentsized
pivots. The holes should be lengthened a little downwards to make
the pivots rest on the friction wheels.
Something more precise than the above general reasoning is of course
necessary for actually measuring the different elements of variation of rate.
This is what Mr. Airy did, or rather laid the foundation for doing, in the
paper I have already referred to; and taking it up at the point where his
calculations ended and his inferences began, I carried it farther in two papers
in the Cambridge Transactions in 1848 and 1852 (vols. 8, 9). His calculations
are rather too long and complicated to insert here, and they may be found
in Pratt’s Mechanics and perhaps some other Cambridge books; so I will
take them up at the same point here.
The first important mathematical result arrived at by Mr. Airy was this:
If  is a disturbing angular force on a pendulum when it is at the angle 
after zero (reckoned + when it tends to increase ), and  the extreme arc,
then the increase of time of one vibration due to the disturbance, which we
will call

 =
1
g2 Z  d
p2 − 2
this integral being taken between the limits through which the disturbing
force acts. He also found a corresponding formula for the increase of arc;
but that is of no use towards ascertaining how much the arc really will be
increased by the continual action of the disturbance, as it is soon limited by
friction and resistance of air in a way which cannot be calculated.
Before we can make any use of this value of 
 we must see what  is in
the particular escapement. In order to do this let us call the angle which
the impulse face of each pallet makes with the dead face ; then, since the
tooth, taken as a prolonged radius of the wheel, ought to be a tangent to
the dead face,  will be also the inclination of the tooth to the impulse face
at the beginning of the impulse; and for this purpose we may assume it to
continue the same throughout, though in fact it increases a little.5 Let p be
5If  is the motion of the wheel on the pallet during each beat, the angle of the tooth
with the pallet face will be  +  +  + 
 at the end of the impulse on the down pallet,
and  +  −  − 
 on the up pallet:  cannot be more than 5 in a 30-toothed wheel, and
 + 
 is never more than 1 1
2
; and as  is generally about 60, the variation is too small
MATHEMATICAL THEORY OF DEAD ESCAPEMENTS. 60
the distance of each pallet from their arbor, and Pg the moving force of the
clock-weight as it arrives at the points of the scapewheel teeth, Ml the mass
and length of the pendulum (which we may treat as its equivalent simple
one for this calculation); then the equation of motion will be
d2
dt2 = −
g
l
+
Ppg tan 
Ml2 ,
since g tends to decrease  after zero where it is +, and , which represents
the other term in the equation, does the contrary. And as this term is
independent of , we have

 =
Pp tan 
Ml2 Z  d
p2 − 2
.
The limits between which the integration is to be taken are from  = −,
where the impulse begins before zero, to + 
, some rather larger angle where
it ends after zero; and the result will be

 =
Pp tan 
Ml2 q2 − 2 −q2 − 
2
Now before going any farther we may see at once from this, that if  could
be made = 
, i.e. if the impulse could be made to begin just as much before
as it ends after zero, 
 would = 0, and we might save ourselves all further
trouble, and pronounce the dead escapement perfect, or capable of being
made perfect, so far as the impulse is concerned. But it seems impossible to
make 
 −  much less than 300 and in fact it is seldom made so little. And
it will not do to say that as 300 only = .00085, that still leaves 
 very small,
and so the clock must go very well; for it must be remembered, first that

 only means the difference of time of a single vibration out of the whole
number T in a day; and T is 86400 for a seconds pendulum; and further, that

 is not after all the error of the clock between one day and another, but
only the difference between the time of a pendulum swinging freely, and one
kept going (or in mathematical language disturbed) by a clock escapement;
and therefore we shall have to go one step farther and find the variation of

 itself before we can know anything about the going of the clock, since 

cannot be made = 0. But before we do that it will be convenient to examine
the value of it as it stands.
Let h be the daily fall of the clock weight Wg. The drop of the tooth
at each beat, or the space through which the moving force Pg acts, ought
to be nearly = the thickness of the pallet = p( + 
) tan ; and this ×T
(the number of beats in the day) ×Pg would = Wgh, but for the loss in the
friction of the train and the slight difference between the actual drop of the
tooth and its theoretical drop, which is the thickness of the pallet. For the
to affect these calculations materially.
MATHEMATICAL THEORY OF DEAD ESCAPEMENTS. 61
present purpose it is of no consequence whetherWis a little more or less, and
therefore we may neglect this difference and consider TPp tan  = Wh
+
 ; and
therefore the excess of time of the clock pendulum over the free pendulum
in the day, or

T =
Wh
Mla2 p2 − 2 −p2 − 
2
 + 

.
This is by no means a pleasant expression to deal with in a general
way; but it is not difficult to draw the necessary conclusions from it, by
assuming some particular values of the different quantities, in accordance
with what they usually have in clocks. Although the error of the clock is
not represented by 
T, but by the variations of it, still if we can make 
T
very small, the variations of it in the same escapement will be smaller still;
although it might happen, and in another kind of escapement does happen,
that the variations are the least when 
T is at a maximum. But there is no
fluctuation of that kind here; and before going any farther we may observe at
once the advantage of a long and heavy pendulum, seeing that Ml is always
fixed in the denominator of the expression for the rate of the clock due to the
escapement. Moreover it is a fact that a long and heavy pendulum requires
very little (if any) more force Wh to drive it than a short and light one; the
reason of which is that the chief impediment to the motion of the pendulum
is the resistance of the air, and the resistance to the surface does not increase
in anything like the same proportion as the weight, if the bob is of a good
shape. Therefore Wh in the numerator need not be materially increased for
a very great increase of Ml in the denominator, which is directly equivalent
to a very great increase in the accuracy of the clock; and you will see that
the same is true in the other escapements.
The next point to consider is the length of the arc of impulse 
 + .
As we have already seen that 
 −  ought to be made as small as possible,
but cannot be made less than about 300, let us take that difference as fixed,
and see whether the whole angle of impulse 
 + ought to be large or small
compared with a. For simplicity of calculation, let us try the effect of making
a, 
, and  in the proportions of 8, 7, 5, and 8, 5, 3, and 8, 4, 2, keeping

 −  constant, you observe. Substituting those values then in the above
formula for 
T, you will find that it comes out in the proportions of 20,
14, and 13 in the three cases respectively. In other words, it is better not
to make 
 nearly = a, or the impulse to last nearly to the end of the arc;
and it is satisfactory to know that this agrees with the conclusion which old
Mr. Dent came to from observation, though it is contrary to the practice
of most other clockmakers, who seem to prefer that sleepy-looking kind of
escapement in which the second-hand moves very slowly and the ‘excursion’
of the pendulum beyond the impulse is very little. He altered the transit
clock at Greenwich from a long to a short impulse accordingly with good
effect.
MATHEMATICAL THEORY OF DEAD ESCAPEMENTS. 62
Taking it then as proved that 
 the angle of impulse after zero ought not
to be nearly so large as , we shall be able to simplify the above value of 
T
by assuming that 

 is so small that all higher powers of it than the square
may be omitted. And then (2 − 2) 1
2 − (2 − 
2) 1
2 may be expanded by
the binomial theorem, and only two terms of each expansion need be taken,
and the equation will assume the simple form

T =
Wh(
 − )
2Ml3 .
Mr. Airy concluded that the smaller 
 +  is, the better, because it appeared
in the numerator of his expression for 
T. But he left the expression
for the force unreduced into the terms involving the shape of the pallets, in
which we saw that 
+ was lying hid, ready to come out in the denominator
of the fraction; and therefore, as it is also in the numerator, it disappears
altogether, on the assumption that 
 is moderately small, as it ought to be;
and beyond that the above expression for 
T gives no information as to the
proper size of 
 or the length of the impulse.
But then another consideration comes in. If you make the impulse very
short, the pallet will slip away before the tooth has time to catch it; and
the shorter the angle of impulse is the more of it is lost by the inertia of
the wheel (which therefore ought to be light): in fact this is another reason,
besides the necessity for leaving a little of the dead face for the tooth to fall
upon, why the angle  at which the impulse really begins cannot help being
sensibly less than the angle 
 at which it ends. Therefore also there is no
use in making the pallet corners sharp, for the tooth can follow the pallet
immediately, and it had better slide off slightly rounded corner than drop
on to the impulse face with a kind of jump off a sharp corner. On the whole
the result appears to be that the escape had better take place at something
near 1, and consequently the impulse should not begin later than 300 before
zero, assuming  the extreme arc to be 2, which will make

 − 
2
=
1
720, and therefore 
T =
Wh
720Ml3
The value of Wh
Ml varies very much according to the quality of the clock: in
the best astronomical clocks it may be taken to be as little as 1
30 to make
the pendulum swing 2. As the force which arrives at the pallets is now
represented by W, we must treat it as variable together with the arc; and
so, differentiating 
T, we shall have
d
T =
1 sec.
216003 dW
W −
3d
 = 1s2dW
W −
3d
 
If there was any definite relation between the ratio of increase of the force
and the arc, this would give a very easy calculation for the variation of
HALF-DEAD ESCAPEMENTS. 63
rate so far as the impulse is concerned. But there is not, as it depends
on the state of the different parts of the clock. Sometimes it may happen
that the proportionate decrease of the arc from increased friction is just
1
3 that of the force which arrives at the escapement, and then there will
be no variation in the rate. Sometimes you may increase the clock-weight
considerably without making much impression on the arc, if the pallets are
dirty; and generally in an artificial experiment of that sort, except while the
arc is smaller than 2, d
 is likely to be less than dW
3W and then the clock
will lose, even independently of the circular error which tends the same way
and which we know would be 10800  d if it were not in great measure
corrected by the pendulum spring, though it is very difficult to say how
much. On the other hand if you clean and oil the pallets alone the arc is
sure to increase, and yet the clock will generally gain, because the increase
is chiefly due to the diminution of the dead friction, which (as I explained
before) would diminish the time, independently of the term −3d
 belonging
to the effect of the impulse, which retards less on a long arc than a short
one.
Half-dead escapement.—In order to counteract the disposition of
dead escapement clocks to gain as the arc decreases under ordinary circumstances
(which, you remember, is the opposite of what happens in the
recoil escapement), Berthoud a celebrated French clockmaker invented the
plan of making the dead faces not quite dead, but with a slight recoil, so
as to get a sort of compromise between the effects of the two escapements.
Large clocks, which are subject to great variation of train force, are distinctly
better when so made than with quite dead pallets. Moreover the
variations of the arc are rather checked by the half-dead pallets. The largest
variations of arc I ever saw in a good clock, were in one of Mr. Vulliamy’s,
who used to take particular pains to make his pin-wheel pallets quite dead
by cutting them out of a turned cylinder of radius equal to their distance
from the arbor. A very slight recoil, such as you can hardly see in the motion
of the wheel, is enough. But the best authorities are of opinion that a
purely dead escapement is better in astronomical clocks, where the friction
and variations of force are much less than in turret clocks.
Loseby’s isochronal spring.—Another plan for isochronising the long
and short arcs was invented by Mr. Loseby a chronometer maker in London,
and exhibited in 1851. A large circular loop of very thin steel wire is on a
stud from the back of the clock case, say on the right side of the pendulum,
so as to embrace the rod nearly half-way down, just catching it as it swings
to the left side of the loop. The farther it swings of course the more it has to
stretch the loop, and the resistance increases in a high ratio with the degree
of elongation; and it seems that this can be adjusted so as to isochronise the
pendulum in a dead escapement under great variations of the force of the
train. So at least the Astronomer Royal reported after trying some experiments
on it. But it at once occurred to me that such experiments proved
LONG AND SHORT ARCS. 64
nothing as to the effect of such a spring on an astronomical clock in its natural
state, in which the variations of the pallet friction are generally greater
than those of the train and produce the opposite effect, as is evident from
the second term of the equation at page 62, and then the spring would make
it worse. As chairman of the Horological Jury of the Exhibition, I wrote
to this effect to Mr. Airy, who then made a different class of experiments,
this time by artificial variations of the pallet friction, and he issued a fresh
report in 1853, that ‘Mr. Loseby’s invention was not perfectly successful.’
Large and small arcs.—There is one more point in the theory of
dead escapements which requires particular attention. You observe that 3
appears in the denominator of the expression for the variation of impulse
rate, and so it would in that belonging to the dead friction. That is, the
three resisters of disturbance of the rate are the weight of the pendulum,
its length, and the cube of its arc. But the arc in any given clock in its
normal state of friction varies in some irregular way with the force of the
train, i.e. the clock-weight and its fall; and an increase of the weight in any
given ratio may or may not increase the arc in the cube root of that ratio:
but so long as the arc is small, its increase will most likely be a great deal
more than that; and if so there is a clear advantage in increasing the weight;
subject always to this memento, that the circular error also increases with
the arc. I have a note of having once cleaned a regulator and oiled it with
sperm oil, and the arc increased from 1 450 to 2 150, and yet I found no
material alteration in the rate. I am satisfied that the very small arcs which
used to be the fashion are a mistake, and that from 2 to 2 400 is much
better. A writer in H. J. xix. 125 said that, in consequence of this advice,
he had increased the weight and arc of an Austrian clock, which had almost
reduced its errors from minutes to seconds.
Importance of firm fixing.—Whatever increases the arc without increasing
the weight is obviously a great advantage; and the principal things
which do that are diminution of friction and inertia of the train, and steadiness
of suspension of the pendulum. I cannot give a better proof of how
much the arc depends on that, than the effect of hanging the Westminster
pendulum on its proper cock, which is a large cast iron bracket built into
the wall; the arc increased full 450 over what it had been in the factory,
where it was hung on what seemed a perfectly firm support, a strong timber
frame built up from the ground. Even smaller pendulums generally increase
their arc from about 2 in the factory to 2 300 as soon as they are properly
fixed to a good wall on stone corbels or iron beams. This shows the extreme
badness of the common way of fixing large clocks on a stool or timber frame
set upon a wooden floor in a tower, and common clocks by a single nail
through a thin back of the case (see p. 31).
The friction is of course only to be diminished by proper shaping of all
the acting surfaces and making them of the best metals for working together.
Brass wheels and steel pinions, and also brass teeth and steel pallets seem to
PALLETS AND SCAPE-WHEELS. 65
be the best in small clocks, although there are other cases where steel and
steel act better together, as in the horizontal watch escapement. In large
clocks cast iron wheels and pinions suit each other better and wear less
than anything else, as has long been known by the great machine makers,
though scarcely any clock-makers choose to believe it, and of course refuse
to try, being what they call ‘practical men,’ who understand by the word
experience the constant use of one thing or one way of doing it and absolute
ignorance of any other. Mr. Vulliamy used to think steel scapewheel teeth
or pins better than brass ones, and they have been occasionally used by
other people, but I think are now generally disused. At the same time it is
certain that steel pins do best in my escapements which will be described
presently In the best clocks the pallets have jewels, generally sapphires, let
in for the teeth to act upon, and it is quite ascertained that brass teeth suit
them best.
When the pallets are steel it is scarcely necessary to say that they ought
to be as hard and as smooth as possible; especially the former, for if they are
not smooth at first the teeth will make them so in time, but soft ones will
never get hard. They are hardened like files, by being heated red hot and
cooled suddenly, and not tempered at all. The sharp hollow corners, which
are considered by ignorant people a sign of fine work, are apt to crack in
hardening, and as such a corner is always a weak place besides, they ought
not to be so cut out; and the same remark applies to every hollow corner in
every part of a machine, unless something else has to fit into it. Probably it
is best to heat the pallets in lead melted red hot, and cool them in oil, which
is now adopted for some larger steel things, as I have seen pallets twisted
in the ordinary mode of hardening. The same may be said of pivots and
pinions, except that they are tempered and not left quite hard.
Aluminium bronze.—The alloy of copper and aluminium, to which
this name is given, seems to me very superior to either brass or gunmetal
for many horological purposes. It is stronger, much more elastic, smoother,
far less liable to tarnish, i.e. to decay; and for small articles, such as the
scapewheels of clocks, and all the wheels of chronometers and watches, the
excess of the cost over brass would be insignificant. It solders well with either
common ‘silver solder,’ or another with less silver in it. Mr. J. F. Stanistreet,
of Liverpool, an amateur clockmaker, told me he had used it; and it is used
for cheap watch cases.
Weight of scapewheel.—It is important to keep the upper wheels in
the train, and particularly the scapewheel, as light as possible. It is certain
that every blow you hear in the working of a machine indicates some loss
of force, and wearing out of surfaces, and that the machine would be better
without it—unless it is a hammer; and the heavier the blow is, of course
the worse it is. In clock escapements a sudden stop and a blow of some
amount is inevitable; but there is no reason why it should be increased by
making the scapewheel three or four times the necessary size and weight,
LENGTH OF PALLETS. 66
and the drop of the teeth more than is necessary to clear the pallets. I have
already mentioned also that the greater the inertia of the scapewheel, the
longer it is in effectively catching the pallet, although you cannot see the
interval. I have seen church clocks, not merely old ones like that of St. Paul’s
Cathedral, but new ones, with scapewheels a foot in diameter, and weighing
several pounds, and you may sometimes hear the thump of every beat in
the churchyard. Bloxam calculated that a pendulum of 15 lbs. does not
require half as much force as a marine chronometer, if a great deal of it
were not wasted in having to start a heavy train from rest at every beat;
otherwise its weight would be of little consequence. Mr. E. D. Johnson has
made regulators with very light and small trains, in fact, little more than
chronometer trains, and he says they answer perfectly. I may observe here
that the rims of wheels (in which most of the inertia lies), and indeed the
whole wheel, may be made materially lighter with 5 spokes than with 4,
because the arcs are shorter. Sometimes, in the most expensive clocks, they
are made with 6; but 5 spokes leave very little more than 1
6 of the rim open,
on account of their own thickness, as you will see in p. 69; and they seem
to me quite close enough for clock-wheels; and of course every unnecessary
spoke adds unnecessary work and expense; that number is used throughout
the Westminster clock and many others now. Here too, as in the pallets, and
indeed in every possible place, the modern workman who is taught to think
‘high finish’ the perfection of work, or in other words to display as much
finger work and as little head work as possible, files or ‘crosses out’ the
corners as sharp as possible instead of leaving them rounded a little, which
would make the wheel stronger with no appreciable increase of weight. I
believe it would be a very good rule that a sharp hollow corner ought never
to be allowed anywhere, unless something has to fit into it, as it always
makes a weak place, in which, if anywhere, things crack in casting, fly in
hardening, or break in working, and moreover is so easy to do, that as a
proof of good workmanship it is contemptible, even if it were not really bad
besides.
Length of pallets.—A French clock-maker in the Exhibition of 1851
had an apparatus for illustrating the superiority of moderately short pallets
over long ones. It does not require much apparatus to prove that; for assuming
the scapewheel to be of any given size, it is evident that the farther
the pallets are from their arbor the longer is the run of the teeth upon them,
and the more friction there is affecting the pendulum. The usual proportion
seems to be to make the distance of the pallets from their centre =
the wheel’s diameter (generally 17
8 inches in regulators), and embracing 10
teeth, i.e. from one dead face to the other. This seems to me rather an
unnecessary length, and I should prefer 91
2 , or half a tooth under instead of
over one third of the number in the wheel.
Various rules and calculations have been given in books for the length
and position of the pallets, according to the conditions which their authors
CONSTRUCTION OF DEAD PALLETS. 67
thought most important. I think the most important of them all is to keep
the dead friction a minimum, consistently with a sufficient length of pallets
to prevent much force being wasted in clearance. The way to do this is
to make the dead faces always perpendicular to the pressure of the teeth,
i.e. to the circumference of the wheel. Assuming 10 tooth spaces, or 1
3 of
the wheel, to be embraced from one under face B to the other A (fig. 14)
as usual, i.e. 91
2 spaces from one dead face B to the other D, the pallet
centre C will be the intersection of two tangents to the circumference at B
and D. That makes the distance of centres d = 1.84r (r the radius of the
wheel), and p or CB and CD = 1.54r which is quite enough. As one dead
face is above and the other below, the lengths of the pallets as a whole are
unequal, the appearance of which the clock-makers dislike, though it is of
no consequence. If you determine to have them equal, and make d = 2r,
as is usual, and BC and AC = 1.73r, the pressure will be perpendicular to
the dead face B, but not quite so to D: if you make d = 1.72r, and FC and
DC each = 1.4r, the dead face D will be right and the other wrong; if d is
anything between those sizes, one pallet will be rather better and the other
rather worse, supposing the lengths to be equal.
The unimportance of equality of length of impulse on the two pallets
is evident from the fact that in some kinds of escapements, as we shall see
afterwards, there is only one impulse pallet, and there is no loss of force
thereby. The only way in which force is lost, apart from friction, is in the
drop of the teeth from the end of one pallet to the face of the other, or in
other words, the clearance, which is necessary to prevent the point of the
returning pallet from catching the top of the tooth which last escaped from
it. Consequently the thickness of the pallets has to be rather less than half a
tooth space. The slopes or impulse faces may be adjusted thus: Fix an index
CP to the pallets, and put them and the wheel on centres without shake at
the assumed distance on a board. First file down B till there is only just
enough dead face to receive the tooth when the escape takes place at A, and
leave the corner F at first obviously too sharp, i.e. rather too long, and A
too blunt or the corner G nearly square. Mark where the index points at
the moment of escape, and mark 2 from that which = .035 CP = 1
4 in. if
CP = 7 in. File away F till the next escape takes place at that 2 and then
reduce G till that pallet has only just enough dead face for the tooth to fall
on. This will make each escape take place at 1 from zero of the pendulum.
The teeth of dead scape wheels are often made of a most absurd shape,
the weakest and heaviest possible, viz. with the sides radial, and therefore
thinnest at the root, and with a heavy shoulder, and also often too long.
The best form is a simple taper. What are called club teeth, with a lump at
the end, were supposed to hold the oil better, which is apt to run away from
the points, but they seem to be generally abandoned. In the best clocks the
pallets are jewelled with sapphires, which require scarcely any oil.
OTHER DEAD ESCAPEMENTS. 68
Pin-wheel escapement.—There is a very convenient form of the dead
escapement for large clocks, which goes by this name. It is said to have been
invented by Lepaute in 1753, but also by Whitehurst of Derby. The teeth
are pins of brass wire set in the face of the wheel, and the upper half of each
cylinder cut off, as it could not act and would only waste room in the drop.
But I introduced the plan of cutting off a small slice of the under or acting
side also, as shown in fig. 15 (next page), because, unless that is done, you
must either have the wheel very large, or the pins very thin or long pallets, or
a large angle of impulse, which are all objectionable. The advantages of this
escapement are, that it does not require so much accuracy of construction as
the other, and less is lost in the drop, and therefore you can get many more
pins than teeth to act in a wheel of given size, which often saves one wheel
in the clock. If a pin gets damaged it is easily replaced, whereas if a tooth
is damaged the wheel is ruined. The blow on both pallets being downwards,
the action is more steady than it sometimes is in the other. The pallets are
best made with their cross section rather convex, and also ‘half dead.’ The
scapewheel of the large clock at King’s Cross, by which the Great Exhibition
time was kept, and of many others made from my design, is only 4 inches
wide, with 40 pins in it. The lower pallet should be the inner one, and the
higher one outside the wheel, because this makes the action of the teeth on
both of them more direct. If the pallets are on opposite sides of the wheel
with two sets of pins, they may be alike. The pins must then be at alternate
places.
Pin pallets.—Some of the best small French clocks now have an escapement
which at first sight may be confounded with the pin-wheel escapement,
but is really quite different. The scape-wheel is like a common dead one,
and it is set (merely for show) in front of the dial; but the pallets are made
of semi-cylindrical ruby pins; the effect of which is that the half-dead part of
the action is not on the points of the teeth but on their faces. The impulse
is the same as on common jewelled pallets, only with the faces round instead
of flat. I have seen an old clock with similar pin pallets, made of a thick
bristle held at both ends, for the sake of silence, and the fork also.
Single-pin escapement.—This very simple and neat-looking escapement
has been several times re-invented. But I believe the only person who
ever made it really succeed, from better attention to the proportions, was
the late Mr. C. Macdowall, a very ingenious clockmaker, who died in 1872
at the age of eighty-two. There is an interesting memoir of him in the Horological
Journal of Sept. 1873. But, like many other uneducated inventors,
he was very difficult to convince that an independent inventor is not allowed
by the world the credit of a first inventor unless he is so. He also invented
that most useful instrument—the spiral drill; or rather I should say, he
invented the practical mode of making it by twisting a piece of pinion wire,
SINGLE-PIN ESCAPEMENT. 69
Fig. 15: Pin-wheel Escapement
THREE-LEGGED DEAD ESCAPEMENT. 70
Fig. 16: Single-pin Escapement
for the thing itself turned up in wood as an
old Indian invention in the 1851 Exhibition.
Another of his independent inventions was the
‘helix lever wheels,’ as he called them, but
they also appeared in some German clocks in
the same Exhibition; besides some other things
which had been published in well known English
books. He also persuaded himself somehow
or other, that he invented the three-legged escapement
which I shall next describe; but no
one ever saw or heard of it until it had been
made from my design, though he had shown
me all his inventions, and I had helped him to
get both a patent and an Exhibition medal for
his single pin escapement, and old Mr. Dent,
under my advice, had bought the patent for
a considerable sum, and gave him an order for
500 watches on that plan if he could make or get
them made, which he could not; and Mr. Dent
accordingly got some made in Switzerland. I
wore one of them long enough to see that it answered
very well, but the expense of the two
extra wheels which it requires overbalanced the
advantages, though I hear they have been also
made in Paris from Macdowall’s instructions,
the patent not having been taken there, and being
perhaps difficult to maintain here if it had
been disputed; for the thing had certainly been
published, as we found afterwards in a French
book. Its action is evident enough from this picture
(fig. 16). It has the advantage of giving a
great part, you may practically say half, of the
impulse directly across the line of centres (of
the wheel and pallet arbor) and therefore with
very little friction. The pin is made of a ruby,
and should be set very near the arbor. The
older ones were put too far off. Macdowall made
them with a ‘neck-bearing,’ i.e. the pivot was
behind the wheel, or the arbor came through
the frame, and had the wheel pinned or squared
onto it. The pallet piece itself forms the crutch
for the pendulum, the scape-disc being set behind
the clock frame. It should have eccentric fork-pins to adjust for beat.
MY THREE-LEGGED DEAD ESCAPEMENT. 71
Three-legged dead escapement.—It occurred to me in 1851 that all
the best or most direct part of the impulse in the single-pin escapement
might be kept, the more oblique part got rid of, and one of the extra wheels
saved, by using three pins or teeth instead of one; and the result was this
escapement (fig. 17) (for clocks only, not watches), in which the upper tooth
Fig. 17: Three-legged Dead Escapement
is shown in the act of giving the impulse. This is a full-sized view of the
escapement which drove the Westminster pendulum of 6 cwt. for half a year,
until it superseded by another modification of it invented for the purpose
of equalising the force of the impulse. That scapewheel was of steel and
weighed only 1
6 of an ounce or 73 grains, and the clock weight required for
it with a common turret clock movement was only 18 lbs. falling 6 feet a
day, and less than a quarter of what a dead escapement had required; and
considering that more force is lost by the inertia of such a train than in small
clocks, we may say that the fraction Wh
Ml was less than a third of its usual
amount for the best astronomical pendulums swinging the same arc. I found
also that it was possible to isochronise the long and short arcs—at least for
such variations as actually occurred, by making the stopping or horizontal
faces half-dead, as I have drawn them. The distance of the scapewheel from
the pallet arbor should be about 24 times the radius of the wheel, to make it
escape at 1, allowing a little for clearance. It requires careful adjustment,
for the greatest depth on the lower pallet is something less than 1
8 of the
radius of the wheel.
It is necessary in this and prudent in all dead escapements, of large clocks
MY THREE-LEGGED DEAD ESCAPEMENT. 72
especially, to have a spring-fork to the crutch; i.e. the fork-pins attached to
the crutch by springs, so that if the scapewheel is not turning from any
accident while the pendulum is moving, and the pallets jam against the
teeth, the fork springs may give way and let the pendulum go on without
breaking a tooth, as it inevitably will unless so relieved. The pin-wheel
escapement is specially liable to this, because the edges of the pins and
pallets are not sharp as in the common toothed wheel escapements.
Fig. 18: Sir E. Beckett’s Three-legged Escapement
The friction might be still more reduced and the adjustment of the pallets
made easier by making the escapement with long stopping teeth, as in
fig. 18. It would also give room for a longer swing of the pendulum, which
cannot safely be made above 2 in the other form, or the stopping faces will
reach the scapewheel arbor. An escapement of this kind clearly reduces the
SIR G. AIRY’S DETACHED ESCAPEMENT. 73
pallet friction to the smallest amount possible in any dead escapement. It
is however not free from the variations of force in the train. Constancy of
force is only to be got by an entirely different class of escapements, or by
the addition of a train remontoire, of which I shall speak hereafter under
Turret Clocks.
Detached escapements.—There have been various contrivances for
clock escapements on the chronometer principle of leaving the pendulum
free or detached from the scape-wheel except at the time of receiving the
Fig. 19: Sir G. Airy’s Detached Escapement
impulse and of unlocking the wheel. There is an old French one described in
Rees’s Cyclopædia, and Sir G. Airy invented another, which is described in
his before-mentioned Cambridge paper, and has been lately adopted in the
normal sidereal clock at Greenwich. A few of them had been made before
by old Mr. Dent, with half-second pendulums, for which this escapement
does not answer, as Mr. Brock, of George Street, Portman Square, has also
told me. The Greenwich clock however with a seconds pendulum of about
30 lbs., appears to answer remarkably well, and therefore I copy the original
picture, from which its action will be easily understood. The single
pallet CP is exactly like the right hand or down pallet of a dead escapement.
ABD is a detent attached to a fixed block at A by a slight spring,
B being the catch which holds the scapewheel teeth or pins, for it does not
matter which they are. (BD is the flat view of it, omitting the stop at
B.) At D, on the underside of ABD, there is a very slight ‘passing spring’
projecting a little backwards, as shown in the separate sketch; so that when
SIR E. BECKETT’S DETACHED ESCAPEMENT. 74
Fig. 20: Sir E.
Beckett’s Detached
Escapement
the pin at D on the pallet goes to the left it pushes
the passing spring down, and so passes it; but when
it comes to the right it lifts up the detent, because
the passing spring being underneath cannot yield upwards.
That unlocks the tooth at B, and lets another
tooth at P fall upon that pallet, and give the impulse
down its oblique face. The advantages which
Sir G. Airy contemplated were, the abolition of the
dead friction, and the power of making the impulse
begin as much before zero as it ends after zero, the
value of which we saw at p. 60.
But I cannot help thinking the following a better
plan because it gives the impulse without any sensible
friction as in the three-legged escapement just
described, and involves no passing spring, which is always
a delicate arrangement. I had this clock made
and set going in November 1865, and it went till August
1873, nearly 8 years, without being touched,
even with oil, as I wished to see how long it would
go. The arc decreased a little, and it had a slightly
increasing gaining rate in the last few years; but
I never had any clock go so well for anything like
that time, though my gravity escapement clock, to
be mentioned presently, has gone as well for shorter
periods. The train is not a very fine one: with a
fine train, or a coarse one with a remontoire for a
turret clock, I have no doubt this escapement would
go at least as well as any other. But since 1873 it
has not equalled my gravity escapement clocks, and
the gravity escapement is both cheaper and safer for
large clocks than any train remontoire; which may
therefore be considered obsolete.
This figure shows the construction clearly
enough, except as to size. The locking teeth of the
scapewheel reach about .6 in. from the centre, and
the impulse pins .25 in. Their centre is 7 in. below
the top of the pendulum and crutch, and the
impulse begins about 1 before zero, and ends 1 after.
For the scapewheel turns 36 before and 36
after zero; and therefore, if r is the distance of the
pins from the centre, and p the length of the crutch,
r sin 36 must = p sin 1 for an impulse of 2; which
makes p = 3.7r. Consequently the dimensions just
now given are practically right, allowing a little for
SINGLE-BEAT ESCAPEMENTS. 75
clearance, as you must. The pallet piece P is a separate piece of quite hard
steel screwed on to the aperture in the crutch AP; and this requires care in
adjustment, as the depth is less than 1
5 of the radius of the wheel, being r
vers. sin 36; which however is more than in the three legs, for this turns
72 at each beat, and that only 60, this being a single-beat escapement,
which, it seems necessary to inform some persons, wastes no power if the
train does not move at the return beat of the pendulum.
But for that it would be better to have no crutch, but make the action
take place on the pendulum itself; it is hardly possible however to manage
that behind a clock of regulator size, with the pendulum hung to the wall
as it should be. The wheel lies behind the clock in a long cock embracing it
and the crutch. The detent DEF is on a stud F in the back plate, though
it looks here as if it were on the crutch, as the click CE really is. When the
pendulum goes to the right (in this drawing) the click trips over the top of
the detent, and when it returns to the left the click pushes the detent aside,
and sets a locking tooth free, and then the scapewheel turns and a pin
gives the impulse. The shape of the pins should be observed. It will easily
be seen that the scapewheel should be at the bottom of the clock, and the
great wheel at the top, as in my gravity escapement, and also in the dead
three-legs described at pp. 70 and 72. BB0 are eccentric beat pins, by which
the impulse can be made to begin as much before zero as you like, so as to
make the angle which we called  greater than 
 if necessary.
REMONTOIRE OR GRAVITY ESCAPEMENTS.
These are not to be confounded with the thing called a train remontoire,
which I alluded to just now but shall not explain till we come to turret clocks,
as it belongs only to them. A gravity or remontoire escapement is one in
which the impulse is not given to the pendulum directly by the clock-train
and weight, but by some other small weight lifted up, or a small spring bent
up, always through the same distance, by the clock-train at every beat of the
pendulum. And the great advantage of them is that the impulse is therefore
constant; for the only consequence of a variation in the force of the clock is
that the remontoire weights are lifted either faster or slower, which does not
signify to the pendulum, as the lifting is always done when the pendulum is
out of the way. If this can be managed with certainty, and without exposing
the pendulum to some material variation of friction in the work of unlocking
the escapement, which it must perform, its motion and therefore its time
must be absolutely constant, since there is nothing to disturb it. It does not
look a very difficult problem; and yet it puzzled the clockmakers to solve it
in a satisfactory way for about a century, in consequence of certain small
difficulties which nobody would guess until he had the opportunity of seeing
them in action; and after all it was not done by the clockmakers, but by two
MUDGE’S GRAVITY ESCAPEMENT. 76
lawyers, in different ways.
But first it may be asked, is the gravity escapement problem worth
solving? Is not the dead or the detached escapement proved to be good
enough both by experience and by mathematics? The answer is, that in
science nothing is good enough when it can be improved upon: that both
mathematics and experience prove that only by the most careful and delicate
and therefore expensive work, and only on a small scale and with light
weights, can clocks with ‘impulse escapements’ (i.e. receiving direct impulse
from the train) be made to go as well as the best of them do; and although
it is possible, by the addition of a train remontoire, to make even large
and heavy dead escapement clocks go as well as astronomical ones, yet
that apparatus involves not only some extra expense, but what is far more
difficult to provide, some extra attention and intelligence in the people who
have the care of it. We may however dispose of a great number of the
contrivances for gravity escapements by the remark, that they require not
less, but more delicacy of construction and careful handling afterwards than
the finest dead escapement, even if they ‘perform’ any better, which scarcely
any of them do.
Before we can appreciate the merits and the difficulties of this class of
escapements, it is clearly necessary to understand the theory of them; which
I shall be able to exhibit more briefly than that of the dead escapement, as
some of the ground is common to them both, and especially that useful formula
of Sir G. Airy’s for the variation of the time caused by any escapement,
from which I shall start again. But it will help our conception of the process
if we first take some simple form of gravity escapement as an illustration of
their principle; and it does not signify that that form was neither the first
nor the best, on account of certain mechanical objections which we are not
concerned with yet.
Mudge’s gravity escapement (Fig. 21).—The pallets AC, BC, are
no longer fixed on one arbor, but on two, as close to the bend of the pendulum
spring as possible. The acting faces are so shaped and placed that
whenever the wheel moves from B towards A, a tooth will lift one of them
until it is stopped by the nib a or b at the end of each acting face. Here the
pallet A has just been lifted and is holding the tooth that lifted it; as soon as
the pendulum comes, moving to the right, it will evidently push that pallet
out of the way by means of the fork-pin P, and so free the tooth, and the
wheel will begin to turn, and the opposite tooth will immediately lift the
pallet B till it likewise is stopped by b. The pendulum is all the time going
on rising to the right and carries the right pallet with it as far as it likes to
go; when it begins to fall the pallet falls with it, not only to the place where
it was taken up, but to a lower place, corresponding to that of the left pallet
in the picture; and the fall of the weight of the pallet from the place where it
is taken up by the pendulum to the place where the pendulum leaves it, or
the difference between its rise and fall with the pendulum, constitutes the
MATHEMATICAL THEORY OF GRAVITY ESCAPEMENTS. 77
impulse, and that difference is evidently constant, however far the pendulum
may swing.
If the weight of the pallets were partly or wholly counterbalanced, and
they were fixed by springs instead of acting by their own weight on pivots,
it could no longer be called a gravity escapement, but would have the more
general French name of a remontoire; but the principle would be the same,
except that the force of the springs has a law of its own, and is more variable
than that of gravity.
It is easy to show that the effect of a gravity escapement is to make the
pendulum go faster than a free pendulum, by exactly the same reasoning
as was used to contrast the dead and the recoil escapements; or still more
simply, by considering that the remontoire weights are in effect so much
weight added to the pendulum far above its centre of oscillation and therefore
they accelerate it. But this tells us nothing about the variation of the rate,
in case the arc increases or decreases a little under any change of friction;
and we shall see presently that a very curious result comes out with respect
to this, which it is impossible to arrive at except by calculation.
To do this we must find out again what that quantity called  in Sir
G. Airy’s formula at p. 59, is for this escapement. Let the angle after zero
at which the pendulum begins to lift the pallet be called 
, and the angle
at which it leaves the other pallet which has been giving the impulse ±,
according as that takes place after or before zero: so that, as in the dead
escapement, the angle 
 + is the angle of impulse, if the descending pallet
is left after zero, which we shall see is the best arrangement. Let Pg be
the weight of each pallet, and p the distance of its centre of gravity from
its axis at C, and  the angle which p makes with the pendulum when they
are in contact. Ml2 represents the moment of inertia of the pendulum as
usual; strictly speaking we ought to add to it the moment of inertia of the
pallets while they are in contact with the pendulum; but as that makes no
difference in the nature of the result, and in the best escapements one pallet
or the other is always in contact, we may either consider that as included in
Ml2 or neglect it altogether. Then the equation of motion will be
d2
dt2 = −
g sin 
l −
Ppg sin( + )
Ml2 .
We may put  for sin  and 1 for cos  ( being small),
...
d2
dt
= −
g
l 1 +
Pp
Ml−
Ppg sin 
Ml2 .
This is of the same form as in the dead escapement; only here the constant
term involving simply , which always indicates isochronism, has its
coefficient increased; which shows that the pendulum will regularly go faster
than if its own gravity alone acted upon it, exactly as it is accelerated by
MATHEMATICAL THEORY OF GRAVITY ESCAPEMENTS. 78
Fig. 21: Mudge’s Gravity Escapement
MATHEMATICAL THEORY OF GRAVITY ESCAPEMENTS. 79
those small regulating weights which I described at p. 34. The other term
constitutes the disturbing force , from which we are to learn what will be
the disturbance of the isochronism if the arc varies a little; and this result
will also be of the same form as before, except that the limits of  are different,
as it does not act now through the middle of the arc only, but from −
to  and from 
 to ; and even if  should be identical with 
 the action
is not continuous for the falling pallet pushes the pendulum from − to ,
but the pendulum lifts the pallet from 
 up to . Therefore the result of the
integration will be (putting Wh for the sum of Pp sin  for the whole day):

T = −
Wh(p2 − 
2 +p2 − 2)
Ml2(
 + )
;
which differs from the dead escapement formula only in the signs; but we
shall see that that produces another very important difference. First however
we may remark that if  is − (that is, if the falling pallet is left before zero),
or even if it is smaller than 
 (and it cannot be larger with safety to the
locking), 
T is increased, and so will all its variations be when there are
any. Therefore let us assume that  is as large as it can be, i.e. that one
pallet is taken up just when the other is left, or  = 
; and then the formula
becomes much more simple:

T = −
Wh
Ml2s2

2 − 1
We must differentiate this, as before, to see what the variation of rate will
be; but this time we need not considerW or the force of the impulse variable,
because we know it is not—if the escapement is what it pretends to be. Then
d
T =
Whda2

2 − 2
Ml3q2

2 − 1
From which this remarkable result appears,—that if the weight of the
pallets is so adjusted that the pendulum swings through an arc  = 
p2,
the rate will not vary at all, even when the arc does, except what may be
due to the circular error. Unfortunately they both have the same sign, and
therefore the escapement cannot be made to correct the circular error. But
there happens to be a mechanical difficulty in making 
 as large as  p2 or
.71, which would be 850 if  = 2; and moreover Mr. Bloxam came to the
conclusion, as stated in his papers, that from other causes, especially the
variation of density of the air, it is better to make 
 considerably smaller
than .71. Let us see then what the variation of rate from the escapement
will be for some such value of 
 even as far from the theoretical value as 
4 .
In the Westminster clock I know by trial that Wh
Ml at the escapement is
not more than 1
45 ; taking it at that, and  at 2 400, as it is, and 
 = 
4 , you
FAILURE OF EARLY GRAVITY ESCAPEMENTS. 80
will see, if you take the trouble to make the calculation, that the clock will
only gain about a second a month for a decrease of arc of 50, which is larger
than is likely to happen, besides what is due to the circular error so far as
it is uncorrected by the spring.
In those escapements where the falling pallet is left before zero, the
expression for the variation of rate would be
d
T =
Whd
Ml3(
 − ) ( 2 − 2
2
p2 − 
2
+ 2 − 22
p2 − 2)
in which you observe 
− instead of 
+ is in the denominator, and therefore
the variation is much larger than in the other form of the escapement.
Theoretically indeed this might also be made = 0 by making the three angles
satisfy this condition,
q2 − 
2q2 − 2 = 2
2 .
Thus 
 = 900 and  = 780 would be right for  = 2; but these small
differences would be even more inconvenient mechanically than 
 = 850 in
the other case. That construction therefore is decidedly the worst, notwithstanding
the tempting appearance of the pendulum being left free through
the middle of its arc; a fact which would probably never have been known
with certainty without this kind of investigation, as the errors would have
been sure to be attributed to any but the right cause.
Reid mentions, at page 139 of his old book, a curious fact bearing on this.
He says he cut a hole in the side of the case of a gravity escapement clock,
which increased its arc from 1 220 to 1 370, and at the same time made it
gain 42 sec. a day, and a larger hole increased the arc 120 more, and I suppose
the rate. Therefore the diminished resistance, from the pendulum being able
to drive the air before it through the hole, much more than counteracted
both the circular error and the escapement error, making the clock gain this
great amount instead of losing a little under the increased arc. Moreover
such an enormous variation of rate as this shows that the motion of the air
in the clock-case may affect the rate materially. But I must add that I have
twice tried the experiment myself in a still stronger way, by taking off the
clock case altogether from my own gravity escapement clock, and I could
not observe any increase of arc at all—certainly not of 50, nor any alteration
of rate. The arc was however nearly 1 larger than in Reid’s clock before
he cut the holes; and this is another proof of the unsteadiness of very small
arcs I have since found that a small enclosure for a turret clock pendulum
bob did diminish the arc a little.
Probably no one would foresee, without experiment, that the simple form
of escapement in p. 78 would fail. Several of the most elaborate French turret
clocks in the Exhibition of 1851 were on that plan, and people were very
CUMMING’S AND HARDY’S ESCAPEMENTS. 81
much surprised when I showed them that you could make all those clocks
increase their arc visibly and speedily by increasing the clock-weight, which
is directly contrary to the fundamental principle of a gravity escapement.
This form of the escapement was invented by Mudge, a celebrated watchmaker
whom I shall have to mention again, and it had long been known
here that it would not answer, on account of its liability to trip, or to have
the pallets jerked out so far by the motion of the wheel that the nib fails
to catch the lifting tooth, and so three or four teeth run past and the time
is altogether lost. The only way of avoiding this liability is to use a very
highly finished train with high numbered pinions to keep the force uniform,
and then to make that force only just enough to raise the pallets; but that
is inconsistent with the clock being able to work anything but a small dial,
and if it is not kept very clean and the oil fresh, it will be sure to stop. In
short, the clock becomes too expensive and delicate, and requires too much
attention to be tolerated in common use.
Cumming’s escapement.—But even if all these risks were got over,
there is still another radical defect in all such escapements, which does not
appear to have been ever noticed before I pointed it out with reference to
those clocks in the Exhibition. The force may easily be enough to raise the
pallets a little too high, without jerking them over the tooth altogether, and
then the pressure on the nib is quite enough to keep them there, and so the
pallet is taken up by the pendulum at some angle greater than the proper
one 
; and as it falls down with the pendulum to a constant place, the
impulse lasts longer than it ought, and of course the arc is increased. I gave
the name of approximate tripping to this defect, and any escapement which
is liable to it is evidently worth nothing. It seems capable of happening even
where the impulse or sloped portion of the pallet is put on one arm and the
nib on a separate one which is not lifted at all by the wheel, but only by the
pendulum, as in Cumming’s escapement, which was invented very nearly
a century ago, and for a time was thought to answer well. I suppose this
is in consequence of the force with which the tooth strikes the stop pallet,
sometimes throwing it a little out of its place, unless it is undercut or given a
slight recoil the wrong way; and that is objectionable too, because it resists
the unlocking, and does not always resist with the same force.
Hardy’s escapement.—One of the objections to Cumming’s escapement
was the friction of no less than 8 pivots of the 4 arms which had to
move with the pendulum in the course of each vibration. Hardy avoided this
by setting the arms on springs instead of pivots; but that introduced another
and probably a worse evil, because the stiffness of the springs varies with
the temperature, which of course disturbs the rate of the pendulum. That
escapement was consequently removed from the transit clock at Greenwich
many years ago, and a dead one substituted. There were some very good
rates of three Hardy’s clocks published in Pearson’s Astronomy; but they
are practically extinct.
KATER’S AND OTHER GRAVITY ESCAPEMENTS. 82
Kater’s escapement.—The late Captain Kater, who paid great attention
to the theory of pendulums, invented a gravity escapement, which is
very fully described in the 130th vol. of Philosophical Transactions, on the
principle of making the weight of the descending pallet unlock the scapewheel
by falling upon an anchor like a pair of dead escapement pallets without
the impulse faces. He supposed that as the inertia of the anchor would
stop the pallet for a moment, the pendulum would leave it there, and so be
itself free from the friction of unlocking. But here again it was found that
the force of the wheel was apt to displace the anchor unless its pallets were
undercut, and then the resistance was sometimes too great for the gravity
pallets to overcome, unless they were too heavy for the pendulum; and after
many attempts to make it go, that escapement also was taken out of the
only clock to which I know of it being applied, and came into the hands of
Mr. Bloxam, who showed me it. The failure of it is described in his paper
before mentioned.
Gowland’s escapement, which was in the Exhibition of 1851, was
on the same principle as to the unlocking only. He had not even pallets
for the impulse, but a pair of small weights, which hung on long arms or
spikes projecting horizontally from the locking pallets, except when they
were lifted off by similar arms projecting from the pendulum. This prevented
the friction of any pallet pivots affecting the pendulum. The locking pallets
were of Mudge’s form, and were prevented from being driven too quickly
and tripping, by paddles descending from them into a pot of oil—not a very
elegant contrivance certainly, and requiring a good deal of extra force in
the train. I heard no more of it after the Exhibition, at which I was not
surprised.
M. Gannery, of Paris, had an escapement there also, on the same
principle as to the small weights, which were hung by strings from the pallet
arms and received in cups on the pendulum arms, or vice versˆa. But instead
of the oil pot, he made the scapewheel of the usual size with only 9 teeth
of very slow rise and a nib at the end, which therefore lifted the pallets
slowly and seemed to obviate the tendency to trip, so far as I could judge by
merely looking at it. I should think however that the rigidity of the strings
would be quite enough to affect the pendulum, and the friction in lifting
was considerable. Moreover I doubt whether the stopping of the unlocking
weight in any of this class of gravity escapements is decisive enough to make
the difference of the angles of lift and of drop quite constant; and if it is
not the escapement fails. Of that escapement also I heard no more, and the
French members of the jury evidently thought very little of it. Nevertheless,
the scapewheel with 9 teeth instead of 30, which reduces the pressure of the
stops in that proportion, was a great advance in the right direction though
not absolutely new, because the same thing had been done much better
some years before in
BLOXAM’S ESCAPEMENT. 83
Bloxam’s escapement.—This is so superior to the others that it deserves
a more particular description. This drawing (next page) of the full
size in Mr. Bloxam’s own clock, is copied (with a little alteration for distinctness
of exhibition) from his account of it in the Astronomical Society’s
Memoirs of 1853. The pallets are lifted alternately by the small wheel or
pinion with 9 teeth, and with scarcely any friction, as the action is only
for a short distance across the line of centres. The stopping is done by the
long teeth, and the pressure there is less than the lift in the proportion of
the radii of the small and large wheels. The stops are A and B: E and
F are the fork pins which embrace the pendulum. The pallets above at C
are cranked, that their centres of motion may be identical with that of the
pendulum; which is perhaps an unnecessary refinement, especially as the
pendulum spring has no one centre of motion. The size of the wheel determines
that of the pallets, thus: if the radius of the wheel is 1 in. the length
of each pallet down to the stop must be 2.8 in., to make the angle between
the locking teeth and each pallet 90. Mr. Bloxam made the angle 
, at
which the pendulum leaves one pallet and takes up the other, only 200 in his
clock, and  = 1.400, these being the proportions which he concluded were
the best to counteract the effect of variations of density of the air.
The objections to this escapement are, that it is delicate and expensive
to make, both in itself and in the rest of the clock, and if a pallet got
accidentally lifted the wheel would run with great velocity and probably
break a tooth when the pallet stopped it again—an evil to which most of
the previous escapements are equally liable, and it is a very serious one. It
is also liable to trip unless the train is very fine, so that no more weight need
be used than is absolutely necessary. But unless a gravity escapement will
enable the clock to do with a coarse train, it is of no real use; at any rate it is
quite certain not to come into use; and Mr. Bloxam said that he considered
a fine train essential. That in his own clock was the finest and had almost
the highest numbered pinions (18) I ever saw. And therefore after all, this
can only be regarded as a theoretical or scientific solution of the gravity
escapement problem, but hardly a practical one. I expressed this opinion
of it in early editions of this book and stated that old Mr. Dent and I had
agreed that it would not do for theWestminster clock, even if protected from
variations of force by a remontoire in the train. Somebody however thought
he knew better; for in the 1862 Exhibition there appeared for a short time
a small turret clock with this escapement, and a train remontoire, which
was said in the newspapers to have been made under the direction of the
Astronomer Royal. But it could not be made to behave properly, and after
a few weeks was withdrawn.
At the same time, Mr. Bloxam deserves the credit of having first discovered,
though he did not publish the discovery till long afterwards, that the
practical conclusions of Sir G. Airy’s Cambridge paper were erroneous; and
that the errors of a dead escapement cannot be made either insignificant or
BLOXAM’S ESCAPEMENT. 84
Fig. 22: Bloxam’s Gravity Escapement
SIR E. BECKETT’S GRAVITY ESCAPEMENTS. 85
constant; that the dead friction does not correct itself before and after zero;
that the acceleration of a gravity escapement pendulum over a free pendulum
does not signify the least; but that what does signify is the constancy
of that acceleration; and that the variation is least when the acceleration is
greatest, and may be made practically nothing by a particular arrangement
of the angles of impulse. The Astronomer Royal afterwards in effect assented
to all this, first by admitting in 1852 that my gravity escapement, which will
be described presently, answered perfectly, and by himself communicating to
the Royal Astronomical Society Bloxam’s two papers of 1853 and 1858 sent
from Madeira, the latter of them after he was dead; and then actually going
too far and assuming that Bloxam’s escapement was a practical solution of
the gravity escapement problem.
Sir E. Beckett’s Gravity Escapements.—I have now to describe the
only escapements of this kind which have ever come into real use; and that
both for large and astronomical clocks, especially the former. The earliest
form of them need no longer be described, as it has been superseded by two
others, one with a four-legged scapewheel for small clocks, and the other
with a double three-legged wheel for large ones.
The four-legged escapement is shown in this drawing of a regulator
of this kind seen from behind, half the real size. To avoid confusion, only the
centres of most of the wheels are shown, and you see the train is inverted,
to save height in the frame and clockcase. G is the great wheel arbor, and
the barrel is shaded; C the centre wheel, close to the top of pendulum and
pallet arbors, B second wheel, A seconds-hand wheel, and E scapewheel.
DD are the brackets which come out of a large cast-iron plate or back, from
which also comes the pendulum cock, shown by partly broken lines, to leave
the pallet cock visible. PP are the pillars, CST, CS0T0 the pallets, and their
inside pivots (the arbors being very short) run in a flat piece or cock between
the centre wheel and the clock plate or frame. The scapewheel speaks for
itself as to the long locking teeth; but it has two sets of lifting pins near
the centre, pointing alternately backwards and forwards, one set lifting one
pallet and the others the other, the pallets being in different planes, before
and behind the wheel, with one stop S pointing forwards and the other S0
backwards. This cannot be done otherwise with an even-numbered wheel,
and though it can with a five-legged one, that is an inferior construction in
other respects, and is much more difficult to make rightly, and has not one
advantage when it is made. I say this from experience now, as I did before
from theory. For with the strange propensity of mankind for taking more
trouble to do wrong than it would take to do right, some persons would
persist in making the escapement with five legs. I thought it might possibly
save a little force or weight on the train, but it does not even do that; nor
anything else, except give more trouble to adjust: whereas the four-legged
one is so easy that the very first I had made went at once perfectly without
any alteration.
THE FOUR-LEGGED ESCAPEMENT. 86
Fig. 23: Four-legged Gravity Escapement
PROPER CONSTRUCTION. 87
The great feature of them is the regulation of the velocity and the avoidance
of the banging on the pallets and the risk of tripping, either actual or
approximate, by putting a common fan-fly on the scapewheel arbor. And
this becomes possible or effective only by reason of the large motion of the
wheel and fly at every beat: viz. 45 in this escapement, and 60 in the
three-legs. A fly would be of very little use in Bloxam’s escapement, to
say nothing of its other difficulties. In order to leave room for the fly the
seconds-wheel arbor is cut short and set in a cock within the frame, which
leaves space enough for a fly above 2 in. long in each arm, from E to B.
The pallets require no beat screws, as they are only thin pieces of steel
like square wires, which can easily be bent for adjustment; and even for a
40 lbs. pendulum they have to be made very light; they must be cut out of
steel plate, and the lifting faces hardened. The pins are found to do better
also of steel than of brass, and one set of them should be tapped into the
wheel with left-handed screws, so that the action of lifting may not tend to
loosen them. The wheel is either screwed on the arbor up to a shoulder with
a left-handed screw, so that the action tends to tighten it, or is ‘squared
on’ a hexagon and pinned. The scapewheels are also generally cut out of
thin steel plate; but some have been made of a harder kind of gun-metal or
softer kind of bell-metal, and I am not certain which is best. But in either
case the stops must be as hard as possible, either steel quite hard or jewels.
I think steel hard enough, and I do not believe in leaving any place where
there is friction totally dry, though the oil may be the least possible.
Another great advantage of these escapements is that the length of the
teeth or legs, and the largeness of their motion, make the pressure on the
stops, or the work of unlocking by the pendulum, insensible; and therefore
also they are incapable of holding up the pallets so as to cause ‘approximate
tripping’ by any force that you can apply to the great wheel, provided the
escapement is made properly. But with that same genius for doing things
wrong when it is as easy to do them right, some persons have made the angle
CSE, at the stop which is struck upwards, less than 90, and then have said
the escapement failed because it sometimes tripped, as it was pretty sure to
do. For safety it is as well to put the up stop a little higher, and the down
stop a little lower than their proper theoretical places, which are where both
the angles would be exactly 90.
That determines the theoretical distance of the pallet arbors C from E
the scapewheel centre. If its diameter is 4 in. that distance is 5.2, and that is
the proper distance of the top of the pendulum spring above E. The pallet
arbors must evidently be a little lower. Mr. Bloxam made them cranked (see
p. 84) in order to get their common axis in a line with the top of the spring;
but that is an unnecessary refinement, at least for these escapements, and
is never done. And as no point in the pendulum really swings quite in a
circle, I doubt if the friction of the pallets on it would be sensibly less for
their being both made to describe the same circle by cranking their arbors:
FOUR-LEGGED ESCAPEMENT. 88
at any rate it is too insignificant to care about.
The distance of the lifting pins from the centre should not be more than
a 40th of EC, or else the angle of impulse 2
 will be larger than is found
expedient. It is difficult to make the pallets light enough even with a small 

and the larger it is the lighter they must be. The length of their tails down
to the beat pins is arbitrary, but I found the Westminster clock perform
decidedly better with the pallet tails long than short. The length here
shown does very well, and it looks neat to make the two parts reciprocally
parallel. The pins should be placed so that the lifting may take place equally
across the line of centres CE, because then it is done with the least friction.
For this purpose the pins which lift the lower pallet must be set on the radii
which run along the acting faces of the teeth, and the other set of pins half
way between them, with reversed screws, as I said before.
Any gravity escapement requires a heavier weight than a dead or detached
one, other things being equal, because it must be strong enough to
lift the pallets promptly and firmly always; but the superfluous force does
not reach the pendulum, and therefore does no harm, provided the train is
good enough not to waste much force generally in order to get over occasional
weak places from bad wheel-cutting. Nothing tests the defects of a
train like a gravity escapement. If there are bad places in a common clock
train they must be very bad indeed for the teeth not to follow the pallets,
though they may be giving no effective impulse for some seconds; but in a
gravity clock the pallets have always to be lifted; and I have never got a
train yet in which I could not hear some weak place, recurring always at the
same time of day, and requiring at least an extra pound in the weight beyond
what was generally wanted. For that reason, though a high numbered train
is not, or ought not to be requisite for these clocks, it should be a thoroughly
good one; and as defects of cutting affect low numbers more than high ones,
it is better to have them rather high, though they need not be anything like
what are used for first-rate dead escapements. I have the upper pinions of
10 and the centre one of 12, and if these are well cut, and still better if they
are lantern pinions, they are enough; if they are not, you will soon hear and
see it by the escapement, and the train should be rejected as a bad one.
In gravity regulators, for the same reason, the wheel must have a little
run at the pallets before it begins to lift them just as many clocks will
not begin to strike if the hammer tail lies on the pins: i.e., there must be
banking pins KK0 for the pallets to rest on just clear of the lifting pins. And
in turret clocks the banking pins are useful to reduce the are without making
the pallets too thin. They may be simply a thin piece of metal adjusted for
the beat pins to fall on.
It is better to have a full-sized barrel with three lines and a fixed pulley
for a ‘three-quarter length’ clock than two lines and a smaller barrel. A
clock of this kind with a 40 lbs. pendulum swinging 2 requires a weight of
from 20 to 24 lbs., according to the train, to lift the pallets promptly and
INFERIOR MODIFICATIONS. 89
firmly, and loud enough for an observer.
These clocks have also been made to strike a small bell every minute by
a pin on the minute wheel, which enables an observer to go on for some time
without looking at the clock. Of course this requires rather more weight,
and no such extra friction could be tolerated in a dead escapement. My
clocks strike one at the hour on a rather large bell, but that makes no
sensible difference in the weight. When there is a full striking part, the
train must be arranged in the usual position, which is inverted in the mere
going clocks, to save unnecessary height of the frame and the pendulum
being several inches above it, on account of the extra wheel and the length
of the pallets. The great wheel is also put on the left side to keep it near
the side of the case and out of the way of the pendulum. When a pendulum
imparts vibration to the weight, as they do sometimes, the simplest cure for
it is to put a board down the side for the weight to graze when it is near
the pendulum. It has never happened in my clocks, and three lines tend to
prevent it.
Unfortunately I have no daily rate of any of these clocks regularly taken
in an observatory, until we come to the largest of them all; but judging of
my own for long periods by the Westminster clock, which is tested daily, I
have no difficulty in pronouncing it superior in steadiness of rate to any dead
escapement whose rate I have ever seen. And they are made by Mr. Brock,
of George Street, Portman Square, and I dare say by other makers, for half
the price of the old-fashioned best dead escapement regulators with only
12 lbs. pendulums.
Some persons have taken a great deal of unnecessary trouble to modify
these escapements in order to avoid the fly, as if that did any harm; and have
added train remontoires, as if that did any good to any gravity escapement
which really is a gravity escapement—i.e. which has no tendency to trip,
and gives a constant impulse clear of the friction of the train. One of these
attempts to get rid of the fly was exhibited by Dr. Clark in 1862; but the
wheel was stopped with a bang that thrilled all through the clock, which only
tends to knock it to pieces, and keeps everything in a state of vibration. It
was also a much more delicate construction, and I should prefer Bloxam’s if I
had to choose between them; for if you have not a fly, the less the motion is at
each beat the better. Another contrivance for the same purpose, invented by
a French workman here, was used by his employers in a few church clocks,
and then abandoned, and my original form resumed by the makers in all
their turret clocks. The fly should of course be as light as possible, either
of thin steel or aluminium; and the best way to put it on is with a piece of
watch spring pushed in through an oblong hole so as to press always on the
arbor, which should not be very thin. Some persons do not seem to know
that a long fly is more effective than a wide one of the same area.
Another mistake made by several of these inventors, including Dr. Clark,
was that of supposing it was better to let the pallets unlock the wheel in
THE DOUBLE THREE-LEGGED ESCAPEMENT. 90
falling with the pendulum, forgetting that the pendulum is then just as
much affected by the friction of unlocking as if it did it in rising, if that
friction is sensible; and if it is not, still less can it signify whether it is borne
directly or indirectly by the pendulum. It is still worse to keep the pallets
moving in contact with the stops during each ‘excursion’ beyond the angle
of unlocking, for that reduces it so far to a dead escapement. But the worst
of all the ‘improvements’ was by the late Mr. Cooke of York, the eminent
telescope-maker, who also made these clocks, and rounded the stops ‘to
make the unlocking easy;’ which degraded it to an impulse escapement, the
pallets being then driven away by the teeth with a force depending on the
clock weight and friction of the train.
The double three-legged escapement (fig. 24 next page) is so called
because it has two three-legged wheels, ABC and a b c, in different planes,
with one set of 3 lifting pins between them. Here the two wheels must be
squared on the arbor, and the lifting pins need only be shouldered between
them. The pallets also lie in one plane between the wheels, but one stop
S points forward to receive the ABC teeth, and the other S0 backward to
receive the a b c teeth alternately. The reason for two wheels is that with one
three-legged wheel you cannot have the pallets far from upright, which is
evidently the worst position for them, as it requires much more dead weight
to be moved at every beat in order to have weight enough for effective
impulse. It should be understood that there is no particular mechanical
advantage in the two wheels being set with the alternate teeth equidistant,
appearing like a six-legged wheel. They may be set with one set of legs
at 90 and 30 to the other set—or at any other angles to get any greater
inclination of the pallets if desired. However the equidistant arrangement is
the natural one, and is generally used, though not invariably. I need hardly
say that a pair of wheels of this kind are very different from a six-legged
wheel which would only move 30 at each beat, while this moves 6, besides
other differences.
In this case the distance of the pendulum top from the scape-wheel centre
evidently = diameter of scape-wheel. The lifting pins should not be farther
from the centre than a 36th of this, or the pallets have to be inconveniently
light and thin: the pins and arbor may be solid as a three-leaved pinion.
They should be so placed that the one which is holding up a pallet and the
one which is going to lift next may be vertically over each other, the third
being on a level with the centre—i.e., they will stand on the radii which
form the acting faces of the teeth of one wheel, as you see here.
This escapement is the best for large clocks, which must have plenty of
superfluous force to drive the hands in all weathers (which superfluous force
all reaches the pendulum in clocks of the old kind, varying immensely);
but the fly must, on that account, be much larger in proportion than in
regulators, and care must be taken in planning the clock to leave room
for it. In the smallest turret clocks I have always had the fly a foot long
THE DOUBLE THREE-LEGGED ESCAPEMENT. 91
Fig. 24: Double Three-legged Escapement
WOODEN BEAT-PINS. 92
altogether and 11
4 in. wide, and in large ones considerably more. When the
fly is very large, as at Westminster, the friction of a spring on the arbor is
not enough, and there must be a larger ‘roller’ or blank-wheel pinned on the
arbor for the spring to act on. At the same time it was very satisfactory
to find that when the men had once forgotten to screw up the spring after
doing something to the fly, the clock had never tripped in the days which had
elapsed; and I have tried the same experiment elsewhere; but the four-legs
will trip if the fly is loose. The greater obliquity of the pallets, 30 against
221
2
, is the cause of this superiority of the three-legs; and this obliquity may
be increased still more if you like by altering the relative position of the two
scapewheels. But I by no means advise the omission of the fly, even then.
In very large clocks the pallet tails are too thick to bend for adjustment of
the beat, and then eccentric beat pins are used, which require no description.
They are usually made of brass, even in small clocks; but I think it would
be better to cover them with hard wood. The finest clock of this kind I have
seen was a regulator with four-legged escapement made by an amateur,
Mr. George Salt, of Saltaire; and it had ivory beat pins, which certainly had
less chatter than brass ones. The pendulum weighed nearly 40 lbs., and yet
the clock weight was only 15 lbs., with about 4 ft. fall. This shows that
a gravity escapement really requires very little more force than a dead one
with as good a train as possible, though practically I should always make the
weight abundant. One thing must be specially attended to, as a distinction
between these and dead escapements: the beat pins must on no account
be touched with oil or grease of any kind, but left absolutely dry, whatever
they are made of; for the slightest adhesion to the pendulum is fatal; though
in dead escapements the fork should always have a drop of oil, to keep it
as close as possible without being tight. Moreover, care should be taken to
make one pallet begin to lift simultaneously with the resting of the other,
and neither before nor after.
The best evidence of the performance of these escapements is the annual
report of the largest of them all at Westminster, of which I shall have more
to say afterwards.6 My own have often gone for months together without
any difference from Westminster for which I could venture to correct, or to
regulate the pendulum. I have never found on close inquiry that the rate of
the very best dead escapement regulators approached that of Westminster
and several other public clocks of this kind, of which I have occasionally
had reports. I have had accounts of some that had been altered from other
escapements to this, with the effect of reducing errors of minutes to seconds.
The last was from a gentleman who said that his turret clock, made from
this book by a man who had never made one before, has a better rate than
6And I have read in the English Mechanic that one under the charge of Professor
Waldo, of Yale College Observatory, had gone for several months on a rate of only .47 sec.
a week.
GOING PART OF CLOCKS. 93
any astronomical clock he had ever known.
CONSTRUCTION OF THE GOING PART OF
CLOCKS.
Fig. 25 (p. 95) shows the arrangement of the going part of a common regulator,
or a house clock of superior character, except that the pendulum in a
clock of that kind ought to be hung by a cock on the back of the case; but I
have already given a drawing showing that at p. 31; so I show another mode
of suspension here. In the common recoil escapement clocks the pendulum
only weighs a pound, or less, and is hung from a cock merely screwed to the
back plate of the frame, which is a much weaker plan than this. Aa is one of
the pallets on the arbor a and Ef the crutch and fork; which generally embraces
the pendulum, but sometimes goes through it, especially when it is a
wooden rod. The weight is not hung by the single line, but by a double line
going through a pulley, sometimes in the weight itself, but more frequently
hung to it by a hook. This prevents the string from untwisting, and enables
you to do with a thinner string, and it requires a barrel of twice the diameter
which a single string would, and that is worth something when the pivots of
the barrel are as large as they usually are, of which I have spoken already
at p. 59. But it must be remembered that every pulley in a machine, and
especially every moveable pulley, wastes power very sensibly by the friction
and stiffness of the rope, especially when the moving power is at the slow
end of the system of ropes. Theoretically it makes no difference whether a
given weight with a given fall in a week is hung by one rope without any
pulleys or by half a dozen; but practically you will find the weight has to be
increased in a very high ratio for every additional pulley you add. You might
soon reach a number at which no weight whatever would do the required
work, but would all be wasted in overcoming the friction and stiffness of
the ropes. This remark is chiefly important with reference to turret clocks,
since not one architect in a hundred ever consults a clockmaker before he
plans either dial-holes or clock-room or place for the weights to fall, and
then people think it is the clockmaker’s fault if the clock does not perform
as well as if it had plenty of room for the weights to fall and other things to
act properly.
The barrel is fixed to its arbor, of which the back end is a common pivot,
but the front is carried through to the dial K and is squared for the key to
take hold of it. The great wheel G rides loose on the arbor between the
barrel and a collar shown just above G and it is connected with the barrel
by the ratchet and click, of which a front view and description has been
already given at page 15. (There are in fact two ratchets R and r in fig. 25,
but we need not inquire into the functions of the second at present: it will
be explained at p. 104.) The great wheel G drives the centre pinion c, which
COMMON HOUSE CLOCK. 94
always turns in an hour, and its arbor goes through to the dial and carries
the minute hand in the way I will describe presently. The centre wheel C
drives the second pinion d, on whose arbor is a wheel D which drives the
scapewheel E by its pinion e. In moderately good clocks the pinions have
all generally 8 teeth or leaves, and the wheels in that case have 96, 64, and
60 teeth, if the scapewheel turns in a minute as usual: in the best clocks the
pinions are occasionally as high as 16; Mr. Bloxam’s and Mr. Salt’s are the
only ones I ever saw with higher numbers. Of the scape-wheel, pallets, and
pendulum, I have said enough already. In the best clocks, and sometimes
in common ones, the scapewheel arbor comes through the dial and carries
a seconds hand.
Short clocks with half second pendulums are best made with a scapewheel
of the usual number of 30 teeth, as either a large and heavy wheel, or
teeth very closely set, are objectionable. In that case the scapewheel will of
course turn twice in a minute, and the product of the numbers of the teeth
of the centre and second wheels must = 120 × 8 × 8 if the pinions are of 8,
which is best satisfied by 96 and 80. In very inferior clocks the scapewheel
pinion is only 7, and then 84 and 80 teeth will do. The American clocks have
lantern pinions, in which 6 pins are as good as 8 or 9 common teeth, and
therefore the centre and second wheels need only have 72 and 60 teeth for a
half-seconds pendulum. It is not worth while to go on with the calculation
for 2
3 seconds pendulums or others, as the principle of it is perfectly obvious.
Dial work.—If the minute hand were fixed rigidly to the centre arbor,
the clock could never be altered; and therefore the way in which it is fixed
and yet alterable is this: there is a wheel M (in fig. 25) set on a hollow arbor
or pipe which fits easily on the centre arbor, and has its own end squared for
the hand to fit it. A small bent spring with a hole in the middle fits on the
centre arbor, and the hole rests against a shoulder which is turned on the
arbor just in front of the clock frame; the ends of the spring press against
the back of the wheel M when it is pressed back, as it is after the hand is
put on, and it is kept there by a collar and a small pin put through the end
of the centre arbor.
And in this small matter there is room for a very common mistake: the
hand is kept steady by the friction of this spring at one end and the collar
at the other, and it will evidently be much steadier for the same amount of
pressure if the spring fits the arbor tight, and so the friction is between the
ends of the spring and the back of the wheel, than if it is loose on the arbor,
simply on account of the difference of leverage at which the friction acts
when you turn the hand with your own finger. In mere regulators without
any striking part, this does not matter, because there is nothing to disturb
the hand; but when the wheel M, or the equal wheel N which is driven by
it, has to lift a lever every hour to discharge the striking part, it matters a
great deal, because a great deal more friction is then required to hold it in
its place against the pressure of the lever; and yet it seems to be the fashion
COMMON DIAL WORK AND SPRING. 95
Fig. 25: Common House Clock
REGULATOR DIAL WORK. 96
in London to make the hole in the spring round instead of squaring it on to
the arbor; which would take about ten minutes to do. The consequence is
that a clock will sometimes take to losing unaccountably in this way, which
I only first discovered by seeing the minute hand gradually lag behind the
seconds hand; and that defect can only be permanently cured by making
the spring very much stiffer than it need be if it is put on properly, i.e. with
a square instead of a round hole.
Over the minute-wheel M and its hollow arbor there is fixed a thing
called the bridge, which is shown at ML (fig. 25), and has another pipe
enclosing that of the wheel M but not touching it; and the hour-wheel H
with another hollow arbor still larger rides upon the bridge pipe, and is
driven by a pinion n of 1-12th its own number of teeth, which is fixed to
the wheel N of the same number as M. That wheel N is generally set upon
a stud or pin screwed into the front plate, but is better with pivots in the
frame and a cock. The hour hand is set on the end of the hour-wheel socket
either with a small screw or pins. The thing marked Y in front of the hourwheel
has nothing to do with the going part of the clock, but is the snail
which regulates the number of hours struck by the striking part, as will be
explained therewith.
The hour hand in astronomical clocks generally has a small circle to itself
in the lower half of the dial, to prevent its hiding the seconds hand in the
upper half, which it is important that an observer should always be able
to see. Besides it moves with much less friction when so placed, as it then
turns on a thin stud fixed on the front plate of the clock, instead of a very
wide socket. It may either be driven by an intermediate wheel and pinion
from the centre arbor, in order to make it go the right way round, or directly
by the great wheel, which involves less friction and no inconvenience except
the perfectly insignificant one of having to move the hour hand separately
from the minute hand when you want to alter the clock much, which cannot
happen once a year in any good clock.
Dial.—Two different ways of fixing a dial are shown in fig. 25, and both
of them different from the common one, in which four separate pillars are
screwed permanently into the dial and the other ends go through the front
clock plate and are pinned behind it, the main pillars of the clock itself being
only long enough to connect the two plates, and having nothing to do with
the dial. Either of the two plans in the figure seems to me to be better than
this, though it is a matter of very little consequence. The dials of the best
clocks are made of brass plates polished and silvered: the common ones are
of sheet iron: the American and Dutch of wood. The hands are always of
black steel in regulators, but in common clocks they are of brass gilt, which
is a very bad colour on a white face, though very good on a black face. The
same remark applies to watch faces. I never could understand how such an
absurd thing as gold hands on white faces—and still worse on gilt faces—
came into existence, especially as gold hands of that small size have not even
WINDING KEYS SHOULD BE LONG. 97
the vulgar merit of being dearer than steel ones.
Winding keys are generally made too short in the stalk or leverage,
which makes the clock harder to wind and tends to strain the arbor besides,
as you may see from considering that if the stalk was very short indeed,
any force applied to it would be chiefly consumed in trying to bend the
arbor. As there is absolutely no advantage in a short key, this is one of
the many instances of doing wrong for the pleasure of it, when it would be
quite as easy to do right and the effect much more pleasant. All my seconds
pendulum clock keys are from 3 to 5 inches long, according to the weights.
The French spring clocks without fusees, in which the winding is very hard
towards the end, have keys like a very large watch key or a piano-tuner,
to prevent the strain upon the arbor. But this makes the winding a much
longer operation and a very unpleasant one, as you have to stop at every
half turn. Sometimes such keys are given with small English fusee clocks,
for which there is no excuse. You should take care that the wood or ivory
on the handle of a key is quite loose, or it increases the resistance materially
in winding.
Year clocks.—Clocks without striking parts are sometimes made to go
a month, and occasionally even a year. For a month they only require one
more wheel and pinion with a multiplier of 4, between the centre and great
wheels. Year clocks require 3 wheels below the centre, and the pinions ought
to be of 10, 10 and 12 at least, on account of the great weight required, which
will have to be still greater if the pinions are of low numbers. Assuming the
clock to go 380 days, and the barrel to have 16 turns as usual, the product
of the 3 wheels must = 380.24.12.10.10
16 , for which 100, 90, and 76 will be the
best numbers. This is far better than trying to do it with only two wheels
of 192 and 190 (the lowest possible numbers), and pinions of 8, in which the
friction will be very much greater. The best way is to have two barrels and
great wheels acting on one long pinion of 12, with the weight hung by the
same string from both barrels by a pulley which only turns while you are
winding up; and there must be a winding stop to each barrel.
Clock cases are necessarily connected with the construction of the clock.
The old tall case with a base as big as the top, standing on the floor instead
of screwed to the wall, is sufficiently explored to require no more to be said
against it. The case need be no longer than is required for the pendulum,
as the weights can have 3 lines, or smaller barrels, or larger great wheels,
of which the second is the worst. The weights themselves of course have to
be half as heavy again as with the fall one half longer. The best case for a
superior clock is one of which the front and sides take off together. There
need be no door to the face, but only small brass or white metal shutters
over winding holes in the plate glass front, which enables you to lock up the
clock completely and leave anybody to wind it up. Ornamental case making
I have nothing to do with, and it is not much of an exaggeration to say that
MOON DIALS. 98
the value of the inside of a clock generally varies inversely as the decoration
of the outside.
Moon dials.—There is an old calculation that if a pinion of 6 is put
on the hour arbor of a clock—i.e. the centre one—and drives a wheel of 91
with a pinion of 9 on its arbor driving another wheel of 91 with a pinion of
37 driving a wheel of 171, that last wheel will turn in 29d. 12h. 44m, 3.4s.,
which is only about half a second more than an average lunation. A pinion
of 6 does very well for a driving one, though it is much too low a number
for a driven pinion, except of the fly of the striking part. But if the centre
pinion is 12 and the great wheel 182, those two will do for the first pair of
such a lunar train. In that case, as the arbor of the great wheel must turn
for winding, it would be necessary to fix the 37 wheel on the back of the
great wheel, and let that drive either the 91 or the 171 as may be convenient;
for the order in which wheels and pinions are arranged is immaterial as to
the velocity-ratio between the first and the last. The common moon dials
of old-fashioned clocks are only driven by a single tooth on the hour arbor
driving a wheel of 59 teeth by jumps twice a day, leaving an error of 44 m.
in a month, to be set right by hand every now and then.
A simpler moon train, quite exact enough for this purpose may be made
by a pinion of 15 on a 24-hour wheel of the clock driving a 98 wheel with a
pinion of 25 driving a wheel of 113, which will turn in 708.736 hours, which is
only an excess of 7 seconds over one lunation of 708.73415 h., or 3 minutes
in 2 years, which would be quite imperceptible in any dial. But nobody
seems to remember that no flat moon dial can possibly imitate more than
one phase of the moon, either just half-moon, or else the narrowest possible
crescent; for the terminator, or boundary of light and shade on the moon, is
always a semi-ellipse, varying continually from the nearest visible approach
to a semicircle down to a straight line and then back again. The only way in
which real phases can be shown is by a globe half white or gilt and the other
half black, turning on an axis in the plane of the dial in a hole just fitting the
globe. And that only will look like the moon when seen right in front and
from a considerable distance, as the moon is. Practically a vertical axis will
do, though I need not say that the diameter which joins the ‘horns’ of the
terminator is seldom quite upright, and sometimes leans a good deal either
way (see my ‘Astronomy,’ p. 140 of 7th ed.). The axis must be turned by
a bevelled wheel, of which half will come through the dial—or above, if you
want to hide it. But all such contrivances are mere playthings, and show
the moon’s phases much less distinctly than an almanac.
Day of the month dials have to be dealt with rather differently, because
the move must take place only once in the 24 hours, at some time
in the night. Consequently the wheel which carries either a small dial with
figures showing through a hole, or a hand pointing to figures, must have
ratchet teeth driven by a lever or click or tooth moved once a day. There
must also be a slight spring or ‘jumper’ somewhere on the ratchet teeth to
DAY OF THE MONTH DIALS. 99
keep them exactly in the proper place for the click to catch next time. In
the old-fashioned clocks the month wheel simply had 31 teeth, and you had
to move it on by hand in February, April, June, September, and November.
Fig. 26: Day of the Month Dials
I doubt if such clocks, however completely automatic, are really of much
use, for this reason if for no other, that the figures of the day of the month are
always too small to be seen at such a distance as clocks usually are when you
are writing and want the date. Large cards, changed every day, are infinitely
more used. Nevertheless, as the machinery is, or may be, much simpler than
you would suppose beforehand, I may as well indicate the nature of it, on
what seems to me the simplest of the various ways of doing it. But for the
present foolish arrangement of months, which the world seems impotent to
set aside, we should only want six months of 30 days, and six of 31 in leap
years, and in other years seven and five. But, as things are, we have four
kinds of month to provide for. We must clearly have one wheel M with 31
teeth, carrying a hand pointing to a month dial; for that is much easier to see
than numbers peeping through a hole, and it is enough to print every third
number, except at last 28–30–1. Then we want some contrivance to push
on two teeth in April, June, September, and November, three in February
in leap year, and four in other years.
Let there be a 24 hour wheel Day, which, by the pin at D moving on
to d, will move the long lever CEFD so much to the right as will carry the
horizontal click FG over the space of 4 teeth or pins of the month wheel, i.e.
DIALS WITHOUT HANDS. 100
will drive that wheel 4 days forward. That provides for common Februaries.
Then if the lever CD is stopped from going more than the space of one tooth
of M back again at the end of the long months, as of other days, they also
are provided for. It must fall back the space of two teeth at the common
short months, and three teeth at the end of leaping Februaries. Several ways
have been invented for doing this. The simplest is to have a four-year wheel,
or disc Y, with 4 deep February notches in it at quadrants, into which a
long tooth E, on the lever CED, can drop, and short notches for the 30-day
months, and none for the long months, but the outside of the wheel Y is the
space of one tooth off the tooth E generally.
But we have to consider how the year wheel is to be moved at the end
of every month, as it must be, and so as not to be held fast by the tooth E
in any notch. I think the best way is to do it by another lever LNM on a
stud in the clock frame at L, and a gathering click NK, which takes hold of
one of the 48 pins in Y when that lever is lifted, and carries Y one step or
month-space forward when the lever is dropped by the snail M just before
the last move of the month is finished, or as the hand comes up to 1. This
divides the work of moving the two wheels and levers more uniformly than
any other plan, besides making sure of the tooth E being out of a notch
before the year wheel wants to move: not that it would signify on this plan
if it were not, for then the lever LNM would only wait to drop. Each of
the wheels wants a safety click or juniper, A, B, of the usual kind for such
motions. I only put pins instead of ratchet teeth to M, because the click FG
will be safer not to slip out.
The work might be simplified a little and the lifts made less, and the
year wheel need only be a quarter of the size, if you will be content to
move the month hand at the end of February by hand. A week dial is quite
superfluous, and so I have not crowded the picture with one. It only wants
a seven-star wheel by the side of the day wheel, one ray of the star being
moved by the pin D after it has come to d and done its monthly work. It is
desirable to distribute the work as much as possible. The month dial ought
to be at least twice as large as in this drawing, to be seen easily.
In any clock which has all this extra work to do, special care must be
taken that the ‘motion’ wheels (or dial work) are held on the centre arbor
by a squared spring, and a pretty strong one (see p. 96), or it is sure to slip
and gradually drag, though the clock may be going right.
Several persons have taken patents for clocks and watches showing the
time by figures appearing through a hole in the dial instead of by hands.
Not that there is anything new in that, except as to the machinery for doing
of it. Days of the month were generally so done 100 years ago at least; and
my old regulator by Holmes, already mentioned at p. 42, shows the hours
in that way. I do not profess to judge of public taste, but it seems to me
that all such inventions proceed on the fundamental mistake of supposing
that we read the figures of a dial. We do nothing of the kind, but judge at
DIALS WITHOUT HANDS. 101
once from the mere position of the hands and the well-known marks for the
hours and minutes. In fact dials are better and clearer with no numbers at
all, but merely 12 large spots for the hours and five-minutes, and 48 small
ones for the other minutes, as I have often convinced people by asking them
if they want such a dial as they see in several of my clocks. They always
answer ‘Yes;’ and then are much surprised to find no figures, but only the 12
strong marks and 48 small ones. And the hands upon a dial, whether large
or small, are more conspicuous than any figures which can be conveniently
made to appear through a hole, especially if the hands are of the proper
colour—i.e. black on a white or gilt dial or gilt on a black one.
Moreover, there is another objection to those ‘chronoscopic’ dials: the
figure-discs must be driven discontinuously, or by jerks at the end-of certain
periods; and if that is done directly by the watch, as in Barlow’s patent
of 1866, the strain on the wheels is so much greater at the short time of
action, and especially when the units and tens of minutes and the hour all
have to be changed at once, that it is impossible for such a watch to go well.
Besides the mere work of moving the 3 discs, all from the 5-minute wheel
of the train with different intermediate wheels, there are jumper springs to
be moved too. Whether such watches have been ever been made I do not
know; I have only read the specification.
It was patented in 1869 for clocks in a more practicable form by Siddons
and Meese, who brought me one to examine. They have 3 cylinders, A B C,
near together; A with the ten digits 0 1. . . . . . 9 on its face for units of
minutes, B with blank 1 2 3 4 5 (blank being better than 0 there) twice over
for the tens of minutes (making 12 spaces), and C with 1 up to 12 for the
hours. An 8-minute wheel in the clock has 8 pins in it, which are always
lifting a weighted lever, except at the moment when it drops from one pin to
another. The lever has a pall7 or click which first slips over and then brings
down in falling one of 10 ratchet teeth on the side of A, and so changes it
from one figure to another. Whenever A changes from 9 to 0 it also moves
on B one figure by the usual contrivance of numbering machines for railway
tickets, bank-notes, and pages of ledgers; and when BA changes from 5 9
to blank 0, B in like manner changes C one figure, B having 2 levers on
its side corresponding to the two blanks. There are other details of minor
importance in Siddons and Meese’s clocks, for which the patent has been
transferred to Gillett and Bland, of the Steam Clock Factory at Croydon.
As descriptions of the numbering machine are not easy to find, I had
better give one, at least sufficient to illustrate its principle. Take first the
7If this word has any etymology it clearly should be spelt pall, not from the pallium of
an archbishop or a corpse, but from !, to strike, the origin of pallet. ‘Paul’ or ‘pawl’
are mere nonsense, of the same order as the vulgar conversion of the expressive Yankee
word bunkum, for bluster, into buncombe, for no other reason than because newspaper
writers know there is a noble family of Duncombe, or the auctioneers’ conversion of the
site of a house into scite, which only shows themselves to be insciti.
EQUATION OF TIME CLOCKS. 102
simple case of only two wheels or cylinders set near together on the same
axis, but loose, with the 10 digits engraved on their faces, one A for units and
the other B for tens. A carries on its side a small bent lever which generally
hangs loose, but at one place in the revolution, where A is changing from 9
to 0, the lever has its tail caught by a fixed obstacle, and for that moment
the other end of the lever cannot yield, but travels with its wheel. B has 10
pins on its side, and whenever the lever of A is in that condition it catches
one of those pins and so drives on B one step, or changes it one figure. Then
for the hundreds, B has a similar lever on its other side which changes a
wheel C in like manner, and so on for as many figures as are wanted. In
clocks the change of the 10-minute wheel has to be made after 5 so as to
show 0 or a blank next, instead of after 9 as in numbering machines.
Equation of time clocks.—A still more obsolete contrivance, but
worth recording for the principle of its machinery, was that for making
the hands of a clock show solar instead of mean time, at least in a rude
and approximate way, which I suppose was used in the French public clocks
which did so up to the year 1826. Aa in this figure is a bevelled wheel on the
centre wheel arbor, which in this case is made to turn the wrong way round,
and another equal bevelled wheel Bb rides upon it, with a hollow spindle
bc to which the minute-hand is fixed. Between these two is another small
bevelled wheel D of any size, which would merely reverse the motion, if it
was set on a fixed spindle or arbor. But it is not, for it rides on the end of
a bar or lever DE, which itself turns upon the centre arbor and has its end
D beyond the wheel resting on a plate of the odd shape shown at Qq, which
is fixed to the face of a wheel which turns in a year. Now if the lever DE,
or the centre of the small wheel, is moved at any time in the same direction
as the hand is going, it will evidently push it forward just twice as much as
the lever itself is moved, and vice versˆa. If then the equation plate Qq is on
the right side of the clock-frame, the hand will go ahead of its mean motion
whenever D drops below the mean radius of the plate from O the centre of
the year wheel and will fall behind mean time when the protuberant parts
of the plate are uppermost. The plate then may be so shaped as to make
the advance and retardation of the hand agree with the ‘sun before clock’
and ‘sun after clock’ of the equation of time.
There are two other ways of giving a secondary motion of this kind; one,
by substituting a common small wheel or pinion for the middle bevelled
wheel, and putting it between Aa made as a common wheel, and Bb made
as an internal wheel, i.e. with teeth inside its rim; but in that case you must
remember that A and B will have different velocities, and therefore A must
turn in less than the hour. The other method requires neither bevelled nor
internal wheels, and is on the same principle as the one I shall describe more
fully under train remontoires.
Clocks for showing other celestial motions are mere curiosities, and are
always getting out of order from their complication; so I shall not waste time
EQUATION OF TIME CLOCKS. 103
Fig. 27: Equation of Time Clock
MAINTAINING POWERS. 104
in describing them, but go on to something more practical.
MAINTAINING POWERS OR GOING
BARRELS.
Winding up a clock evidently takes the action of the weight off the great
wheel, and so the clock movement stops for the time, though the pendulum
goes on swinging. This of course will not do in a clock of any accuracy,
whether a large or a small one, and as the same methods of keeping the
clock going (or some of them) are applied to both, I shall describe them all
together here, except one.
The oldest of them all is Huyghens’s endless chain. In fig. 28 P in the
‘going wheel’ is a pulley fixed to the great wheel of the going part, and having
short spikes set in it, or roughened in some other way so as to prevent a
rope or a chain hung over it from slipping. A similar pulley rides on another
arbor p, which may be the arbor of the great wheel of the striking part, if
the clock has one, and attached by a ratchet and click to that wheel, or to
the clock-frame if there is no striking part. The weights are hung as you see,
the little weight being only big enough to keep the string in the pulleys; but
the string or chain is much longer, or one at least of the weights is always
lower down than I have been obliged to draw it here. If you pull b, the left
hand of all the strings, down, the ratchet pulley moves under the click, and
the great weight is pulled up by c, without taking its pressure off the going
wheel at all. This plan was generally used in the old 30 hour clocks, but
went out with them, as the action of a chain or even a rope hung in that
way is rough and uneven; and moreover the pulleys must be of only half the
usual diameter for the same time of going.
Harrison’s going barrelis the maintaining power used in all regulators
now. The larger ratchet wheel r is the one designated by the same letter
in fig. 25 (p. 95); and the click R is fixed to that wheel, which is connected
with the great wheel by a spring SS0. While the clock is going the weight
acts on the great wheel G through the spring; but as soon as you take off the
weight by winding, the click Tr, whose pivots are set in the frame, prevents
the great ratchet from falling back, and so the spring still drives the great
wheel during the time the clock takes to wind, especially as it need only just
keep the escapement going, for the pendulum will take care of itself for that
short time. The drop of the great click over the teeth of its ratchet may
be heard every 10 minutes or so while the clock is going. Watches have the
same apparatus, with a spring click.
Bolt and shutter.—Another contrivance, which is now used only in
large clocks, is an arbor with a weighted lever at one end of it, with a click
in the form of a spring bolt on another lever; when the weighted arm is
lifted up the click ‘takes into’ the teeth of some one of the train wheels, and
OTHER MAINTAINING POWERS. 105
Fig. 28: Endless Chain
OTHER MAINTAINING POWERS. 106
Fig. 29: Spring-going Barrel
SIR E. BECKETT’S BOLT AND SHUTTER. 107
the weight then keeps the clock going till it works itself out of gear in a
few minutes and drops. The weighted lever is outside the clock and is made
with a cap or shutter which shuts over the key-hole when it is down, to make
sure of your lifting it before you begin winding. With the usual ingenuity
for doing things wrong, this click is very often made not as a sliding bolt,
but with a hinge, so that there is one position of the lever in which it jams
against the teeth and stops the clock for good, unless the winding man finds
it out and releases it, which he probably will not. Sometimes too the click
sticks and sometimes it slips, even if made rightly. There is another defect
besides in the common bolt and shutter, viz. that it may work itself down
and rest upon the winder or key before the winding is done if the man is
slow about it, and then it does no good and the clock stops for the time.
Improved bolt and shutter.—To prevent these evils, and to simplify
the construction, I introduced the plan of substituting for the ‘bolt’ a segment
D, in fig. 37, p. 131, of a small wheel suited to the teeth of the great
wheel, and making the arbor C, which carries that and the shutter M, to
pump in and out of gear, and the shutter not covering the key-hole, but
made as a circular arc to the centre C, which all but touches the winder
when it is on. The winder has a ring, shown by the circle at M, fixed round
its end, which prevents it from being put on until you have lifted the shutter,
and put it into gear with the great wheel, to hold it up. As you go on winding,
the clock goes on and the shutter descends, now behind the ring, which
secures your pulling it out of gear again when you take off the winder, and
yet it will keep in action full 10 minutes if left to work itself out. This plan
is now generally used in superior large clocks. The weighted arm should be
long, so as not to require a heavy weight to be lifted.
I shall describe hereafter another totally different plan for keeping a very
large clock going when the winding takes a long time; but as the spring going
barrel does very well for small clocks, and the improved bolt and shutter
for any but a clock of quite unusual size, I shall postpone that description
till we come to the Westminster clock. For the same reason I need not
repeat the description of Sir G. Airy’s going barrel, which was applied to
the Exchange clock, but is so expensive that it is certain never to be used
again. A full description of it was given by him in vol. 7 of the Cambridge
Phil. Trans. The object of it was not only to keep the power always on
the clock, but exactly the same power; for the power of the spring falls
below that of the weight, and that of the bolt and shutter doubles it just at
the times of putting it on and taking it off; but that is of no consequence,
except in a revolving pendulum clock, for which his apparatus was invented;
he afterwards simplified the construction, but it is still an expensive one,
and the thing can be done at a tenth of the cost by the Westminster method
without either loss or duplication of force.
There is another maintaining power which has a tempting and scientific
look, but is not so good as it looks. A rim at the back of the great wheel,
SPRING CLOCKS. 108
M (fig. 29), has internal teeth at A—troublesome things to make—and in
them works a wheel ABP on a stud B in the end of the barrel, and also
in a pinion C fixed on the arbor which runs loose through the barrel ends.
When you wind up you apply some force P to the intermediate wheel, and
the same pressure P is communicated to the great wheel because BP = BA,
P being whatever is necessary to lift the weight. Let W be the effective
Fig. 30: Sun-and-planet Power
􀀀􀀀@@􀀀􀀀 @ i @ 
?
6
C H
P
A B
M
W
weight at A when the clock is going: at B it is WCA
CB = W0; and P = W0
2 ,
since AP = 2AB ... P = W
2
CA
CB; which cannot possibly = W, however small
the winding pinion is, and if it is very small it takes a long time to wind.
So this maintaining power must be deficient, though it may do for clocks
with the common escapements, which will go for a few minutes with very
little power on. Besides that, the winding arbor has to work under double
friction of the pressure of twice W, both above and below it. For all these
reasons I have never adopted it, either for large or small clocks.
Spring clocks.—Hitherto we have supposed all clocks to be kept going
by a weight. But many clocks have no weight, but have a spring made of
a long ribbon of steel coiled up in a barrel for their moving force. This
construction however belongs so peculiarly to watches that I shall defer
the description of it till we come to them. I will only mention here that the
French clocks, like French and Swiss watches, generally have the great wheel
AMERICAN CLOCKS. 109
fixed to the barrel, which of course makes the force on the train unequal. In
that case the barrel arbor goes loose through the barrel ends and is fixed to
the inner end of the spring, and has also a strong ratchet squared on to it,
with a click on the clock frame, which holds it when you are not winding up.
And a barrel of this kind is of itself a ‘going-barrel,’ for it keeps the power
on as much while you are winding as at other times—in fact rather more.
English spring clocks always have a fusee with a chain, made as in the figure
of a chronometer movement, which will be given in the chapter on watches,
to equalise the force on the train. I understand that this class of clocks is
now sold more than any other English ones, with half-second pendulums,
either in cases made to stand on a bracket or to hang up against a wall.
American clocks.—There have been great fluctuations in the quality
of these clocks since they first came here above 40 years ago, and there is
now a great variety of them, and they are certainly cheaper than most if
not all others of the same general quality. Their principal defect is in the
lightness of the pendulums. I have improved several of them by increasing
its weight. The wheels and plates of the frame of these clocks are stamped
out of sheet brass, and they contain several ingenious contrivances. They
have advanced considerably in appearance at any rate since the original
Sam Slick form; and, by the way, it seems that the original Samuel Slick
was one Eli Terry, whose name ought to be preserved in a book on clock
making. But even these new ones are equally defective in the weight of the
pendulum, though they are longer; and yet I can hardly suppose that the
makers of such clocks are as ignorant as a shopman here, who confidently
assured me that the weight of pendulums is of no consequence! It would
not cost a penny more to make them heavier. Some superior ornamental
clocks and regulators appear to be made at the Howard watch and clock
factory at Boston, U.S. I read lately in the English Mechanic that they
make regulators as well as turret clocks with my gravity escapements, and
that their own principal regulator has the four-legged escapement.
The old-fashioned ‘Dutch,’ i.e. German, clocks, with wheels of boxwood
driving lantern pinions of wire stuck in wood, have been in a great degree
driven out by the Americans with their superior appearance. But a more
ornamental kind of German clocks is now made, and I see in the Horological
Journal of October, 1873, that there are now nearly 2,000,000 clocks a year
made in the Black Forest ‘from the modest wooden clock up to the costly
regulator,’ and that there are 1429 clock manufacturers there, employing,
one way or another, 13,500 people. Many of these are called trumpet and
cuckoo clocks, in which the sound is made by a small pair of bellows, worked
at every blow of what would ordinarily be the striking. The cuckoo is heard
much farther over a house than striking. I need hardly say that the bird
who appears at an open window is only a pretender, and does not contain
the bellows in his inside.
AUSTRIAN CLOCKS. 110
Improved French clocks.—The old-fashioned French chimney-piece
clock, of which the form is well known, was generally inferior to the commonest
Dutch clock as a timekeeper. But a very superior kind has been
introduced of late, far better than anything made in this country for two or
three times the price. They have the pin pallets made of jewels, described
at p. 68, and good pendulums of fair weight for their size. They have also
a peculiar means of putting themselves in beat if they require it; for the
pallets are set what is called ‘spring tight’ on their arbor, i.e. embrace it
with a spring collar which will yield under sufficient pressure, though tight
enough to give the impulse to the pendulum. If one pallet happens to work
too deep, from the clock being out of level, it reaches the bottom of the
teeth, or perhaps even the slight recoil of the pin pallets against straight
teeth is enough to push it back a little into equal beat with the other pallet.
These clocks have also adopted the English, or ‘repeating,’ striking part,
which will be described afterwards. Every one knows that the old-fashioned
French and German clocks oftener strike wrong than right, and are apt even
to be set wrong in winding up the striking, which never happens with English
or with the improved French ones. The ornamental English clock trade
has ceased to exist, having been entirely driven out by these, and also by
the
Austrian clocks,with cases about 21
2 feet high, which first appeared
in our 1862 Exhibition. Their chief defect is the shortness of the arc of
vibration, which makes them very sensitive to the least disturbance, not
merely as to rate (as I showed at p. 64), but even as to going at all. They
generally strike the quarters in a peculiar, and, I think, very puzzling way,
i.e. 1, 2, 3, 4, on a single bell, and repeating the hour at every quarter; so
that from 12 to 5 you have no idea what the clock means to say.
Self-winding Clocks have been made as long ago as the 1851 Exhibition.
I have seen one by Mr. Horstmann, at Bath, with an endless chain
made of a perforated wide watch-spring running over pins in the main wheel,
and worked on the usual endless chain plan, but by a piston in a tube filled
with naphtha, which expands and contracts with the temperature. I cannot
say how far it is successful; and such clocks are evidently of no real use.
Sometimes one sees an independent pendulum swinging in the hand of a
bronze lady, apparently motionless, on the top of a small clock; but she really
has a small twist at every beat in connection with the clock below, and
that pendulum does nothing. Another curiosity sometimes exhibited is a
balanced hand turning all alone on a glass dial. This is managed by a watch
movement in the counterpoise, which tends to turn a weight inside it all
round the watch in twelve hours. It is so poised that when the weight hangs
at right angles to the hand it will lie horizontal, pointing to either III. or IX.
When the weight is farthest from the centre, and therefore most effective,
the hand must point upwards; and when the weight is nearest the centre
the hand preponderates and points downwards, and similarly at intermediWATER
CLOCKS. 111
ate positions. The weight in fact always hangs downwards absolutely in the
watch, and the hand relatively revolves round it.
Water clocks.—It is evident that a flow of water may be made to drive
a clock in various ways. A few years ago I was asked to see some water
clocks in which the water came into a hollow spindle, and thence into four
arms radiating from it. As each arm passed its lowest position it opened a
cock in itself which discharged the water, and no more was allowed to enter
from the hollow spindle until that arm came again to the top; so that the
descending arms were always weighted with water, and the ascending ones
empty and light. In some cases the weight was increased by a bulb or closed
bucket at the end of the arm; and some of these were striking turret clocks,
and they required very few wheels. Whether they ever came into use I do
not know. I should think it would be difficult to keep the water from spoiling
the rest of the machinery, and if such clocks require any attendance there
would be no material saving over a common clock which requires winding.
Electrical clocks, properly speaking, are clocks going by electricity,
instead of by a weight wound up periodically; but no such clocks have yet
been invented capable of keeping as good time as the commonest weight
clock. They may be divided into two classes. The first are those invented
by Mr. Bain in 1840, modified more or less by other people, of which the
principle was this: the pendulum bob is apparently a hollow brass cylinder,
with the axis horizontal, and passing over two permanent magnets, without
touching them, which are fixed to the clock case at one end, and nearly
touch each other with opposite poles, which are marked N and S on the
several magnets shown in fig. 32 (p. 114), omitting the upper set for the
present. The cylinder really contains a long coil of insulated wire, of which
the two ends run up to a pair of suspension springs, which make a complete
galvanic circuit with wires somewhere connected with the poles of a battery,
and capable of being ‘broken.’ The pendulum pushed a light sliding rod
backwards and forwards, which made and broke contact. Whenever the
circuit was complete there was attraction one way or the other between the
magnets and the coil, and that attraction was enough to maintain the swing
of the pendulum against friction, and the work of driving the train which
it also had to do. For the escapement was rather a ‘propelment,’ like the
action of the pendulum on a common recoil escapement if you take off the
weight, for then the pendulum will drive the train the wrong way, which
may of course be reversed. But these clocks never answered in any practical
sense; nor would anything but the strongest evidence, independent of the
inventor, convince me that any independent pendulum directly maintained
by electricity can succeed in keeping good time for any considerable period.
Shepherd’s clocks, by which it was announced that all the time of the
1851 Exhibition was to be kept, seemed more promising, but they soon failed
totally there, and the time was kept by Dent’s large clock, made from my
design, now at King’s Cross. In them the electricity was employed to lift
JONES’S ELECTRICAL CLOCKS. 112
a small gravity arm at every alternate beat, which gave the impulse to the
pendulum by falling on a pallet like the down-pallet of a dead escapement,
which had the advantage of giving a constant impulse when it gave any.
But unfortunately it did not always lift. And any one who sets to work to
invent electrical clocks must start with this axiom, that every now and then
the electricity will fail to lift anything, however small: and if his clock does
not provide for that, it will fail too. It is therefore unnecessary to describe
Shepherd’s plan further now, as I did in former editions.
The other class of so-called electrical clocks are those where a ‘normal’ or
governing weight-clock drives or controls other subordinate ones; and these
again may be either (1) a mere dial, or ‘motion-work,’ driven by electricity
attracting a lever which works an escapement; this was Wheatstone’s invention,
about the same time as Bain’s: or (2) when the normal clock keeps up
the motion of a pendulum which drives an escapement—Ritchie’s plan; or
(3) Jones’s, where the normal clock controls the pendulum of a common and
inferior kind of clock wound up as usual, the pendulum being of the same
length as the normal one. I have placed them in mechanical, not historical,
order.
The first has never completely succeeded, and probably never will, from
the cause already stated. Old Mr. Dent also tried at it for some time, but in
vain. Mr. R. L. Jones, when manager of the Chester station about 30 years
ago, hit upon the ingenious plan of controlling rather than attempting to
drive a subordinate clock, by sending a current over its pendulum (in the
same way as Bain’s) at every beat of the normal or governing clock. It does
not matter if the current sometimes fails for a few seconds, or even minutes
unless the subordinate pendulum has time to get more than a whole beat
wrong, in which case the error would be soon augmented into two when the
connection was resumed, which is rather a serious evil; and I understand
this plan has been abandoned in some places which adopted it.
Mr. Ritchie, of 25 Leith Street, Edinburgh, has gone a step farther, and is
able to dispense with the winding of the subordinate clocks by making the
normal clock drive subordinate pendulums, which drive the escapements,
and will maintain themselves for a few beats if the electricity fails for that
short time. This will evidently bear less of such failure than Jones’s plan;
but still it appears from sufficient experience and the testimony of the Astronomer
Royal of Scotland and others, that it answers very well. The
construction of the escapement is a matter of some consequence. It is perfectly
easy to drive a wheel and train by common recoil pallets, provided
the wheel is good-natured enough always to stand still while the pallets are
not moving it; but not if the hands are subject to disturbance by wind;
and the very smallest motion of the hands would make a large one of the
scapewheel. Mr. Ritchie accordingly uses several forms of pallets designed
to hold the wheel as well as to drive it. The principle of them all is that of
dividing them into two like the pallets of a gravity escapement, rising and
RITCHIE’S ELECTRICAL CLOCKS. 113
falling with the pendulum.
Fig. 31: Ritchie’s Electrical Clock
In this figure (31) the pendulum is returning from the extreme right, and
has just deposited the right pallet, BFb with its end pressing on the tooth
at b, and so trying to turn the wheel that way. But it cannot turn until the
pendulum has gone farther and lifted the left pallet which is now locking
the wheel at G. As soon as it does that, the weight of B moves the wheel,
and itself falls a little more until another tooth locks at F. Then the left
pallet falls and presses on a tooth at a, but cannot move the wheel until
F is unlocked, and so on. In large clocks exposed to wind, a click is added
to prevent the wheel from being blown backward by a force of wind greater
SHORT AND SLOW PENDULUMS. 114
than the weight of each pallet for the moment; it cannot be blown forward
by reason of the stops FG.
As the secondary clocks are kept in order by the normal one, they will
bear a short or slow pendulum on the principle described at p. 29; and so a
clock with a one or even a two seconds pendulum can be comprised in the
length of an ordinary half-seconds ‘dial,’ as they call those very short clocks,
Fig. 32: Ritchie’s Pendulums
which look no bigger than their dials. Accordingly Mr. Ritchie makes these
pendulums, as in this figure (32). The lower half of the pendulum is rather
ELECTRICAL TIME BALLS. 115
longer than the upper, but both have bobs of wire coils in a cylinder, passing
over a set of magnets as before described. The suspension is by two springs
at S, as shown in the right hand part of this figure, which is the section
across the plane of vibration; and one is connected with one battery wire,
and the other with the other, the pendulum itself being made with two rods;
and so the current goes down one and up the other, being reversed at each
beat as before. In this way also a double attraction is got, as both bobs act
in the same way. The small ball above the lower bob is for regulating the
pendulum. The left hand figure is the front view.
This is taken in substance from a paper by Mr. Ritchie read to the Royal
Scottish Society of Arts in April 1873, and published separately. His clocks
are in use in connection with the Liverpool Observatory, besides Edinburgh
itself, and a variety of other places. The great objection to having all the
clocks of any large establishment worked by only one is the possibility of all
time coming to an end by any temporary failure of the one which ‘makes’
the time of all. It would be prudent to have two normal clocks always ready
to be connected with all the subordinate ones in case one has to be stopped;
and the normal clocks should be good ones capable of going without any
control.
When the last edition of this book was published, the Royal Institution,
which is a sort of head-quarters of electrical science, had just been converting
all its clocks into electrical ones, not on any of the controlling plans,
but on a driving one, by currents from a sort of small turret clock with a
hollow electrical coil for a bob, swinging a very large arc over two permanent
magnets. As I expected, and intimated then, it turned out a failure, and
was given up after a few years.
Another controlling plan is Lund and Blockley’s, in which a V-shaped
fork is brought down over the minute hand exactly at the hour by electrical
connection with a standard clock, so as to bring it to the time if it is a
little out either way. That requires a complete clock wound up and going
as usual, only it need not go very well independently. There are also clocks
driven by pneumatic connexion with a standard one; but I have no authentic
information about their success.
Time balls and guns are let off by electrical connection with a normal
clock which attracts an armature on a trigger which lets off the ball or fires
the gun when the connection is completed by contact springs in the 12 or
24 hour wheel and the minute wheel simultaneously. In like manner the
Westminster clock reports itself to Greenwich daily. A time ball is usually a
large wicker globe covered with painted canvas, fixed to a piston which falls
down into a bell-mouthed tube just air-tight enough for the air to act as an
elastic cushion. It is hauled up by hand a few minutes before the time for
falling. But these also sometimes fail like electrical clocks, and a better plan
is to let a common strong clock electrically controlled discharge the ball or
gun mechanically, just as it lets off a striking part.
CLOCKS STRIKING ONE. 116
STRIKING CLOCKS.
The simplest form of a striking clock is represented in fig. 33. It only strikes
one at every hour, which is sometimes more agreeable than striking the full
hour, especially where you can easily see at once what the hour is. It is
very seldom that anybody has to count the striking of a clock except in the
night. Striking one requires no striking part, or separate machinery to be
wound up, the hammer being lifted by a snail (or sometimes, but worse, by a
pin) on any wheel which turns in an hour, and dropped as the minute hand
reaches the hour. It cannot be done however without affecting the friction
of the clock, and therefore its rate, except with a gravity escapement or
some equivalent contrivance to prevent the inequality of force from reaching
the pendulum; and the remark I made at page 96 about the importance
of fitting the dial spring on to the centre arbor with a square instead of a
round hole, applies still more strongly here, as the friction of that spring has
to overcome the resistance of the hammer spring. The short spring against
Fig. 33: Clock striking one at the hour
which the hammer shank falls is to prevent it from jarring on the bell, and
ENGLISH OR REPEATING METHOD. 117
this is necessary in every case both in large and small clocks, unless some
other contrivance is resorted to for the same purpose, such as I shall speak
of under turret clocks. In common clocks this check is given in a simpler
way, as shown in fig. 34, where the square top of the stiff spring S butts
against the square piece on the hammer shank, whose own elasticity lets the
hammer strike the bell and then pulls it back again just out of contact. A
piece of vulcanised India rubber tied round the pillar also answers very well.
This figure is a front view of the common construction of an English
striking clock: the foreign ones are different, as I will explain presently. The
wheels shown only by circles (with a few of the scapewheel teeth) are within
the frame; only those with teeth are outside, and they are indicated by the
same letters as in p. 95. The hammer tail is raised by 8 pins in the second
wheel of the striking train, which corresponds to the centre wheel of the
going train. The pinion of that wheel generally has 8 leaves, and is driven
by the great wheel of 78, which therefore turns in 12 hours; not that that is
at all material, and of course higher numbers would be better. The striking
wheel drives the wheel above it once round for each blow, and that wheel
drives a fourth (in which you see a pin P) six or any integral number of turns
for one of the third wheel, and the fourth wheel drives a fly to moderate the
velocity of the train and the time of striking.
The number of blows to be struck is regulated thus: the dial-wheel N
has a pin on its face which raises the lifting piece LONF a little before the
hour, just far enough for it to lift the long click C out of the teeth of the
rack BKRV, which then falls back (helped by a spring at its tail) as far as
the tail V can go by reason of the position of the snail Y on the hour-hand
wheel H; which has steps in it, one for each hour, so as to let the rack fall
the distance of one of its own teeth for every hour the clock ought to strike.
This fall of the rack makes the noise called warning a few minutes before
the clock strikes. The reason why it cannot begin to strike yet is that the
pin P cannot pass a stop which is turned inwards from the lifting piece,
through a large hole in the frame, until that piece drops again, which it does
exactly at the hour by the advance of the pin in wheel N. Then the striking
train is free, and that little piece KG, called the gathering pallet, which is
squared on to the prolonged arbor of the third wheel, gathers up the teeth
of the rack, one for each blow of the hammer: the click is lifted as each tooth
passes, and prevents the rack from falling again, and at last all the teeth are
gathered up and the tail of the pallet is stopped by the large pin K in the
top of the rack, and the train can go no further.
The great feature of this English striking work is that you may ‘strike’
the clock as often as you like within the hour, or stop it any number of
hours, and yet it will always strike right, because the striking depends on
the position of the snail attached to the going part, and not at all on the
number last struck. These clocks are therefore sometimes furnished with a
string to the outside, from the click, so that you can pull it in the night and
REPEATING STRIKING WORK. 118
Fig. 34: Common Striking Clock
NEW FRENCH STRIKING WORK. 119
hear the hour. But this is just the wrong way of doing it: for if you hold
the string too long the click will miss some of the teeth and the clock strike
too many, and if you drop it too suddenly the rack will not have fallen its
full distance and it will strike too few. The right place therefore to put the
string is to the lifting piece, as at F. (The piece Qq belongs to something
else which I shall speak of presently.)
The improved French clocks, whose escapement I noticed at p. 109, have
a better mode of stopping the striking than the usual one in English house
clocks: the better one is used in our turret clocks when they have the rack
movement. Instead of the gathering pallet G (fig. 32) on the third wheel of
the train being stopped by a pin in the tail of the rack with a heavy blow,
the striking is stopped by the pin P in the fourth wheel coming against a
stop in the long click C, which drops into a deeper notch in the rack than
the others at the last blow of the hour, and so falls low enough to catch that
pin.
Strike and silent.—There are several ways of throwing the striking
work out of gear, so as to keep the clock silent. I think the best, though
not the usual one, is that shown in fig. 32, a small lever whose end x falls
before and stops a pin in the rack when the other end of the lever is put up
to si by an index or handle coming through the edge of the dial. I have seen
methods used which are very likely to stop the going as well as the striking
of the clock by leaving the rack to fall. Another way is to make the piece
LONF push forward so as to escape the pin at N, and be never lifted; and
this is unobjectionable.
It may save people a little time if I tell them what hardly anybody seems
to know, that you may move the hands of an English clock forward through
all the hours without waiting for any of them to strike, except 12, where
the rack-tail has to get over the great step in the snail; and even that is
often provided for by sloping the front of that step and the face of the pin
V, to let the snail push it aside, the tail being elastic enough to give way
a little. In the same way the tail of the lifting piece at N is always twisted
a little to let the lifting pin pass it backwards without lifting, so that you
may turn the hands back and the clock will not strike at all, unless it has
already given warning. The snail is sometimes set on a separate wheel below
the hour-wheel and moved by jumps by a pin in the minute-wheel M; this
is called the star wheel and jumper; but I can see no use in it, and therefore
shall describe it no further.
Locking-plate striking work.—The principle of the striking work still
used in most foreign clocks, French, German, and American, is shown in
fig. 35 (p. 121), though the actual arrangement of the pieces may be different.
It is generally used also in English turret clocks. You see the rack and its
click are gone, and instead there is a wheel Y called the locking plate or
count wheel, which turns in the 12 hours, and may therefore be put on the
arbor of the great striking wheel, or driven by the pinion of the striking
IMPROVED CONSTRUCTION. 120
wheel. It may be considered as marked out into 78 divisions, and notches
made in it at the distances 1, 2, 3, &c., into which a lever OQ can drop,
which is connected with the lifting piece. That is generally made with two
stops upon it, one a little behind and below the other; or else there are two
levers, one lifted by the other, with the stops upon them respectively; and
the pin P in the pin-wheel, or in large clocks, on the fly arbor, stops against
the first when the clock has done striking, and against the other when the
lifting piece is lifted by the wheel N in the dial work. But I introduced an
alteration in this respect in turret clocks, because one of the stops on the
lever must be out of the right position for direct action of the pin. Instead
of two stops on the lever, there are two pins on the wheel, P and p, one
a little behind and nearer the centre of the wheel than the other, and p is
caught by the stop when it has been lifted high enough to let P escape and
‘give warning.’
There is, or ought to be, a disc C with a notch or cam in it on the arbor of
the third wheel, which turns once for each blow, and so moves faster than the
locking plate, and therefore is more certain to lift the lifting piece quite out
of the way of both pins before the pin-wheel gets once round; otherwise the
clock might be, and clocks without this cam sometimes are, prevented from
striking at all, especially if the parts are not adjusted with great precision.
The lifting piece evidently cannot fall again until another notch in the locking
plate comes under the tooth Q. Sometimes the lifting piece LON is made in
two pieces, one lifting the other, but I see no advantage in it, except where
the pivot C happens to be at an inconvenient distance from the locking plate.
In turret clocks with three-wheeled trains it is generally more convenient to
make the wheel C turn only half round for each blow, and then there must
be two cams or two drops in the disc, as shown in the view of a large quarter
clock at p. 140.
Half-hour striking.—For striking one no lift by the locking plate is
required, but only a long notch reaching from 12 to 2; and for the same
reason the clock can be made to strike one at the half hours by dividing the
locking plate into 90(= 78 + 12) and leaving a wide notch between every
two hours, and putting a half-hour pin into the wheel N (fig. 32) besides
the hour one. Most of the French clocks are so made; but they have the
inconvenience of striking one three times between 12 and 2; so that between
those hours the striking tells you nothing. I once saw a turret clock made to
strike one feebly on a smaller bell, from the going part, as shown at page 116,
which gravity escapement clocks will bear, though not others. It was not
satisfactory, and led me to devise the following plan.
To make 121
2 and 11
2 silent, with the locking plate movement, we evidently
want something which will stop the lifting piece, LON in fig. 37
(p. 131) of a clock of this kind, from falling after it has been lifted to give
warning, until the next hour. And the way to do that is to have a 12-hour
wheel (the one with 24 ratchet teeth in fig. 37) with two steps in it, as you
HALF-HOUR STRIKING. 121
Fig. 35: Locking Plate Striking
DIFFERENT METHODS OF DOING HALF-HOURS. 122
see, which come under the tongue of the lifting piece just over that wheel
at those two half hours. The best way to drive it is by a gathering pin or
single tooth, which is shown in the hour wheel marked 40, and which moves
the ratchet wheel one tooth just after warning. There is also a spring click
or jumper to keep it in its place, which wheels driven in that way always
require, to make sure of the gathering tooth taking them up again. But
another thing has to be attended to. The locking plate, instead of having
78 teeth or spaces, as when there are no half hours, or 90, as when all the
half hours strike, must have 88, and each notch must again be wide enough
for striking one, only it must be divided as if there were no half-past twelve
or one, for one o’clock is the same as one half hour between twelve and two.
Half-hours with Rack Movement.—I have never seen this in any
English clock. Indeed the English house clock-makers seem determined to
lose every bit of the trade rather than allow any single improvement to be
made here, and so they are losing more and more yearly. The modern French
arrangement of the rack movement has the rack above the ‘motion’ or dial
wheels, acting by gravity without a spring, and the striking is stopped by the
long click dropping lower at the end of the rack than it does in the teeth, and
low enough to catch a pin in the third wheel, instead of the gathering pallet
being stopped by a pin in the rack and always tending to force it back. Half
hours are struck by a separate lever being brought under a pin anywhere on
the rack allowing it to fall one tooth only, the lifting piece being of course
lifted by a second pin in the hour wheel at the half hours. In order to stop
the striking at 121
2 and 11
2 there would have to be a 12-hour wheel with 2
steps or long teeth, as before described, to prevent either the rack or the
lifting piece from falling, whichever might be most convenient. But this is
not of so much use in small clocks standing in a room, when you can look up
and see whether it means one o’clock or not, as in large ones, where it is a
great convenience, and saves the much greater cost of quarters with the two
more bells. It would never do to have a turret clock striking the hours on one
of the quarter bells, as it would produce frequent confusion when they are
heard at such a distance that people would not be sure whether they heard
the smaller bell or not. It was done for some months at Westminster by the
genii who managed and advised things there, as will be noticed afterwards.
When Mears’s Big Ben II. cracked enough to spoil the sound, but no more,
they stopped the striking of the hours on him, and had them struck on the
fourth quarter bell, until I got the confusion that it caused noticed in the
newspapers, and then they resumed striking on the great bell with a much
lighter hammer, which is there still. And for fear that should knock a piece
out of it, like the one in the famous broken bell of Moscow, they put a huge
wooden tea-tray under it to catch the piece, and there it is to this day, with
a hole in the middle for the clapper ‘tail to come through,’ which reminds
one of a celebrated poem of either Southey or Porson, for it is attributed to
both.
QUARTER CHIMES. 123
The locking plate striking is specially objectionable for moveable clocks,
and for any that are liable to run down for want of winding, like the American
ones; because if the striking once gets wrong, or stopped from not winding
up, or let off by accident, or the clock stopped by housemaids, it strikes
wrong afterwards, until it is struck round to the right hour again. The
American clocks have a wire specially provided for this purpose, but the
French have not, and you have to put your finger in behind the left side of
the clock and lift the lever you will feel there, to make it strike as often as
is necessary to bring it right; which is a great nuisance, and in some cases
almost or quite an impossibility. Striking on springs is a bad imitation of
a large bell, and is very inferior to a common bell, except when heard very
near.
Quarters.—If the clock is to strike the quarters, a third ‘part’ or train
of wheels is added on the right side of the going part, with as many bells and
hammers as may be required. There is indeed a method of making the same
striking part do both for the hours and quarters, by sliding the hour hammer
tail out of gear with the pins, and the quarter hammer tails into gear, and
vice versˆa; but it saves very little in cost, and is very seldom used; and it
requires a much heavier weight or stronger spring, and stronger wheels, if it
is to be done effectively. In that case there can be no quarters at the hour;
but that is of no consequence, and perhaps rather an advantage with ding
dong quarters. The construction of a quarter part is substantially the same
as of the hour striking part. If there are only 2 bells, the 2 hammers are lifted
by pins on each side of the striking wheel, or they may be the same pins if
the arbor of one hammer is put above that of the other. They should be so
placed that the interval between each pair of blows, or each chime, is twice
that between the blows of each chime, whether there are 2 or 4 bells. When
there are more, the interval between each chime requires to be as much as
3 spaces instead of 2. When there are more than 2 bells the hammers are
worked by a chime barrel, because the chimes are not generally the same
thing repeated, as they are with ding dong quarters. But this belongs more
to turret clocks, under which I shall go more fully into it. The chime barrel
is generally put on the third wheel, but it would require less force to turn
it on the second, for the reason I gave before, that the more wheels there
are between a slow power and a quick work, the more is lost in friction, in
a proportion beyond what anybody would expect. As the barrel naturally
turns in an hour, the proportion of the pinion and great wheel would be just
the same as in the going part.
The quarters may be let off either by the English repeating method, or
by the French locking plate. If they are merely the same chime repeated 2,
3, and 4 times, the repeating movement should be used, as it has the same
advantage as in the hour striking part. But if each quarter is a different tune,
it should not be used, because repeating the striking of the quarters in that
case will throw the whole tune into confusion; though this plain distinction
QUARTER CLOCKS. 124
is often overlooked. The connection between the two striking parts, when
the quarters have the locking plate, is made by that wheel performing the
function of the wheel N in figs. 34, 35, in discharging the hour, as the 4th
quarter finishes.
The repeating quarter movement is not so simple: the principle of it
is this:—The quarters have a rack, snail, &c., just like the hours, the snail
being fixed on the wheel N so as to turn in the hour, and with 4 steps instead
of 12 (see p. 118). The rack is so placed that when it falls for the 4th quarter
(its greatest drop) it falls against the hour lifting piece somewhere between
O and N, so as to raise it and the click C. It is then held up by the lever
marked Qq catching hold of the pin close by it, and as the last tooth of the
quarter rack is gathered up it pushes Qq aside again, which lets the lifting
piece drop and the hour begin to strike.
There is a very simple construction of a clock for striking repetition
quarters only, when it is wanted in the night, by pulling a string which goes
round a spring barrel, and so winds it up as far as it is allowed to go by
the position of the quarter snail on the going part, which stops some pin or
lever connected with the barrel. This may be easily made to indicate half
quarters; for if there are 8 steps in the snail, then at about 50 min. past the
hour the lever could go 7 depths and the clock would strike 3 ding dongs and
one bell more; and it may either begin or end by letting off the hour. This
construction is in substance that of repeater watches, of which the striking
part is both wound up and let off by pushing in the handle.
Quarters–Tunes.—By this I mean chimes not merely repeated. And
as these clocks for halls and rooms have come much more into fashion since
the Westminster chimes were heard, I will give a picture of the construction
I arranged for them in a clock of my own before I designed that clock, and
which was followed in several others made by old Mr. Dent and afterwards
by other makers. The chime tunes themselves I shall leave till we come
to turret clocks. Y, the locking plate, is fixed on the arbor of the second
wheel, which turns once in an hour, driving the chime barrel marked 50
for Westminster chimes, as will be explained afterwards. For the present
it is enough to say that it turns twice in the hour, making 10 chimes, but
the fourth and first quarters together are the same as the second and third
together, and therefore it is not necessary to have a barrel with 10 different
sets of pins on it, but only 5. The wheel on its end therefore has 50 teeth,
and is driven by the second wheel of the train, of 100, which also drives
a pinion of 10 on the third wheel, which consequently turns once for each
chime of 4 bells. That wheel also has two pins in it, P and P0, P being
rather nearer the centre, and they are alternately stopped by the piece at
L projecting sideways from the lifting detent LON, of which the arbor is
carried in cocks from the frame, as you see, its arm OQC being in front of
the front plate of the clock and OL inside, near the back plate where the
third wheel is. The chime barrel is also really set in cocks, not in the solid
QUARTER CHIMING CLOCK. 125
Fig. 36: Quarter Chimes, Striking Part
STRIKE AND SILENT. 126
frame, in order that it may be adjusted as to its teeth after the clock is put
together, which often saves a great deal of trouble, but it would confuse the
figure to show them here. The fly should be longer than will go inside the
frame, to clear the arbor below it, and that also is set in a long cock behind.
The action is extremely simple. The 4 pins in the hour wheel N lift the
long detent a little before each quarter, and then the pin P0 slips under the
stop L, which then catches P, the wheel moving on a very little. At the
quarter the detent drops off N, and before the third wheel or its pins come
round again the locking plate has lifted the detent by the inclined edges of
its notches, such as Q, so high that both pins clear the stop L; the motion of
the locking plate here being much greater than in an hour striking plate like
fig. 35 and figs. 37, 40 afterwards, where consequently a cam wheel turning
faster is required to make the lifting safe. The locking plate keeps up the
detent for 1, 2, 3, or 4 chimes as required, and you see that by this method
they can never get mixed, as they can with the repetition or rack movement.
If they have got to strike wrong they only want ‘striking round’ till they are
right again, and that is easily done thus. You see the right-angled lever
BAD, with Si and St, for silent and strike, against two pins in the frame.
When you lift the tail D to Si the bevelled end B lifts the detent by a pin
in it, just enough to ‘give warning,’ and it cannot fall again. But when
you bring it down again to St the detent does fall and the quarters strike
whatever the locking plate is ready for, which lets you know whether they
require more ‘striking on’ to set them right.
But we have still to let off the hour striking. In large clocks that is best
done independently, as we shall see; but in small ones it is done by the end
of the detent being raised by the snail kind of rise at Y in the locking plate
as the fourth quarter finishes, which lifts C, the rack click of the striking
part (see fig. 34). That is one way of doing it. Another, which I designed for
a later clock of my own, allows the hours to strike even if the quarters are
silenced, by retaining the usual lifting piece of the hours (which in the former
plan is gone) and making the quarter detent stop it from falling again till
the quarters are done—if they are in action; if not it simply does nothing.
The quarters are silenced by pressing a spring against the side of the fourth
wheel, by a slider at the edge of the dial.
Alarums.—If you suppose a short hammer instead of a pendulum fixed
to the pallet arbor or the crutch of either kind of recoil escapement, it would
swing backwards and forwards very quickly, and strike both sides of a bell of
proper size placed so as to inclose the hammer. This is the way an alarum
strikes, and not by the lifting of a hammer at distinct intervals. The hammer
is driven by a wheel like a strong recoil crown escapement wheel (p. 19) with
a spiked pulley or barrel attached to it by a ratchet and click, over which a
rope goes, with a small weight at one end, and a smaller one at the other to
keep the rope stretched and to wind it up by. The alarum can only go when
a stop lever is lifted by a pin on a collar which is fixed on the hour hand
TELL-TALE CLOCK. 127
wheel by a friction spring, so that it can be set to go off at any hour you
like. You must not wind it up till within 12 hours of the time it is intended
to go off, or it will go 12 hours too soon.
Tell-tale clock.—This is said in one of the Parliamentary papers about
the Westminster clock to be an invention of Mr. Whitehurst of Derby, for
watching watchmen and telling whether they are on the watch and in the
proper place all the night. That unpleasant little clock which one hears
striking the quarters 3 or even 4 times in some Westminster Abbey sermons,
is of this kind, and there are some in the lobbies of the Houses of Parliament.
There are a set of spikes sliding in holes in a 24 hour dial, one for every
quarter of an hour, which can be pushed in by pulling a handle in the clock
case during a few minutes of that quarter only. So if any pin is found sticking
out in the morning it indicates that the watchman was either asleep or away
at the time belonging to that pin. The plate carries the inner ends of the
pins over an inclined plate or roller at some other period of the 24 hours,
which pushes them all out again ready for work the next night.
Musical clocks.—Clocks that play tunes—not short quarter chimes,
but tunes of several minutes, either on bells or organ pipes, are not clocks
in respect of their music, but simply musical boxes or barrel organs turned
by an independent spring or weight and let off at the required time by a
lever from the clock. I shall speak of chimes on church bells farther on. And
nothing else occurs to me as belonging to small or house clocks of sufficient
use or importance to require notice. So I pass on to the larger branch of
the art, which has been the subject of greater improvements within the
last 30 years than in the previous century, and has reached a degree of
accuracy equal to that of the best astronomical clocks, and superior to that
of chronometers, and that not only without an increase, but with a great
reduction in the price.
CHURCH OR TURRET CLOCKS.
It may be supposed that as the work of these clocks only differs from that
of house clocks in the size of the hands and the weight of the hammers they
have to move, you have only to enlarge the machinery and the business is
done. But there is a very important fact in the way of that conclusion: viz.,
that as you increase the strength of machinery you increase its weight in
a ratio as much higher as the cube is higher than the square of any of its
dimensions; and when you increase weight you increase friction, and friction
is a word which ought never to be long out of the mind of a clockmaker,
or at least of a clock-designer, inasmuch as the timekeeping part of a clock
is the only machine whose sole business is to overcome its own friction,
resistance of the air, and variations of heat, and to do that in a constant
and uniform manner. And there is this further difference between large and
CHURCH CLOCKS. 128
small clocks: in small ones the force or weight required to work a hammer
of an ounce or two is generally about the same as is required to keep the
pendulum going, and so the two ‘parts’ or trains are about equal in strength;
whereas in large clocks the lifting of the hammer generally requires a great
deal more power than driving the hands and pendulum, and therefore ought
to have much heavier and stronger machinery. Nevertheless the object of
some clockmakers seems to be to make the going train of large clocks as
heavy and the striking train as light as they can.
Pendulum.—I have already treated of pendulums for large as well as
small clocks at considerable length, and there is little to add with reference
to large clocks only. I will only repeat that the construction and suspension
of the pendulum are of primary importance.
The great majority of clockmakers, till lately, set their faces against
compensated pendulums, and used nothing but wooden ones. And so long
as the clocks themselves are no better than they are, it would undoubtedly be
a waste of money to compensate the pendulums, as the escapement errors
will far exceed the temperature one. But when you have got a first-rate
clock in other respects, it is absurd to prevent it from going accurately by
not giving it a pendulum without which it cannot keep the same rate in
hot and cold weather. It is true that a 2 seconds, or even a 11
2 second
compensated heavy pendulum, is a rather expensive affair if well made; and
with a common dead escapement probably the advantage is on the whole
in favour of a 13 ft. wood pendulum of 3 cwt. over a 5 ft. compensated one
of half the weight, which will enable a clock with such an escapement as
I shall describe to keep within a second a week of Greenwich time. The
fashion of extravagantly long pendulums has very properly gone out, as
their inconvenience and liability to be affected by the wind overbalances
any advantage from them in a moderately good clock. There were several in
Yorkshire until lately as long as 56 feet, or 4 seconds: 20 feet = 21
2 seconds,
which old Doncaster church had, is the utmost length I should allow; and
I gave the calculations for a cheap form of compensated pendulum of that
length at p. 41.
Position of clock.—The worst of all positions for a large clock is the
usual one, on a stool on the upper floor of a tower, for the reason I have
already given at p. 64. The best is on stone corbels built deep into the
wall. The Westminster clock lies on independent walls, which of course are
stronger still. Where this cannot be done, cast iron brackets bolted through
the wall will do, or iron beams across the room if it is not very wide. Wooden
beams are not to be trusted. When the clock is fixed as firmly as this, the
pendulum may be hung from the clock frame, if that is itself strong enough,
and the pendulum cock properly fixed to it, or cast with it, though the wall
is generally to be preferred for a long and heavy pendulum, if the clock
stands near enough to it. But again it is inconvenient to have a very large
clock so close to the wall that a man cannot get some access to it from
FRAME. 129
behind. Therefore no general rule can be laid down for the fixing of turret
clocks, except that firmness is the first consideration, to which everything
else must give way according to the circumstances of the tower. I have
already mentioned at p. 64 the increase of arc caused by hanging a heavy
pendulum from the wall instead of a strong wooden frame from the ground;
and as the escapement errors vary inversely as the cube of the arc, the clock
should go more than twice as well with the firmer suspension; and in fact it
does.
Frame.—The old established form of clock frame was a sort of cage of
vertical and horizontal bars, some of which contain the bushes for the pivots
of the wheels, and have to be unscrewed from the principal bars in order
to get any of the wheels out. It was a great improvement on this to fix the
bushes themselves with screws instead of riveting them into the bars, as it
enabled the wheels to be taken out separately, instead of all dropping loose
at once and perhaps bending their back pivots as soon as the front bar was
taken off. Mr. Vulliamy introduced this plan, and old Mr. Dent used it
in the Exchange clock, of which a perspective view is given in Tomlinson’s
Cyclopædia under Horology. But he soon afterwards adopted a still better
arrangement, borrowed in principle from the French, who were strangely
ahead of us in this branch of clockmaking, until shortly before the 1851
Exhibition.
The French clockmakers are entitled to the credit of having introduced
the horizontal frame cast in one piece, with the great wheel set in bushes
or cocks below it, and the smaller wheels above in separate frames of the
A shape bolted to the great one. But much more has been done since that.
Dent’s clock, with a spring remontoire, which I designed for him for the
1851 Exhibition, where it kept better time than had ever been attained
before, for nearly 6 months, will be described afterwards, though even that
has been superseded by the simpler and stronger construction of the gravity
escapement clocks. I will now describe a moderate-sized turret clock of that
kind, for a bell up to 5 or 6 cwt., and therefore only needing the striking part
winding once a week, which will not do for large ones, and striking one at the
ten proper half-hours as before described. This was made for a clock-tower
of my house by Mr. Joyce, of Whitchurch, Salop, the maker of the great
Worcester Cathedral clock, striking on a 41
2-ton bell, and a vast number of
smaller clocks. I ought to mention at the same time that Messrs. Potts, of
Leeds, in 1881, put up a still larger one in the finest clock-room in the world,
about 40 ft. square, in the tower of Lincoln Minster, striking on Great Tom
and four new quarter bells; and Gillett and Bland, of Croydon, who made
the clock for some still larger bells in the Manchester Town Hall. But all
these, and a multitude of others not quite so large, by these makers, and
by Smith of Derby, belong to the class which will be described afterwards,
winding every one or two days in the striking parts. Dead escapements have
now become quite obsolete for all large clocks that are intended to keep time
ARCHITECTS AND CLOCK TOWERS. 130
within the maximum that ought to be allowed, viz. 5 seconds a week; for I
hear that some of these large clocks do not vary 5 seconds a month, except
from some temporary cause. Therefore, although I retain the description
and picture of one pattern of a dead escapement clock farther on, the time
is come to treat the gravity escapement as the standard one for this purpose.
It is very easy too to make this next picture serve for a dead escapement by
putting the necessary A-shaped small frame on to carry the pallets, making
the third wheel which drives the gravity three-legs into a dead pin wheel, as
described at p. 69.
Very few architects have the least idea, or will condescend to learn, how
large a clock-tower must be to hold a clock of moderate size properly, or
bells either. Their notion seems to be that it is the duty of what they call
their ‘clients’—they being the ‘patrons,’ I suppose—to let them build what
they think pretty, and then get other people to make it useful if they can. I
must inform their ‘unfortunate clients’ then, that they cannot have a clock
of the best construction suitable for a bell of only 4 or 5 cwt., and one or
more dials of 4 ft. diameter, unless they provide a clock-room at least 6 ft.
square, and 7 is better, and at least 30 ft. fall for the weights. The frame in
such a tower as that is best built into the wall about half a brick deep at each
end, as mine is, and of course made quite level and firm. It will then be firm
enough to carry the pendulum, without resorting to an independent cock
built into the wall. Mine is about 3 cwt., and just 99 in. long to the bottom,
being 11
2 seconds, which happened to be more convenient than a 11
4 seconds
one, besides being rather better. As it is generally necessary to carry the
ropes up to some place above the clock-room to get all the available fall,
you have to provide space for them also, and evidently more than if they go
straight down from the barrels, which is better if you have fall enough, as it
saves a good deal of friction in several ways. This depends on the height of
the clock-room from the ground, and the use you want to make of the lower
part of the tower, which should all be considered beforehand, but never is,
except by people who look after their own work, who alone get it done well.
Any one who is generally acquainted with clock-making will understand
from this picture more than could be shown in it without confusion. The
barrels, or great wheels of both parts, are set under the frame in bushes of
the construction a and d together in p. 136, so that they can drive second
wheels in bushes of the form b on the top of the frame, which top is about
11
2 wide, and is now always planed in a machine, to carry all the cocks
and bushes quite firm and level. There are three cross bars cast in it at
convenient places, which are utilized also for carrying cocks for ‘leading off,’
for hammer-tails, winding-pinions, and anything else of that kind. The great
going wheel generally has 120 teeth, and is 12 or 13 inches in diameter, and
drives (first) the hour wheel with 40 teeth, on the arbor of which is the
bevelled wheel driving other bevelled wheels up to the dials, both outside
the tower, as usual, and in mine inside also to a dial at the end of a long
SMALL GRAVITY TURRET CLOCKS. 131
Fig. 37: Small Turret Clock with Gravity Escapement
SMALL GRAVITY TURRET CLOCKS. 132
passage in the house. That leading off goes downwards obliquely, and is
omitted in the picture. The half-hour snails, with the main bevelled wheel,
are clamped to the hour wheel by thumb-screws, to enable you to set the
hands when necessary; and it drives no more wheels in the train, because it
makes a better distribution of the teeth to leave it independent. The great
wheel therefore drives the one marked 100 with a pinion of 10, which will
turn in 15 minutes as the 40 wheel takes an hour, whatever may be the time
of the great wheel, which is generally made 3 hours in these clocks. The
15 min. wheel of 100 drives another pinion of 10, ... in 1.5 min., and that
having a wheel of 90 drives the scape-wheel pinion of 9, which, with the
double three-legs and a 11
2 -sec. pendulum, turns in 9 seconds. But if the
pendulum is 11
4 sec, the scape-wheel will turn in 6 × 11
4 or 71
2 sec., and its
pinion must either be 8 driven by 96 or 9 driven by 108.
In all clocks of this kind the pallet-arbors are set in small cocks, on the
large one which carries the pendulum, and the scape-wheel itself has only
a short arbor in 2 cocks behind the other wheels. The pendulum swings in
a long slot in the flange at the top of the frame, reaching from one cross
bar to the other; and the escapement fly also in another space, with the two
three-legged wheels between the back bar and another which carries all the
wheels. There is room enough for all this, and a sufficient length of barrel,
in the width of frame that the striking part requires, which is always a good
deal more than the going part, on account of the greater thickness of the
rope, and the cams and levers and the winding wheel. The frame is generally
41
2 in. deep, with a wide flange turned inwards all along the top, to set the
various cocks on.
There is a little inconvenience in the third wheel turning in 11
2 min. instead
of either 1 or 2, as you want an index of some kind to mark seconds
for regulating, unless you go entirely by the striking. But this train distributes
the teeth so much the best that I adhere to it, and get over the other
difficulty either by a pair of small wheels in the proportion of 3 to 2, the
smaller carrying a seconds hand, or else depend on an index placed over
the rim of the 90 seconds wheel, which is graduated up to 30, so as to give
the seconds in every half-minute, leaving you to see by the other dial, on
the hour arbor, which half-minute it is. With a 2-sec. pendulum there is no
such difficulty; for the scape-wheel then turns in 12 sec, and its pinion of 10
driven by a wheel of 100 lets that wheel turn in 2 minutes; and that may
have a pinion of 10 driven by 100, which will turn in 20 min. instead of 15,
and consequently wants a pinion of 12 to an hour wheel of 36. Several other
numbers also would do; but we shall see afterwards how the second wheel
may be used to obtain greater precision in the time of beginning to strike
than you can get from an hour snail, a good way off the escapement too,
if the second wheel turns in 15 or 20 minutes. And if you want to apply it
to the half-hour striking also, which only requires two pins (T in fig. 40.,
p. 140) instead of one, it must turn in 15 min. The great wheel need not
WIRE ROPES BEST. 133
turn in any particular time. Sometimes I have had them for 4 hours. In
the Westminster clock it was convenient to have it turning in 3 h. 45 m. A
minute-hand is, or should be, always set on the hour-wheel arbor, with a dial
to set the clock by, which is best done by letting the gravity escapement run
or stopping it for the necessary time, which is another advantage of these
clocks.
Wire ropes.—The introduction of wire ropes, instead of the old hemp
ones of 5 or 6 times the thickness, did a great deal towards enabling the
barrels and clock frames to be made smaller than the clumsy things of old
times, which it is no longer necessary to describe, as wire ropes and iron
barrels have become universal. But I find it is still necessary to warn people
against using zinced wire ropes. I found long ago that for some reason or
other zincing iron wire or sheet iron tends to make it brittle, and sometimes
the zinc splits off, while tinning it has the contrary effect; only it does very
little towards preventing rust, for galvanic reasons. But the best way of
preventing rust on wire ropes is to keep them well greased with a mixture
of tar and grease. Paint splits off with the bending of the ropes.
Striking from the great wheel was another important improvement
which followed from the use of wire ropes with many more turns of the
barrel for one winding up, and especially those of steel wire, which may be
thinner still. The saving in friction, and consequently in weight, and the
strength required, is more than any one would suppose; and that also has
become universal in all clocks, except those of makers who have steadfastly
set their faces against all improvements, and consequently never dare to
accept contracts guaranteeing the rate of time-keeping prescribed above, or
the raising of hammers that will bring the full sound out of bells, which the
old clocks never did. I will explain afterwards the construction of the cams
which are now generally cast on the great wheels, but in very large clocks
are also faced with steel. For an eight-day striking part I have come to
the conclusion that the best arrangement is to have about 18 cams working
two hammers, so that each hammer-tail and cam has the same action as if
there were only half the number of cams. In some of Dent’s earlier clocks
the hammer-tails were on opposite sides of the wheel, with two sets of cams,
each having half the number. But this is unnecessary if they are placed as in
fig. 37, keeping quite clear of each other, which is easily managed, taking care
to place them so as to make the intervals between the blows exactly alike; i.e.
their centres must be on prolonged radii of the wheel, 11
2 cams apart. The
reason for having 2 hammer-tails instead of one shorter and working over
half the space, is that the pressure of such a short lever sometimes cuts off
the ends of the cams if the lever end was not blunted enough, though there
are plenty of such clocks going without any such result. On the whole it is
better to avoid the risk, except with small bells not above 2 cwt., which only
want hammers of 4 or 5 lbs. If there are 22 or 24 cams, of course the teeth of
the great wheel, and of the small one on it, which drives the locking-plate,
STOPS FOR WEIGHTS. 134
must be increased; and remember that when there are two hammers that
36-wheel must still be twice the number of the cams, as each cam strikes two
blows. I assume the locking-plate wheel to have one tooth for every blow
struck, though you may vary the number if you keep the right proportion;
e.g. you might have 30 and 66, instead of 40 and 88. Both these wheels are
in front of the frame. The great wheel of 108, or 3 × 36, drives a pinion of
9, which therefore goes one third round for each blow, and accordingly has
3 cams to lift the detent. The winding pinion should pump into and out of
gear, as there is no use in giving the clock the friction of turning it. Its back
pivot is accordingly set in a cock bolted to the cross bar in the middle of
the frame, with a key that drops into a nick round the arbor to keep it in
its place. In the drawing it looks as if the second hammer lever pivot was
in the winding-pinion one; it is only optically so, as they say of stars, which
may either be really inside a nebula or billions of miles behind it.
The half-hour striking arrangement has been already described with reference
to this (see p. 120). The jumper spring is on the right side of the 24
ratchet wheel with the 121
2 and 11
2 o’clock steps on it.
Returning to the going part, the maintaining power which I always prescribe,
except for very large clocks, has been already described (p. 107).
Some clockmakers found, after much trouble (of which they were warned
before), that the spring-going ratchet will not do for gravity escapement
turret clocks, except very small ones. Where the dials are so large as to
require more weight than can be wound up without an auxiliary pinion like
the striking part, I think the Westminster maintaining power is the best (see
also fig. 40); though this one in fig. 37 does perfectly well, and is generally
used for larger clocks.
Stops for weights.—Where the weights do not go down to solid ground
there ought to be a large box full of broken stones, not gravel, for them to
fall on if a rope breaks. The reason why stones are the best is that they
give the weight something to do in breaking them a little more, which uses
up a good deal of its force. Sawdust or chips are too elastic, and sometimes
throw the weight off on to the floor, and therefore through it, as happened
at St. Albans lately, from over-winding. Gravel is too hard to break, but
still gravel or even sand will take off a great deal of the force of a blow in
displacing it; but I am convinced that stones are the best. They may be
covered with a thin board, to look tidy. Their depth should never be less
than 2 ft., and more according to the bigness of the weight and the possible
drop. But another kind of stop also is requisite where the weights go out of
sight, to prevent over-winding, i.e., winding right up to the fixed pulley. A
mere straight stop to catch the top of the weight will generally do, because
it gives check enough to make any man who is winding feel it, though of
course there is a little risk of the jerk and strain, for which extra strength of
rope must be provided; but this will not do when a great multiplying power
has to be used. Nor is it at all safe to rely on human stupidity attending
FOUR-WHEELED TRAINS. 135
to any mark on the rope, which there was at St. Albans, even if there is
always light enough to see it and the real winding man is told about it, who
is probably a mere blundering deputy of the one who ought to do it. At
Westminster, you will see farther on, that I provided an absolute stop to
the turning of the handles beyond the proper times, both when the clock
is going to strike and when it is fully wound. But ropes on long ungrooved
barrels do not travel uniformly enough for that method to be adopted with
them; and besides that, the ropes often overlap, though they had better not.
It would be easy enough to make each weight raise a lever with a sort of
click to it, which would ring a bell when the weight has got to the top, in
several ways. And now that electricity is coming into use for everything, the
weights might make a contact to complete an electrical circuit when they
reach the top, and so might make any kind of noise which the winder could
not fail to hear, or drop a lever to stop him.
When the weights do not hang from the barrels, but the ropes have to
be led off to a fixed pulley somewhere, it is necessary that it should be so
far off and in such a position that each rope may feed straight off and on
the barrel, without either separating or grinding against itself. It is so much
better to let them hang down, that I would rather have them hang so by 3
lines, which requires no more pulleys, and only two-thirds of the height of
2 lines, than lead off for anything less than 15 or 20 times the length of the
barrel. But more than 3 lines increase the friction enormously, and should
never be used; nor should 3 together with a fixed leading-off pulley, which
makes 4 lines or 3 pulleys. The weights in this clock go down within the
frame, close to the walls, and are boxed all the way down. Even if they did
not, the tower must not have been much smaller, on account of the fly, in
which length is of great value always for steadiness of striking, and you must
have a reasonable space for the handle to turn in winding, even if it goes
the right way, as it does here, not requiring the man to stand beyond it.
Four-wheeled trains.—These horizontal frames evidently require rather
more length than a well-arranged cage frame, in which the wheels stand over
each other, and they would require still more to contain a four-wheeled train.
Turrets are sometimes made so small that a horizontal frame clock even of
3 wheels cannot be got in. The clock can be got into less length by making
the frame something like a pointed arch, which is also a strong form. Many
years ago I designed some small quarter clocks for a confined space, to be
sent to Mexico, and the arrangement on page 138 brings the work within the
smallest possible limits. I believe they were the strongest clocks of the size
that had ever been made. There are no loose bars whatever to the frame,
and instead of cylindrical bushes (fig. 38 a) which can only be let in near
the middle of the bar, the bushes are mostly of the form c, which admits
of greater variety of position, and also enables the wheels and other pieces
to be taken out singly with greater facility than the let in bushes. Another
bush, which is used in clocks with horizontal and arched frames, is that at
FOUR-WHEELED TRAINS. 136
b, which is the best of all for convenience of fixing, and adjusting the place
of the wheels, and taking them out separately.
There is yet another kind of bush which I used first at Westminster, and
it is the best for the barrel arbors of clocks with a horizontal frame. A hole
of the shape d, is cut out of the piece, which is then cast as a projection
downwards from the frame, large enough to hold a bush of the form a, and
with a slot below just wide enough to let the arbor drop when the bushes
are pulled out. Otherwise it is necessary to bolt large pieces, or cocks, on
to the frame, and the back piece is sometimes difficult to get off. I shall call
these ‘drop-bushes’ accordingly. At Westminster they are not used for the
barrels, but for the third wheel arbors which drive the flies.
In connection with bushes it is necessary to warn people against making
oil holes in them, which is sometimes done from overlooking the difference
between the slow-going pivots of clocks which do not need oiling once a year,
and the quick ones in other machines which require constant feeding with
oil or they will heat. Such holes in clock bushes are very soon drained of
oil and become receptacles and feeders of dirt and grit. What little oil is
needed easily works in from the ends of the pivots, the old oil being first
wiped off. I shall say a little more about oil at the end of this part of the
book.
Fig. 38: Different Kinds of Bushes
Fig. 39 is a front elevation of those Mexico clocks, showing as much as can
be shown at one view without confusion, and representing the wheels only as
circles for the same reason. They have 1 sec. compensated pendulums with
bobs of nearly 11
4 cwt.; where there is room, of course it would be better
to use 11
2 or 13
4 sec. pendulums. They are calculated to strike the hour on
a bell of 4 or 5 cwt. with quarters in proportion, and will drive four 6 ft.
dials very well. The whole length of a quarter clock on this pattern is only
30 inches, and for one without the quarters 21 inches. The flies may require
LARGE FLIES BEST. 137
rather more, according to the size of the hammers. One fly may go behind
the other if necessary. Those who build clock-towers should remember that
there must be room for a man to stand and wind up the clock besides. The
hole in the upright bar where the pallets are shown, is only in the back bar,
which is widened out for it, and the two lumps which form the pendulum
cock are cast on the back. The cross bar which carries the locking plate
78 is only wanted on the front frame, and is omitted on the back one, as it
would interfere with taking out the barrel. All the levers are so placed as to
clear the ropes when they have to be taken upwards. The small cam wheel
for lifting the locking lever of the striking part answers very well: that of
the quarters is in fact the locking plate itself. If there are no quarters at the
hour, the pinion of 20 should be 30, and drive a separate locking wheel of
36, which will turn in 2 hours, as 12 cams are used in that time.
Size of fly.—There is no more frequent mistake in turret clocks than
that of making the fly too small to preserve uniformity of time in striking,
and the defect is generally incurable for want of room. When the fly of the
hour striking part is too small the velocity increases after the first few blows;
and with quarters on four bells especially, some blows come quick and others
slow, according as the heavy or the light hammers are being raised. You
must have a considerable superfluity of force beyond what will just raise
the hammers, and the regulation of time must be done by the fly. I do not
however see my way to prescribing any rule for the size in proportion to the
weight of hammers or bells beyond this, that each arm of the fly of any large
church clock ought to be fully 2 ft. long; and for the very large bells which
have lately come into fashion again, the flies must be still longer. Length is
much more effective than width. There may be from 4 to 8 turns for each
blow or each quarter, according to the size of the clock. At Westminster we
could get no uniformity of striking quarters with a fly going faster than 4
times to each chime; 6 or 7 is generally the best number.
When it is impossible to get room for flies of proper length and size to
equalise the time, something may be done by using a three-armed fly, but
that is by no means equal to one with two arms of sufficient length.
I find it necessary to add, that the flies should on no account be in front
of the clock, for that involves the use of a winder with a very long pipe to
clear them, which is harder to wind and strains the arbors. Fig. 47 will show
how to get plenty of room for them behind in clocks of almost any size. In
very large ones, such as Westminster, a vertical rod may be carried up and
the flies put quite away at the top of the room. I have seen it done also in
much smaller clocks where there was no room otherwise for the flies.
LARGE FLIES BEST. 138
Fig. 39: Four-wheeled Train Clock
LARGE QUARTER CLOCKS. 139
LARGE CLOCKS WITH QUARTERS.
Fig. 40 (t. o.) is a front view of a larger clock than those previously described,
substantially according to the plan which I settled for old Mr. Dent’s factory
many years ago, whereby we reduced the cost of large quarter clocks to little
more than a quarter of what it used to be, and at the same time greatly
increased both their accuracy and strength. This only shows two quarter
hammers for simplicity. Indeed four could not be shown in an elevation, as
the levers must then all be on one axis or pin, and the cams come irregularly,
as will be explained under quarter chimes. As Fig. 37 was of an eight-day
clock, to which a quarter part might be added much like the hour part, this
is of larger clocks, with heavy bells, and winding up the striking parts every
day or two days, according to the available fall. It is impossible to strike
heavy bells properly with an eight-day clock unless it has a very unusual
fall, and even then it would want very inconveniently long barrels, and the
old-fashioned clocks never did strike properly.
The hour great wheel here has only 10 cams, which I consider the best
number for the arcs that have to be described by the cams and the hammertails
or levers, when we are free to use any number, which we cannot in
eight-day clocks. Therefore this requires only 16 turns of the barrel for 24
hours, or 156 blows, and 2 or 3 more for a few extra hours; or say 35 or 36
turns for winding every two days; and therefore quite short barrels will do,
with wire ropes as much as 1
4 in. thick, which are enough for all but very
large clocks beyond the ordinary patterns.
The going part is always made to go a week, or rather 8 days and a
fraction, to provide for the forgetting of a day.
It is impossible to give any rule for the size of the great wheels, as it
clearly ought to depend on the work they have to do. For bells from about
30 cwt. to 53, a common range for the tenors of large peals, an 18-in. great
striking wheel is the best pattern to keep, as it is inconvenient to use many.
A 24-in. wheel with only 10 cams of proper size and strength will do very
well for bells up to 5 or 6 tons, or even 10 tons, if the teeth and cams are
wide enough. The great going wheel may be from 13 up to 16 inches for
any four dials from 7 up to 12 feet, and there are very few larger. The other
wheels may be in proportion. The scape-wheel legs should be from 5 to
6 inches long, and you must allow plenty of room for a long fly, not less than
9 or 10 inches, especially for large dials, which should have a considerable
superfluity of force, to drive the hands in all weathers. For that reason the
scape-wheel arbor is put on a higher cock than before. The pendulum is
carried in the same way by the frame. If it is a very large one it is well
to put one or two brackets or strutts from the wall to the back part of the
frame near the pendulum, but that is not necessary generally, as this kind of
frame for 18-in. great wheels is only 5 ft. 6 in. long, and forms a kind of arch
when its feet are firmly bolted to the corbels, which I need not say should
LARGE TURRET CLOCK. 140
Fig. 40: Large Quarter Clock
DISCHARGE OF STRIKING PARTS. 141
be a great deal deeper than there was room to show in this drawing. If they
are iron brackets they should be built into the wall and wide at the top also,
to prevent any risk of sideway motion under the swing of the pendulum.
For 10 cams the great wheel had better have 100 teeth, and the pinion
10; or 120 and 12 of course run rather easier, which pinion will evidently go
once round for each blow. But if you want the clock to go 4 days without
winding and to have only one hammer, 16 cams will be better, and 192 teeth
in the great wheel, driving a pinion of 12 two-thirds round for each blow.
And then you may make the cam wheel on that pinion with 2 hollows in it
one-third and two-thirds of the circumference apart, and they will always
come right, because the number of the hours is odd and even alternately, if
it is put in the right position; which you will find more easily by trial than
by explanation here. But this would not do when half-hours are struck by
the hour part, for two odds then often come together, such as 3 and 1, 5
and 1, &c. The general calculation for all numbers is this. Let p be the
leaves of the pinion, which must be a multiple of 3 if you are to use that
method; n the teeth of the great wheel, and m the cams. Then 2
3p must
= n
m or n = 2
3mp: p must be taken as 12 for this purpose, and ... n = 8m.
If p has 10 leaves and is only to go once round, n must evidently = 10m.
It is not convenient to have two large hammers with a ringing peal, as it
is difficult to get room for them in the frame, though it is easy enough for
stationary clock bells. But it is unnecessary to consider all that if the clock
winds up every day or two, which is always best for large ones. A few cocks
and bushes are omitted in the drawing to avoid confusion.
In other respects this striking part is the same as in fig. 37. But I now
show the plan for letting off the striking of the hours more exactly than can
be done by the slow motion of the hour wheel and its snail, especially as it
is a sort of outrider to the train. This was first done in the Westminster
clock, but the plan now described for the first time was not expedient there
on account of the great size and weight of the discharging levers. Here you
see that the long lever or detent DS is carried over to the second wheel of
the going train, which has a square pin T on one of its spokes; and there is
another square pin S on the detent, now shown below the other, the clock
having just struck. But at some minutes before striking S gets raised above
the circle in which T moves, which can be done, because at that time T is
out of the way. Just before the detent is going to drop off the snail T has
come under J, and J cannot fall again till T slips from under it, which will
take place with perfect accuracy at the last beat of the pendulum for the
hour, as the motion is large enough to be visible, and a very little way off
the scape-wheel. This is inconsistent with altering the hands less than 15
or 20 minutes, except by running the clock, as you easily can with a gravity
escapement. In the Lincoln Minster clock Mr. Potts provided in this way
for the quarters also, as did Messrs. Smith at St. Paul’s and Beverley, which
however are not of so much consequence as the first blow of the hour. The
WAY OF FIXING TWO QUARTER LEVERS. 142
second wheel must in that case turn in 15 minutes; but without the quarters
it may be either 20 or 15. The pins S and T should be so placed and shaped
that the pressure may not tend to stop the wheel. (See also p. 281.)
As I have already shown the maintaining power which is best for clocks
not requiring an auxiliary winding wheel, I show here the one which is best
for those that do; though the other, of which a piece is shown at B, may be
used for them. This is the one that I designed for theWestminster clock, and
the principle of it will be described there. The winding pinion and the bars
which carry it, the front one fixed and the back one hanging from the arbor,
are out of the vertical, because the action of gravity is wanted to make the
pinion and back bar which carries it fall on to a fixed stop, when the winding
is done, or suspended for a short time. The back bar also carries the click
which takes into ratchet teeth cast on the back of the great wheel. It might
go into the other teeth, but for the risk of catching only on their tops and
slipping, so that ratchet teeth are safer, and practically cost nothing when
once the patterns are made to cast from.
The arrangement of the quarter part for 4 bells is practically the same
as for 2, except that all the levers must be on one steel pin, which should be
screwed tight at its ends to help to keep it stiff. Either for 2 hammers or for
4, the best way is to cast one set of cams on one side of the great wheel and
another on the other, at the proper distances to make the interval between
successive chimes at least twice as great as between the blows in each chime.
For 4 bells two other sets of cam rings may be cast in one, and all bolted
together. Some clockmakers prefer an independent cam barrel driven by the
great wheel, to which there is no objection except the extra friction, which
I once found to make the difference of requiring an auxiliary winding-wheel.
When steel cams are used they are all bolted to a wide ring or barrel cast
with or bolted to the great wheel, the nuts being inside it. I shall have more
to say about cams afterwards. Four quarter hammer-tails cannot well be
turned inwards as the hour one can, in the form which makes the pressure
on the arbor only the difference instead of the sum of the two forces on the
lever. But they can have their wires in the middle, instead of their fulcrum
or arbor being there, as you see in the Westminster clock, and in that way
the friction on their arbor is reduced to a minimum, the wires being put as
near the cams as possible. (See also p. 281)
Two quarter hammers—or two alternate hour hammers—can also be
placed as in this fig. 41, which I designed long ago with the same object of
keeping the power and the work on the same side of the arbor, and many
large clocks were so made at Dent’s factory. It involves cams on both sides
of the great wheel, which are as easily cast as on one side. The rope also
should always pull on the same side of the barrel as the cams, in order that
the pressure on the great arbor may be the difference instead of the sum of
the weight and its work, and consequently the friction much less. You may
fancy that these frictions of pivots, and of teeth when the cams are not on the
CAMBRIDGE AND WESTMINSTER CHIMES. 143
great wheel, cannot come to much compared with a great striking weight,
or a hammer of many pounds weight raised 9 in., or about 6 vertically, 156
times a day; but you will find very few clocks in which the weight × its daily
fall is not more than twice or even three times its theoretical ‘duty,’ or the
hammer × 78 ft., which excess is all due to these various frictions.
Fig. 41: Two-quarter Hammer
If no quarters are struck at the hour it is better to have 12 cams, the
locking-plate being on the great wheel arbor, so that they will turn in
2 hours. In that case the pinion may as well be of 12, driven by the great
wheel of 96, and therefore turning 2
3 round for each quarter chime as before
described for hours in some cases.
Lifting the hammer by pins on the striking wheel, as in house clocks, is
totally wrong in large ones, and it is nearly discontinued. The pins necessarily
begin to act a good way from the end of the lever, and therefore at
the greatest disadvantage as to leverage, and that at the very time when
the hammer is rising most vertically (in the usual way of hanging) and requires
the most force to lift it. The lifting should be done by cams, which
begin to act on the end of the lever, and are properly shaped to act with
the least possible friction throughout, as I shall explain under the Teeth of
Wheels. Pins with rollers on them are of very little use, and do not obviate
these objections, and are weaker than fixed pins: they are nearly if not quite
abandoned.
Cambridge and Westminster chimes.—Considering the thousands
of men who had listened for 3 or 4 years together to the famous St. Mary’s
chimes at Cambridge, during three quarters of a century, it is odd that no
DONCASTER QUARTERS. 144
one ever thought of copying them in any other public clock. The last but
one Lord Lansdowne tried it, but his clockmaker Mr. Vulliamy made the
mistake of ordering and hanging the bells of four successive notes before
writing to ask me about them; whereas they ought to be such notes as E,
D, C, G; or the fourth bell must be a musical ‘fourth’ below the third: bells
are always counted from the highest note or smallest bell. At the Royal
Exchange, in 1845, they did get so far as to adopt the Cambridge notes; but
the Gresham professor of music thought he could improve upon the tunes,
and spoilt them. I have been told by a Cambridge man of the last century,
that they were invented by the well-known Dr. Crotch in 1780, from an air of
Handel’s, who has generally had the credit of inventing them, and perhaps
deserves it.
Doncaster quarters.—For some time after I thought of introducing
them at Westminster, it was assumed that the hour bell must be an octave
below the third quarter, and that they were therefore impossible with a peal
of only 8 bells, if the quarters were to be struck at the hour. Moreover
playing 10 chimes in every hour, requires nearly twice as much power in
the clock as playing 6, which is sometimes a consideration when there is
not much fall for the weights, and it makes a little difference in the cost.
Again, if you look at the Cambridge chimes (p. 145) you see that the blow
on the lowest quarter bell (called 6), is repeated too quickly in one place
for a heavy hammer to be relifted immediately; and accordingly in all very
large clocks it is necessary, and it is always desirable, to have two of those
hammers, lifted alternately. Avoiding it by a separate barrel, driven by the
great wheel, is a much worse plan. For all these reasons, in a few church
clocks, made before 1860, I adopted the plan of omitting the quarters at the
hour; but I should not do so again with these quarters, because the hour
chime is the best of them all, though ding dong, or any other mere repetition
quarters, are neither useful nor pleasing at the hour. I also made a slight
alteration in the third quarter in those clocks, to avoid the quick relifting
of the largest hammer, and it sounds very nearly as well as the Cambridge
one. The quarter bells are therefore, 2, 3, 4, 7, of a peal of 8 at Doncaster
and Scarborough parish churches, and the cathedral at Fredericton, where
the three-legged gravity escapement was also first used.
Worcester and Chester Cathedral.—But after a time I came to the
conclusion, and other people have gradually adopted it, that it is not at all
necessary to have the third quarter bell an octave above the hour bell, and
that the ear is quite satisfied if the fourth bell is two notes, or even one,
above the hour, because the interval of time between the quarters and the
hour ought to be from 6 to 10 seconds with large bells. Accordingly in the
great peal at Worcester, the Rev. E. Cattley, the author of it, and I, as
the designer of the clock and bells, agreed to take advantage of the tenor
of the peal for the fourth quarter bell, though it is only 11
2 notes above
the great single hour bell of 41
2 tons; and thereby we got far more powerful
QUARTERS ON FOUR BELLS. 145
quarters than if we had kept them 2 notes higher. At Chester Cathedral,
and St. Chad’s, Headingley, near Leeds and some other places, the 4th
quarter bell is only one note below the tenor, as at Doncaster, though they
are the full Cambridge quarters; and that is the plan which I now always
recommend when there are 8 bells, or even 6, with an extra one added above
for the first quarter. At Ossington Church, having only a small peal of 6,
I recommended to my namesake the late Speaker, a lower bell (out of the
peal) for the hours; and the same at S. Shields lately.
The following are these several arrangements, which are suitable for any
key, and therefore I have indicated them by the bells in a peal of 6, which
these quarters require, leaving the hour to be any note below the lowest
quarter bell.
Cambridge and Doncaster and Royal Exchange.
Westminster. Scarborough.
2nd n31269>
=>
;
4th
1st 1236 1st 3126 o 2nd9>
=>
;
4th
3213
2nd n3126
3rd (6213
3rd (1326 3213 1326
6213
3rd (2613 3213
1236 1st 6213
I call the bells 1, 2, 3, 6, in all cases for more easy comparison, though
they would be of various numbers according to the peal they belong to,
on account of the numbers being always reckoned from the smallest, in the
order in which they ring. Indeed a peal of 6 could not have these chimes
at all without an odd bell, either above as at Headingley, or below as at
Ossington.
You see from the table that the Cambridge chimes are repeated twice in
the hour, and therefore the cams may be fixed on a barrel which turns in
any multiple of the 5 chimes in that table. In some clocks the 5 sets of cams
alone are put on a barrel driven by the great wheel, but with much more
friction than in other clocks that I know with bells of about the same weight;
one, with this second barrel, required a double multiplying power to wind
it up, while another, with the cams for an hour on the great wheel itself,
winds quite easily with a single pinion. At Westminster, as you may see in
the frontispiece, there are 3 sets of cams, or what may be called an hour
and a half’s chimes, on the great wheel, i.e. on a wide barrel attached to
it, because it happened to be convenient with the great fall we have there.
The cams may be cast in separate rings of cast steel, but it is better to
have smooth-faced steel cams screwed firmly to a plain barrel, as they are
at Westminster, and in all the best very large clocks now.
The interval between each chime (i.e. between the chimes of each quarter)
requires some attention. At Cambridge it is 3 times the interval between
the blows of each chime. That appears to me decidedly too slow, and at
LIFTING OFF HAMMERS. 146
Westminster, Doncaster, &c., I made the interval only two spaces instead
of three. That again is perhaps rather too quick, and at Worcester, and all
the subsequent large clocks for which I have given designs or specifications,
there are 21
2 spaces, which sound the best of all. The barrel, or each portion
of it which contains the 5 chimes, must then be divided into 55 spaces, of
which each blow occupies 2, and the intervals between the chimes 5 spaces.
When there are two hammers for the 4th bell, as there always should
be, those cams may, and should be, made longer than the others, as there is
then ample room for it; which diminishes the pressure on them, and makes
it more continuous, and so tends to equalise the time. This is important,
because the 4th quarter bell is much the heaviest, and there is the least
interval between its blows.
In all quarter clocks, striking on a peal of ringing bells, provision should
be made for lifting off the hammers, or they are almost certain to be broken
when the bells are rung, and perhaps the bells cracked besides. This is easily
done by a lever; or, when the hammers are very heavy, it is better done, as
Mr. Cattley arranged at Worcester, by an eccentric brought down over all
the levers just where they come out of the clock. The hammers must not
only be lifted off the bells, but so high that the cams do not lift them at all,
or all the wires will soon be broken by the jerks. And as the clock is thus
relieved of its work, it is better also to make the turning of the eccentric, or
pulling down the lever, let down a wooden brake on the fly arbor, to help
the fly to stop the velocity and diminish the blow on the stops.
Quarters on two bells.—I have little more to say about turret clocks
with these than I said about house clocks at p. 123. The bells must be at
the musical interval called a fourth, and the higher of the two should be an
octave higher than the hour bell if there are quarters at the hour; though
that is not so material, and they may be the 1st and 4th of a peal of 6, or
even 5, or the 4th and 7th of a peal of 8, because there should be a longish
interval of time between the quarters and the hour, which saves the ear from
being offended with the want of the proper musical interval. The old York
Minster quarters, and a few others, were at the interval of a fifth (which in
music, though not in arithmetic, is larger than a fourth), but they do not
sound so well.
Time of striking.—The quarters are generally made to let off the hour,
as described at p. 126. But where accuracy of time of striking is required,
this plan is insufficient; for it makes the first blow of the hour depend on
the time both of letting off, and of striking the quarters, both of which may
easily vary several seconds. It is therefore essential to accuracy that the
hour-striking should be let off by an independent snail of its own, exactly
at the hour, with the quarters let off the requisite number of seconds before
the hour; though the other three quarters may be allowed to strike at their
proper times. Even this is not sufficient where extreme accuracy is required,
as I have already explained. The hammer should also be left ‘on the lift,’
CHIME TUNES. 147
or nearly ready to fall; which is in other respects also a good thing in a
very large clock, because it relieves the wheels and the stopping pieces from
a heavy pressure, and throws it all on the cams and hammer work, which
must in any case be strong enough to bear it. In this case it is necessary
to put a small click somewhere, to act on a pin in the fly arbor to prevent
the train from running back when you wind up the clock: indeed it is as
well to put one always, as the winding always tends to drive the train back.
Where there is no special provision for accurate striking, as above, care
must be taken to make the discharging snail large, and its corners sharp and
hardened, and those of the discharging lever or lifting piece also. See also
p. 141.
Chime tunes.—There has been a considerable revival of the old fashion
of having tunes played on bells by machinery for a few minutes at certain
hours of the day. The old machinery for this purpose was extremely simple,
consisting of a large barrel 2 or 3 feet in diameter, generally made of wood,
with strong iron pins screwed into it like a huge musical box barrel, and
pulling down levers which lifted hammers on the bells like a common striking
part. If there were several tunes on the barrel, either that or the bed of levers
had an endway motion, shifting at the end of each tune, or shifted once a
day by the clock. The Royal Exchange chimes are of this kind, only the
barrel is of cast iron, with a vast number of holes in it, in which pins or
short cams are screwed to play any tunes that the bells admit of.
Some new ones of the old kind have lately been put up in St. Albans
Cathedral by Mr. Godman, a clockmaker there whom I have mentioned
before, entirely from his own design. The barrel is 7 ft. long, of wood on
iron rings, and the levers are worked by cams of ‘phosphor bronze’ screwed
on, for 8 tunes on 8 bells, which I think are quite tunes enough, and more
than were generally used in old times. The tunes shift themselves. The
Westminster quarters are also put there on the same plan and in connection
with the chimes in a room above the clock. Notwithstanding the superiority
of those I am going to describe next when constantly looked after by a
competent person, which they require, and which of course costs money, I
have returned to the opinion that for ordinary churches, where there are
seldom any funds to spare, the old-fashioned chimes are the best.
The chimes in some foreign churches are played by hand, I understand,
without anything that can be called machinery. The hammers, being light,
are easily lifted a little by a man playing on keys like a piano, only with his
fist instead of his fingers. I have seen tunes played on church bells here with
even less machinery than that. They just tie the bell-ropes to the clappers,
and the lower ends to rings on a board screwed down to the belfry floor,
bringing the clappers so near to the bells that a slight pull will make them
strike. The man ‘operates’ them (in American grammar) by pulling some of
the ropes with his hands and pushing others with his arms, and so manages
to play a feeble sort of tune.
CHIME TUNES. 148
NEW CHIME MACHINERY.
The new kind just now referred to were introduced by Gillett and Bland
of Croydon, and by Lund and Blockley of Pall Mall, both of whom bought
some patent rights of an inventor named Imhoff, and have both made improvements
of their own. The principle of the invention consists in this, that
the hammers are raised by a long barrel full of cams which have nothing to
do with dropping them, but are continually at work raising any levers that
happen to be down. The levers are then caught and held by triggers, which
are let off by quite small pins on a wooden barrel just like that of a common
grind-organ. The barrel can also be taken out and changed, besides each
barrel holding several tunes which change themselves by an endway motion.
This figure shows Gillett and Bland’s mode of lifting. Each lever has a
jointed beak which is lifted by one of the 7 cams on the barrel belonging to
that lever; and when it has been caught by the trigger at the other end the
cam slips away, and the beak drops, so as to clear the cam next below, and
gets caught again by the next to that, because it falls on to a block which
stretches out the beak. This gives a greater lift for a given number of cams,
and so allows more cams to be put in the barrel and more lifting to be done
with a given velocity.
Lund and Blockley’s lifting barrel has only 4 cams, and they lift from
90 before the vertical up to their highest position, by means of a hinged
piece dropped from each lever. They also strike the Westminster quarters
by means of the same set of pins as the tunes: which I must say I disapprove
of altogether compared with a proper quarter-striking part. I have seen an
otherwise very satisfactory large clock of theirs, with chimes on a peal of
16 large bells for the Bombay University; and some smaller ones. Gillett
and Bland’s principal chimes are at Worcester Cathedral, Boston and Croydon
Churches, Bradford and Rochdale town-halls, and at Eaton Hall. The
performance of both kinds is more accurate and satisfactory than in the
old-fashioned machines; but, like most superior machines, they require a
great deal more care and consequent expense than the old rough ones. No
chiming machinery can bring the full tone out of bells, especially the large
ones: but this is stronger in lifting as well as more exact in letting off than
the old kind. Every bell requires two hammers, and at Worcester some of
them have three, because of the quick repetition in some of the tunes.
It is necessary to give one caution most strongly to ambitious chimecultivators.
Avoid ‘chords,’ or two notes sounded (professedly) at once. At
Croydon they thought they knew better, and a more horrible performance
I never heard from the rudest old-fashioned chime barrel of 200 years ago.
I believe the chords have since been abolished.
Another caution is, not to attempt chimes on large and small bells together.
For some reason, which neither I nor the bell-founders know, it is a
fact well known that bells below 4 or 5 cwt. cannot be made to sound homoCHIME
TUNES. 149
Fig. 42: New Construction for Chime Tunes
CLOCK HAMMERS. 150
geneous with large ones. I shall have more to say of that in the chapter on
bells. They attempted it at Boston, and have got 42 bells (including the 8
of the peal), some of only a few pounds weight cast in Belgium, and chimes
to play on them all together. I and other people who went specially to hear
them considered them a failure. Even quarter chimes are never satisfactory
when large and small bells are mixed. The same result is unpleasantly conspicuous
at Eaton, though the bells there are not so numerous, and were all
cast in Belgium together.
Clock hammers.—Turret clocks generally strike on bells of a different
shape from the hemispherical house clock bells, which do not answer beyond
a very small size, as I shall explain more fully hereafter. Most people (except
artists, who always draw them wrong) are aware that the general shape of
church bells is that shown in figs. 43, 44. The clock hammer CS is always
fixed at right angles to the swing of the bell, for two very obvious reasons:
first, if the bell was free to swing under the blow of the hammer, the first
blow of every hour would set it swinging a little, and at every blow after that
the bell would either be out of the reach of the hammer altogether, or else
jarring against it; and another reason (if it is worth while to talk of other
reasons after this) is, that if the hammer was put in front of the bell, all its
machinery would have to be moved out of the way before the bell could be
rung at all.
Fig. 43: Clock Hammer
The hammers of large clocks also differ from small ones in acting by
gravity, as you see. But they equally require a check spring, or some other
MODES OF HAMMER FIXING. 151
contrivance to keep them from jarring the bell. When a church bell is rung
up, i.e., swinging once round for each blow, and set mouth upwards, the
clapper lies on the bell, but not so heavily as a clock hammer would, because
it stands at a higher angle. The usual kind of hammer spring is shown in
fig. 43; and sc in fig. 44 shows as much of the spring as there was room
for. The spring is sometimes made adjustable, by having long holes for the
Fig. 44: Hammer Over Bell
screws to go through, so that you can bring it farther from or nearer to the
bell as may be required in course of time. India-rubber buffers under the
hammer shank are better in some positions, and have the advantage of never
breaking, and being easily replaced or altered in thickness. I used them at
Westminster.
I believe it is the fashion on the continent to fix the clock hammers with
their pivots above the bell, when it has not to swing; and it has the advantage
of securing a long hammer shank, and therefore less angular motion for a
given lift, and moreover the effective weight of the hammer is not so much
lost in the lift as it is in the common position. But on the other hand, with
bells as tall as the foreign ones are, the hammer shank stands much more
vertically than in the other way, and the rebound from the buffers or check
spring is greater, and a greater lift (obliquely) from the bell is required to
get the same momentum of the hammer; not that that imposes more work
CRANKS. 152
upon the clock. At Westminster we were obliged to adopt that plan, on
account of the construction of the tower and bell-frame, and there it had
this incidental advantage with regard to the great bell, that we were enabled
to get the hammer tail T directly over the end of the lever in the clock, by
setting the hammer frame, or the pivots which carry it, a little out of the
cardinal position relatively to the tower, and so all cranking was avoided
and a vast quantity of friction saved.
Cranks.—Nobody who has not tried it can have any idea how much of
the force of a clock is wasted by having to lift the hammer through cranks.
Where the hammers are not very heavy, you may sometimes use what I
shall call couple-levers (for a reason which any mathematician will know),
of the form in fig. 45 a, instead of a pair of cranks; but when the hammers
are heavy, and the arbor of the lever has to be long, I find it is impossible
to avoid some elastic torsion in it, which wastes quite as much force as the
friction of a pair of cranks, and makes the hammers rise with a tremble,
which checks the force of the clock and strains everything severely. For
the same reason large cranks should be made with a light connecting bar
as in fig. 45 b, which increases the strength enormously and helps to keep
everything steady. The cranks and lever arms and hammer shanks and tails
should all be long. I know that in modern towers, which are nearly always
built too small for properly hanging the bells, there is often great difficulty
in getting room for clock hammers and cranks at all; but wherever there is
room, the action will be easier and more effective if all these arms are made
long instead of short.
When the clock is above the bells, as in the Leeds town-hall, and the
Royal Exchange, it is a very common mistake to put a tail to the hammer
to pull down first, which of course involves the necessity for another to pull
up again. It ought to be done as I designed it at Leeds (if there is room)
by pulling up at once from a lever set inwards or on the same side of the
arbor as the hammer itself, unless it happens from some local peculiarities
that this would involve as many cranks as the other way.
In several of the former editions I gave a design for catching the hammer
at its rebound without any buffer-spring; but I have never heard of it being
tried, and therefore I do not repeat it, and have modified fig. 44 accordingly
to show a common buffer-spring.
The weight of hammer and its lift can only be determined by experiments.
Different thicknesses and qualities of bells require different hammers.
I have generally found that large bells whose diameter = 12× the thickness
of the sound-bow or thickest part (which is the best proportion) require
hammers of about a 50th of their weight to bring out the full tone, and
small bells require heavier ones. The lift has to be less for small bells than
for large: the least that is effective in bells above 3 or 4 cwt. is 6 in. (measured
obliquely in the direction of the motion), and beyond 13 in. we did not
find any improvement in the sound of either of the great Westminster bells.
DIALS OF PUBLIC CLOCKS. 153
Fig. 45: Forms of Cranks
Generally they are a great deal less either in weight or lift, and often in
both, and therefore you hardly ever hear a church bell sound so loud under
the clock striking as in ringing with the clapper. Thinner bells, as the larger
ones of peals usually are, do not require such heavy hammers as thick ones;
but it must be remembered that no hammer arrangement will get as good a
sound out of a thin bell as a thick one, because it is radically inferior both
in quantity and quality of sound. But I shall have more to say of that in
the chapter on bells hereafter. I only add a word of warning against a piece
of ignorance by which I remember a very fine old bell being cracked in a
few months—viz. making the clock hammer to strike it with a sharp edge
instead of a flat or slightly rounded face, as it ought to be.
DIALS.
The striking of church clocks, and perhaps of public clocks in general, is of
more value than their dials, except in places where the public congregate.
Indeed dials a good way above the eye are of no use for indicating the time
very accurately, on account of the parallax which affects the minute hand,
except when it is nearly vertical. Moreover many church towers would be
utterly defaced by dials; And it is to be hoped that the splendid church of
SIZE OF FIGURES. 154
St. Mary’s, Beverley, now that its fabric has been restored to a condition
worthy of its architecture, will not long retain those abominable dials in the
tower windows, which belong to the age when the inside of the church was
divided into private boxes, in which people might eat their dinner or play
at cards without their neighbours or the clergyman knowing anything about
it.
But as dials must frequently be used, architects might as well condescend
to learn something of their proper size, as they profess to provide places for
them, as they do for bells, frequently in utter ignorance of what the provision
ought to be. Luckily there is such a simple rule for determining it generally,
which has now been long published, that they have no excuse for doing it
wrong. That rule is that the diameter of the dial should not be less than
a tenth of the height of its centre from the ground. If you want to verify
this you have only to look at the dials of the Leeds Town Hall, planned
by an architect with the usual knowledge of such things, 150 feet high and
only 11 wide; and those of the Bradford Town Hall are no better, but I do
not know the exact height; or that of St. Pancras Church, 61
2 feet wide and
about 100 feet above the ground. The neighbouring railway station however
has inside it a large dial 15 feet wide, at the height of 55, looking down the
largest space under one roof without pillars in the world, viz. 700 feet long
and 240 wide (the length of the transept of St. Paul’s Cathedral, and more
than the length of the nave of any cathedral except Norwich, Winchester,
and St. Alban’s, the longest of them all). The external dial of that station
is rather too small; but that, and some others which comply with the above
rule are given in this list, which I have compiled from various sources.
But if dials are sometimes too small, the opposite mistake is often made,
of figures much too large, which is not a compensation but an aggravation
of the evil, for they practically contract the size of the dial, in two ways;
first by contracting the plain surface in the middle, over which the hands are
most distinctly seen; and secondly, the larger the figures are, the more they
run into each other and fill up the space of the figure ring itself, and make
it still more difficult to distinguish the place of the minute hand. Ignorant
people fancy that you see what o’clock it is by reading the figures; as if any
single figure which you see in a clock dial indicated the figure which you read
off; except for the hour hand, and the hour also is at once recognized by the
position of the hand. You see the long hand pointing to VIII, and you say,
‘20 minutes to something.’ Both for the hours and the minutes everybody
really judges from the position of the hands, and 12 large spots would do
as well or better than figures. I have several clocks without any figures
at all round the principal dial, only 12 strong marks; and I never found
anybody who even observed the fact that the figures were absent until it
was pointed out to him, or complained of the want of them then. I came
to the conclusion after various trials, that the figures and minutes together
ought not to occupy above one third of the radius of the dial; the figures
CONSTRUCTION OF DIALS. 155
Dials. Diameter. Height.
ft. in. ft.
Mechlin 1 40 about 300
Westminster 4 22 6 180
St. Paul’s Cathedral 2 17 126
Shandon Church, Cork 4 16
Pancras Station 4 12 9 150
Scarborough old Church 1 12 on a hill
St. James’s, Piccadilly 4 10
King’s Cross Station 4 9 90
Bow Church 2 9 70
Manchester Infirmary 4 9 80
Royal Exchange 4 9 90
St. George’s Church, Leeds 3 8 4 57
St. Martin’s in the Fields 4 8
Horse Guards 2 7 5
Marylebone Church 3 7 about 60
St. Luke’s, Chelsea 4 6 10 72
The Queen’s Stables 6 10 about 50
may be two thirds of that one third; and the minutes from half to two thirds
of the remaining one ninth of the radius, with every fifth minute strongly
marked by a larger spot than the others. The Westminster dials might
have been clearer, considering their great size. They are not of my design,
except that I gave the architect some suggestions for them, which are partly
followed and partly not followed. They are unnecessarily confused with iron
frame-work, and the clear space is unduly contracted by some broad rings
supposed to be ornamental. The Midland Station dials are much better.
The only colours that seem to answer for dials and hands are black or
dark blue with gilt figures and hands, or some very light coloured ground,
such as white glass, with black hands and figures. Good gilding will last
fifteen or sixteen years, as at the Royal Exchange, in the worst London atmosphere:
bad gilding of course wants renewing much oftener, and is probably
the dearest. Gilt hands on a light ground are a complete failure. The
external counterpoises, if there are any, should be painted the same colour
as the ground of the dial, except where they are very short in proportion
to the hands, as at Westminster, in which case they cannot be mistaken at
any distance for the hands themselves, and practically increase their visible
length.
Dials may be made of almost anything—stone, slate, plaster, brick, iron,
copper, and many old ones are of wood, which however is the worst of all,
as it always shows the joints. In many cases the stone of the tower makes
the best dial. Generally it requires painting; but if it is such a stone and
CONVEX AND CONCAVE DIALS. 156
in such a position that it will keep nearly white, it will do very well with
only the black figures and minutes painted on it, and black hands, but by no
means gilt ones. Dials on brick work must of course be painted. It is quite a
mistake to suppose that a dial requires a very smooth surface. Some of the
most distinct I have ever seen are painted on rather rough stone work; and
brick will do as well, either all flat, or with the figure circle a raised ring of
iron, or of any plaster that will stand. There are many dials of cast iron; but
I should never make more than the figure ring of iron, unless there is a large
hole in the wall which wants covering; and even then it is generally better
to fill it with glass, which has all the effect of a dark ground outside and is
often convenient within. Slate makes a good dial, but if it is not painted it
becomes a pale grey colour. I believe 6 feet diameter is the largest size that
can be got in one piece, but the joints are almost invisible if well done.
Copper dials are the commonest of all, and up to a moderate size, probably
the cheapest, except of course when the dial is simply painted on the
wall. But they are generally made in the very worst form that could be
invented, viz., convex: the effect of which is that the point of the minute
hand is thrown a long way off the dial, and the parallax is so great that you
cannot tell what it is pointing at, except when it is nearly vertical, when
seen from below, as a public dial always is. One way to avoid this is to countersink
the middle, in which the short hand travels, leaving the long hand
to lie close to the raised figure ring. I have lately seen some dials made of
mosaic work, like pavements, by Messrs. Rust, of 16, Albert Embankment,
which look very well, and the price was not more than of copper dials; and
they can easily be made concave.
Concave dials.—It occurred to me some years ago that all the convenience
of the light copper dials might be got, with even more closeness of
pointing than in a flat one, and with as much stiffness as the convexity gives,
and with less distortion of appearance, simply by making them concave instead
of convex. If you draw a vertical section of a convex and a concave
dial, and three lines of sight, from the top, the bottom, and the middle of
each, to a spectator in the street, you will see at once that the convexity
makes the upper half appear much smaller than the lower, whereas in the
concave one the two halves appear even more alike in size than in a flat dial;
and the closeness of the hand pointing is evident. There are now a good
many of such dials, and no one who has seen them can fail to perceive their
superiority to convex ones.
Hands.—Large clock hands are so universally made of copper that it
is hardly worth while to notice any other construction. There is indeed—
or was, a notable exception, in Sir C. Barry’s famous gun-metal hands at
Westminster, which is not likely to be repeated. The hands of the clock at old
Doncaster church, which perished in the fire of 1853, were of mahogany, and
stood very well; but I should think copper ones are lighter, even including
the stalk or centre piece. Where they are very large, say 5 or 6 feet long,
ILLUMINATED DIALS. 157
the best form for them is that of the minute hands at Westminster, viz. a
tube of thin copper, whose section is two segments of a circle, with a few
diaphragms at intervals of about 2 feet to keep them stiff. The strength
of this construction is enormous, and it is also good for throwing off snow,
which sometimes accumulates on hands with broad edges heavily enough
to stop the clock. Smaller hands may be made quite strong enough with a
convex front and a flat back, the section being an arc and its chord, or even
as a single flat piece of copper with the edges turned over square. A mere
rib or hollow bead raised along the middle of a hand makes it strong enough
for all ordinary sizes, but it does not look well. ‘Galvanised’ sheet-iron
hands have been tried, but the zinc peels off, and they must be pronounced
a failure. The minute hand should always be straight, and plain, with a
bluntish point. At the broadest part, or near the dial centre, it should be
about a 13th of its length, tapering to about half as much near the point.
The hour hand should be the same breadth, ending just short of the figures
in a broad piece called a heart, of any shape you like.
There should always be some external counterpoises to large hands, both
for wind and weight. They should not be above 1
3 the length of the long
hand, and should be broad, but of a shape not to be confounded with the
heart of the hour hand. The advantage of counterpoising the hands to some
extent for the action of the wind is evident; and the other use of an external
counterpoise is to diminish the tendency of the hand either to twist the
arbor, or what is more likely, to work itself loose and shake over from one
side to the other every time it passes the vertical, as Reid says the old hand
of St. Paul’s cathedral used to do, and as Sir C. Barry’s heavy hands did at
Westminster to such an extent as to stop the clock. The only way to prevent
this shake is to fit the hands on a tapered square or hexagon at the end of
the arbor, and not a prismatic one. The latter may be called engineers’
fitting, and is perfectly right for many purposes but perfectly wrong for
this, for which the old clockmaker’s taper fitting alone will answer. It is
found better not to put the whole counterpoise for very long hands outside:
from one third to one half is quite enough, leaving the remainder to be done
by adjustable counterpoises inside, which should be long rather than short,
as they then do the same work with less weight and friction on the arbor.
Illuminated dials.—Occasionally it is possible, as at the Horse-Guards
east dial, to illuminate a common white dial by reflection from a lamp on
a roof projecting below it. This answers well enough for dials to be seen a
short distance only, in the few cases where it can be done. Where it cannot,
the common way is to make the dial of glass, or all of it except the figures
and the rings to connect them which form a solid framework of cast iron.
The glass is ground behind, or painted, or covered with muslin stuck to
it, and gas lamps are put behind it. But all these things have such a bad
appearance by day that the advantage of illumination is dearly purchased
at that cost. Now however a white glass is made by Messrs. Chance of
DIAL WHEELS. 158
Birmingham, and perhaps by other makers, which forms a very good and
always clean white dial by day (if left open for the rain to wash its face) and
a bright one by night: the hands and figures must be black as with other
white dials. It should be 3-16ths of an inch thick, or 22 oz. to the square
foot; the middle of large dials has to be in two or three pieces, which must
be divided by bars not radial, or they will look like hands at night; and all
but the figures and minutes should be gilt.
The gas lamps of illuminated dials are generally kept alight all day,
turned down as low as they can be without going out. They are usually
tamed down in the morning and up at night by a 24 hour wheel in the
clock, which has pins screwed into its rim and taken out again from time
to time by the man who takes care of the clock. So long as any of the
pins are in the position to hold up a weighted lever connected with the gas
cock, it is turned down, and when the lever drops off it is turned up. In
the Westminster clock three fan-shaped pieces were prepared on a 24 hour
arbor, which can be opened out to 18 hours or contracted to 6, according
to the length of illumination required; but it was afterwards determined by
the authorities to turn the gas completely off and on by hand. There was a
clock in the Exhibition of 1851 with completely automatic or self-adjusting
machinery for turning gas off and on at the proper time throughout the
year; and Gillett and Bland did the same in the Bradford Town Hall clock;
but the tower is so small and crowded with bell beams, that they were
actually hot by day, and I advised putting out the gas by day at least. The
machinery puts it quite out now. It cannot be done at all accurately by any
uniform automatic motion, because the clock times of sunrise and sunset
vary irregularly from the equation of time (p. 5), and very slowly near the
solstices, but at other times from 12 to 15 minutes a week.
It is desirable to have a wall, if possible, behind illuminated dials, instead
of having them practically in the clock room; partly because the wall may
be made useful as a reflector, and so save gas, and also because it protects
the clock itself both from the variations of heat and from the watery vapour
caused by burning the gas. Reflectors are a great saving of light and of
cost. It must be remembered also that the counterpoises of the hands on
glass dials must neither be long ones outside, nor immediately behind the
glass inside, or they will cast a shadow and be confounded with the hands
at night. There should always be ventilation over illuminated dials.
Dial wheels.—The construction of the dial-work of large clocks differs
very little from that of small ones. The principal difference is that the
numbers of the wheel teeth are differently distributed. Instead of two equal
60 min. wheels, there is a pinion on the minute-hand arbor which drives a
wheel corresponding to the wheel N in pp. 95, 118, 121, only moving slower;
and that wheel has a pinion on its arbor which drives the hour-hand wheel as
in house clocks. If tt1 are the numbers of the wheels and pp1 of the pinions,
they have only to satisfy this condition, tt1
pp1
= 12, bearing in mind also that,
OBLIQUE LEADING OFF. 159
from their position, the radius of one wheel must be as much less than of
the other as that of its pinion is greater. The larger wheel is generally put
on the hour-hand arbor. The most convenient numbers are 90 and 100 for
the wheels, and 25, 30, for the pinions, or in smaller clocks 72, 80, and 20,
24.
The bevelled wheels leading from the clock to the dials ought to be of
a good size, not less than 5 inches wide in small clocks, and 7 to 9 inches
in large ones. They need not be very strong, as they have only to move the
hands; but the advantage of their being large is that any given amount of
shake in the teeth allows less angular motion of the hands. In the old way
of fixing clocks on a stool in the middle of the room, which I have already
shown to be the worst, there was generally a vertical rod from the clock
running up the middle of the room, with 2 horizontal bevelled wheels, one
on the bottom worked by the clock, and the other at the top working 4
others leading to each dial; and in that case it is necessary that the bevelled
wheels on the vertical rod should be larger than all the others, both the
first one in the clock, and the others leading off to the dials; otherwise the
4 leading-off wheels will take into each other as well as into the horizontal
wheel. Where the vertical rod does not lead into the middle of the room this
does not occur, but there must then be two nests of 3 wheels each, if there
are 4 dials, besides the two wheels in the clock. I have seen several more
wheels added, through a singular piece of ignorance that it is not the least
necessary that the rod which leads upwards should be vertical. I was rather
glad that it was necessary to put it very oblique in the Westminster clock as
an example of such treatment (see frontispiece). With bevelled wheels of the
common shape, intended to lie at right angles to each other, the rod must
be in a vertical plane parallel to the clock wheels, but there can seldom be
any difficulty in that: if there should be, the bevelled wheels have only to
be made for the proper angle.
Even in such a clock as that of the Royal Exchange, undoubtedly the
best that had been made up to that time, the odd mistake was committed
of supposing that nests of bevelled wheels could not be connected obliquely.
When I remodelled the clock in 1854, I removed all the intermediate bevelled
wheels, and connected the central nest of them with the one in the clock
by an oblique rod, like that of Westminster. When there is only a small
parallel displacement it is managed by a loose cross riding with sufficient
play endways in the sockets of two half universal joints on the rods. Where
the rods are too much out of the straight line for that, a short oblique
rod is interposed with common universal joints at each junction, and these
will do well enough where the obliquity is not very great, provided always
the oblique rod lies between two parallel ones; otherwise the velocity is not
uniform. But where the obliquity is great, rigid rods with the bevelled
wheels on them are better, for the wheels may be at any angle. Nevertheless
universal, or half universal joints, are properly used wherever a rod is either
UNIVERSAL JOINTS. 160
too long to do without several supports, or where there is any risk of there
being an unequal strain upon it in one direction, or where bevelled wheels
can be saved by a jointed rod with very slight deviation from straightness.
Turret clocks are generally made with the minute-hand on the internal dial
turning the wrong way round, to provide for the case of the external dial
arbor being able to go straight through the wall from the back of the clock,
as it does when the clock can be placed immediately behind a single external
dial.
I have lately seen a new kind of universal joint, almost ridiculously simple,
in an universal or any-way-pointing drill, called Morrison’s, from America.
If you take a common spiral wire bell-spring and twirl one end of it while
you hold it bent at any angle, the other end will twirl uniformly; which is not
the case with very oblique universal joints. This kind of connection might
often be used with advantage in leading off, and with less loss of force than
from the friction of bevelled wheels, though of course there is some slight
loss of force in continually bending the spring. The spring must be strong
enough not to let the wind move the hands.
Fig. 46: Universal Joints
Sometimes the clock has to be placed a long way below the dials, 30 or
40 feet or more, and then it is necessary to provide both for the weight and
the want of stiffness of such a long leading-off rod; and this is best done by
a pair of friction plates and rollers at the top. The lower plate is set on the
beams which carry the nests of bevelled wheels or motion work: on that lie
three small flat cheese-shaped rollers on a horizontal tripod, with a hole in
it for the long rod to go through quite loosely; and the other plate is fixed to
the top of the rod, which is in fact hung by it, the rollers carrying the weight,
and with no sensible friction on their own centres, for the three-legged pivots
have no weight upon them. This kind of suspension is also used for heavy
weathercocks which work a wind-dial inside the house, and the ease with
WEATHERCOCKS. 161
which a very heavy weight can be turned in that way is surprising.
Weathercocks.—As these are generally fixed by clockmakers in such
cases as those last mentioned, I may as well mention that a weathercock
which is intended to answer steadily to the wind, ought not only to be long
in the vane and thin in the tail, but equipoised; and so far from the vane
being perforated for ornament, it should be double, with the two flat sides
or vanes spreading out at a small angle from the axis. When the cock works
a dial it must be fixed to a rod working loosely in a tube, and the top
of the tube covered with an inverted funnel on the rod; as also the rods
or wires which work the clock-hammers should be funnelled, over a short
pipe soldered to the leads, wherever they are exposed to rain: otherwise the
wires lead down the wet into the clock. And the weights and ropes should
be enclosed in a case to keep them from the rain and wind, if they are in an
exposed place. (See also p. 283.)
Ventilation of clock-room.—The clock-room at the Exchange was at
first made with the object of keeping out the dust and damp in every possible
way: even the slits in the floor for the ropes had sliders to them; the clock
was enclosed in a glass case, the plate-glass cover originally placed over the
escapement being found not enough to keep it from the damp. When the
clock was repaired, and some of the brass-work replaced with iron in 1854
(for a reason which I shall mention hereafter), I suggested the removal of
all this glass, and encouraging instead of preventing a draught through the
room. This was done; and although the wet used to stand in drops upon
the clock before in damp weather, it has been perfectly dry ever since. The
same thing has been found in small clock-cases: they may easily be too airtight.
I do not mean that there is any objection to enclosing a clock in a
case, and of course it is absolutely necessary where the clock-room cannot
be kept locked against everybody but the man who has the care of it; only
there should be a draught through the room, and the case itself not too close
to let air through it. If the room can be kept warm enough to prevent the
damp from condensing on the clock it is better still.
TRAIN REMONTOIRES.
I have postponed this branch of the subject till I had gone through all the
more ordinary work of turret clocks. A train remontoire differs in principle
from a remontoire escapement (of which I have already treated) only to this
extent: the small weight or spring which gives the impulse to the pendulum
is not wound up at every beat, but at some longer intervals, seldom more
than half a minute; or the remontoire work, you may say, is put one step
farther back, acting on the scapewheel instead of on the pendulum. So that
if a train remontoire of constant force and friction is made to act on a dead
scapewheel, the only variation of force to which the pendulum is subject
BEVELLED WHEEL REMONTOIRE. 162
will be that arising from the pallet friction. In small clocks the variations
of the pallet friction are generally much greater than of the train friction,
and therefore a remontoire would be of little or no use; but in large clocks
with heavy wheels and large hands to drive, the contrary is the case; and
there accordingly, either a train remontoire or a remontoire escapement is of
great use, provided they really do what they profess—which many of them
do not.
The simplest form of train remontoire acting by a weight is that described
in Reid’s book, on the endless chain principle, which I have already described
for a going barrel at p. 104. The scapewheel is not driven by the clock train,
but it has a spiked pulley on it which carries one loop of the endless chain,
and the other is carried by a similar pulley on an arbor driven by the train
and turning in the same time as the scapewheel. This remontoire arbor
has a few long spikes sticking out from it, at different distances along the
arbor, and they are just long enough to reach the middle of the scapewheel
arbor, and can slip past it through a nick cut for the purpose, whenever that
nick comes into the right position, which it does once in every turn of the
scapewheel; then the remontoire arbor turns and winds up the endless chain
a little until the next spike falls against and is stopped by the scapewheel
arbor, till its nick also presents itself and lets that spike slip through, as you
see in this drawing.
Nevertheless, that construction is far from satisfying all the conditions
of a remontoire. The action of a chain cannot be made smooth and uniform,
and a rope or string passing only half round a pulley is sure to slip in
time, and so the remontoire would fail. Moreover, Reid says that although
the Edinburgh clock went very well for a time, yet it became necessary to
remove the remontoire in consequence of the banging of the spikes against
the scapewheel arbor. That however would be easily cured by a fly; which
may now be considered a necessary element of every remontoire: for there
are several other kinds.
One is the bevelled wheel remontoire, which was used in many of the
French turret clocks in the 1851 Exhibition. I have already explained the
principle of it, so far as the bevelled wheels are concerned, at p. 102; but
something more is now required. In fig. 47 (t. o.), consider the dark disc FG
and the pulleys omitted for the present (we shall want them presently for
something else). X is part of that wheel of the clock which would naturally
drive the scapewheel s if there were no remontoire, and if it were fixed to
the arbor of the pinion t which X does drive. It also drives another pinion
P on an arbor PQ which I call the remontoire arbor, because it carries two
long spikes not quite in the same straight line, or not at right angles to
PQ, which can pass alternately through two nicks in the scapewheel arbor.
When the arbor is stopped the train and the wheel T do not move; but the
weight of the middle bevelled wheel R, with any weight (+ or −) attached
to it, always presses down the far side of wheel S, and of the scapewheel s
BEVELLED WHEEL REMONTOIRE. 163
Fig. 47: Bevelled-wheel Remontoire
CONTINUOUS MOTION REMONTOIRES. 164
fixed on the same arbor, and that force is practically constant. When the
scapewheel arbor lets a remontoire spike pass, the pinion P turns half round
and lets the train move a little, and lift up the right side of wheel R, and
therefore lift up its centre half as much, and then the other spike is held
by the scapewheel arbor. The fly may be driven by the wheel D anywhere,
either on the remontoire arbor or any other. We shall see another way of
driving it presently.
Continuous motion remontoire.—In connection with this I will describe
a remontoire exhibited in 1851, by Messrs. Wagner, the great turret
clock makers of Paris, for the purpose of getting a continuous motion for
telescope-driving clocks, or clocks to drive a barrel on which times of observation
may be recorded at less intervals than a second, with all the advantage
of a vibrating instead of a revolving pendulum. The action for the vibrating
pendulum which is driven by the scapewheel s is exactly what I just now
described, except that there is no spike wheel and no sudden letting off.
Instead of that there is a large pulley p on the arbor of the wheel T which
lifts the remontoire arm VRW. This pulley drives a much smaller one on
the arbor of a fly FF, which runs inside a tin drum without a bottom, which
is hung over it by two wires WW from the end of the remontoire arm. The
weight of the drum is counterpoised so as not to let it preponderate too
much. The fly is the thing which regulates the velocity of the clock train,
which is always moving; the farther the drum falls over it and cuts off the air
within from the air outside, the faster the fly will turn, and vice versˆa; and
things are so adjusted that the continuous motion of the clock train driving
the fly will just keep pace with the average motion of the scapewheel driving
the pendulum by beats as usual. If the clock falls behind the proper speed
the remontoire wheel and its drum falls a little and lets the fly go quicker,
and if too fast it rises and the velocity of the fly is checked. The one in the
Exhibition seemed to go very steadily; and as there is nothing in all this
at all difficult to make, I am surprised that more complicated contrivances
should be used for such purposes as I have mentioned.
Mr. De la Rue and Mr. Cooke appear to have hit simultaneously on
the following plan for a telescope-driving clock, which retains the advantage
of a vibrating pendulum, and may have a gravity escapement also. In the
figure at p. 163 suppose the two opposite bevelled wheels to be respectively
fixed on the ‘centre arbors’ of two clock trains, the left hand one ending in
a vibrating pendulum, and the right in a conical pendulum or a fly. And
let the arbor of the intermediate wheel (omitting all the wind apparatus
FGF) be held by a spring instead of the constant weight C. At every beat
of the pendulum the left hand train will stop for a moment, but the flywheel
train, of which the barrel is to drive the telescope, will go on by its
own momentum, and because the spring allows the intermediate wheel, and
therefore the right hand wheel and its train, to move a little. If that train
is inclined to go too fast, the spring will diminish the force upon it; and if
INTERNAL WHEEL REMONTOIRE. 165
too slow, will increase it. Of course the weight and fly are to be adjusted so
as to make that train go naturally as nearly as possible with the other.
A still simpler telescope-driver was invented by Mr. R. F. Bond, of
Boston, U.S., brother of the well-known Professor of Astronomy there. As
I understand the description, one arbor of the clock has two wheels on it,
one fixed, and the other connected with it by a spiral spring. The second
of these wheels is either the scapewheel or the one below it, and the other
ultimately drives a fly, which allows the train to so continuously, the spring
equalising the force sufficiently every beat. Mr. Cooke said it did not answer,
but Mr. Bond replied with a testimonial from the late Rev. W. R. Dawes,
F.R.A.S., who had the reputation of being the best observer of his time, that
the ‘performance was exquisite; that it kept the thread of the micrometer
dividing a star for nearly an hour together with a magnifying power of 800
or 1000 on, and that no jerk or interruption was perceptible.’ Lord Lindsay,
P.R.A.S., invented another, too complicated to describe here, on the ground
that neither Cooke’s nor Bond’s clocks would drive a large telescope fitted
with spectroscopic apparatus steadily enough for that purpose.8
The Royal Exchange clock was originally made with a gravity remontoire,
though it was afterwards altered. Instead of bevelled wheels, Mr. Dent used
an internal wheel, i.e. one with teeth on the inside of the rim, instead of
the outside. That wheel D (fig. 48, t. o.) had the letting off spikes on its
outside; at least a wheel on the same arbor had, which is the same thing. It
was driven by the centre wheel of the clock, and whenever it moved it lifted
the remontoire arm and weight by means of the small wheel B lying between
the internal teeth and the wheel C on the arbor of the wheel F which drove
the scapewheel: that arbor being of course independent of, though in the
same line with the arbor of the wheel D and its pinion. The remontoire
was let off at every 20 seconds; which however is not so good an interval as
30, because it is not easy to distinguish whether the hands are pointing to
10 seconds before or 10 seconds after the half minute; whereas it is perfectly
easy to see whether they are pointing to a minute or a half-minute, if the dial
is properly made, as I have already described. This facility for taking the
exact time from the dial by the jump of the hands is one of the advantages
of a train remontoire, where the momentum of the hands is not too great.
There is yet another way of making a train remontoire without either
bevelled or internal wheels. In fig. 49 (next page) E is the scapewheel, and
e its pinion driven by the remontoire wheel D which rides with its pinion d
fixed to it on a stud in the remontoire lever AP. The centre wheel C drives
that pinion and a smaller one g on a wheel which drives another pinion f
on the fly arbor, which has also the remontoire spikes AB attached to it.
The numbers of the teeth are so arranged that the fly will turn once for
8All these contrivances are described in the R.A.S. Notices, vols. 27 and 33, and Horological
Journal, of February and April 1868.
SPRING REMONTOIRE. 166
Fig. 48: Royal Exchange Remontoire
each turn of the scapewheel, and the scapewheel arbor has only two notches
in it, so as to let off one remontoire spike every seconds. It is evident that
the scapewheel is always driven by the remontoire wheels and weight, and
not affected by the clock train. There were several French clocks of this
construction in the Exhibition of 1851, but they all had the fly driven by an
endless screw, which is objectionable because it involves an immense amount
of friction and the motion of the train was so slow that you could hardly
distinguish the jump of the hands.
Spring Remontoire.—But it must be observed that all these gravity
remontoires are still subject to the friction of the remontoire wheels
themselves, which is not inconsiderable, although it is much less, and less
variable, than that of the clock train and hands. To avoid this, it was long
ago attempted to contrive a spiral spring remontoire which would drive the
scapewheel without any sensible friction. One of these is described in Reid’s
article in the seventh edition of the Encyclopædia Britannica; and another
was invented by Sir G. Airy,9 and two or three specimens of it were made
by old Mr. Dent. They all went on the plan of connecting two wheels, or a
wheel and pinion, on the same arbor by a spiral spring, one being fixed to
9See Horological Journal, xvii. 22.
SPRING REMONTOIRE. 167
Fig. 49: Simplest Train Remontoire
ALTERATION OF EXCHANGE CLOCK. 168
the arbor and the other riding upon it; and the consequence was that the
scapewheel was always subject to the friction of the other wheel set upon
its arbor and pressed tight upon it by the action of the spring, which was
probably worse than the ordinary friction of the train; and they were all
failures.
This difficulty however may be got over by a very simple contrivance
which I invented in 1849, and which was used in several large clocks, and
would have been in many more but for its having been superseded by the
cheaper and simpler gravity escapement already described (p. 85 to 93). In
fig. 50 (next page) E is the scapewheel and e its pinion, not fixed to the
arbor of E nor riding upon it, but upon an independent stud k screwed to
the clock frame. In front of the pinion a small bush is pinned on to the same
stud which carries the pivot of the scapewheel arbor, on which is set a large
watch spring s, of which the outer end is held by a pin h screwed into a
small plate fixed to the front of the pinion, so that the pinion acts on the
scapewheel by the intervention of this spring without any friction except
that of the coils of the spring upon each other, if they touch at all. The
wheel D which drives that pinion also drives another on the fly arbor f. If
the scapewheel turns in a minute, there will be two nicks across its arbor, as
in fig. 47, for the remontoire spikes or stopping springs to act upon. But if
it turns in two minutes, as the pin scapewheels generally do, a different plan
is adopted: the scapewheel arbor is then brought through to the front of the
clock frame and has a small steel cylinder set upon it, with two nicks across
its face, not its side, one broad and shallow and the other deep and narrow;
the remontoire springs set on the two arms of the fly have corresponding
shapes, so that one will pass through the broad nick only and be stopped
by the narrow one, and the other will pass through the deep nick but be
stopped by the shallow one. The fly in this case makes half a turn for every
quarter turn of the scapewheel, and therefore its pinion must be only half
the size of the scapewheel pinion. In very large clocks such as the Exchange,
in which the gravity remontoire was replaced by a spring one in 1854, the
fly is made separate from the remontoire arms, with a ratchet and click as
usual to let it run on a little by its own momentum; but in smaller ones it
does very well to put the remontoire spring stops on the fly itself.
The wheel shown at F with a kind of detent in it, is for setting up
or letting down the spring with reference to the remontoire arms, and so
increasing or diminishing the force on the scapewheel.
This was the construction of old Mr. Dent’s large clock in the 1851
Exhibition, now at King’s Cross station, which was found only 3 seconds
wrong at the closing of the Exhibition, though it had never been altered
during the 24 weeks it was there, after its preliminary regulation. I never
knew any clock with such a rate as that, and yet it has only a common
unjewelled pin-wheel escapement, and a 11
2 sec. zinc and iron pendulum,
and most of the wheels are of cast iron. It has sometimes gone since for
ALTERATION OF EXCHANGE CLOCK. 169
Fig. 50: Sir E. Beckett’s Spring Remontoire
CAST-IRON WHEELS. 170
several months together without any noticeable variation.
The Exchange clock was immensely improved by that alteration, and
made as good as that of the King’s Cross clock in general, but I have no
exact record of its rate. I must confess however, that this kind of remontoire
is not safe to put into clocks left in any common hands, as I have found by
experience that the first time the clock wants cleaning or repairing—or even
without that opportunity—a stupid workman, or master, makes a point of
destroying the remontoire. I knew one case where it was done as soon as
an ordinary clockmaker got the care of it—and that at Manchester, the city
of machinery. This cannot happen with a gravity escapement, which is also
much cheaper. The Exchange clock has been altered by Gillett and Bland
to the double three-legged gravity escapement, which is now the standard
one for all large clocks. Therefore it is no longer necessary to explain further
details of the spring remontoire, as in former editions.
Cast-iron wheels.—The success of the contrivances for cutting off the
variations of force from the pendulum led to another alteration which helped
to reduce the price of large clocks considerably; and that was the making
all the wheels below the escapement, and all the dial wheels, of cast iron
instead of brass or gunmetal. Mr. Vulliamy had before recommended that
as a good construction for cheap clocks, but it had always been thought
that they could not be also good ones on account of the greater friction of
the train. I believe that apprehension was very much exaggerated, even for
clocks of the common construction, provided of course the escapement is
light and well made; but as soon as you cut off the friction of the train from
affecting the escapement it is obvious that cast-iron wheels are just as good
as brass or gun-metal. The clockmakers in general violently denounced it,
probably for no better reason than that it lowered their prices enormously,
the price being now only £200 for clocks of greater power and far greater
accuracy than those for which £500 used to be charged not many years ago.
The cast iron wheel controversy came to a head in some of the Lancashire
papers soon after the making of the clock, from my design, for the
Manchester Infirmary; and the advocates of brass wheels had clearly no case
whatever. Their three points against cast iron were friction, rust, and liability
to break. The friction of the train is absolutely immaterial with a
remontoire, or a gravity escapement, and no large clock can go with great
accuracy without some such contrivance. The next objection is obvious
nonsense, because all except the acting surfaces are painted, and they are
of course oiled as in all other iron wheel machinery. The liability to break
is a mere question of experience. Those who condemn them for clocks must
be very ignorant of the extent to which cast iron wheels finer than are ever
used in church clocks are used in every factory in Yorkshire and Lancashire.
I made particular inquiries once as to the sizes down to which the teeth are
cast in iron wheels for spinning machinery (for that is what I mean by cast
iron wheels), and I found that they are cast with quite sufficient accuracy
CAST IRON AND GUN-METAL. 171
with teeth as small as 1
10 inch thick; which is smaller than any I have seen
used in clocks, because there is very little saving in cost in using iron wheels
so small as that. The great saving of course is in the large wheels of the
train, and the dial and bevelled wheels, of which a good many of the same
pattern and no very fine pitch are required.
Before I leave the cast iron wheels I should observe that they work better
with cast iron pinions than with steel ones: indeed cast iron and steel seem
never to work well together, at least in no clock-work that I am acquainted
with if there is much pressure between them. I have seen cast iron fly
ratchets used with steel clicks, by clockmakers who would not listen to the
proposal of iron wheels and pinions for any but the commonest clocks, and
they had to be removed, and replaced either by wrought iron or brass ones.
I have seen and heard of brass teeth worn out in an almost incredibly short
time, long before iron teeth in the same clock showed any signs of wearing.
Moreover few people have any idea how rapidly brass is corroded and in
fact destroyed by such an atmosphere as that of London and other large
towns. I have several times seen the brass tubes which had been used in dial
work, and thin pieces of brass elsewhere, brought back to be replaced with
iron because they had become completely rotten. It was so at the Royal
Exchange in eight years.
In this respect gun-metal is better, which is copper and tin instead of
copper and zinc, but for large wheels it is no way superior to iron; and it
is generally made too soft. It is equally absurd to polish iron work, except
the acting surfaces; that rusts even sooner than brass begins to corrode; in
fact very often in a week after the clock is put up. Then somebody who
has the care of it floods it all with oil, and it is filthy ever after. The only
proper rule to lay down is that all non-acting surfaces should be painted. In
the Westminster clock even the small brass wheels in the escapement are
painted like the iron ones.
The truth is that all this ‘finishing’ of non-acting surfaces is what old
Dent used to call ‘working for fools.’ It has literally no other object (as
plenty of clockmakers have confessed to me) than to make an impression
on the ‘fools’ (in and out of the trade) who go to see a new clock in the
first month after it is put up, and never see or want to see it again. Such
people as these think it a much finer thing to have a clock look bright for a
month and never keep time within a minute a week—or a day, for what they
know—than ‘to look like a patent mangle,’ but keep time within a second a
week.
I must warn people however against some altogether cast-iron clocks
which got into vogue some years ago by their extreme cheapness, if they
could be called cheap at any price. I heard constant complaints of them,
and had to subscribe once to help a friend to get rid of one and substitute
another of a proper kind. I shall give presently a form of specification
showing how much of a large clock may be of cast-iron.
SPECIFICATIONS FOR PUBLIC CLOCKS. 172
A few years ago I learnt when it was too late that a deputation from
the corporation of a considerable town had come to London to negotiate for
a first-rate town-hall clock, and after wandering about for some time they
fell into the hands of ‘an eminent firm’ who boast of sending clocks all over
the world, and engaged to pay them more than would have bought the best
possible clock for one which was warranted to keep time within 5 minutes
(not seconds) a week; whether it actually does perform that feat I do not
know, but I heard casually of some other of its successes, which gave hopes
of it breaking down altogether.
Another common cause of bad church clock making is the inveterate
habit of jobbing for the benefit of a townsman by giving the order to a
watchmaker who never made a turret clock in his life, and who immediately
goes or writes to one of the few real makers for the cheapest clock that
will serve his purpose, and probably charges for it as much as the people
could have got a first-rate one for, if they had had a competition of the best
real makers of large clocks, or even gone to one of them alone. The local
watchmaker, by way of carrying out the fraud completely, generally insists
on the real maker putting, not his own, but the pretender’s name on the
clock. If this were merely a question between the makers who consent to do
so, and those who will not, I should leave them to find their own remedy;
but as it affects the general credit of our public clocks, I think it right to
give this warning, though it will probably not be read by one in a hundred,
or attended to by one in a thousand, of those for whom it is intended. It
would be far better to do the ‘native talent’ job in a straight-forward way
by letting the local watchmakers draw lots for a bonus of £20, and then
advertise for tenders under proper conditions, such as I suggest below.
The practice of insisting on clockmakers tendering for bells, except quite
small and common ones, is almost equally objectionable. Every now and
then, one party or the other has paid dearly for it themselves; for which also
I do not care; but the more material thing is, first that two profits have to
be got out of the transaction without any real necessity for a middle man,
and that there is practically much less responsibility and control than when
you deal directly with the bell-founder. You might as well insist on the
clockmaker fitting up an observatory with telescopes,10 or trust a builder to
put in painted windows and the organ in a church.
SPECIFICATIONS FOR PUBLIC CLOCKS.
Every now and then I happen to see specifications for large clocks, either
prepared by somebody belonging to the office which has to order it, or in
10There was indeed one clockmaker quite competent to do both, the late Mr. Cooke,
of York; but then he made the telescopes himself, and was one of the best makers of his
time.
SPECIFICATIONS FOR PUBLIC CLOCKS. 173
the form of a tender sent in by some advertising clockmaker, and I hardly
know which are generally the worst, except that the author of the tender
does know what he is about, and takes care to put in as many adjectives and
as few substantives as he can, and the author of the specification never does
know what he is about. An elaborate specimen of this kind was shown to
me some years ago, from a Government office, which stipulated among other
remarkable things, that the pendulum was ‘to vibrate 2 seconds, but to be
as long as the room admitted of.’ It was also to have convex copper dials a
quarter of an inch thick, and a dead escapement; which were three specimens
of the author’s practical knowledge of the present state of science. The
specification, though of many pages, did not contain a single thing, except
the probably impossible pendulum, of the slightest value towards securing
what (I suppose) was wanted, either in the way of time-keeping or striking.
Sometimes the providing of a clock and bells is entrusted to the architect,
by people who are not aware that modern architects rather boast than are
ashamed of being totally ignorant of every thing of the kind. I have heard
people who ought to know better say, that ‘the only way is to throw all the
responsibility of everything connected with the building on the architect,’
and utterly puzzled when I asked them what those fine words meant, or
what would they do if everything turned out wrong, as it generally does in
that case. I will therefore give a specimen of the specification suitable for a
large church clock, though I cannot adapt it to all possible circumstances;
and a much stricter one is requisite for a general competition than for one
limited to a few makers whose work I know to be of the best kind. Indeed no
specification can secure a good clock from a bad clockmaker; and it ought
not to be necessary to warn people (but I find it is) that those who blow
their own trumpet loudest in advertisements are very often the least to be
trusted, especially in an article of which most purchasers are quite incapable
of judging, until it is too late. All that a stringent specification can do is to
frighten away bad makers from tendering at all; and for that purpose the
first clause of the following form is useful in a general competition, provided
is certain to be enforced.
1. To make and fix a clock with m dials of n feet diameter, and striking
the hours and Westminster quarters, on bells which are or would be
the 2nd, 3rd, 4th, 7th, and tenor of a peal of 8, the tenor weighing
——.
2. The dials to be concave and made of copper, or painted on the wall,
if smooth enough, or with the figures and minutes of cast iron, in
rings. If the dials are to be illuminated they must be of cast iron, and
should have opal glass 22 oz. to the foot, except behind the minutes,
which may be 16 oz. to the foot. There must be no straight radiating
pieces of iron in the middle. [Architects should be made to understand
SPECIFICATIONS FOR PUBLIC CLOCKS. 174
(if possible) that dials intended to be illuminated must have a clear
opening in the wall of the full diameter of the dial.]
3. The long hands to have a short external counterpoise, painted the
same colour as the dial, if not illuminated, and the hands, figures, and
minutes to be gilt. If illuminated, the hands, figures, and minutes to
be black, and all the rest gilt. The long hands to be straight and plain.
4. The escapement to be the double three-legged gravity, and care must
be taken to leave room for the fly of sufficient length, and to make the
angles such as to run no risk of tripping, and generally according to
this book.
5. The pendulum to have zinc compensation with iron rod and tube, and
bob not less than 2 cwt. To beat 11
2 seconds for a clock with several
large dials, but may be 11
4 for a smaller clock, or if there is no room
for a 11
2 second pendulum. It is to swing 21
2
 from zero, and to have
a block under it in case the spring breaks, and a degree plate.
6. The clock must lie on stone corbels or iron beams, or brackets bolted
through the wall, and the pendulum cock either bolted to the wall,
or rising from the clock-frame, which is to be generally on the plan
at p. 140 of this book; but the great wheel arbors are to be in drop
bushes of the form d, at p. 136.
7. There is to be a minute dial, and either one for seconds or a wheel
marked for that purpose, with a fixed index.
8. To have the improved bolt and shutter maintaining power (p. 107) or
the Westminster one for a very large clock The going part to go a little
over eight days.
9. The striking parts to be wound up every one or two days, except in
small clocks [or they will never strike efficiently]. All the striking to be
done by steel-faced cams on the great wheels. The 4th quarter bell to
have two hammers (see p. 133). In smaller clocks cast-iron cams will
do.
10. The hour striking to be let off independently of the quarters, and the
first blow to be struck exactly at the hour, the hammer being left on
the lift: the other quarters to begin exactly at 15, 30, and 45 minutes.
11. The hour hammer to be not less than a 60th of the weight of the
bell, and to be raised not less than 9 inches; the quarter hammers to
increase in weight upwards from a 60th to a 40th of the weight of their
bells, and all the hammers to be raised enough to bring the full tone
out of the bells: small ones at least 6 in., and the hour one at least 9.
SPECIFICATIONS FOR PUBLIC CLOCKS. 175
12. There must be either levers or eccentrics to lift the hammer levers
completely off the cams, when the bells are ringing, if there is a peal.
13. The small wheels of the going part to be of brass or hard gun-metal,
driving lantern pinions. All the larger wheels and the pinions driven
by them may be of cast iron, and their being of brass or gun-metal
will be considered no reason for a higher price. All bushes to be brass
or gun-metal. The large pivots to be case-hardened, the smaller ones
and their arbors to be of steel. The pulleys to be large and pivotted
in brass bushes.
14. The barrels of sheet iron brazed, with iron or steel wire ropes not
coated with zinc [which makes them crack], and the pulleys to be so
placed that the ropes do not grind, or go twice over the barrel.
15. The flies not to be in front of the clock, and to be long enough to make
the time of striking quite uniform, and slow enough. The fly ratchets
to be either squared or keyed on, and not merely pinned. The ratchets
not to be of cast iron, and each to have two clicks. [Many smashes
have occurred for want of attention to these two conditions.]
16. All the iron-work except acting surfaces to be painted blue [black is
more difficult to see if anything is wrong, and if not painted iron only
gets rusty].
17. If the weights go out of sight there must be something to stop or warn
against winding them too far. And also a large box with 3 feet deep
of small stones, to catch the weights if they fall; unless they go down
to the ground of the tower, when they can only break flags.
18. All wheels to take out separately by unscrewing the bushes; and pulleys
to be placed where they can be oiled.
19. On all points not specified, the clock is to be made according to the
directions of this book, applicable to clocks of the kind now required.
20. The clockmaker to provide (or design and superintend) a strong wooden
case for the clock, with glass showing the minute dial if it is in the belfry,
and so arranged that the striking parts can be wound without
opening the case; unless the clock is in a room always locked up, and
protected from weather. In many places it is necessary to have a case
for the weights, and pulleys at the top, if exposed in a bell-chamber.
21. The estimate to state the cost of the clock and dials, and of the fixing,
case, &c., separately.
THE WESTMINSTER CLOCK. 176
22. Half the price to be paid on the clock being completed, to the satisfaction
of such person, not objected to for good reasons assigned by the
clockmaker, as the committee may appoint, and the other half when
it has gone for three calendar months continuously, without varying
more than five seconds in any week—tested by the striking of the first
blow of any hour. [This is an ample margin to allow now that we know
from the Westminster and other clocks that they may be made to go
without much more than a second a week variation. Every town now
has the means of testing its clocks by electric telegraph time at the
post office, but not so exactly as it ought to be. And if there is any
neighbouring observatory, or meridian instrument, properly attended
to, that is much better.]
CONSTRUCTION OF THE WESTMINSTER
CLOCK.
The frontispiece of this book is a front elevation of this great clock, or so
much of it as can be shown in one view without confusion, for which purpose
I have drawn the wheels and pinions only as circles. As I have inserted the
numbers of the teeth, and the size of all the parts may be taken from the
scale, I shall say no more than that the frame is 151
2 feet long and 4 feet
7 inches wide. The going part does not occupy above 2 feet of this width,
the front bushes of the wheels being carried on a separate bar lying on the
two cross pieces of which the ends are shown in the drawing bolted to the
great back and front girders.
Double-barrelled Crab.—The space between the front of the going
part and of the great frame happens to be convenient for the fall of the
ropes from a double-barrelled crab (fig. 51 next page), which is fixed upon
the iron beams BB which go across the room from east to west to carry
the ‘motion work’ or nests of bevelled wheels above the clock, of which the
first pair are shown in the drawing. This crab is the only means of getting
anything into the clock room which is too heavy to be carried by a man up
the stairs. It consists of two small equal barrels, with four pulley grooves
in each, each having an equal wheel at the end turned by equal pinions on
the winding arbor. The rope passes over the outer halves of the two barrels
4 times, one end falling down the clock shaft or well for the weights while
the other rises; and it can either be used with a single rope, or with pulleys.
The pall P is in effect a silent click to hold the rope when the handle H is
let go; and it will turn over on the horizontal pillar at the top of the crab,
to act the opposite way when the barrels are worked the other way.
The great advantage of it is that it avoids the crowding and overlaying
of a long rope on the barrel, which makes the work harder at every fresh
‘overlay,’ as it practically increases the diameter of the barrel; and that
DOUBLE-BARRELLED CRAB. 177
Fig. 51: Double-barrelled Crab
DOUBLE-BARRELLED CRAB. 178
becomes so intolerable that the plan of pulling off the rope by hand after
three or four coils on the barrel has to be resorted to in long lifts; and that
again involves the difficulty of having to slide the coils back to the beginning
of the barrel, holding the rope by the hands of several men, or by some
supplementary machinery, for very great weights, as was done with Big Ben
in 1859. ‘Great Paul’ was raised on 3 May, 1882, by a double-barrelled crab,
or rather two of them, and pulley blocks besides; with only this difference,
that the ropes were crossed between the barrels to give greater frictional
hold; but that also causes a considerable friction of the ropes against each
other, and is really unnecessary. A crab like this, not with the ropes crossed,
driven by steam, was used for taking up the ribs of the great domes of the
1862 Exhibition. I had recommended it in the 1860 edition for taking up
heavy bells,11 and in the later editions I suggested a further improvement,
shown in fig. 52 (next page), by putting the pinions right in the middle
between the wheels, and making them all roll on blank ‘pitch circles’ (see
chapter on teeth of wheels), besides having small teeth cast by the side of
the circles. This will take a great deal of pressure off the barrel pivots,
and also off the driving pivots where it does mischief, and transfer it to the
rolling circles, where it is useful in driving and relieves the teeth, and would
almost drive without any. They may consequently be made much smaller,
and the wheels also, and yet with the same power as a much larger crab
of the common kind; especially if 4 wheels are used: which also has the
advantage of relieving all the pivots equally. 18 inch wheels with 11
2 inch
pinions would be strong enough for all ordinary work of single multiplying
crabs. And it is easy to add another wheel and pinion for larger ones.
The teeth of the pinions and wheels respectively should be made as will
be explained under ‘Teeth of Wheels,’ the pinion teeth alone projecting
beyond the pitch circle. The rolling circles must be hard, or they will bruise
each other. The arrangement of the frame also will depend on the work
for which the crab is intended; I only show what affects its principle. The
horrible noise of the common pall may be avoided by putting a wedge-shaped
one between any two of the rolling circles, with a slight spring acting on it,
according to the direction of driving for the time. This will act as a silent
pall as soon as you let go the handle.
Returning to the clock, the back of the frame is 2 feet 5 inches from the
west wall of the room, which is the east wall of the ventilating chimney or
air-shaft of the Houses of Parliament running all the way up the tower. The
room is 28 feet by 18, and the clock lies, as shown in the drawing, on the
north and south walls of the shaft or well for the weights, which is 174 feet
high, and the floor of the room is 21
2 feet below the top of two iron plates
11The differential pulley with an endless chain in notched grooves is now largely used for
moderately heavy weights, the chain being pulled by hand as in the old-fashioned 30-hour
clocks; but it will not do for great weights.
DOUBLE-BARRELLED CRAB. 179
Fig. 52: Another form of Double-barrelled Crab
REGULATION OF THE CLOCK. 180
which cover the walls and are spread out behind and built in quite through
the wall of the airshaft, so as to prevent any possibility of endway motion
of the clock frame, which is bolted to the plates. The pendulum cock is
a large frame work cast in one piece and also built in through the wall,
quite independent of the clock frame. The pendulum chamber is made of
sheet iron within the weight shaft, in order to protect the pendulum from
the wind: you can descend into it by a ladder and a trap-door; which can
seldom be wanted, as there is a degree plate set on the floor under the clock,
which is a little lower than the general floor of the room, and is covered with
a grating lying on the beams which carry the returned end of the ropes.
Regulation.—The mode of regulating the pendulum by small weights
has been sufficiently described at p. 35. Whenever a larger alteration is
required, in consequence of thunder-storms or an accidental disturbance of
the pendulum, either stopping the scapewheel or letting it trip one beat by
lifting a pallet alters it 4 seconds, whereas you cannot put a dead escapement
forward at all, nor stop it without considerable risk of spoiling a tooth.
The pendulum weighs altogether very nearly 700 lbs., of which the bob
is about 4 cwt. In other respects it has been already described at p. 30.
The spring is a 60th of an inch thick and 3 inches wide, and the free part
of it 5 inches long. The great pin through the upper chops has nuts on its
ends to adjust it to the exact centre between the pallet arbors. Those are
not shown at page 31, because they are not generally used. The pendulum
cock, and the position of the floor behind the clock, are so arranged that a
tall man can stand with his head inside the cheeks of the cock so as to look
square at the escapement; which is
The double three-legged gravity escapement, as shown at p. 91.
The scapewheel teeth are equidistant and 6 inches long; and though the
clock has to drive about a ton and a half of hands and dial-work through
all weathers, the pressure and friction on the stops are so little that I could
find no difference in the weight required to lift the pallets (by a thread over
a small pulley) whether the teeth were bearing on them or not,—i.e., it was
less than the friction of the pivots and the pulley. The weight required to
lift each pallet through the angle of impulse was an ounce falling .9 of an
inch, which is therefore the amount of impulse received by the pendulum
at each beat. In other words, the daily momentum of clockweight required
to drive the pendulum, or Wh in all the calculations about escapements,
is only about 200 pound-feet, while Ml is 9100, a much smaller proportion
than in the finest astronomical clocks, but yet larger than it was in the
three-legged dead escapement which we had at first (p. 70), on account of
the loss of force by the impact of the pendulum on the pallets. The fly is
11 inches long in each vane and nearly 2 inches wide: it is set on the arbor by
what may be called a silent ratchet, or a steel-faced roller with stiff springs
bearing endways against it, but obliquely, so that the fly can run forwards,
but not backwards. It is almost impossible to make the escapement trip by
MAINTAINING POWER IN WESTMINSTER CLOCK. 181
any force you can apply to it by hand; and it once went for several days
without tripping though the fly had been accidentally left loose.
Maintaining power.—The going part of this clock takes about 20 minutes
to wind up, and therefore none of the common maintaining powers would
do. A bolt and shutter (see p. 107) might indeed have been made to lift
higher than usual and so keep in action longer; but it would have had to be
very heavy, and moreover there was the risk of the man being interrupted
while winding, or stopping to rest, and so letting it run out of gear or stick
fast. Sir G. Airy had proposed a modification of his Northumberland telescope
apparatus, which I have already mentioned as having been used in
the Exchange clock; but that is also liable to run out of gear, and is open to
other objections; and so the following much simpler plan was adopted. The
barrel in any case would require an auxiliary pinion to wind it, taking into
a wheel on the end of the barrel itself, close to the great wheel; and the only
addition is, that the back end of the winding arbor runs in a loose bar, which
hangs obliquely from the back pivot of the barrel (as shown in the drawing),
and has a click on it which acts upwards in a set of ratchet teeth cast on
the back of the great wheel. When the clock is going and not winding, these
ratchet teeth pass under the click, just as in Harrison’s going ratchet (see
p. 104); but as soon as you begin to wind they stop the click and the bar
from rising as it tries to do, and the great wheel itself thus becomes the
fulcrum for the winding up of the barrel, and so the clock weight is for the
time transferred to the great wheel directly, instead of through the barrel.
The winding arbor fits loosely in both the bushes, because the back
pivot and its bush in the bar gradually move a little upwards as the great
wheel turns, while the front one of course remains fixed in the clock-frame.
When it has moved as far as it was thought prudent to let it go, a long
tooth on the winding arbor catches against a stop in the back frame, and
the man cannot wind any farther without turning the handle back a little
to allow the bar to drop and the click to take up another mouthful of the
ratchet teeth. The unusual length of the winding arbor, 4 feet 2 inches,
makes this sideway motion insignificant for 10 minutes motion of the great
wheel: if the frame were narrower it could still be used, taking care to put
the stop so as to prevent too much oblique action. Very few clocks take as
much as 5 minutes to wind up the going part. If you take the trouble to
calculate the pressure, you will find that there is rather more force on the
clock in winding than usual; which however is of no consequence. If the
winding pinion were larger in proportion to the wheel the difference would
be greater; but it might always be equalised by hanging a weight on the
loose bar, just enough to counterpoise the difference. The winding pinion
pulls out of gear with the wheel in the usual way.
The dials are 221
2 feet in diameter, or very nearly 400 feet in area, and
are made of cast iron frame work filled with a very expensive kind of opal
glass, which appears to me no better than some much cheaper glass of the
DIALS AND HANDS. 182
same colour by Chance of Birmingham, which is used in other clocks. The
dials and the hands together cost no less than £5334, which is more than
the whole cost of the clock and all the striking work up in the bell chamber.
I shall have more to say of this in the history of the clock. The minute
spaces are a foot square, and the figures 2 feet long. The dials would have
been clearer, and the hands more visible upon them, if the framework rings,
beyond the minutes and the figures, had been omitted, as they diminish the
clear space in the middle of the dial by about one third of its area. The dials
stand 5 feet from a whited wall which is the main wall of the clock room
and clock-tower, and in front of which are the gas lights for illumination. I
had provided by request that the clock should be able to light up and turn
down the gas if required, in the way described at p. 158, but it was finally
thought better to light them by hand, and I think so too. There is nothing
peculiar in the dial-work except its size, which may be judged of from the
drawing of the clock and fig. 51 (p. 177), and the fact that the minute wheel
arbor is 8 feet long and 31
2 inches thick; it is of course tubular, except at
the ends. The dial centres are exactly 6 feet above the top of the walls, or
180 feet from the ground.
Hands.—The minute hands, as made from my design, after the architect’s
two successive sets had failed, are thin copper tubes of a section
formed by two segments of circles, with a few diaphragms soldered in, set
on a gun-metal stalk or central piece, which also forms a partial counterpoise
both for wind and weight outside, there being another of cast iron
inside the clock room, to divide the pressure between the two ends of the
arbor. This copper tube of each minute hand only weighs about 28 lbs.,
though they are 91
2 in. wide near the centre, running off to 51
2 at the end;
the gun-metal stalk of each hand weighs very nearly 1 cwt.; but the whole of
that weight is near the centre, and so its moment of inertia at each beat of
the pendulum affects the clock very much less than if the same weight were
distributed all along the hand. It is remarkable that from the momentum
of the hands, and the general elasticity of the leading off rods, they move
continuously, and with no visible jump as usual. The length of each hand
and its external counterpoise is 14 feet; and the total weight of each hand
with its external and internal counterpoises is now within 2 cwt., whereas
Sir C. Barry’s 4 minute hands and counterpoises (of which I shall have to
speak in the history of the clock) weighed a ton and a quarter. His hour
hands are still there; for though very bad in construction and three times
as heavy as they need be, their motion is so slow that they do not sensibly
affect the clock as the minute hands did, and so they may as well stay until
they become unsafe. One of them cracked and had to be taken off. The
hour hand arbor is a tube 51
2 inches wide, and lies on large friction rollers
both behind the dial and within the clock room. It was easy enough to put
the clock room end of the minute hand arbor on friction rollers too, as it
of course projects beyond the other; but at the other end it is managed by
QUARTERS. 183
setting the pivots of 4 smaller rollers in a pair of rings screwed outside the
hour hand tube, and cutting holes in that for the rollers to go through and
reach the minute arbor, so that those rollers move in a 12 hour orbit of their
own, besides the pair in action for the time turning on their own pivots.
Quarters.—There is nothing very peculiar in the striking of the quarters.
The position of the levers and cams is evident from the picture. The
wires go up alternately on opposite sides of the winding-wheel arbor to prevent
their fouling each other; each bell has two hammers because in that
way we get longer cams with less pressure on them, and on the levers. The
hammers are all nearly a 40th of the weight of their bells, which I am satisfied
is the proper proportion for bells on this scale of thickness, which is
that of the smaller and thicker bells of church peals, as I shall explain more
fully afterwards. The levers are all 191
8 in. long, and their centre is nearly
36 in. from that of the wheel. The cams are of wrought iron with hard steel
faces, screwed onto a cast iron barrel which is bolted to the great wheel, and
they are constructed on the circular section which I shall describe for cams
under the Teeth of wheels. Between the clock and the bell chamber there is
another low room in which the cranks are, for leading off from the vertical
wires to the 4 quarter bells. These wires are in fact wire ropes: I had them
substituted for the iron rods which were at first used both in the quarters
and the hour striking parts, and thereby got rid of an amount of concussion
and noise in striking, which sounded as if the clock was shaking to pieces.
Now the action in the clock room is so silent that you hear nothing except
the bells and the passing of the click which stops the train from running
back in winding.
Hour-striking part.—The great striking-wheel has 10 cams 21
2 in. wide
cast upon it, and these have steel faces screwed onto them. The lever has
a thick part in the plane of the cams and a longer and thinner piece lying
behind the wheel and having the hammer rope attached to it, or rather a
short rod with a swivel and nut to take up the rope. The rope is half an
inch thick, the same as is used for the striking weights, and is about 25 feet
long and reaches up to the horizontal arm of the great hammer lever, which
projects 5 ft. 4 in. from the pivots, which are forged as part of the collar
in which the great bell hangs (see page 151). The hammer shank is also
double, going through 8 holes in the cast iron head, which weighs 4 cwt.12
and is lifted 13 in. from the bell, or about 9 in. vertically. Then is an
iron plate screwed to the hammer shank, which falls on india-rubber buffers
5 in. thick, carried by a kind of long stirrup hung from the bell frame. The
other hammers are prevented in the same way from jarring on the bells. The
construction of the bell frame, which is entirely different from the usual form
of frame for swinging bells, made it impossible to fix the hammers or the
12It did weigh 7 cwt., but was reduced when the bell became partially cracked, as related
afterwards.
HOUR-STRIKING PART. 184
buffers in any other way: not that there is any objection to this, except that
it is more expensive, and the hammer shank is farther from being horizontal.
The second wheel turns 2
3 round for each blow, as I explained that it
might at page 141, and the third wheel and 4 turns for each blow. The fly
arbors are placed vertically in order to get room for the flies, which have
to be put near the top of the room. The vanes of the hour fly are each
2 ft. 4 in. square and extend 3 ft. from the arbor: the quarter ones are
rather larger. To prevent all risk of accident, the ratchets are not pinned
but ‘squared’ on the arbors under the flies themselves with an octagonal
fitting, and each fly has two clicks. The stops are set on springs to diminish
the blow at stopping, and the striking work is stopped on the lift, both
for accuracy of discharging and for diminishing the constant strain on the
wheels and arbors. Each striking weight is, or was before the hour hammer
was reduced, nearly a ton and a half; and you may observe that each of the
three parts is so arranged that the weight hangs between the arbor of the
great wheel and the teeth or cams which have the heavy work to do, so as
to reduce the pressure and friction on the arbors as much as possible. If this
striking part had been made as they often are, and lifting by pins instead
of cams, the weight would very likely have had to be 3 tons, or more than a
man could wind up in a day.
The mode of letting off the hour-striking is peculiar. It was one of the
original conditions, that the first blow of the hour should always be struck
within a second of the real time; and in order to do this it was not sufficient
that the clock should go far more accurately than usual, but there must also
be the means of making the hammer fall exactly when the clock reaches the
60th second of the last minute of the hour. First then it was necessary to
leave it on the lift and nearly ready to fall as soon as the striking part is
discharged; and secondly, to have some more sudden and precise means of
discharging it than the slow motion of a snail turning in an hour. It was
at first intended to do it by the train remontoire described at p. 161; but
when it became expedient to abandon this and rely on the improved gravity
escapement which I invented after the clock was partly made, it became
necessary to contrive some other plan for discharging the striking part with
equal accuracy: and this is it. PQ is the ordinary discharging lever lifted
by the snail on the hour arbor, P being the first stop against which the
arm EF on the third wheel of the striking train is stopped when it has done
striking.13 The second or warning stop D is not on PQ, but on a short
independent lever CD. BAS is another lever set on pivots A on the cross
bar of the great frame, and its heavy end S is lifted and dropped by a snail
on the 15-minute wheel of the escapement; when it drops it tips up the
13This lever, and several others, are omitted in the elevation of the clock (frontispiece), as
they could not be shown without confusion; and as the snails are all shown, any intelligent
reader will understand where the discharging levers must be: there is an intermediate one
from the quarter snails to the quarter locking lever.
HOUR-STRIKING PART. 185
second stop lever CD, not merely by dead weight, but with a blow, which
is certain to overcome any friction there can be between the two stopping
Fig. 53: Mode of Discharging Exactly
pieces. The lever BAS drops every quarter of an hour; but it does nothing
except when the stopping piece is resting against the second stop, i.e., when
the clock has given warning for the hour. It is let off at the 58th second, or
the last beat but one of the pendulum in the hour, and the train just gets
far enough into motion to let the hammer fall as the seconds hand makes
its last jump for the hour, and it acts with the greatest precision.
This precision in letting off the hour-striking made the want of it disagreeably
apparent in the quarters, which were at first discharged in the
usual way by a snail on the hour arbor which leads off to the dial work;
and we had to put a larger snail for them on a separate arbor under the
escapement wheels, free from the shake of the hands and dial work; this
answers very well and there is never more than 2 seconds difference now in
the time of discharging the quarters. The 1st, 2nd, and 3rd quarters all begin
to strike at those times respectively; but the 4th quarter is let off about
20 seconds before the hour so that it may have done striking before the hour
begins at the real time.
That, by the bye, is an objection to a train remontoire let off at the usual
half-minute intervals, viz., that it makes the interval between the quarters
and the hour disagreeably long, if the hour is to begin striking exactly at
the hour as it should do. Even 20 seconds is too long an interval for any but
WINDING OF STRIKING PARTS. 186
very large bells. However since the invention of these gravity escapements
train remontoires may be considered extinct, as they cost much more, and
are no better, and are almost certain to be destroyed, or at least put out of
action.
Winding of striking parts.—Each of these takes about 5 hours to
wind, and requires double multiplying wheels, which are as to size repetitions
of the large wheels and pinions of the train, with a modification of the shape
of teeth, which will be explained afterwards, because different shapes are
proper for driving and for driven teeth, though that is very seldom attended
to. The striking parts wind twice a week; for although they might have been
made to go a week, the weight would have had to be twice as much—and
more, on account of the increased friction; and a man could not have wound
up each of them in an ordinary working day. Moreover the whole work must
have been heavier and larger and had a greater strain upon it. Even in much
smaller clocks than this I always design the striking parts to go less than a
week. I do not believe that there is a clock in the world that strikes a large
bell, say above a ton weight, properly, with winding once a week; unless it
happens to have an unusually large fall for the weights.
There were various suggestions made both publicly and privately for
winding the clock by water, by a steam engine, and even by a kind of
weighbridge or sinking platform to be worked involuntarily by people walking
overWestminster bridge, which would have to rise between every two walkers
to do any good: a turnstile would have been a much more practicable thing. I
forget whether anybody proposed to turn the tide to account for the purpose,
but I daresay they did. It never occurred to these inventors that the interest
on the cost of construction and the expense of looking after any such machine
would far exceed the wages of two winding men for five or six hours twice a
week.
In most large clocks the winding pinion simply ‘pumps’ out of gear with
the winding wheel on the front end of the barrel, and it does not much
signify if it is left in, as the friction caused by it is not much. But this would
not do for a pair of large wheels, and there was not room to make the great
winding pinion pump out of gear. Moreover it was absolutely necessary to
have some contrivance for automatically stopping the winder a little before
every striking of the part he is winding; which occurs in no other clock, as
none takes anything like a quarter of an hour to wind either part, and if it
did you need only slip off the handle. That is managed thus. In each striking
part a long lever (omitted in the frontispiece to avoid confusion) stands in
the way of a tooth or arm on the winding arbor: when the man begins to
wind he must lift this lever up on to a certain hook which will hold it up so
long as the weight of the lever rests upon it; but when the weight is relieved
the hook falls back: this is done by the snail a few minutes before the clock
is going to strike, and just a minute before it strikes the snail lets the lever
drop again, and the hook being then out of the way, it drops completely and
RATE. 187
stops the winder; and he then throws the winding-wheels out of gear, and
in again when the striking is done.
This throwing out of gear is also done by a new method: the first pivot of
the second (150) winding-wheel arbor is set in an eccentric bush, which can
be turned in its own holes by a lever with a handle to it, as you see in the
drawing, and the eccentricity is just enough to take the teeth of that pinion
out of gear with the great winding wheel, leaving the 2nd wheel in gear with
the winding-pinion (14). Besides this the ropes themselves stop the winder
when the weights are wound up to the top, by throwing another lever off
a hook on which it has to be set before the man can begin winding. In all
these winding and maintaining power contrivances there are some further
provisions for enabling the man to turn the winding handle back a little, to
let the barrel ratchets down softly on to their clicks, but it is hardly worth
while to describe them.
Rate.—Provision is made in the clock for reporting its own rate of going
to the Greenwich observatory at any convenient hour or hours every day,
by electric telegraph, as I have already described under ‘electrical clocks’ at
p. 111; and it has been arranged by the Astronomer Royal that it should give
two signals a day, at an hour before and after noon, for greater accuracy. The
average performance of the clock is reported by him annually to the Board
of Visitors of the Observatory, and for years the report has been practically
the same. Last year, 1881, its error was under 2 sec. on 84 per cent. of the
days of observation; between 2 and 3 sec. on 14; between 3 and 4 on 2. They
were almost exactly the same in 1872.
Sir G. Airy sent me, for the purpose of the inquiry into the barometrical
error (see p. 49), the complete rating of the clock for 1872, except Sundays
and a few odd days. Rejecting three abnormal disturbances, one of which
reached 8 sec. in a week of thunderstorms, and two others of 5 sec., which
came suddenly, and evidently from something done in the clock-room, because
the daily variations never reached 2 sec. at any other time, the average
daily variation was only 0.2 sec. on each side of zero, or 0.4 sec. altogether;
and taking it on all the Saturdays in the year, the average weekly variation
was just 1 sec, or exactly half that of one of old Mr. Dent’s best regulators
which I happen to have had for nearly two years while we were trying the
Exchange clock. Therefore the first blow of the hour may be presumed to
differ considerably less than a second from GMT, and is practically always
right within 2 seconds. In hearing it at a distance you must allow nearly
5 seconds a mile for the velocity of sound.
Some enemy set afloat the statement that the clock is ‘controlled’ by
electrical connection with Greenwich, in some such way as is described at
p. 112, instead of merely reporting its own performance; and the story has
been repeated by people who ought to have known better, or might easily
have learnt, by writing either to the Astronomer Royal or me, or from
any edition of this book after the first. A signal is sent back from GreenHISTORY
OF THE CLOCK. 188
wich at some hour daily, for the information of the winding men, but they
never touch the pendulum unless the error is 2 seconds, which happens very
seldom.
History of the clock.—It is no longer necessary to relate as fully as in
1860 the history of the 16 years of disputes relating to this clock; for it was
the subject of violent disputes before I had anything to do with it. I shall
only say as much as may possibly be useful with reference to any similar
transaction hereafter. Not that I expect such warnings to be attended to,
except perhaps in exactly the wrong way; for I know very well that the
tendency of the official mind to get things done with as little trouble as
possible is infinitely stronger than to get them done as well possible. I was
only brought into this business originally with the view of saving somebody
else trouble; and as soon as it was found that by the legal effect of the
contract I had real power to direct the work, every possible effort was made
to get rid both of it and me. No official who joined in those attempts cared
three half-pence how the clock was made. Luckily I did care, and knew what
would become of it if I gave it up. And as the biographers of Sir Charles
Barry have told their story on his behalf, I shall also, without the least
resentment against them, repeat mine, of which not a word has been ever
contradicted.
No one who has read in the Parliamentary papers the early correspondence,
beginning in 1844, can have the smallest doubt that the architect
had made up his mind that the late Mr. Vulliamy should make the clock,
and no one else. Mr. Vulliamy himself was so confident about it, that even
after the Astronomer Royal had utterly condemned his plan for it, as ‘only
suitable for a large village clock,’ and recommended old Mr. Dent, he said
to me, ‘Dent will never make that clock.’ After that, the matter went to
sleep till November 1851, when the Duke of Somerset, then Lord Seymour
and First Commissioner of Works, asked me to act as referee with the Astronomer
Royal, on his recommendation. I examined the plans at the Office
of Works, which had been sent in in 1846, and found that Vulliamy’s was
quite as deficient in strength (for which Sir G. Airy had commended it) as
it was in all provisions for accuracy: indeed more so, because accuracy is a
question of degree; but such a clock as that, striking on a bell of half the
weight that had been fixed upon, would have destroyed itself in week. By
some strange omission, Dent had never been told that the bell was to weigh
14 tons, and he had assumed it to be much less, and consequently his plan
was defective too, though not so defective, and that only in size, not in principle.
The plans of Whitehurst, of Derby, which Sir G. Airy had reported
on more favourably than Vulliamy’s could not be found in the office; and
it was evident that Dent’s had been somewhere else, where they had been
very roughly handled, dirtied, torn, and mended, which was certainly not
done at Greenwich.
Whitehurst was dead, and Vulliamy had refused to accept the Astronomer
EARLY DISPUTES ABOUT THE WESTMINSTER CLOCK. 189
Royal’s conditions as to the performance of the clock, which the Clockmakers’
Company also pronounced impossible, though they have been far
exceeded in accuracy now. So we agreed that it was useless to apply to
any one but Dent, and that the only practicable way was to ask him if he
would make for any definite sum such a clock as we should require, from
his own knowledge and our information as to what was intended, and such
general plan as we could give him, in the unfinished state of the tower. He
agreed to do so, for a sum which was soon found to be inadequate, and the
arrangement was altered into his keeping a separate account of all outlay
on the clock, and receiving 10 per cent. profit on it, which ultimately came
to £4080, only an eighth more than Vulliamy’s estimate for a clock totally
unfit for the work.
The Duke of Somerset went out of office soon after giving Dent the order
in 1852; and then began, and lasted through the reigns of his successors, Lord
John Manners and Sir W. Molesworth, a series of intrigues and attempts
to get rid of or alter old Mr. Dent’s contract, and then to repudiate his
successor F. Dent, and then—or rather, all along—to get rid of me; for
they all knew very well that for various reasons the Dents alone could not
contend against them, nor go on with the work at all. Sir C. Barry demanded
working drawings of the clock from Dent, who told him very truly that there
were none, and would be none, except such sketches as I might give his men
from time to time. Then he applied to the Astronomer Royal for them, who
desired me to make and send them. I answered that I should do nothing
of the kind: the Office of Works might show him the signed plans if they
liked (as in fact they did), which were all that could possibly concern him;
at any rate I should make no others. Thereupon Sir G. Airy resigned; and
as his knowledge of large clocks was purely theoretical, and not one of the
suggestions he had made could be adopted, his resignation saved a good
deal more of unprofitable correspondence. The Office of Works made that
another excuse for trying to get rid of me, and went so far as to consult the
Attorney and Solicitor General about it.
Then they tried the obstructive policy of refusing any information about
the tower, in spite of my warning that the only consequence would be that
they would probably have to pay for altering the clock when it got there;
for which they cared nothing, as the nation and not they would have to pay
for it. Still the work went on, and as the inscription on it records, the clock
was made in 1854, and after going in the factory for 5 years was fixed in the
tower in 1859, and was set going permanently in 1860.
Sir C. Barry was particularly anxious to design the hands, and I rather
unwillingly and with some misgiving consented, having already reason to
put very little faith in his mechanics. He first produced some cast iron ones,
of such frightful weight that I would not even let them be put on. He then
tried some of gun-metal, which were lighter, but still far too heavy for the
clock, besides being so fixed on by his engineer that they fell over a minute or
HISTORY OF THE WESTMINSTER BELLS. 190
two every time they passed the vertical. And so we removed them, at least
the minute hands, and made new ones, as described at p. 182, which have
always gone quite easily, except once when loaded with snow which froze
upon a partial thaw, and broke down hundreds of miles of telegraph wires
at the same time that it stopped the clock. Before Dent’s final bill was paid,
the Astronomer Royal inspected the work, though his legal control over it
was gone, both from his resignation, and from other causes, and he candidly
expressed his entire approval of it, and especially of the escapement, on
which its performance chiefly depends. It is due to Lord Llanover, though
he is dead, to say that in his time I had no trouble with the Office of Works.
As soon as it was finished, Mr. W. Cowper Temple, who had then been
made First Commissioner of Works by Lord Palmerston his step-father, told
the House of Commons, with evident satisfaction, and the gratitude natural
to some people, that my connection with the clock had ceased, and that
it was handed over to the Astronomer Royal. The next I heard of it was
that he had replaced the great check spring of the hour-striking part by
a contrivance of his own, which soon produced a smash, and then the old
spring was quietly restored, and is there now, and there have been no more
such experiments. I must however do him the justice to say that he had
previously written to me ‘that the clock would be far better in my hands
than in any other person’s;’ not that there was really any more for me to do,
beyond nominal superintendence of the clockmakers who have the care and
winding of it by an independent contract, viz., the successors of the Dents
in the Strand. By an odd coincidence, I had the pleasure of giving a sort of
clinical lecture on the clock to as many members of the Horological Institute
as the room would hold, on the 21st anniversary of our signing the plans for
it, 29 January 1873.
THE WESTMINSTER BELLS.
I had better give the history of them also here. In 1852 Astronomer Royal
declined to have anything to do with the bells, as he did not profess to understand
them; and nothing was done towards getting them, beyond some
abortive correspondence with me by Sir W. Molesworth, and his giving a
commission to Sir C. Barry and Professor Wheatstone to learn what they
could about bells at the Paris Exhibition of 1855, which proved to be nothing.
In 1856, Sir B. Hall (Lord Llanover) asked me to take them in hand,
and it was then arranged that I, with Sir C. Wheatstone, and the late
Rev. W. Taylor, who had paid some attention to the subject in a theoretical
way (and must be distinguished from his namesake the bell-founder),
should be the referees. Sir C. Wheatstone never acted, beyond telling us
the result—or rather, no result—of his inquiries at Paris, and Mr. Taylor
would take no responsibility beyond giving the final certificates. I therefore
HISTORY OF THE WESTMINSTER BELLS. 191
prepared a specification, which was sent to the three English bell-founders.
Mr. Mears refused to accept the referees because they had among them
spoken ill of his two condemned Royal Exchange peals, of his great York
Minster bell, and a rather larger one which he had sent to Montreal. He
also declared that nobody else could make the bells; and his tender was not
the lowest. Mr. Taylor’s (of Loughborough) was; but he wanted some terms
which could not be acceded to. Messrs. Warner required the referees to take
the responsibility of giving the patterns for the bells; i.e., they confessed
that they did not know how to make such large bells of the proper notes:
they had previously copied all their bells from existing ones. However I was
able to do that for them, and so their tender was accepted, though they
demanded ten guineas a cwt., while the usual price was seven, and they
were to recast any of them (unless condemned for bad casting, in which case
they were to recast for nothing) for £2 a cwt., and also to cast any small
experimental bell the same price.
They made the great bell first; and from some mismanagement it came
out thicker than the pattern, and two tons heavier than was intended, and
required a clapper twice heavy as we had reckoned on by analogy to other
bells. Undoubtedly we had a right to reject it; but it appeared a sound
casting, except some holes at the top, and was generally praised by the
public who heard it, though there was always something unsatisfactory in
its tone. And no wonder; for after being rung occasionally for some weeks, it
one day cracked, no doubt from the weight of the clapper which it required
to bring out its tone, and when it was broken up there was found a great
flaw in it, where the two streams of metal meeting round it had never joined.
So we were in every way well rid of Big Ben the first.
The founders however had cast then the fourth quarter bell of four tons
successfully, and there was no intention of taking the job out of their hands.
But they demanded a price for recasting enormously beyond the £2 per cwt.,
which they had agreed to before, evidently presuming that neither of the
other founders would be employed. Mr. Mears had learnt something by
experience, and no longer objected to the referees, and offered to recast the
bell at a more reasonable price, and so this time his tender was accepted.
He however was still more unlucky; for he produced a bell which partially
cracked also, after a few months striking; and Dr. Percy pronounced it, on
cutting a hole down to the bottom of the crack, and analysing the metal,
‘a defective casting, porous, unhomogeneous,’ and at the place where it is
cracked, not of the composition I had prescribed, and therefore much more
brittle.
Mr. Mears also determined to conceal this porosity from the referees by
filling up the holes with cement, before he let us know that the bell was
ready to be seen. And when I publicly charged him with having done so, he
put a bold face on the matter, and brought an action for libel, and had, no
doubt, found half-a-dozen engineers and brass-founders ready to swear that
HISTORY OF THE WESTMINSTER BELLS. 192
porous castings are as good as sound ones. But he also found that I had
got a piece of the bell analyzed, and knew that the composition was wrong,
besides the porosity and its concealment. So his counsel accepted his costs
without a verdict, after making a speech in which he confessed and declared
that the composition had miscarried, and become unhomogeneous; that he
had filled up the holes, because he thought them immaterial—as if he was to
be the judge of that; and that it was impossible—i.e. that he did not know
how—to cast large bells without holes in them!
His successor, who had bought Mears’s declining business, twenty years
afterwards thought he would try again, evidently with the object of advertising
himself, on my once more publishing the fact that Big Ben II. was
a disgrace to its founders. His workmen who had been with Mears had
to confess the concealment of the holes, and again they and all his party
asserted that it is impossible to cast large bells without holes, and that it
was their regular practice to fill them up with cement coloured with bell
dust: which both Taylor and Warner’s people utterly contradicted, and I
have every reason to believe, quite truly.
Though Dr. Percy had been asked to examine the bell as soon as the
cracks were discovered, he was not allowed by Mr. Cowper Temple, then
First Commissioner of Works, to cut into it for nine months after. If that
had been done at once, as I desired, Mears’s action would never have been
heard of.
He had also got a report from Sir G. Airy, who, although he declined
meddling with the bells before because he did not understand them, felt
no difficulty in giving judgment on them afterwards, with the help of two
musical assistants and fiddle ‘tuned to the pitch of the Italian opera’—as if
the pitch of the Italian opera had anything to do with the question whether
five bells are good or bad, or in tune with each other. Mr. Turle, the organist
of Westminster Abbey, had given his opinion before we certified them, that
the four quarter bells were ‘all that can be desired, both in tune and tone,’
which are very different things (for a set of iron pots may be in tune), except
that ‘the fourth is a shade too flat’ But Sir G. Airy came to a very different
conclusion, viz., that the fourth bell was a note and a half too sharp, and the
first about the same, the third ‘rather sharp,’ and the second alone right.
On the whole, he was ‘much dissatisfied with those bells,’ and thought two
at any rate must be recast. Afterwards he began to have a little misgiving
about it, and thought it might be advisable to try again before recasting
them; but he never did try again. I suppose it had then occurred to him,
as a mathematical fact of which he certainly was not ignorant, that the two
bells could not be a note and a half too sharp without being a sixth less
in diameter than they are, or else a great deal thicker. He also pronounced
the great bell, which Dr. Percy had not then ascertained to be cracked three
inches deep, and to have almost every possible unsoundness, ‘perfectly sound
for all practical purposes, and the cracks probably superficial,’ and that it
TEETH OF WHEELS. 193
only wanted a lighter hammer faced with tin!
This seems to have been too much even for Mr. Cowper Temple to swallow;
for although he sent me one of the polite and intelligent epistles which
I used to receive from him and Mr. Alfred Austin, then the secretary of that
office saying that he ‘disagreed with every word of the stricture I had sent
him on Sir G. Airy’s report’ (as if his adoption of it made it less ridiculous),
he afterwards consulted Mr. Turle again, and no quarter bells were recast,
nor was the great hammer faced with tin; and after getting Dr. Percy’s report
he told the House of Commons that the bell was, not ‘perfectly sound,’
but ‘irretrievably cracked,’ as it is, though the defect is much less perceptible
than one would expect. The hours were struck on the fourth quarter
bell for three years, which made them difficult to distinguish at a distance,
and after a paragraph in the Globe to that effect, the striking was resumed
on the great bell with a lighter hammer striking in a different place, which
was easily done by my arrangement for turning the bell any degree round
by giving it a mushroom or button-shaped top (see p. 151). When the new
great bell of St. Paul’s has taught people the difference between a cracked
bell and a sound one, perhaps ‘this great country’ and ‘the model legislature
of the world,’ as it is the fashion to call them, may screw up their courage
to the vast undertaking of recasting their own great clock bell at the cost of
six or seven hundred pounds.
The cost of the bells, including £750 for recasting ‘Big Ben’ was under
£6000, while the cost of the iron frame provided by the architect was about
£6600 partly in consequence of its being made too weak at first, so that it
shook under every blow of the hammers, as I had told him that it would.
And as the clock, with my hands, cost only £4080, while his hands and dials
alone cost £5334, you see that the actual clock and bells cost much less than
the architect’s appendages to them.
TEETH OF WHEELS.
There are various treaties on this subject, and I only intend to say as much
on it as it is necessary that a clockmaker should understand, if he means his
wheels and pinions to run together smoothly instead of wearing themselves
out by jerking and scraping, which I have known to happen in a very few
years. The most comprehensive view of the whole theory of tooth-drawing
(at least of this branch of the art) is in a paper by Sir G. Airy in the 2nd vol.
of the Cambridge Transactions, and it was further expanded by Professor
Willis in his Principles of Mechanism.
Some persons have a mistaken impression that the object to aim at in
constructing wheel-teeth is to make them roll on one another without any
rubbing friction. This can indeed be done by what are called involute teeth,
of the shape described by a point in a string unwound off the circumference
HELIX-TEETH. 194
of a wheel: but they are really useless because they are so oblique that
they produce a squeezing pressure between the two wheels which is more
than equivalent to any saving in friction. The great thing to aim at in
describing teeth is to make the relative velocity of the wheels uniform from
the beginning to the end of the contact of each pair of teeth, which of course
involves also the absence of all concussion or drop of the teeth. Another
point is to have the action entirely or chiefly between the teeth which are
separating from each other, and not between those which are approaching,
which is commonly expressed by saying that the action should be after the
line of centres of the wheels and not before it. The reason of this will be
evident at once if you draw some teeth with a very rough outline, so as to
give an exaggerated view of the effect of friction, for you will see that there
is a degree of roughness which will make the teeth jam against each other
and not let them slide at all as they approach the line of centres, but that
no degree of roughness will do this when they are leaving contact or are past
the line of centres. The most perfect thing is when the contact takes place
for a very short distance only close to the line of centres; and this can only
be with very small teeth, and therefore very high numbers (except with
involute teeth, which I have already said will not do for another reason).
There is indeed a contrivance, which I have somewhere seen called White’s
gearing, for getting this kind of action with large teeth in heavy machinery,
by putting several large-toothed wheels close together, with the teeth of each
a little behind the other, as in figure 54 a (next page): but this is never used
in clockwork.
Helix-teeth.—A modification of this plan, though very unlike it in appearance,
has been occasionally used in clocks under the erroneous name of
the helix lever. The teeth certainly do at first sight suggest the idea of an
endless screw, but are essentially different, the arbors being parallel, and
not at right angles as in an endless screw. If you suppose a good many very
thin toothed wheels put together side by side, each with its teeth a little
behind its neighbour, they will present a surface like a rough tooth with a
sloped face, as in the upper part of this figure a. Then go a step farther and
suppose the rough edge to be smoothed off, and the result will be a smoothfaced
oblique tooth, like the lower one in the figure, which will drive teeth
of corresponding obliquity on another wheel, and the contact will be solely
at the line of centres, where there is no friction. But when the teeth thus
become smooth, there will evidently be a great endway pressure on each
arbor, which there is not while the teeth are square, or belonging to separate
wheels put together. This endway pressure may however be neutralised
by again putting two such wheels together with the teeth sloped opposite
ways as at b. There was a German turret clock on this plan in the 1851
Exhibition, which certainly went with a very small weight; and small clocks
with the single helix tooth had been made in England many years before
by Macdowall (see p. 68) which also required less force than usual, from the
EPICYCLOIDAL TEETH. 195
Fig. 54: Helix Teeth
smallness of the friction in the teeth. I do not know that the advantage is
worth the expense; but as this construction is very little known, I explain it
in case it may be turned to any use hereafter.
Epicycloidal teeth.—It may be said without exaggeration, I believe,
that all the teeth now used in machinery are constructed either as epicycloids
or hypocycloids, and the meaning of those words is this:—If you roll a circle
AGP on another circle ARY, the curve RP traced by any point P in the
rolling circle is called an epicycloid to the circle ARY; and if you roll the
small circle AGP within a larger than itself, such as AQX, the curve PQ
traced by P is a hypocycloid to that circle. And it is remarkable that if
the tracing circle is exactly half the size of the one in which it rolls, the
hypocycloid PQ is a straight line, and part of the diameter of the large
circle, and therefore teeth so described are called radial teeth. Now suppose
ARY is the circumference of what is called the geometrical or pitch circle
of a wheel which is intended to drive another, and AQX the pitch circle of
the wheel to be driven, which is generally called the ‘follower,’ but which
I think it better to call the runner, as followers do not usually run before
their driver; then it is easy to see that the arc AP of the tracing circle is
equal both to AR and to AQ, and also that the epicycloid is always more
TEETH OF DRIVER AND RUNNER. 196
Fig. 55: Epicycloidal Teeth
PPPPP
J
J
J
J
J
J
J
J
J
JJ
A
O
G
X
P
Q
R
Y
Runner
Driver -
convex than the hypocycloid, and therefore that the point P in the tracing
circle is always the point of contact between two teeth so traced, and the
velocity of the two wheels is always the same as if their pitch circles rolled
upon each other without any teeth at all; and therefore it is constant in all
positions of the teeth. It is hardly necessary to observe that the teeth of
the driver, to act after the line of centres, must be wholly outside its pitch
circle, and those of the runner wholly within. The part of a tooth within the
pitch circle is generally called its flank or root, and the part outside is called
the point, or the addendum, and sometimes the curve, because the flank is
generally made radial, i.e. a hypocycloid described by a circle of half the
diameter of the pitch circle. For it is further to be observed, that although
the points of the driver and the flanks of the runner must be traced with
the same circle, it is not the least necessary that the points and the flanks
of the same teeth should be traced with the same circle.
In clockwork the wheels always drive and the pinions run, except the
12 hour wheel in the dial-work, and the winding wheels and pinions if there
are any. It can be proved, as you may see in Professor Willis’s Principles
of Mechanism, but the proof is too long to give here, that no pinion of less
than 11 leaves (except of a kind which I shall describe presently) can be
TEETH OF DRIVER AND RUNNER. 197
driven entirely after the line of centres. A pinion of 10 can very nearly; and
there is so much difference between the force required to drive pinions of
8 and those of higher numbers, that some spring clocks with Macdowall’s
escapement which answered perfectly with pinions of 10 or 12, failed with
the common pinions of 8, for want of force to drive the two extra wheels in
the train. Professor Willis gave the following table of the lowest numbers
which will work together with all the action after the line of centres:—
Driver 54 30 24 20 17 15 14 13 12 11 10 9 8 7 6
Runner 11 12 13 14 15 16 17 18 19 21 23 27 35 32 176
Fig. 56: Drivers and Runners
The practical inference from this is, that if you use these numbers, or any
higher ones, together, the driving teeth require no flanks and the running
ones no points: indeed if you mean to prevent any action before the line of
centres, the runners obviously must have no points, because if they have they
will be geometrically identical with the teeth of a pinion intended to drive
the wheel after the line of centres when reversed. Suppose for instance, what
is nearly the case in the Westminster clock, that the great striking wheel at
one end of the barrel and the great winding wheel at the other are both of
the same size and number of teeth, and that their pinions are also the same;
then as the striking wheel always drives, but the winding wheel is always
driven by its pinion, the striking pinion and the winding wheel ought to
PROPER USE AND CONSTRUCTION OF LANTERN PINIONS. 198
have no points to their teeth, and the sections of the two wheels and pinions
would be as in fig. 56, the right hand representing the striking part and the
left the winding, and the action being in both cases, you observe, after the
line of centres AC, as the arrows indicate.
It is evident that the same wheel cannot properly drive two unequal
pinions with radial teeth. Whenever the same wheel has to drive two such
pinions, the flanks of the pinion teeth and the points of the wheel teeth must
be traced with the same circle, and that circle must not be larger than half
the size of the smaller pinion, or else it will make the teeth of that pinion
weaker at the roots than even radial teeth are, which are of course narrower
at the bottom than the top, and therefore are a weak form, especially in
small pinions. A case of this kind occurs in every clock on the patterns I
have described at pp. 131 and 140, and in the Westminster clock, and in
short wherever the second wheel in the going train does not turn in an hour,
and the dial work is driven independently. In this case, the 40 teeth of the
hour wheel (or whatever the number may be) require no points, and should
be hypocycloids described by a tracing circle of half the diameter of the
other pinion of 10 or 12 which is driven by the great wheel, if the teeth of
that pinion are radial.
Lantern pinions.—But there is another, perfectly different kind of pinion,
which is much better for small numbers than radial teeth or leaves, viz.
what is called a lantern pinion, and in old books, a ‘trundle.’ These two
figures (t. o.) will show its construction better than any explanation. I
believe it is the oldest form of pinion in the world, but it had almost (if not
quite) fallen into disuse in England, when it was restored in Dent’s turret
clocks about 30 years ago. They work with much less friction than common
leaved pinions of low numbers, when driven, the run upon them being less
and the action wholly after the line of centres, and the shape of the wheel
teeth requiring less accuracy to drive them smoothly. They are not however
proper for driving, because then you see the action comes all before the line
of centres. In some French turret clocks the winding pinions are nevertheless
wrongly made as lanterns, and the pins themselves pivotted instead of
rivetted in their sockets so as to turn while they are working, which makes
the working loose and shaky and the pinion itself very much weaker than
when the pins are fast, and saves very little in friction besides.
For the purpose of geometrical construction, we may first consider the
pins as being of infinitely small thickness, and then the teeth which drive
them would be of the dotted form PR fig. 57, being epicycloids traced on
the wheel with a circle the full size of the pitch circle of the pinion. Then in
order to get the shape of the teeth for pins of the actual size, you must gage
off half the breadth of the pin from each side of the tooth, which reduces
it to pr and you may leave on just as much point as will keep hold of the
departing pin P until another tooth has got well hold of the next pin just as
it crosses the line of centres. This operation of reducing the theoretical to
PROPER USE AND CONSTRUCTION OF LANTERN PINIONS. 199
Fig. 57: Lantern Pinions
LEAVED PINIONS. 200
the actual tooth is practically equivalent to tracing the tooth with a smaller
circle: how much smaller, will depend on the number, i.e. on the thickness,
of the pins, in proportion to the size of the pinion. I find that a lantern of
8 or 10 requires a tooth which fits a leaved pinion of the same number so
nearly that I can see no difference in the curves on a pattern as large as
9 inches diameter; and even with 12 the difference is very small; although a
theoretical lantern pinion with pins of no thickness requires the same shape
of teeth as a radial pinion of twice its size. I have no doubt that a lantern
of 8 runs as easily as a leaved pinion of 12, and of course it requires only 2
3
the number of teeth in the wheel, and is also itself stronger, and much less
liable to break, both in hardening and in working afterwards.
I may however repeat the caution that cast iron wheels do not work so
well with steel pinions, which lanterns necessarily are (or rather, they, soon
wear them out), as with cast iron; and therefore if the great wheel only is
of iron and the smaller ones of brass or gun metal, the pinions should be
made of cast iron or steel accordingly. Also it should be borne in mind that
you cannot draw out an arbor with a lantern pinion endways, by unscrewing
the front bush only and therefore they should not be used where you cannot
conveniently get at the back bush to take it off. These pinions are used in all
the American clocks and also in the cheap German or ‘Dutch’ clocks, both
of which, it is well known, will go with an amount of dust in their insides
which would stop a clock with leaved pinions completely. But the English
clockmakers will not use them in small clocks; and as English small clocks
are not yet made in factories as large ones are, and as they are everywhere
else in the world, the men who make them up have the power of obstructing
every such improvement, and exercise it by immediately charging a higher
price for every deviation from the common form, or for everything which
they fancy is going to be applied to some new use.
The leaved pinions of English house clocks are made out of ‘pinion wire,’
which is in fact a very long pinion drawn through a hole like wire, and
the leaves are turned off to form the arbor and pivots (see p. 14). The
American and Dutch clocks prove clearly enough that lantern pinions can
be made at least as cheap as others; and if any man of skill, capital, and
determination would follow the example of Mr. Hobbs in locks, and set to
work to manufacture clocks in a factory of his own, we should soon see
this and other improvements made, and the clock trade recovered out of
the hands of foreigners, to whom it has been in a great measure sent away
by this combination of workmen, who will ruin this and every trade in the
kingdom if they are allowed to have their own short-sighted way.
Inasmuch as English clocks are thus made by hand, and therefore probably
no two are exactly alike, it is necessary to have a tool for marking
the places where the holes for the pivots of the wheels are to be drilled, to
bring them to the proper depth for working. This depthing tool is something
like two vices framed together parallel to each other, each carrying a thick
INTERNAL WHEELS. 201
sliding pin sideways through each of its jaws. These 4 pins have a small
hole or ‘centre’ at the inner end and a point at the outer. The pivots of
the pair of wheels to be fitted are put in the 4 centred ends of the pins,
and the machine is adjusted by trial till the wheels are felt to work together
comfortably. Then the points at the outer ends of each pair of pins indicate
the distance of the centres of the wheels, and may be used to mark that
distance on the frame-plate. If you cannot get two wheels to work together
without shake (so long as they are driven the same way) by any adjustment
of their depth, the teeth are wrongly cut in one of them at least, and they
have no business to be used.
Internal wheels are wheels with the teeth turned inwards in which case
the rim must evidently be raised in a different plane from the spokes. They
are never used in clock-work, except for some special purpose, such as Sir
G. Airy’s maintaining power in the Exchange clock (p. 107) or in a sun and
planet wheel for the same purpose, neither of which are desirable, and in
some train remontoires (p. 166). Whenever they have to be used they are
best made with pins driven into the flat rim, especially if they have to be
driven and not to drive. Otherwise the same rules apply to the construction
of internal teeth as to external ones. They almost necessarily involve the
fixing of the wheel or pinion which works into them on a stud instead of on
an arbor with pivots, which is generally objectionable and ought never to
be allowed if it can be helped, either for wheels or pulleys.
Bevelled wheels.—When the direction of motion has to be changed,
as it often has in leading off to dial-work in turret clocks, bevelled wheels
are used (as shown in p. 163). They may be made to act through any other
angle just as well as 90. The only condition to be satisfied is that the teeth
should in every respect converge to the point where the two arbors would
meet if prolonged, as if they were on the faces of two cones. Nevertheless in a
great many bevelled wheels, the sides of the teeth do not converge properly,
the spaces being made of the same width all along, and so the teeth converge
too much, and have no contact at all except just at their outer edges. The
reason of this is that if the sides of two adjacent teeth are cut in the common
way with the same cutter, the breadth of the cut is the same throughout,
and not narrower at the inside than the outside, and therefore the teeth
evidently taper too much. Fortunately there is seldom much pressure on the
bevelled wheels in clocks, and therefore the defect is not very material: but
still it is one, and its frequent occurrence is another reason why the bevelled
wheels should be large in diameter rather than in thickness; for the larger
they are the less pressure there is on the teeth, and the less any inaccuracy
of cutting is felt (as it is in wheels of all shapes), and also the less shake
of the hands and wheels there will be for any given amount of shake in the
teeth.
Skew-bevelled wheels.—It may be worth while to know that bevelled
wheels can be made with oblique teeth, to work with their arbors not in the
PROPER FORM OF CAMS. 202
same plane, provided they have only to work one way; but the friction is
very great if they work what may be called the wrong way, and even in the
right way the friction is more than in the usual conical wheels. I have never
myself seen any clock where it was necessary to resort to this construction,
which may be found in books on machinery, and therefore I only mention it
in case anybody may have occasion to resort to it.
Cams may be defined as teeth which have to raise a lever, or a sliding
rod, and not a succession of teeth, and therefore each cam must work up to
its end, and drop the lever there, whereas in wheels a second pair of teeth
may and always should come into action before the preceding pair have quite
separated. The simplest form of cams to raise a lever is that shown in any
of the pictures of striking work of house clocks, figs. 33 to 36, viz. a set of
pins stuck into the side of a wheel which catch the lever at some distance
from its end and work up to the end and then let it drop off. This does well
enough for very light hammers requiring only a small clock weight, but is
the worst plan that could be invented for large ones. If you take the trouble
to draw a wheel with 8 pins in it, each pin acting on the lever through about
36 (leaving the difference between that and 45 for the clearance) you will
see that the angular lift of the lever towards the end of its motion is only
one third of what it is at the beginning, and therefore 2
3 of the clock weight
is wasted during part of the lift. And that is by no means all; for if you look
at p. 150 you will see that, as turret clock hammers are usually fixed, the
weight of the hammer acts more vertically or requires more force to lift it
at the beginning of its motion, where the pin has least leverage or power,
than at the end, where it has most; and besides all this, the loss of power by
friction in driving through short levers is much greater than through long
ones with less angular motion. Under all these circumstances it is no wonder
that the weight required to make a large clock strike is often three or four
times the theoretical ‘duty’ of the clock, or the equivalent of the hammer × its lift × as many blows as it strikes for once winding; i.e. that 2
3 or 3
4 of
the force is wasted in bad leverage and friction: whereas in the Westminster
striking part little more than 1
4 of the theoretical duty of the clock weight is
lost in friction, leverage, and the necessary clearance or drop for the lever.
The first condition therefore which the striking cams ought to satisfy is
they should begin to act at the end of the lever. It is not necessary that the
action should be quite at the end all the way through, provided it is so at
the beginning, where the lift is hardest for the clock, and at the end of the
action so as to let the lever drop suddenly; for which reason also rollers are
worse than half round pins, besides the reasons just now given against using
pins at all. The curve which does keep the cam acting on the end of the
lever throughout, and as a tangent to itself, without any scraping, is called
in mathematics the tractrix. If you wish to describe it, the way is this. Set a
smooth round board of the size of the cam wheel with stiffish paper pasted
over it (to efface the grain of the wood) on a pin through the centre on a
MODES OF TRACING CAMS. 203
horizontal table; and set also on the table, on another pin, a model of the
intended lever, with a vertical pencil at its intended point, so as to press
upon the paper, the lever being weighted a little. Set the lever on the line
of centres and turn the wheel; it will drag the pencil over its surface in a
curve which is the tractrix , unless it has been disturbed by some inequality
of friction between the paper and the pencil, or at the axis of the lever;
which is so likely to happen that you cannot safely rely on this construction,
unless you find that a good many of the curves so traced agree with each
other.
It fortunately happens however, that there is an epicycloid which agrees
with this so nearly that it may be used without sensible error. Suppose r is
the radius of the circle which forms the bottom of the cams (i.e. their theoretical
pitch circle, allowing nothing for clearing the end of the lever) and l
the length of the lever. The lever will work as a tangent on its end throughout
(without any appreciable error for such length of cam as is ever wanted)
on epicycloidal cams traced with a circle whose diameter = pr2 + rl − r.
Thus if r = 8 in. and l = 4 in. the radius of the tracing circle will = .95 in.
Another advantage of these cams is that you may cut them off at any length,
provided only you keep the lever of the proper length; if you alter that you
will get scraping friction, and soon wear out either the cams or the lever.
If you prefer having circles to deal with instead of epicycloids, there is
another form of cam, which was suggested to me by Mr. Effingham Lawrence
(another horological lawyer, like Mr. Bloxam, and all the members but one
of that jury in the 1851 Exhibition, both English and foreign), and which
acts quite as well as the epicycloid or tractrix, provided you take care not to
alter the length of the cam: i.e. you must not put more or fewer cams on the
wheel than they are designed for, and you must take care that the proper
distance of centres of the wheel and lever is preserved. In fig. 58, CAL is
the line of centres, and AB the space for one cam on their pitch circle; by
which I mean the space occupied in lifting, for you see a little space is left
below the line of centres before the next cam begins, to prevent the lever
dropping onto the cam itself, which shakes the clock most injuriously. AP
is the arc of the lever. Draw AT, which is a tangent to the two circles at A,
and BT a tangent to the cam circle at B. That point T will also evidently
be the place where a tangent to the circle AP at P would meet the others;
or in other words, T is the centre of a circle BP, to which the lever itself
will be a tangent both at the beginning and the end of the lift, although
the contact will be a little way from the end during some intermediate part
of the action. The backs of the cams must be cut out a little deeper than
down to the pitch circle, to let the lever drop freely; and it is important to
remember that the end of the lever itself should not be left sharp, or it will
cut off the ends of the cams if they are not very hard, and perhaps break
them if they are. I know that by experience.
It does not occur to me that cams can ever be required in clock-work for
OIL FOR CLOCKS. 204
Fig. 58: Modes of Tracing Cams
lifting a vertical rod sliding like a stamper. If any such case should occur,
involutes of the wheel circle would be the right shape for the cams.14 There
may also be cases where it would be worth while to pull down a long striking
rod by pins in the wheel catching a square hook at the end of the rod, and
dragging it on with a little sideway motion until it is struck off the pins by
a horizontal stop: this would avoid all the lever work and all friction except
at the striking off of the hook.
Oil for clocks.—I believe it is now generally understood that sweet oil
is the worst that can be used for machinery, large or small, except when
it is purified in certain ways not known to the public; and then it is too
expensive for use in large or common clocks. For them purified sperm oil,
such as is now made wholesale for other machinery, is quite good enough.
Common neat’s-foot oil may also be purified into a very good oil, which
will hardly freeze here. It can only be done in cold weather; it should be
shaken in a bottle with water until it becomes a thick white soup, and then
left to stand, and the fine oil that gradually comes to the top skimmed off,
taking care to get none of the thick. If it is done in a warm temperature, oil
appears at the top as fine, which has no business there, and will not remain
fine in cold weather.
I have found two advantages in using the animal and sperm over vegetable
oil, which some persons may be glad to learn. Working in iron with
the common olive oil dirties your hands so that it is very difficult to clean
them, whereas animal or sperm oil helps to clean them. It also preserves
iron from rust far better and longer, and does not turn green on brass, i.e.
14This is no exception to the epicycloidal rule, for an involute is in fact an epicycloid
traced by a circle of infinite size, i.e. by a straight line.
OIL FOR CLOCKS. 205
does not produce verdigris. I understand that petroleum is better still for
preventing rust. It is difficult to make amateur clock-cleaners understand or
remember that putting oil to pinions driven by brass or gun-metal wheels
wears them out; but this does not apply to cast iron; and all pivots should
be oiled, and acting surfaces generally. Oil must never be put to the beat
pins of a gravity escapement, or it will make them stick to the pendulum
quite enough to affect its rate; but it should be to the pallet pivots. I have
known the want of it, both there and in the common pallet pivots, affect
the arc sensibly.
It must be remembered that oil has always a tendency to run away from
small points of teeth, the ends of pins, &c., to the thicker parts of the wheel.
In some French clocks the teeth of the dead scapewheel are accordingly made
with a kind of lump at the end; but this wastes more space in the clearance
or drop, and it is never done in English clocks, so far as I have seen; nor
do I know anything that will answer—except putting on fresh oil when it
is wanted. Dirty oil should always be cleaned off before putting fresh oil
on. When it has got very thick it sometimes requires soda in warm water
to remove it.
WATCHES AND
CHRONOMETERS.
The early history of watches is no less obscure than that of clocks, though
many centuries later. Tradition assigns the invention to the town of Nuremberg,
in the fifteenth century. According to a once famous book, Derham’s
‘Artificial Clockmaker,’ of 1714, and Beckmann’s ‘History of Inventions,’
they appear to have existed in the time of our Henry VIII., and of Louis
XI., of France, and especially of the Emperor Charles V., who used to keep
many watches going, as near together as he could. Erasmus had a watch
given him by a Polish nobleman, early in the sixteenth century. And by
Queen Elizabeth’s time they had become pretty common, and are alluded to
by Shakspeare in Twelfth Night—‘I frown the while, and perchance wind up
my watch.’ The London Company of Clockmakers was incorporated in 1631;
and not long after that, the invention of the spring balance, the distinctive
element of watches, was contended for between Huyghens and Dr. Hooke,
who both claimed the invention of the pendulum for clocks (see p. 22). It
seems clear that Hooke first enunciated the discovery of the isochronism of
springs in the short sentence, Ut tensio sic vis; or the force varies as the
degree of tension: which rule however we shall see presently has two rather
curious exceptions.
The main-spring of a watch is a thin ribbon of steel coiled up in a barrel
round a strong spindle, to which one end of the spring is fixed, the other end
being fixed to the barrel. When it is wound up the coils lie close together
upon the spindle or arbor, and as the spring runs down, the coils separate
from the arbor, and lie close to the barrel. The simplest construction, still
used in most of the foreign watches, is for the barrel arbor to be the winding
arbor, having a ratchet wheel squared onto it, held by a click on the frame
or plate of the watch, and the great wheel is on the barrel itself; and in this
case, as I explained at p. 101, with reference to spring clocks, no temporary
maintaining power ‘going barrel’ is required to keep the watch going while
you are winding it up. But it is obvious that as the force of the spring
206
MAIN-SPRINGS. 207
is greater when it is tightly wound up than when it is loose, the force of
the train will be very far from constant throughout the day, although that
may not affect the going of the watch from one day to another. On the
other hand, there is found to be a very singular exception to that rule of
Dr. Hooke’s, stated just now, inasmuch as there is a position of the spring
coiled in a barrel in this way, in which there is no material variation of its
force for a few turns. And certainly some of the foreign watches made in
this way go very well.
Even if a watch does go rather faster at one time of the day than another
(which it is not certain that such watches do), it is of no consequence,
provided they go uniformly from day to day; and there has been strong testimony
published in the Horological Journal, that they do, when well made, of
course. I have seen watches with tapered main-springs (though the foreign
ones are not tapered), in which you could not perceive any difference in the
force, by the usual testing apparatus of a weighted lever, whether the spring
was wholly wound up or not. And if this is so, the addition of any more
machinery, being superfluous, is mischievous, and only increases the expense
and size of the watch, and risk of the chain breaking, perhaps the most com-
Fig. 59: American Main-spring Barrel
mon of all accidents. There is evidently a tendency in watch-making now to
dispense with such machinery, except for marine chronometers, which are
required to go uniformly at all times of day, and not merely from day to day.
Accordingly, both in Switzerland and America, which are gradually stealing
away our common watch trade, as well as that in many kinds of clocks,
AMERICAN MAIN-SPRING BARREL. 208
the fusee and chain (which I will describe presently) are almost universally
omitted.
Fig. 60: American Watch
But in that case there is another risk
of breaking, for when the spring breaks,
the barrel recoils violently from the sudden
removal of the pressure, and often
breaks some teeth of the great wheel fixed
upon it. Partly to avoid this, and also
for general improvement in strength and
arrangement of the train, the American
watches, as made by the ‘Howard Company,’
under a patent by a Mr. Reed of
1857, have the spring contained in an
immovable barrel, which is a solid part
of the upper plate of the frame (calling
the dial side the lower). The outer
end of the spring hooks to the barrel as
usual, and the inner end to the winding
arbor, on which the great wheel rides,
with a spring maintaining power, just like
those of a clock described at p. 104. For
safety also, the main-spring is held by two
clicks, much stronger than the single one
generally put into fusee watches, and the
maintaining spring is also very strong.
Fig. 59 is a plan of this, and fig. 60 a
section of the whole watch. It may be
observed also that a watch of this kind
turns the same way in winding as one
with a fusee, whereas the common foreign
watches turn the opposite way: not that
there is any real importance in this, except
that the absence of uniformity sometimes
causes people to wind a new watch
forcibly the wrong way.
To prevent that, Breguet invented
what is called the tipsy key, not that that
adjective belongs to the ‘winder,’ in the
clockmaker’s sense of a key, but in the
more human sense. The handle is connected
with the pipe by a pair of ratchets,
which would be called clutches in
large machinery, which which can pass
each other one way, but not the other;
ENGLISH WATCH MOVEMENT. 209
and they are kept together, and then hardly visible, by a spiral spring,
which gives way, and lets one pass over the other if the handle is turned
the wrong way. The best shape for a winding key is like a pencil with a
rough handle, to enable you to twirl it more easily between your fingers.
You thereby apply less force, and are less likely to do mischief by wrong, or
over winding; and moreover you keep the watch steady, instead of turning
it in your left hand, and agitating the balance at every turn.
If you compare figure 60 with 61, you will see that in the latter, which
is the common English fusee and chain watch, the third wheel of the train
has to be sunk in the plate below the centre wheel, whereas in the American
watch (fig. 60) it stands free and clear. There are a few other things in this
arrangement which had better be postponed till other parts of the watch
have been described, and we will proceed with the description of the common
English watch construction, and therein first of the
Fusee.—That piece is a hollow-sided cone, which you see in this picture
of a chronometer or English watch movement, with a chain round it and the
barrel, and the great wheel is no longer on the barrel, but on this conical
piece called the fusee. When the spring is wound up and its force is greatest,
the chain acts on the small end of the fusee, and therefore with the smallest
leverage; and as the spring unwinds, the chain acts on a thicker part of
the fusee, and it can be, and in good watches is, so adjusted that the force
on the train and escapement is constant. It was suggested by Mudge, the
inventor of the lever escapement in the form now used in 99 out of 100
English watches, that the usual position of the chain is wrong: and so it is;
for you see in fig. 61 that it acts on the opposite side of the fusee to the
centre pinion, and consequently the pressure and friction on the fusee pivots
(which are necessarily large ones) is the sum of the force of the spring on
the fusee and of the great wheel on the pinion; whereas if the spring acted
on the same side as the pinion, it would only be the difference. I confess I
know no reason why the common arrangement should be adhered to, except
that it is the common one, which is generally considered reason enough for
anything bad.
The train of wheels in a watch is much the same as in a clock except
that the scapewheel is not the wheel which turns in a minute and carries the
second hand, but is another faster wheel. In a pocket lever watch the balance
generally beats in 2-9ths of a second, and in a chronometer either in that
time or in 1
4 sec. The scapewheel generally has 15 teeth, and therefore turns
in 6 seconds, or something near it. In a good lever watch the pinions are
generally 7, 8, 8, 10, and the wheels 63, 60, 64, 75; in a pocket chronometer
the pinions are 8, 10, 10, 12, and the wheels 80, 75, 80, 72; in box or marine
chronometers the numbers are still higher, the pinions being 10, 10, 12, 14,
and the wheels 80, 80, 90, 90. Box chronometers are generally made to go
rather more than 2 days, though they are wound up every day, and they
have a small hand on what is called the ‘up and down’ circle in the dial,
WINDING STOPS. 210
Fig. 61: English Fusee Watch
indicating how far the barrel has run down. In these watch trains it must
be observed that where a slow wheel has fewer teeth than a quick one, the
teeth must be larger, or the wheels could not be put into the frame. I think
no pinion so low as 7 should be admitted, and I cannot understand why 9
should be a prohibited number in clocks and watches, as it seems to be, or
at any rate was until I introduced it frequently in turret clocks.
Common watches have the balance above the upper plate. What are
called three-quarter plate watches have a large piece of that plate cut
away, and the balance lies about level with the rest of the plate, and most
of the wheels have their upper pivots in cocks screwed to the lower plate.
This saves thickness in the watch.
Winding stops.—A watch, or a spring clock, with a fusee, is stopped
from being overwound by a long tooth which you see in fig. 61, sticking
out from the thin end of the fusee. There is a spring lever with a hook
fixed to the frame with a little play on its pivot, so that when the chain
comes to that end, or the fusee is full, it pushes the lever just far enough for
its hook to catch the tooth, and so stops the winding. In foreign watches
THE ‘UP AND DOWN DIAL,’ 211
without a fusee, a thing called the Geneva stop is used: it consists of a
small wheel on the barrel-arbor, with only one tooth in it, and the rest of
the circumference filled up blank; this tooth works into the teeth of another
loose wheel, with the hand on it in fig. 62, which has only as many teeth as
the turns that the barrel has to make in winding, and has also a blank space
in its circumference. The one-toothed wheel turns the loose wheel through
the space of one tooth for every turn of the barrel, and when those teeth are
all past, the one-tooth jams against the blank in the loose wheel and lets
the barrel turn no more, and so stops the winding. These two wheels are
above the upper plate. The same thing might be put on a fusee arbor, but
the spring stop is preferred.
Fig. 62: Up and Down Dial
The ‘up and down dial,’ just now described, on the usual construction,
involves an additional pair of wheels. But Mr. A. L. Dennison of America,
now settled here, who is said to have been the originator of watch-making by
machinery (which at last is taking root here, at Messrs. Rotherham’s wellknown
watch factory at Coventry), patented a modification of the Geneva
stop which enables this kind of indicator to be added without any more
wheels. It consists merely of adding a short arbor and hand to the loose or
second or star wheel of the Geneva stop which is applied to watches on the
American plan described at p. 208. These pieces are shown in this figure 62
of which the right hand part is the plan and the other the section. This
is not of so much value in a common watch as in a chronometer, but is
convenient to be able to see at a glance whether you have wound your watch
up fully, without the risk of straining it in trying.
WATCH DIAL WORK. 212
The dial wheels of a watch are more like those of a turret clock than
of a house clock in the division of the numbers of the teeth, as there is no
occasion for the intermediate wheel called N in pages 95, 118, to turn in an
hour, as it does in house clocks to discharge the striking, and even in silent
clocks for uniformity. The hand sockets are also only held on by friction
without any spring. In other respects the train of a watch is substantially
the same as that of a small clock until we reach the escapement, except that
there is one more wheel in the train, for the reason given just now. The dial
pinions in a good watch are 12 and 14, and the wheels 42 and 48; in a box
chronometer they are 14 and 18, and 54 and 56.
Balance spring.—The rest of the machinery of a watch only differs in
size from that of a clock, until we come to the escapement and the balance.
We shall consider the various escapements presently, but the object of them
all is the same as in clocks, to produce an escape of teeth by the vibration of
a balance, the time of which depends on its own moment of inertia and a coil
of very thin steel wire called the balance spring, and sometimes popularly the
hair-spring from its thinness, and sometimes (very absurdly) the pendulumspring,
though it is of the very essence of a pendulum to act solely by gravity
and the essence of a balance to be free from the action of gravity, or else
the ‘balance’ is not balanced and the watch will go differently in different
positions. The spring by which a pendulum is hung produces no sensible
effect on its time, and is only used to avoid the friction any other mode of
suspension.
The balance-spring is fixed at its outer end to a stud in the watch, and
at its inner to the balance arbor or staff at the neutral position of the spring
the balance is at the middle of the escape. In some kinds of escapements
therefore the balance cannot stand still if the watch is wound up; and in
all of them the spring tends to bring the balance back again after it has
gone a certain distance, depending on the force of the escapement and the
cleanness of the pivots and teeth on one hand, and the strength of the spring
on the other, and then the balance swings an equal distance beyond zero
the other way. Whereas in the original clocks with a balance but no spring
(p. 19) it was only the recoil of the escapement that brought the balance back
again, and such a balance could not have been used with any kind of dead
escapement, because it would never have returned. Moreover, considering
that a pendulum moves by gravity, through an arc of only 4 or 5 with a
variation never amounting to 300 in a good clock, while the balance swings
independently of gravity through an arc of sometimes 400 and sometimes
no more than 100, it is evident that a watch escapement must be a very
different thing from that of a clock.
When I say that a balance is independent of gravity, you must remember
the distinction between mere mass, which we denoted by the letter M in
treating of pendulums, and mass acting as a force by means of its weight, i.e.
by the earth’s attraction, which we called Mg. The mass and the moment of
NOT ALWAYS ISOCHRONOUS. 213
inertia of a balance have quite as much to do with its motion as they have in
a pendulum, but the force which makes it vibrate or return from the impulse
given in the escapement is not gravity, which must be entirely excluded, for
the reason just now given. It was to this balance spring that Hooke’s law
of the force varying as the tension or space moved through (which always
implies isochronism) was meant to apply, and does apply pretty generally;
but not invariably, because it is found that not every length of a given
spiral spring is quite isochronous, but only certain lengths, which have to
be determined by experiment.
The time of vibration therefore depends on the moment of inertia of
the balance directly and the force of the balance spring inversely; and in a
given spring the force varies inversely as the length. Consequently you can
quicken the vibration either by reducing the moment of inertia or the size of
the balance, or by shortening the effective length of the spring. The latter
method is used in all common watches, and the former in chronometers and
watches in which extreme accuracy is aimed at.
Regulation of a common watch, to make it go faster or slower, is done
by a lever or index SPT (fig. 63), which turns on a ring set on the watch
plate (through which the staff or arbor of the balance has to pass from the
inside to the outside of the watch frame), and it has two small pins at P
which embrace the spring, one end of the spring being fixed to the frame at
R and the other end to the balance at S. It is evident that as you turn the
regulator to the right you shorten the length of the acting part of the spring
and so make the vibrations faster, and if you move it to the left, slower. If
the regulator has been moved as far toward fast as it can go and the watch
still looses, the spring must be taken up altogether at R; and then in order
that the balance may still be in the middle position of the escapement when
the spring is neutral, the piece S by which it is attached to the balance is
itself a ring which fits tightly round the staff and can be moved when the
balance is taken out, to alter the position and length of the spring.
It must have occurred to everybody who has had to regulate a good
watch for very small errors that there is a want of some better method than
the common one both for moving the regulator and for seeing how much
you move it. Occasionally, but very rarely, the index is made to move by
a tangent screw, turnable by the watch key, and I am surprised that good
watches are not always made in this way. But I have lately seen another,
in the American watches referred to at p. 211, which is still more delicate,
and also easier to make. The index is resisted one way by a slight spring
fixed to the plate, and a common screw, in the same direction as a tangent
screw, acts upon it the other way. This avoids the shake of a tangent screw,
and you know that however little you turn the screw you move the index
some distance. In these cases you must learn by trial how much half a turn
of the screw accelerates or retards the watch per day, and after that you
can regulate it to the utmost nicety—so far as its errors are amenable to
REGULATION OF WATCHES. 214
Fig. 63: Regulation of Watches
regulation.
Another method suggested by the late Mr. Dent is shown in fig. 63.
Instead of being made with a point, the index has fine bevelled edges lying
quite over the index plate, which is to be made with oblique divisions and
two or three cross lines, like the scale generally engraved on a dividing rule:
this enables the eye to measure much smaller divisions than could be either
seen or cut upon a degree plate of the common form. But this does not
remove the difficulty of moving it a very little, and the screw is manifestly
better. The old plan of a segment of a wheel turned by a pinion with the
index fixed to it (fig. 64) is better than the common one, and I do not know
why it is disused.
This mode of regulating by shortening the effective length of the spring
is not accurate enough for chronometers for another reason, viz. that all
lengths of the spring are not quite isochronous for different arcs of vibration,
and therefore if you have got the spring adjusted for an isochronous
length, it will become unisochronous if you shorten it a little; and moreover
a spring moving in that way, partly held fast at the ends and passing loosely
through curb pins at P, is not so steady as one held fast only at the ends.
Chronometer balances are therefore regulated by timing-screws, which are
FORMS OF BALANCE SPRINGS. 215
Fig. 64: Old Plan
screws with heavy heads set in the rim of the balance: screwing them in
of course diminishes the moment of inertia and quickens the balance, and
vice versˆa. In chronometers also the spring is generally made as a cylindrical
spiral and not a flat one. Some chronometer makers have doubted
whether there is any advantage in the cylindrical form, but it is now almost
universally adopted, and therefore I suppose the balance of experience is in
favour of it. It is now said that the best form is one that combines both or
a cylinder returned into a flat spiral both at top and bottom.
But the quality of the spring is probably of more importance than its
form. A medal of the highest class was awarded in the 1851 Exhibition
to M. Lutz of Geneva for some balance springs, made by a secret method,
which bore being pulled out nearly straight, and laid on a hot plate without
suffering any change of form, which was not the case with any others which
were then submitted to us. I see that aluminium bronze has been successfully
used in Saxony for balance springs; but I know nothing more of them.
Glass balance springs.—These were suggested by Berthoud but have
been very little used. The rate of a chronometer with a glass spring, which
Dent sent to Greenwich many years ago, was very good; and they have the
advantage of varying so much less than steel or any other metal in elasticity
that they require very little compensation of the balance. I do not know
why they have not been more used, unless it be from the fear of breaking
them when anything is done to the watch. It appears that with them, as
with steel springs, the watch always gains after a new spring has gone a few
months, as if it acquired more elasticity by working; and this is analogous
to what takes place in bells, which become more sonorous, i.e. more elastic,
TIMING FOR POSITION. 216
after a few months ringing.
Timing for position.—As a watch sometimes lies flat on a table, and
sometimes vertical, and not always in the same position in your pocket, it is
necessary that the balance should keep the same time in all positions, both
horizontal, and with either iii, vi, ix, or xii, upwards. With a heavy balance
it is impossible to get the same arc of vibration when the watch is vertical
Fig. 65: Box Chronometer in Gimbals
and horizontal, because the friction of the pivots is much greater when they
are acting on their sides than on the point of one of them. If you take a
small chimney-piece clock with a balance and hold it sideways so that the
balance becomes vertical and its staff horizontal, you will see the vibration
diminish very much, and then the least want of isochronism in the spring
will set the rate wrong. Marine chronometers, which are only very large
watches, are therefore always set horizontally in a box, in gimbals, as in this
drawing, which keep the watch horizontal, even when the box is tilted by
the ship: if the box is tilted at E or W, it turns on the outer pivots NS of the
gimbal ring, and if the N or S side is tilted, then the box and ring together
turn on the inner pivots at W and E leaving the watch steady. The level
of the pivots should be only just enough above the centre of gravity of the
watch to make it keep its level, for if the c.g. is much below the points of
support the watch will swing when they are moved.
Ship time-pieces.—There is another kind of ship-clocks made to hang
against a wall, not pretending to the accuracy of chronometers, but a very
neat and convenient and cheap form of time-piece for other places as well
as ships. They are a large 8-day lever watch with the balance staff and
the scapewheel arbor vertical, and therefore the third wheel in the train a
CHIMNEY-PIECE CLOCKS. 217
contrate or crown-wheel as at p. 19. Like other things, they are of very
different qualities with the same external aspect. They do not work well
without a fusee, though many of them are made so for cheapness and the
contrate wheel arbor ought to have an end-stop to the pivot which tends
to push away from the scapewheel pinion and work upon its shoulders, and
the two vertical arbors ought still more to have their lower pivots resting
on stops, either of hard steel or jewels, to take the weight and friction off
their shoulders. End stops are sometimes put to the horizontal arbors of
highly finished clocks; but as there is no end pressure on them, I think it is
hardly worth while there, though it is in the two cases I have just mentioned.
Chimney-piece clocks with balances (the only ones which housemaids will
allow to go, unless they are too heavy to move) ought always to have them
compensated, for otherwise the great changes of temperature to which they
are exposed will make it impossible for them to go right, as I shall now
explain.
COMPENSATION OF BALANCES.
Watch balances, or rather the springs on which their time depends, vary
much more with heat and cold than pendulums, and therefore compensation
is still more essential if you expect great accuracy of rate; and if it were not
that watches are kept at a pretty even temperature during the day by near
contact with men’s bodies, their variations in hot and cold weather would
be enormous: women’s watches being generally worn loose, go worse than
men’s for that reason. A small portable clock with a balance uncompensated
goes twenty times worse than the commonest pendulum clock. The balance
itself also expands a little with heat, as a pendulum does, but the effect
of that is small compared with the variation of the force of the spring.
It appears from some experiments made by Berthoud in 1773, and others
by Dent communicated to the British Association in 1833, which nearly
agreed, that the loss of time due to expansion of the balance for a rise of
temperature from 32 to 100 is not a 5th of that due to the loss of elasticity
and elongation of the spring, and that the two together amount to no less
than 61
2 minutes a day; and a variation of 33 would produce a variation
of an hour in 3 weeks; whereas we saw that a common iron wire pendulum
would only lose 10 sec. a day for such an increase of heat, and a wooden one
not more than 11
2 seconds.
The first watch compensation was made by Harrison, who has been mentioned
several times already as the inventor of various horological improvements;
and he received the first parliamentary reward for improvements in
chronometers with a view to finding longitude at sea. His method is quite
disused now, and indeed he was himself dissatisfied with it, and suggested
that the compensation ought to be done in the balance and not by any
COMMON METHOD. 218
contrivance for altering the effective length of the spring, which was the
principle of his own and all the early compensations. For this purpose he
put the curb pins (P in fig. 63 p. 214) on a compound bar, of which one
side was made of brass and the other of steel. As brass expands more than
steel, the bar bends to the steel side when the heat increases, and thus the
curb pins were moved along the spring, as they are by hand in the common
regulator. It is not necessary to dwell on any of the various modifications of
this plan, as they are all now abandoned for the balance of compound bars,
which appears to have been first made, as well as a mercurial compensation
balance, by Julien le Roy, a celebrated French clockmaker, but afterwards
much improved by the first Arnold, Earnshaw, and various other English
makers. A great variety of these early contrivances may be found in Rees’s
Cyclopædia by those who are curious about them.
The plan which is now always used, with some modifications in certain
cases, as I shall explain afterwards, is exhibited in this drawing: tat0 is the
Fig. 66: Common Method of Compensation
main bar of the balance, with the timing screws tt0 for regulation at the ends;
and tb, t0b0 are two compound bars, of which the outside is brass and the inside
steel, carrying weights bb0 which may be screwed on at different places.
As the heat increases, those bars with their weights bend inwards and diminish
the moment of inertia of the balance. The only secure way of making
these balances is to cut them out of a solid steel disc round which melted
brass is run which brazes itself fast on. This plan of uniting the metals was
introduced by Earnshaw, it appears, besides various other improvements in
the construction of chronometers, in which very little alteration has been
made in nearly 100 years. The principal expense of a really compensated
balance is in the time required for adjusting it, which can only be done
by trial. Many watches are sold with balances only constructed for compensation
but never adjusted, and therefore under or over compensated, or
THE CHRONOMETRICAL THERMOMETER. 219
with no regularity in the action of the compensation; and some still worse,
with a mere sham compensation, resembling a compensated balance only in
appearance, sometimes not even cut through.
The chronometrical thermometer is simply a watch with a balance
compensated the wrong way, i.e. with the brass inside and the steel outside,
so as to increase the retardation from heat and the acceleration from cold.
The use of it is to measure the quantity of heat or cold received during
any given period without recording the actual degree of heat or cold at
any particular time. It is therefore used at the Greenwich Observatory
for trying the rates of compensated chronometers under great variations of
temperature.
Secondary compensation.—When chronometers had brought to great
perfection, so as to go with scarcely any sensible variation of rate while they
were kept within moderate limits of temperature, it was observed that they
always lost if the temperature either rose or fell beyond those limits; and on
the other hand, if the compensation adjusted for two extreme temperatures,
then the watch always gained at mean ones. I believe it has never been
disputed that old Mr. Dent was the first person to explain the cause of this
error, in the Nautical Magazine in 1833; and he gave the following illustration
of it: The diminution of the force of the spring proceeds uniformly in
proportion to the increase of heat, and may therefore be represented by a
straight line inclined at some angle to another straight line which is divided
into degrees of temperature. But the inertia of a compound balance such
as I have described cannot be made to decrease quite as fast as the heat
increases; and therefore its rate of variation can only be represented by a
curve, and can only coincide with the straight line representing the variation
of force of the spring in two points, either the two extremes, or two means,
or one mean and one extreme point: in other words, the compensation can
only be exact for some two temperatures for which you may choose to adjust
it.
The same thing may be shown mathematically as follows: Let r be the
distance of the compensation weights from the staff or axis of the balance,
and we may call them both together M, and for this purpose we have nothing
to do with the rest of the balance. Let dr be the increase of distance of the
weights for some given decrease of heat. Then the new moment of inertia
of the balance will be M(r2 + 2rdr + dr2), and the ratio of the new inertia
to the old will be 1 + 2dr
r + ( dr
r )2; and now the term ( dr
r )2 is too large to be
disregarded as it may be in the similar formula for pendulums, because dr
must be much larger in proportion to r than it is in a pendulum, as we have
seen already. Again, the ratio of the moment of inertia for an equal increase
of heat to its amount of inertia in the middle state will be 1 − 2r
r + ( dr
r )2,
assuming that equal successive increments of heat produce equal variations
of r, which however is not quite the case, as it is in pendulums. Consequently
the increase of moment of inertia, for a given rise of temperature is less than
GREENWICH TRIALS. 220
its decrease for an equal fall by 2(dr
r )2, or the compensation fails to that
extent in one of the three states of cold, middle, or hot temperature.
The correction of this error is called the secondary or auxiliary compensation,
and it is the point to which I think every chronometer invention for
the last thirty-five years has been directed, chiefly because the chronometers
are now exposed to such extreme and unnatural variations of temperature
in the Greenwich trials—nearly as much as 100, that the attention of the
makers seems to be withdrawn from everything else; and every year’s tables
display an increased number of contrivances for this purpose, but no
increased accuracy in the recorded rates of the best of them.
Greenwich trials.—When the rates of some chronometers were returned
to Greenwich after one of the Arctic expeditions, the Astronomer
Royal reported that they had been kept so warm that they afforded no test
of the relative value of the different modes of compensation employed in
them. I think it might also have been inferred from that fact that the trials
at home in such unnatural variations of temperature are only calculated to
test a single and comparatively immaterial quality of the chronometers, and
to frighten away from public trial every invention for the general improvement
of the instrument in other respects. Any nautical man who wants
chronometers for real use would rather have one that would not vary a second
a week in such temperatures as it is likely to be exposed to in any voyage
in a ship’s cabin, than one which may possibly go better than it at some
extreme and improbable variation of temperature, but worse in all ordinary
and probable variations.
Mr. Hartnupp’s report of the trials of above 1000 chronometers at Liverpool,
in 1872, says that the best of them, with the ordinary compensation,
generally gain 6 sec. a day more at 70 than at 55 or 85, if the compensation
is adjusted for these two temperatures, and that those which have the
same rate at 55 and 70, or at 85 and 70, lose 1.5 sec, for a change of
15 below or above the temperatures for which they are compensated. He
adds, that the connection between rate and temperature remains constant
for a long time.
Eiffe’s compensation balance was the first invention for this purpose
which was disclosed; and a reward of 300l. was therefore given him by the
Admiralty on the recommendation of the late Astronomer Royal. At the
very time while this invention was under trial at Greenwich, Mr. Molineux
took out a patent for one precisely similar; which is only one of the usual
proofs that when the time is ripe for an invention, it is almost sure to be
made by several people at once, of whom one gets rewarded—or suffers, by
a patent. Mr. Eiffe described several methods for effecting the secondary
compensation; the one which he chiefly relied on, and which has been followed
by some other makers, is a balance in which the compensation bar, or
a screw in it, is made to reach another in the form of a spring with a small
weight upon it, when it has bent inwards to a certain extent, and it carries
DENT’S BALANCE. 221
that other with it, so as to diminish the moment of inertia still more than
the single compound bar. It seems an obvious objection to this, that it is
discontinuous, i.e., that the secondary compensation comes into action suddenly
at one change of temperature only. Nevertheless it appears to answer
as well as or better than many others which are free from that objection.
Fig. 67: Dent’s Balance
Dent’s balance.—That objection was obviated in Dent’s balance, of
which also there were several forms: this is the one which he proposed as
the best in his pamphlet on the subject. The flat cross-bar rr0 is itself a
compensation bar with the brass below and the steel above, so that if the
compensation weights bb0 were set upon upright stems from the bar they
would be bent in towards the axis when the heat increases. But they are
in fact set upon some other bent compensation bars st, st0, of which the
brass is inside the bend, and consequently the weights approach the axis
more than if they were set on stems of fixed length; and as they can be set
anywhere on the stems the compensation is thus adjustable. The reason
why the bent bars stand outwards across the principal bar is to leave room
for the balance spring, which is attached to the smaller cross-bar d shown
in fig. 67, in which spring is omitted to avoid confusion. This compensation
has the advantage of being continuous.
LOSEBY’S V. DENT’S COMPENSATION. 222
Loseby’s balance was an ingenious alteration of a previous mercurial
compensation of Le Roy into this form. DD are the weights on the usual
compound bars BB, for the primary or principal compensation. Besides,
there are two small bent thermometers with the bulbs at F, and the tubes
at E, into which the mercury runs as the heat increases, and so more of the
weight of the balance is carried inwards than is due to the mere bending of
the primary bars. The tubes are sealed with a little air included. CC are
the usual timing screws independent of the compensation. The action here
is equally continuous with Dent’s, and Loseby’s chronometers generally got
a very high place in the Greenwich lists during the seven years in which
he sent them there; and he would have done wisely to be content with
that success. But he applied no less than four times for a reward for his
invention, and the Astronomer Royal four times reported against his claim,
on the ground that his balance was neither the first to do what was wanted,
nor was proved to be the best. Mr. Loseby then sent to the Admiralty a
long memorial, containing a comparison of the rates of his chronometers
Fig. 68: Loseby’s Balance
with others in the Greenwich lists for 5 years, to prove that his was the
best; and the last horological paper to which old Mr. Dent put his hand
before his death was a counter statement, showing that a proper analysis of
those very trials exhibited Loseby’s compensation to be decidedly inferior
to Dent’s own, and not at all superior to Eiffe’s or several others of which
the constructions were not disclosed.
After his death in 1853 the controversy was carried on in the Society
of Arts’ Journal by Mr. Loseby and me, as he had assumed that I wrote
KULLBERG’S COMPENSATION BALANCE. 223
Dent’s paper for him, and so I extended the analysis to the whole seven
years during which Loseby’s chronometers were at Greenwich, and with the
same result. The nature of the analysis is simple enough, viz. this: If you
divide the 6 months of published rates in each year into 3 periods, one
containing all the coldest weeks, another all the hottest, and another the
mean temperature weeks—and whether you make the division into equal
periods, or into two periods of 6 weeks of extreme temperatures, and 13
or 14 of mean, or make it just where the register shows that the greatest
breaks of temperature actually occurred—the result was always the same,
that Loseby’s compensation was the most successful in only one of the seven
years, three other makers’ each once, and Dent’s three times. Sir G. Airy,
the Astronomer Royal, was therefore clearly right in rejecting Mr. Loseby’s
claim to a public reward, whatever may have been his personal skill in
preparing a single chronometer for trial in a year, and so, on the whole,
getting a high place in the list.
Kullberg’s compensation balance has been so successful in the Greenwich
trials that I add a description of it to those mentioned before. The
drawing in the next page shows its shape, but not the peculiarity of its construction;
for the brass is attached to the top of the cross-bar AC, but to
the bottom of the curved rims CB, the effect of which is that the ends of the
cross-bar are carried downwards by heat, and the weights P upwards, and
more inwards than if the cross-bar did not bend, as it does also in Dent’s
balance; DD are the timing screws. The principle of it is better illustrated
by the second sketch, of half the balance seen edge-ways and with its action
enormously exaggerated. The thick line is the steel and the thin one the
brass. The principle of its action is the same as Dent’s, but it is simpler
and stiffer I doubt whether it is necessary to have a curved rim at all, and
whether sufficient compensation could not be got by making the pieces CB
straight, each lying close by the staff AE. Mr. Kullberg has also made balances
of the common form but with much wider rims hollowed outwards,
looking like a pulley with a very flat groove. The expansion sideways of the
outer brass rim tends to flatten it, and so makes it easier to bend inwards
under the expansion of the brass end ways; but he says he has not yet succeeded
in getting sufficient secondary compensation in this way; as was the
case also with
Dent’s prismatic balance.—This was also invented by the first Mr.
Dent and improved by the second, for the purpose of effecting the primary
and secondary compensation together, or a sufficiently near approximation
to it, by a simpler construction than any of the others. The steel part of
the balance is the usual flat bar; but the brass is an obtuse-angled bent
prism. This invention was founded on the fact that a bar of that form bends
more easily from the angle than towards it, and therefore the compound bar
bends in more easily and farther than it does outwards, for equal degrees of
heat. It has the advantage of making the balance stronger also. It was not
CHRONOMETERS INFERIOR TO CLOCKS. 224
Fig. 69: Kullberg’s Compensation Balance
supposed that this would make the secondary compensation complete for
the extreme temperatures of the annual Greenwich trials; but there seems
no doubt that it is better than the common flat bar compensation.
Fig. 70: Dent’s
Prismatic Balance
There have been sundry other inventions for secondary
compensation. Indeed nearly every maker in
the Greenwich lists professes to have one of his own.
The late Astronomer Royal invented one in 1875 and
went so far as to get an Admiralty order that it should
be used; but the trade pronounced it a failure, and the
order was first suspended and then withdrawn. It is difficult
to compare the general performance of the best
clocks with that of chronometers under severe trials.
The best recorded rates of chronometers seem to be a
daily variation of not more than half a second during
the time of trial; which, however, might come to a good deal if continued.
I am inclined to say that the rate of a very good watch in ordinary use,
and a lever quite as much as a chronometer according to my experience, is
sometimes nearly equal to that of the best clocks for some months together.
For ordinary use no secondary compensation is at all necessary.
WATCH ESCAPEMENTS.
There is a greater variety of escapements which may all be said to be in
use in watches than there is in clocks, omitting in both cases merely fancy
ones of which only a few specimens have been made rather for show than
for use, and which I do not think it worth while to describe, either for clocks
or watches.
Vertical escapement.—The original watch escapement, which has remained
in use for about two centuries, but is almost gone, exactly corLEVER
ESCAPEMENTS. 225
responds to the old crown-wheel escapement in clocks described at p. 19.
This figure (71) shows the mode of arranging it in a watch. There are in
fact two crown wheels in it, for the wheel with its arbor vertical, the minute
wheel of the train, is one, and the scapewheel itself is another. The plain
rimmed wheel is the balance. It has all the properties of the recoil escapements
in clocks, and is very inferior in accuracy to any of the others, and
now has hardly the advantage even of cheapness over the lever, which is the
standard English watch escapement.
Fig. 71: Vertical Escapement
A very simple vertical escapement, i.e. one involving a crown wheel, was
invented (or perhaps re-invented) for cheap watches by the late Mr. John
Gray, a well-known dentist. The teeth lie dead on a thick verge or cylinder
except at the moment when they pass through notches cut across it; and they
give an impulse in passing. It involves no more friction than the horizontal
escapement, the commonest in foreign watches. The crown wheel prevents
the watch from being thin, but one which Mr. Gray lent me for trial was
not thicker than most silver watches, and went very well.
Lever escapement.—This in its original form was invented by Berthoud
about 100 years ago, and according to the picture of it in Rees’s Cyclopædia
it is identical in all but the position of some of the parts with the rack-lever
escapement, of which Litherland of Liverpool used to be the great maker:
the first watch I ever had was one of that kind. If you suppose the crutch of
the dead escapement of a clock to end in a piece of a wheel, of radius equal
to the crutch, and working into a pinion set on the arbor of a balance, just
like the regulator in fig. 64 at p. 215, that is the rack-lever escapement. The
objections to it are the friction of the rack, i.e. of the wheel and pinion, and
the dead friction on the pallets.
These were almost entirely got rid of by the modification of it which
was invented by Mudge about thirty years afterwards, and which used to be
called the detached lever, but is now generally called the lever escapement
simply, since the rack has gone out of use; and the term ‘detached’ is now
ARC OF VIBRATION. 226
applied to another class of escapements. It is a curious fact in the history of
watchmaking, that a parliamentary committee in 1793 thought fit to award
to this Mr. Mudge (or his son for him) 3000l, the same sum as Arnold
and Earnshaw had had from the Board of Longitude, in opposition to the
opinion of that Board, for a chronometer escapement which was not worth
a farthing, and indeed turned out worth a good deal less than nothing to
his son, who spent a considerable sum in making them. However he well
deserved his 3000l˙for the invention of this lever escapement, of which 100
times more are now made in England than of all the other escapements
together, and which is quite equal to the best in accuracy of performance.
The following is the construction of it (see next page).
The scapewheel and pallets are precisely those of a clock dead escapement;
but the pallets AB are set on a lever which turns on their arbor C and
has a notch at the end, into which a pin P in a small disc on the verge of
the balance works, being in fact a single tooth of the old rack-lever pinion.
The teeth only just lock on the dead part of the pallets, and the pin and
the notch are so arranged that as soon as the escape has taken place the pin
slips out of the notch, and so the balance is detached from the lever during
the remainder of its swing. When it comes back again the pin re-enters the
notch, moves the lever just enough to send the tooth onto the impulse face
of the pallets, and then the scape-wheel acts on the lever and balance until
that tooth has escaped and another tooth has dropped onto the dead face of
the other pallet, when the pin passes out of the notch in the other direction
and the balance is again free. The dead faces have a little recoil the wrong
way, to prevent the risk of the teeth slipping off while the balance is free; and
besides that, there is a ‘guard-pin’ S on the lever, which moves through a
notch in the ‘roller’ at the same time that P moves through the lever notch:
S has no actual contact, but it is there to prevent the lever from shaking
back and making a false escape while the balance is free. The pallets are
always jewelled, except in very cheap watches, and the staff or verge of the
balance ought always to have jewelled pivot holes, and in good watches the
staff of the lever also has.
It should be noticed that you cannot let a lever watch run down, for
repairs or any other purpose, by merely taking out the balance, because
the lever will stop it. This is sometimes inconvenient; and another part of
Mr. A. L. Dennison’s plan is to set the upper pivot of either scapewheel or
lever in a bridge or cock, which can be taken off so as to let the train run
down. The same remark applies to the chronometer escapement, but not
to the vertical, horizontal, or duplex, in all of which the staff of the balance
does the escaping directly on the wheel.
The balances of lever watches are generally made to vibrate about three
quarters of a circle, or 270 from zero, when the watch is clean and lying
flat, which always diminishes when they are in the pocket, and also as the oil
thickens. Nevertheless, under a sudden jerk or twist, the balance sometimes
ARC OF VIBRATION. 227
Fig. 72: Lever Escapement
HORIZONTAL OR CYLINDER ESCAPEMENT. 228
swings quite round, and then the pin strikes the lever again, and occasionally
(though very seldom) hard enough to break itself. Several inventions have
been made to enable the lever to give way a little when that happens, but
I cannot find that any of them have been successful, however promising
they may have been in appearance, and on merely trying an experiment.
Several of them are described in the Horological Journal, ii. 53, xii. 80, and
a very ingenious one in April 1882, by Mr. Hillgreen, dispensing with the
lever altogether by putting the pallets on the balance arbor, not rigidly, but
connected by the balance spring, so that the balance may swing as far as it
likes. But as no escapement can be pronounced successful until it has been
proved by long experience, I only thus refer it.
Fig. 73: Horizontal Escapement
Horizontal or cylinder escapement.—It seems strange that Graham,
the inventor of the dead escapement, should not have been the author of its
adaptation to watches, and should have invented instead a very different one,
in appearance at least, which is now almost as universally used in foreign
watches as the lever, which you see originally came from France, is in English
ones. The verge of the balance in fig. 73 is expanded into a comparatively
large hollow cylinder in the middle, large enough to hold both a tooth of the
VIRGULE ESCAPEMENT. 229
Fig. 74: Horizontal Escapement
scapewheel and a short stem on which each tooth stands; and about 150
also of the side of the cylinder is cut away, leaving only the shaded portion
ab in fig. 73, or AE in fig. 74; in which the tooth Bb has just escaped, giving
the impulse to the balance by its oblique face acting on the edge of the
cylinder as it passes out. The point of the next tooth Aa then falls on the
outside of the cylinder, just as a tooth in a clock escapement falls on the
dead face of the pallets, and it rests there till the balance returns, and then
the outside of that tooth begins to give the impulse until it escapes into the
inside of the cylinder and is stopped there, as at D, till the balance returns
again. The inferiority of this to the lever escapement is evident, inasmuch as
the balance is always subject to the friction and pressure of the teeth; and
moreover if the staff of the balance gets broken by a fall it is expensive to
replace with a new one, which it is not in the lever. In the best watches the
cylinder is made of a ruby, and the wheel is generally made of steel, instead
of brass as in the other escapements. There is a French escapement rather
like this, called the virgule escapement, in which the teeth are in the plane of
the wheel as usual, with small pins rising from them near the points, which
act on a hollow cylinder, smaller than in the horizontal escapement. At one
beat of the balance a pin only passes from the outside to the inside of the
cylinder without giving any impulse. At the other beat the emerging tooth
DUPLEX ESCAPEMENT. 230
acts upon a long impulse face or pallet added to the cylinder and gives the
impulse. They are very little made. Most of the foreign watches have the
horizontal escapement.
Duplex escapement.—This is probably so called because the scapewheel
has two sets of teeth, one for the locking and the other for the impulse.
The inventor of it is not known. Its action is peculiar and requires
some attention to understand it. It is even more distinctly than the virgule,
a single beat escapement, for the scapewheel only moves sensibly at every
other beat, i.e. at every vibration of the balance in one direction only: not
that this makes any difference in the time of revolution of the scapewheel,
because in all double beat escapements only half a tooth-space passes the
pallets at each beat, whereas in the single beat escapements a whole space
passes, or one tooth runs immediately into the place occupied by the previous
one: the effect of which is that in a duplex or a chronometer escapement
the scapewheel almost looks as if it did not move at all. Vv is the verge of
the balance, which is made of a ruby and has a nick in it through which the
long teeth of the scapewheel can pass: one of them is represented as just
escaping, and at the same moment one of the impulse pins S is just ready
to act upon the tooth or pallet P on the verge, and so to give the impulse
to the balance. By the time S has got to t the next locking tooth B has
fallen upon the verge and is stopped there as shown by the dotted line bv.
When the balance returns, the nick slips past the tooth bv, and the balance
goes on till the pallet has got into the position p, with the nick quite beyond
the tooth, and then the balance comes back again in the impulse direction;
the tooth enters the nick and the escape begins, the impulse pins moving
from s to S and from t to T without giving any impulse, except the small
amount which the balance receives from the long tooth acting on the nick
in the verge until it escapes in the position here shown, as before.
Therefore the balance here also is never free, but the cylinder on which
the friction takes place is smaller than in the horizontal escapement, and
what is of still more consequence, the impulse is given directly across the
line of centres in the most favourable way, which constitutes the great merit
of the escapement, and makes it rank next to the chronometer or completely
detached escapement, which I shall next describe. But it requires great
accuracy of construction and is liable to stop from any sudden twist of the
watch which prevents the balance from once swinging far enough for the
nick to clear the tooth; and on the whole it seems to be going out of use,
as being neither so cheap nor so safe as the lever, and not so good as the
chronometer escapement, which is used in all watches requiring very great
accuracy. But that also is liable to stop in common wearing, and some levers
go quite as well, and I prefer them on the whole.
Chronometer, or detached escapement.—The principle of this escapement,
as of the lever, seems to have been invented in France, by Julien
le Roy; but also, like the lever it acquired its now standard form in EngCHRONOMETER,
OR DETACHED ESCAPEMENT. 231
Fig. 75: Duplex Escapement
CHRONOMETER, OR DETACHED ESCAPEMENT. 232
land, under the improvements of the first Arnold, who died in 1799, and
Earnshaw, the latter of whom appears to have beaten with his ordinary
chronometers the picked ones both of Arnold and his other rivals of that
time, such as Brockbank, Emery, and others. The second Arnold, who died
in 1842, was as different from the real chronometer man, as many sons are
from eminent fathers, and owed his reputation first to his name, and afterwards
to his partnership with old Mr. Dent, who told me that the business
had fallen so low as to be a losing one when he joined it for a few years.
I do not, however, see any material difference in principle between Arnold
and Earnshaw’s escapements, except that Arnold’s detent DTV (fig. 76)
turned upon a pivot at D with a spiral spring round it, while Earnshaw’s
is set upon a straight spring as in this drawing, which diminishes the friction.
That is doubtless a great advantage, but I cannot help thinking that
Earnshaw’s personal skill had a good deal to do with the superiority of his
chronometers.
It should also be known that Earnshaw was the first watchmaker who
had sense enough to set at defiance the vulgar and ignorant prejudice for
‘high finish’ of the non-acting surfaces, and to leave them ‘in the gray,’ as it
is called. But so long as smooth work which everybody can see is easier than
accurate work which few people can judge of, watches, like other things, will
be got up for show. Old Mr. Dent used to say, ‘We must work for the fools.’
Nevertheless, in large clocks we have got rid of this folly to a great extent,
and convinced people that painted iron can go better and last longer than
polished brass, when the work is properly constructed.
This drawing (fig. 76) shows the form in which the chronometer escapement
has now been made for many years. The verge has a small tooth V
upon it which pushes aside a lever or detent VTD as it passes in one direction,
but can pass the other way without moving the detent, by merely
pushing aside a very slight spring TV set on the end of the detent, which
is therefore called the passing spring. The detent is attached to the watch
frame by a spring at D, like a stiff pendulum spring, so as to avoid the friction
of any pivots, as its motion is very small, and it has a stop T against which
the teeth of the scapewheel are stopped as soon as the escape has taken
place. It then rests itself against a pin E. The impulse is given exactly as
in the duplex escapement, by the scapewheel teeth A acting directly on the
pallet P projecting from the verge, although their form is rather different.
The impulse begins as soon as the tooth V has unlocked the detent: it is
shown exactly in that position in the figure. The detent stop is a little undercut
for safety, as the pallets are in the lever escapement, and it is always
made of a jewel in good chronometers, and so is the impulse pallet. The
chronometer escapement has been made on the duplex plan, of long teeth
for the locking, and short for the impulse, but that has never been generally
adopted.
CHRONOMETER, OR DETACHED ESCAPEMENT. 233
Fig. 76: Chronometer Escapement
TOURBILLONS. 234
Fig. 77: Lever Chronometer Escapement
Lever chronometer escapement (fig. 77).—This is a combination
of the lever and the detached escapement, which has been several times
re-invented, although—or because—it has never turned out as good as it
looks. Therefore it may be useful to preserve its epitaph as a warning. Its
action is this. The pallets AB (fig. 77), which look like the lever escapement,
only just lock, and have no impulse. The balance is here represented at the
moment of unlocking A and the impulse going to begin at C, exactly as in
the common chronometer. By the time the impulse is finished the tooth
now between A and B will arrive at pallet B and be stopped there. As the
balance returns it will unlock B, which lets the wheel run a very little, just
enough to carry that tooth past the pallet into the position shown in the
figure, and transfers the locking to A again; and this is what corresponds
to the passing of the passing spring in the chronometer. Things are then
again in the condition ready for the unlocking of A and giving the impulse
as before. This, like the French virgule escapement, wastes a little of the
motion of the wheel in passing from one locking to the other without any
impulse.
Tourbillons.—I saw in the Horological Journal that what is called the
tourbillon escapement was reported to have done the best in 3 years’ trials
REMONTOIRES. 235
of chronometers at the Neufchˆatel Observatory. It is not however really
an escapement at all, but an additional piece of machinery which may be
used with one escapement as well as another, like a train remontoire. The
scapewheel and balance are set in a frame which revolves every minute, or
thereabouts; and the object is to make the watch correct its own ‘errors
of position’ by making the balance pass through all positions frequently.
Consequently it would not be of much use for marine chronometers, which
are always kept horizontal by being set in gimbals. The tourbillon frame
is driven by the third wheel of the train: what would be the fourth wheel
is fixed by its rim to the watch plate a little above it, the tourbillon arbor
going right through them: the pinion of the scapewheel rides round the fixed
wheel as a ‘planet,’ as the tourbillon revolves; which is the same thing as
if the fixed wheel revolved and the tourbillon frame stood still, except that
the scapewheel makes one more revolution for every turn of the tourbillon,
or as many as if the fourth wheel teeth were increased by the number of the
scapewheel pinion, that being the effect of sun and planet wheels, just as
there is one more sidereal than solar days in a year (see p. 2).
Remontoires.—The escapement for which Mudge received the parliamentary
reward I have already spoken of, was on the remontoire principle,
and there have been others on the same principle. But they have never
come to any good and I do not believe they ever will in watches, although
they are very useful in large clocks with any except a gravity escapement of
good construction. But the conditions are essentially different in so many
respects that no inference can be drawn from one which can be of any use
for the other. It is sufficient to say that the friction of the train and dial
work is the great source of variation in large clocks, and that the pendulum
arc varies very little; while the variation of the arc of the balance in
a watch is very large indeed in different states of the oil and in different
positions; and nothing is more requisite to impress on horological inventors
than this, that nothing more complicated than what is now in use has the
smallest chance of being adopted. And for that reason I do not think it is
worth while to increase the size of this book by describing any other of the
numerous escapements that have been invented at various times.
Repeaters—or striking-watches, have so much gone out of use that no
English workmen now even profess to make them. All that are sold at all
here come from Switzerland. In watches as in clocks, time-keepers which
profess to perform many feats generally perform them all ill, and frequently
require mending to make them go at all. I shall therefore merely indicate
the general nature of the machinery of repeaters: full descriptions of it may
be found in Reid’s book and in Rees’s Cyclopædia. Watches were never
made (so far as I know) to strike spontaneously: but pushing in the handle
knob is made to wind up the spring of a striking part to such an extent
as the position of the dial-work allows it to go, as I have already described
under the striking work of clocks at p. 124. The watch then strikes the
KEYLESS WATCHES. 236
hour either on a very flat bell or on a ring surrounding the works, like those
spiral springs on which small clocks sometimes strike, and the quarters, and
perhaps a half-quarter afterwards, on two other rings, or on another less
sonorous part of the hour-bell.
KEYLESS WATCHES, &c.
A watch may be made to wind without a key in several ways. One plan is to
put a kind of gathering click to the handle knob, which pushes in and takes
hold of a ratchet set on the barrel, or the fusee if there is one, and winds
it up as you pull the handle out again. But this was very liable to get out
of order, and was also objectionable because it pumped air into the watch,
which produced condensation of moisture; and the following plan (fig. 78)
was invented by a foreigner and adopted by Dent and some other makers: d
is a wheel set on a ratchet on the barrel arbor, so that it will only turn the
barrel the right way (there is not room to introduce this machinery in fusee
watches of the common size); c in the left hand figure is an intermediate
oblique bevelled wheel between d and a pinion b on the handle. It is evident
therefore that if you turn the handle a the right way you will wind up the
watch, and if you turn it the wrong way you will do no harm.
But besides this you can set the hands by the handle; for there is a small
wheel e on the hand arbor with another f by the side of it on a lever fgh,
by which that intermediate wheel can be thrown into gear with d as well as
e, the lever coming through the side of the watch-case; and then it is clear
that by turning the handle either way you can turn the hands. If you have
to turn the same way as serves to wind the watch you do also wind it a little
(and therefore if it is fully wound you cannot set the hands that way); but
if the other way, then you do not move the barrel, as the wheel d slips on
the ratchet.
Another keyless watch, by Mr. Kulberg, described imperfectly in the
Horological Journal of April 1869, appears to be now more generally used
than that just described. I cannot afford space here for more than a statement
of its principle, and a fuller description would be of no particular use
to anybody. The wheel d in the last figure is driven by the pinion b in the
pendant, without the oblique bevelled wheel, and that wheel d (for setting)
drives another, and that other the centre or cannon pinion of the minute
hand, in much the same way as in Dent’s when pushed into gear. But the
winding is done differently. The wheel d is set on what is called a platform,
having a sideway motion something like a remontoire frame in a large clock;
and the first thing turning the knob and wheel does is to move the platform
a little (when it is not pushed into gear for setting) so as to move itself into
gear with the fusee, which it then proceeds to wind. The platform is kept
out of the way generally by a spring, so that neither the fusee nor the centre
SELF-WINDING WATCH. 237
Fig. 78: Keyless Watches
pinion is touched by either of the wheels on the platform.
Mr. A. L. Dennison patented another keyless watch, which is fully described
in his Specification, No. 356 of 1872. There are also other methods
(see Horological Journal, April 1874). The advantages of these modes of
winding and hand-setting are that the watch has never to be opened, which
lets air and dust in, and so the back requires no hinge, which never works
quite air-tight, but snaps on as a separate piece; and also that the inner case
or ‘dome’ is saved.
Self-winding watch.—Napoleon I. had a watch which wound itself up
as he walked, by means of a weighted lever with a slight spring under it,
which danced up and down at every step, and had a click taking into a
ratchet on the barrel.
Pedometer.—A similar lever may be made to drive a train like a watch
train, but without any escapement, and then it in fact counts the number of
your steps and indicates them on a dial. You can adjust it for the number of
steps which you usually take in a mile, and then it measures the distance you
walk, in a rough and approximate way; but it ought to be understood that
STOP WATCHES. 238
it is really nothing but a step-counter, and unless it is properly adjusted,
and you are walking at the rate for which it is set, it is worth nothing for
measuring distances accurately.
Stop watches.—It is sometimes convenient to have the means of marking
a short interval between two observations with a watch, or to mark the
exact time of an observation without looking off the thing you are watching.
Several contrivances have been invented for this, most or all of them
involving some kind of duplication of the seconds hand. In one there are two
seconds hands on concentric arbors connected by a very weak spiral spring,
and when you push in a pin one of them is stopped, while the other will
go on for some seconds without the connecting spring having force enough
to stop the watch. But this is clearly objectionable, and a better plan is
to have the two hands or their arbors connected by a sort of eccentric or
heart-shaped piece acted on by a spring which brings them together again
either forward or backward, through whichever is less than half a revolution.
Several watches of different constructions, on this split-seconds plan were exhibited
in 1851, and others have been invented since, called ‘chronographs,’
and other names.
One of them is of this kind, so far as I can describe it here. Pushing in
a pin for a moment drives on a ratchet wheel with a few square teeth half
a tooth-space; and that raises (as we may say) a spring lever, which carries
a pinion with a disc or ‘roller’ on it (which is always going with the train)
into frictional contact with another disc on the arbor of the extra seconds
hand, which is thus set going with the train. Pushing in the pin a second
time drives the ratchet wheel another half space, and so lets the lever fall
again, into a space between two teeth, and takes the discs out of contact,
and might leave the hand standing at whatever point it has reached: which
might be useful for some purposes, but is not in fact done; because it is of
more consequence to have the hand returned to 0, and you can look where it
has reached before returning it. That is done thus:—the second movement of
the pin also brings a ‘jumper’ spring to bear on the heart-shaped piece which
is fixed on the hand arbor (as before described), and so sends it backward or
forward to 0 according as it is left before or after 30 sec., or half way round
the dial.
In watches of this kind, at least in some shown to me by Lund & Blockley
of Pall Mall, the stop-seconds hand is central, which gives it the benefit of
the full size of the dial, and enables the space of each ordinary minute
to be subdivided into fractions of a second corresponding to the time of
vibration of the balance. For this reason also a single beat escapement, like
the chronometer or lever-chronometer or duplex, is not so good for these
split-seconds as a double beat one, such as the lever or horizontal or the
old vertical, in which the scapewheel moves equally for every beat of the
balance, and not only for alternate ones. The falling of a small time-ball
in a suitable frame (see p. 115) is easily made to push in the pin the first
WATCH CASES. 239
time, and when you take up the watch afterwards you see by the difference
between the two seconds hands how much it is before or after Greenwich
time.
Fig. 79: Recording Watch
There is also another perfectly different plan, which enables you to make
a mark on the dial at the exact time when you push in the pin at the time
of observation. In fig. 79, DD is the dial of a large watch, with the seconds
hand EAB in the middle: the hand is double, and the lower piece of it ends
in a little spoon with some thick ink in it and a hole in the bottom through
which a point from the upper hand EAB can pass and make a mark on the
dial. That hand is pulled down very suddenly by a lever DPC which slips
over a stop of a shape difficult to describe, being pushed in by the knob K,
and is immediately thrown out of contact again with the link AC, by means
of which it pulls down the hand.
Dials of watches and of small clocks are either made of gold or silver
(which soon tarnishes) or of copper covered with enamel, which is a kind of
glass. Such dials with black hands are more distinct than any other kind,
and if the black figures are burnt in with black enamel, the dials would be
everlasting and never want painting. I noticed the absurdity of gold hands on
gilt dials before, at p. 96. Some of the public clocks in Paris have enamelled
dials, which are far more expensive than white glass ones would be.
Watch cases.—I am not aware that there is anything else of a rudimentary
character, or belonging to the principles of watchmaking, which requires
notice. Minute details of watchmaking can be learnt by nothing but experience;
whereas clockmaking is easily learnt by any person of mechanical
ability. Case-making is not horology, and I have nothing to say about it,
except that the cases of what are called hunting watches, which fly open
WATCH-MAKING MACHINERY. 240
with a spring when you press the handle, cannot be so close against air and
dirt, as those which snap tight together. Persons who are afraid of breaking
their watch-glasses, may be tolerably safe with ‘half hunting watches,’ which
have only a small and strong glass in the middle of the cap, which may then
fit tight, and need never be opened except when the hands want altering.
The closeness of the case makes a great difference in the time a watch will
go without cleaning. They generally want at least cleaning about every two
years; though very good ones, with all the escapement work jewelled and
well-made, will go 4 or 5 years with no material variation of rate, which I
think may be regarded as one of the greatest triumphs of mechanical art.
At the same time it should be remembered that letting either watches or
clocks go too long without being cleaned and oiled is very bad economy; for
as soon as the oil is all gone wearing out of the pivots begins.
American watch-factories.—In the Horological Journal for April 1869,
and January 1873, there are accounts of some of these factories, where
watches are made by machinery, so that every piece will fit every watch
of the same pattern; on the same principle as Hobbs’s locks. There can
be no doubt in the mind of any one who understands machinery that this
is the best, as well as the cheapest way of making machines which require
precision and uniformity. Adjustments will after all have to be made by
hand, and a machine which has always to be in motion is not quite on a
level with a lock. The degree to which machine-making of machinery can
be carried cannot be defined `a priori. To a certain extent the same thing
is done at the celebrated watch-factory of Messrs. Rotherham at Coventry,
and also at Prescott in Lancashire, where watch ‘movements,’ i.e. the train
set in the frame, are chiefly made. I can give no description of the American
machinery here, but its elements are stamping plates and the holes in them
and the wheels, and then cutting the teeth of many wheels together. Although
labour is dearer in America than here, this machinery enables them
to undersell English watches of the same quality, as the Swiss also do with
cheaper labour and more organization, though with less use of machinery;
and if our English makers do not bestir themselves they will lose the trade
in all but the best watches, as they have already lost that of both cheap and
ornamental clocks.
BELLS.
There is still less to say of the history of bell-founding than of clock-making.
Indeed it is hardly a progressive art; for as soon as the right shape and
composition are discovered, and the means of making a sound casting, there
is nothing more to do, except to see that that is done. Small bells, probably
not cast but hammered, and of gold, are, we know from the Bible, as old as
the time of Moses; and some such old bells of sheet copper and even sheet
iron are said to have been found at Cologne and in Ireland. The Romans
also had them apparently. They can only be very thin, and of a very inferior
sound to our thicker cast bells. The nearest modern approach to them is the
Chinese gong, which is made exactly of our bell-metal, but hammered, which
that metal oddly enough admits of when it is heated and cooled suddenly
in water. Gongs, like thin bells, sound very ill except when you are near
them, and have less power than the same weight of metal cast into a bell of
a much higher note. The following is the short history of cast bells given in
some of the Encyclopædias:—
‘The large bells now used in churches are said to have been invented
by Paulinus, bishop of Nola in Campania, about the year 400. They were
probably introduced into England very soon after. They are mentioned by
Bede about the close of the seventh century. Turketul, abbot of Croyland,
who died about 870, gave a very large bell to that abbey; and his successor
Egelric cast a ring of six others. Pope John XIII. consecrated a very large
new cast bell in the Lateran Church in 968.’
It is said in Otte’s Glockenkunde, the latest German book on the subject,
but one which does not contain much information of a practical kind, that
bell-founding flourished in all the monasteries in the twelfth century, and
that there were travelling bell-founders who went about casting bells where
they were wanted. I suspect this practice went on very much later; for it
is impossible to believe that there were regular bell foundries in anything
like the number of places from which the ‘legends’ on still existing bells
testify that they have come. The great clock-bell on the south-west tower
at Canterbury was recast in the cathedral yard as lately as 1762. Indeed
241
OLD BELL FOUNDERS. 242
the carrying of very large bells along the roads of old times would have been
a more serious affair than casting them. A great deal of curious matter
of all kinds, historical, practical, and artistic, has been collected by the
Rev. H. T. Ellacombe in a quarto volume on ‘The Bells of Devon and Bells
of the Church’ generally, who rings peals himself at above the age of eighty.
I shall confine myself to the practical.
The founders of church bells in England have for many years been very
few. The most famous bell-founding family on record were the Rudhalls
of Gloucester, who are known to have flourished there from the time of
Henry VIII., and some people think still earlier, till about 60 years ago.
They cast the Westminster Abbey and Chester Cathedral bells, and the
Magdalen bells at Oxford (of which the large ones are too thin), and a great
many others. Farther back the Purdues of Salisbury seem to have been
equally famous for a long time. One of them cast the great single clock bell,
called Peter, of Exeter, and some of the bells of that the large ringing peal
in the kingdom, though now exceeded by those of Manchester and Bradford,
which are only chimed by machinery—a very inferior mode of sounding bells.
Miles Gray was the great founder of the eastern counties in the seventeenth
century: the famous tenor bell of the noble church of Lavenham is his, which
is considered the best in England for its weight, 24 cwt. The firm of Watts,
Eayres and Arnold existed in Leicester and St. Neots for two centuries, and is
now represented by Taylor, of Loughborough, whose foundry now has more
than the old celebrity of the Rudhalls and Purdues, and the more modern
Whitechapel foundry of Phelps, Lester, Pack and Chapman, and several
generations of Mearses, until the last destroyed its reputation by a multitude
of very bad bells, and finally their Big Ben exploit, before spoken of. The
only other founders of bells or peals worth notice now are the Warners,
of Cripplegate, whose Big Ben I. was very nearly as large and heavy as
Taylor’s ‘Great Paul,’ but very inferior to it in sound and casting. They
made the quarter bells at Westminster, of which the largest is about 4 tons,
and several others for Leeds, and other town-hall clocks, of about the same
size, and the whole, or the greater part, of several large peals at Doncaster
and Kensington parish churches, and St. Nicholas, Aberdeen, Fredericton
Cathedral, and many smaller ones. Gillett and Bland, the clockmakers at
Croydon, who have been mentioned before, now make their own clock bells,
and, I believe, ringing peals also, but I have not heard any of them. There is
a nice new peal of eight at St. Andrew’s, Wells Street, by Lewis, an organbuilder
also, at Shepherd’s Lane, Brixton, but too thin, the tenor being
E flat, and only 21 cwt., which should be F. The firm of Moore, Holmes,
and Mackenzie, at Redenhall, Norfolk, have a patent for making the clapper
of a ‘raised’ bell fall out of contact as soon as it is struck; but I know nothing
more of them; nor of several others who advertise as bell-founders, which
may mean anything. Tom of Oxford, by Hodson in 1680, is decidedly the
worst of all our great bells, though he also made good bells of moderate
FOREIGN BELL-FOUNDING. 243
size close by at Merton College. The tradition that Tom came from Oseney
Abbey is a fiction; and even if some predecessor did, it is a melancholy fact
there is no personal identity and very often no resemblance between an old
bell and its recast successor. The Oseney bells were once called the best
in England, and were moved to Christchurch Cathedral, but have been all
recast long ago.
Great Tom might be recast for nothing into a very much more powerful
and an infinitely better bell (for it hardly could be worse) by reducing the
weight about a third, though, if the College does recast it, they are not
likely so to reduce it for the sake of a hundred pounds or so. I wonder none
of the Christchurch men have managed to get it cracked before now, and
so compelled the College to recast it. Mears’s great bad bell of York ought
to be treated in the same way; and if that were reduced a third in weight,
which is a little more than a note in sound, it would still keep its rank as
the third largest bell in England. It is all but useless now. Every now and
then there is a movement for getting something done with it, and getting
the clock made to strike on it (which the present clock is not strong enough
to do), but it always dies away again. Whatever is the price of copper,
and therefore of bell-metal, the founders invariably charge two guineas a
cwt. for re-casting, i.e. they give you back at that price as much metal as
they receive; and as the price of new bells generally fluctuates round seven
guineas, you may expect to get a new bell about five-sevenths of the weight
of the old for nothing.
Bryant of Hertford was a celebrated maker of both clocks and bells early
in this century. There are some nice peals of his at Waltham Abbey, Saffron
Walden, and St. Alkmund’s, Shrewsbury, a town full of peals, both
bad and good. The best peal of 5 bells I ever heard, at Castle Camps in
Cambridgeshire, was by Dobson, who lived at Downham but failed and died
in the Charter House. He is said not to have been equally successful with
larger bells. All these have disappeared, besides many smaller ones; among
which I ought to mention Daniel Hedderley of Bawtry, as the founder of the
fine old peal at Doncaster Church, which was inferior to none, but is closely
imitated both in weight and tone by the new one of 1858 by Messrs. Warner,
which will be given presently.
The art of bell-founding is evidently no better understood abroad than
here. There were some beautifully cast bells from various places on the continent
in the 1851 and 1862 Exhibitions, but they were nothing remarkable
in sound, and the best in appearance are by no means always the best in
sound. Notwithstanding the laudation of a Belgian foundry by a musical amateur
of no experience in bell-making, the Boston bells cast there (p. 148),
and the heavier peal which the Duke of Westminster was advised by another
musician to get there for his chimes at Eaton, are by no means equal
to many modern English bells of corresponding size, and the small ones are
a decided failure. That however is from another cause which will be noticed
ANALYSIS OF OLD BELL-METAL. 244
afterwards, but it proves that the Belgian founders have no special secret.
The art had reached its lowest point about 30 years ago, when three bad
peals in succession were cast for the Royal Exchange. I doubt if there was
a fairly good peal of bells cast from about 1830, or perhaps earlier, till the
Doncaster one in 1858. Certainly the previous Doncaster peal of 1835 by
Mears, which was burnt with the church in 1853, was very inferior to the
older one of 1722, and to many others of the last century and the earlier
part of this.
When we began the Westminster bell business in 1855, I found there was
as good as nothing of a practical kind to be learnt from books, and what
little there was was contradictory, and some of it evidently wrong, and not
always right even on the simple arithmetical relation of the musical notes to
the different sizes of similar bells (using that word in its mathematical sense,
of all the proportions varying alike). Accordingly, when I had to undertake
the designing of those bells, for the reason which I had to state at p. 190
I stipulated for the power to make experiments as to thickness, shape and
composition; and in every one of them I found reason to alter the traditional
practice of the founders more or less. The result has been that nearly as
good bells can now be made as ever, and they would be quite as good if it
were possible to get copper of the old quality; but we had a convincing proof
that it is not, in the fact that several pieces of old bells that were analysed
at the School of Mines contained fully .25 of tin, or tin in the proportion of
1 to 3 copper, while our experiments showed that modern copper will bear
no such quantity of tin without being too brittle to be safe for ringing. This
is only one of a thousand proofs that the effect of science upon ‘common
things’ is simply to make them worse than they used to be. No doubt in
this case the reason is that more copper is got out of the ore. So also they
have found out a way of spoiling lead by robbing it of the little silver which
nature has put into it as a protection from being so easily convertible into
sugar of lead, which is poison, by the action of soft water with anything that
turns it acid, and especially if it is laid on oak, which the lead of old church
roofs always was. Lincoln’s Inn Hall had to be re-roofed with slate because
the lead on oak had decayed into holes in less than 20 years, while the old
lead on many church roofs of oak has lasted for 500 years.
It is surprising how little even musicians bear in mind the distinction
between making bells in tune with each other, which a set of cast iron pots
might be, and making them individually good in tone: and the best musician
in the world is no judge of that unless he knows by experience what sort of
tone is attainable by good bells of something like the same size as those he
has to judge of. Mears’s two first peals at the Exchange were duly certified
by musicians of repute, and I dare say they were in perfect tune, but most
of them were thoroughly bad bells—so bad that after being twice paid for
they were condemned to be recast again in spite of the musical certificates.
The fault of the present peal by the late (not the present) Mr. Taylor is that
NOTES OF BELLS. 245
they are too thin as I warned him that they would be if he aimed at getting
those notes with that weight of metal. I suspect also that the composition
is too soft, or has too little tin, as that was a very common fault of modern
bells until the Westminster experiments.
Fortunately a peal of bells not quite in tune can be tuned, although the
tone or quality of a bad bell cannot be mended. They are made flatter by
turning a little off the inside of the sound-bow or thickest part; and they
can be sharpened a very little by cutting off the edge so as to reduce the
diameter of the mouth; but this blunting of the edge is very apt to spoil the
bell, and it is seldom done now. (See p. 281.)
Notes of bells.—The whole theory of the designing of bells to produce
the required musical notes is deduced from this mathematical law—that
the number of vibrations in a second, in similar bells varies as (thickness)2
diameter ;
or in other words, the depth of the notes or the time of vibration varies
as diameter
(thickness)2 . Consequently, if you want to make (a very bad thing) a
peal of bells all of the same absolute thickness (not the same proportionate
thickness), their other dimensions must be as the square roots of a set of
numbers in the inverse ratio of the vibrations belonging to the proposed
notes. But if the thickness itself varies with the diameter, then the sizes will
be simply as those numbers; and therefore all the dimensions of ‘a peal of
8 tuneable bells,’ according to the old phrase, which means a peal sounding
the 8 notes of the diatonic scale, will be in this proportion—
1, 8
9 , 4
5 , 3
4 , 2
3 , 3
5 , 8
15 , 1
2 ; or
60, 531
3 , 48, 45, 40, 36, 32, 30;
and so on for a larger number of bells, each being half the size of the octave
bell below it. These are the lowest numbers which will represent the inverse
ratio of the vibration of the 8 notes without more fractions; and they are
easy to remember as a standard, from which any others may be deduced,
these being the diameters in inches of a peal of bells in the key of D flat, of
the best weight or thickness for such a peal, supposing that the small bells
were not made thicker for their size, and therefore larger for their notes, than
the large ones, as they always are, to prevent them from being overpowered
when they are all rung together as will be seen from the peals which I shall
give presently.
It may save some trouble to observe that in designing peals of bells we
have nothing to do with what is called musical temperament, which was
long a vexed question in organ tuning, inasmuch as a peal of bells is always
played or rung in the same key. That question would arise if you took the
7th and 6th of a peal of 8 bells (counting, remember, from the smallest) to
make them the 8th and 7th of a smaller peal; for in that case you see the
531
3 and 48 inches would not be in the right proportion, of 9 to 8, but the
531
3 ought to be 54; though both would be called E flat, and the error is
PROPER SCALE OF THICKNESS. 246
too slight to be perceived except by very good ears. The same occurs in
playing the Westminster and Cambridge, or the Doncaster quarters on the
2nd, 3rd, 4th, and 7th of a peal of 8, as described at p. 144; for the sizes of
those bells will be, as we saw just now, 32, 36, 40, 531
3 , whereas the 36 in.
ought to be only 35.55 to make it exactly in tune as the second of a peal of 6
or of 10 bells. Without regard to temperament, bells (on any given scale of
thickness) two whole notes apart are always as 4 to 5 in diameter; 11
2 note
apart, as 5 to 6: 3, as 3 to 4; but an interval of 3 notes (i.e. 4 bells) of the
diatonic scale always includes one half tone, such as BC or EF. Three bells
must have no half-tone interval.
Weight of bells.—The weights of similar bells, i.e. of those in which the
thickness and all the dimensions keep the same proportion to each other,
vary as the cubes of the diameters, or any of the other dimensions; and
therefore the weights of a peal of 8 such bells would be in this proportion
(making the tenor 100 for facility of calculation)—
100, 70.23, 51.2, 42.2, 29.63, 21.6, 15.18, 12.5.
The Westminster bells, which would be the treble, second, third, sixth, and
tenor of a peal of ten, are very nearly in this proportion; for in them the
thickness does vary as the other dimensions, except that the smallest was
made a little thicker than the others for its size, in order that its sound
might be strong enough. Bells 11
2 note apart are as 58 to 100 in weight; and
half a note nearly as 5 to 6.
But we have still to ascertain what is the proper weight for any given
size or note. From the practice of some of the modern bell-founders you
might suppose that it may be almost any weight you please, at least within
very wide limits, as one sees bells of about half the weight of old ones and
yet of the same note; and then people are surprised that they sound worse.
Postponing for the present the consideration of bells to ring in peals,
any one who takes the trouble to compare the weights and the cubes of
the diameters in the list of the principal large bells of Europe at the end
of this book, will see that the bell-founders of all ages and countries have
agreed in fixing rather narrow limits for the variations of weight in proportion
to the diameter of their bells. And this is by no means from any blind
following of each other; for there is a good deal of variety in the shape and
the distribution of thickness over the different parts of the bell, although it
all ends in this near agreement of the proportions of weight and size; which
would be nearer still, but for the foreign bells being generally taller than
ours.
Taking 6 ft. diameter as a convenient standard to reduce them to, you
will find that the least weight for a bell of 72 inches would be 72 cwt.,
which is easy to remember; or in smaller figures, 9 cwt. ( = 1008 lbs.) for
3 ft. diameter. And such a bell will be nearer B flat than any other note,
OLD V. MODERN THICKNESS. 247
according to the proposed universal pitch, in which A has 880 vibrations in
a second, or that number multiplied or divided by some power of 2. The
diameter of bells on that scale is about 13 times the thickness of the soundbow
or thickest part; for if some of them are rather thinner there, they
are thicker above the sound-bow, and so the total weight is the same. But
nearly all the great European bells, as you may see from comparing their
sizes and weights, are very considerably heavier than that scale, and the
average modulus for them may be taken at 4 tons for 6 ft. diameter, or
10 cwt. for 3 ft., and in that case they will be nearly a note higher. The
Westminster bells are very nearly on this thicker scale, or their diameter is
nearly 12 times their thickness; and so is the new Great Paul bell: indeed
apparently on a still heavier scale, but it is somewhat taller for its width than
the other great English bells. Some of the bells in the list (if their recorded
weights are right) are still heavier than this, which I shall generally call the
12, and the other the 13 scale; which last gives the before-mentioned size of
5 ft. for a D flat bell, weighing about 42 cwt., instead of 30 or less, as D
bells are often made now, but never with my consent.
This 13 scale agrees more nearly in weight than any other simple proportion
with that used by the old bell-founders in the large bells of peals,
which were made rather thinner than large single bells, and the small ones
thicker, to prevent them from being overpowered by the large ones. The
tenor of the great peal at Exeter weighs only a 16th less than its weight
on the 13 scale of the Doncaster peal; and ‘the great bell of Bow,’ and the
tenor of York Minster, and the similar one at Sherborne (lately cracked and
recast) are still nearer to it; although anyone measuring their thickness at
the sound-bow only might fancy they were on a thinner scale. The Exeter
one, for instance, is only d
15 at the sound-bow, but the waist is 2 inches thick,
or d
36 , and not d
45 as some modern founders would make it, and the weight
is that of a rather thick bell. I am satisfied however that no sound-bow
ought to be so thin as that proportion, and that even thickening the waist
does not compensate for it. There is a fulness and softness in the sound of a
thick bell which a thin one never has. The old bell-founders evidently knew
that it is a law of nature that a given weight of bell-metal is only capable of
sounding a very narrow range of notes with good effect; and if you infringe
that law and make your bells thinner for the sake of getting deeper notes
out of them, you are as certain as usual, in fighting with laws of nature, to
pay for it by a more than equivalent loss in the quality of the tone.
And it happens that this loss is even greater now than it would have
been a century ago, on account of the difference in the quality of the copper
which I have already spoken of. It is less tough in working, capable of
holding less tin without becoming too brittle, and apparently incapable of
a certain softness of sound which even thin old bells sometimes have, but
thin new ones never. Indeed it must be admitted that some of the finest old
SCALE OF WEIGHTS AND SIZES. 248
tenors are what we should now call thin. They would probably have been
better still if they had been thicker. As a peal of bells is a luxury, meant
to give pleasure to those who listen to them, and not a necessary of life,
it is astonishing that people will go on raising large subscriptions for them
without taking the least trouble to ascertain that they get what is really the
best thing for their money, and forgetting that you pay for the same weight
of metal whether the bells are thick or thin, only in one case you get them
of the right notes for their weight, and in the other case wrong, and so make
the bells bad instead of good.
The following is a table of diameters and weights of an octave of bells,
including all the half-notes, on the 13 scale of thickness, and also on the
12 scale; from which you may easily interpolate a 121
2 scale; and larger or
smaller bells than these may be at once deduced from those an octave above
or below them in the same scale. Single bells, and especially small ones,
should always be on the 12 scale, or very near it; but the tenors of peals
on the 13 scale. The smallest bells of large peals are generally still thicker,
sometimes as thick as a 10th of their diameter, and often an 11th; and
therefore they exceed any weights deduced from this table, as you may see
in the large peals which will be given presently:—
13 Scale. Diameter. 12 Scale.
cwt. inches. cwt.
72 Bfl. 72 C 80
60 B 671
2 Dfl. 66
51 C 64 D 56
42 Dfl. 60 Efl. 461
2
38 D 571
2 E 41
31 Efl. 54 F 34
26 E 51 Gfl. 281
2
21 F 48 G 24
18 Gfl. 45 Afl. 21
15 G 43 A 17
121
2 Afl. 40.5 Bfl. 14
11 A 38.4 B 12
9 Bfl. 36 C 10
Until about 14 years ago the largest ringing peals in England and therefore
in the world, was that of Exeter Cathedral, which is the largest still,
and those of York Minster, Bow Church, and St. Saviour’s, Southwark, otherwise
called St. Mary Overy, which were all practically of the same size.
The Bow peal is the best of the three, the new York one, which was cast by
Mears after the fire of 1840, caused by a clock-maker leaving a candle burning,
being very inferior to the old ones from the same foundry and patterns.
The Southwark peal is half a note lower, being a little thinner, and for that
LARGEST MODERN RINGING PEALS. 249
reason worse.
Bow Church, 1762, and
Exeter Cathedral Bellsa old York Minster, 1765.
cwt. qr. lb. ft. in. ft. in. cwt. qr. lb.
72 2 2 6 0 Bfl. 10 C 5 41
2 53 0 25
40 3 19 5 31
8 C 9 D 4 91
2 34 2 6
33 2 11 4 95
8 D 8 E 4 31
3 26 0 13
28 0 4 4 6 Efl. 7 F 4 01
3 21 0 23
19 0 19 3 111
4 F 6 G 3 8 16 0 4
18 0 4 3 81
2 G 5 A 3 5 13 2 22
10 1 2 3 31
4 A 4 B 3 21
2 12 0 7
8 2 0 3 0 Bfl. 3 C 3 0 10 0 0
8 3 10 2 103
4 C 2 D 2 10 9 1 5
7 3 22 2 83
8 D 1 E 2 81
2 8 3 7
247 3 9 205 0 0
aThe tenor and 5th were recast by Taylor, 1902, and the whole peal rehung in iron
frames. The old tenor weighed 62 cwt. 2 qr. 11 lb., though reputed as weighing 67 cwt.
1 qr. 18 lb.
The two largest modern ringing peals are those of St. Paul’s and Worcester
Cathedrals, both by Taylor, of the patterns and composition which I
arrived at as the best after the experiments made for the Westminster Bells,
modified a little by some later ones, as I shall explain farther on. The
St. Paul’s peal is on the whole better than Exeter, of which some of the
bells are bad; and the Worcester peal is quite equal, if not superior to that
of Bow.
All the 5 largest bells at St. Paul’s are only on the 14 scale of thickness,
and they would have been better on the 13 scale, but the tenor inconveniently
heavy to ring. On the other hand the 9 smallest are all practically 3 in. thick,
which also I do not approve of nearly so much as the graduated thickness of
Worcester, except the treble there, which gave a great deal of trouble from
the highness of the note, and is not satisfactory. But the two trebles there
are simply a mistake, and the peal of 10 sounds a vast deal better than the
peal of 12, as is always the case. It is not so bad at St. Paul’s, because
the notes are lower and the bells heavier and slower. But even there the
12 sound confused, and inferior to 10. At Worcester three extra bells have
been added to make some more half-notes, DAC, for the chimes, which I
omit in the list of the peal. In both cases I shall notice the great single
bells separately. The Rochdale Town Hall has a peal for chimes only, almost
identical with Worcester. It should be noticed that the addition of an odd
SOME CHIMING PEALS. 250
St. Paul’s, 1878 Worcester, 1869
ins.
in. cwt. qr. lb. in. cwt. qr. lb. thick.
Bfl. 69 62 0 0 12 Dfl. 63 50 0 0 4.8
C 611
4 44 2 0 11 Efl. 56 34 2 12 4.07
D 551
4 30 2 22 10 F 50.4 26 1 8 3.7
Efl. 521
2 28 0 7 9 Gfl. 471
4 21 2 11 3.44
E 475
8 22 1 18 8 Afl. 421
2 15 2 11 3.1
G 431
2 16 2 21 7 Bfl. 381
2 12 0 0 3
A 395
8 14 0 4 6 C 36 11 0 24 3
Bfl. 385
8 13 2 14 5 Dfl. 35 10 1 21 2.9
C 363
8 11 3 21 4 Efl. 321
2 8 3 0 2.8
Dfl. 34 10 0 3 3 F 301
2 7 3 10 2.7
Efl. 321
2 9 1 15 2 Gfl. 291
2 7 0 22 2.44
E 31 8 1 16 1 Afl. 28 6 3 19 0
Total 271 3 1 Total 212 2 2
13th bell only half a note below the treble, instead of the whole one, makes
a useful small peal of 8, omitting the 4 largest of the great peal, subject to
the difficulty of making a satisfactory treble of a higher note than F or F sh.
at the highest. That bell at Worcester is a fair one, though the G sh. treble
is not. The upper 6 of a peal of 10 make a proper peal of 6.
The largest modern peals, all by Taylor, are those of Manchester and
Bradford Town Halls, and of St. Paul’s Cathedral; but the Bradford peal
cannot be rung, only chimed by machinery. The St. Paul’s peal is really
a more powerful and better one than Exeter, though that is rather larger;
but some of the bells are too thin and otherwise inferior. Sir Christopher
Wren, very unlike most modern architects, who will not condescend to learn
anything of such matters, but consider themselves qualified to give orders for
anything that is wanted, whether architectural or not, had prepared a tower
capable of bearing such a peal in full swing with perfect safety. It does not
even shake sensibly under the ringing, which is the case nowhere else that
I know of with a moderately heavy peal. The next largest modern ringing
peal is that of Worcester Cathedral, especially without the two trebles. The
St. Paul’s peal, being heavier and slower, bears them better; but even there—
and everywhere—it is impossible to hear the 12 as distinctly or as pleasantly
as 10. For playing tunes there is no objection to any additional bells, as halfnotes
outside the diatonic scale, which alone is fit for ringing. There are two
other chiming peals still larger, which I ought to give, at the Bradford and
Manchester Town Halls (see next page). Both of those also are by Taylor.
This Manchester peal is the best proportioned of them all, except that even
SOME CHIMING PEALS. 251
here perhaps the small bells vary too little. You see the large bells are on
a thicker scale than St. Paul’s, while the small ones are thinner and lighter
for the same notes, but quite heavy enough, as I proved by the Doncaster
peal (p. 252).
Bradford, 1873. Manchester, 1876.
ringing
in. cwt. qr. lb. in. number. cwt. qr. lb.
A 771
4 87 0 0 12 G 911
2 . . . 162 3 0
B 67 59 2 0 11 A 80 . . . 100 2 0
Csh. 593
8 41 2 9 10 B 70 . . . 71 0 0
D 56 38 0 10 9 C 653
4 10th 52 0 0
E 50 24 1 14 8 Csh. 611
2 . . . 43 2 0
F sh. 453
8 18 3 14 7 D 583
4 9 39 0 0
G 431
2 15 3 25 odd Dsh. 55 . . . 31 2 0
Gsh. 411
2 13 3 23 6 E 523
8 8 27 0 4
A 391
2 12 2 22 5 F 503
4 7 23 0 11
B 351
2 9 0 22 4 F sh. 473
4 . . . 21 1 7
Csh. 333
4 8 2 17 3 G 451
4 6 17 1 7
D 33 8 0 11 2 Gsh. 433
4 . . . 16 0 6
E 303
4 7 3 2 1 A 411
2 5 14 1 3
Total tons 17 3 10 B 373
8 4 10 0 14
In the Manchester peal the
10 numbered bells are hung
for ringing. The tenor has
been recast rather larger than
at first, after being cracked
by the clock hammer, which
weighed nearly a 30th of the
bell, which is decidedly too
much.
C 363
8 3 9 3 14
Csh. 345
8 . . . 8 3 0
D 333
4 2 8 2 9
Dsh. 32 . . . 7 3 14
E 311
2 1 7 2 7
F 331
2 . . . 7 1 5
F sh. 291
2 . . . 6 3 4
Total tons 34 5 2 3
It is a pity that Town Councils will not make up their minds to have
peals of bells before instead of after their towers are built, and that architects
cannot learn that bells sound worse for being crowded together, and better
the higher up they are: in other words, that bell chambers ought to be
as large and as high as possible, as they were in old cathedrals and large
churches. Now they seem to resort to every possible device to make them
small, and the towers so weak that even if they are large they will not
bear a peal of large bells, as was the case with that of St. John’s Chapel
at Cambridge, which is as large inside as Worcester Cathedral tower. The
Bradford tower is no wider than that of a moderate old village church tower,
PEALS OF EIGHT BELLS. 252
and so is that of Eaton. Rochdale is still smaller.
I have given them all in flats or sharps as they were sent to me, though
there is no real difference between bells called D flat and C sharp, except
that D flat sometimes means that the bell is nearer D than C. Of course
the notes very seldom happen to be exactly those of the received standard
pitch, and there is no advantage in their being so.
I next give two modern peals of eight, of successive sizes. They would
differ by only half a note and not (nominally) by a whole one, but that
the ‘sweeps’ were rather different, and I don’t believe they really differ by a
note. But as I have said throughout, notes are of no consequence provided
only the bells are in tune among themselves. The Doncaster peal was cast
by Messrs. Warner at the same time as the quarter bells of Westminster.
The Croydon one, by Taylor in 1870, is substantially the same, but a little
heavier, especially in the smaller bells, which the bell-founders are always
struggling to increase, with no benefit that I can see. The Burton peal is at
St. Paul’s church there, which was built by Mr. Bass, substantially from my
design, as well as the bells. Ossett is near Wakefield:—
Doncaster, 1858, Warner. Burton and Ossett, Taylor.
in. cwt. qr. lb. in. cwt. qr. lb.
Efl. 54 30 1 0 8 F 51 25 3 21
F 48 21 0 24 7 G 45 19 0 0
G 431
4 15 1 10 6 A 401
2 13 1 9
Afl. 41 13 0 0 5 Bfl. 381
2 11 3 14
Bfl. 37 9 0 0 4 C 35 9 3 9
C 34 8 0 10 3 D 321
2 7 1 25
D 321
4 7 0 11 2 E 301
2 7 1 9
Efl. 31 6 2 5 1 F 271
2 6 2 4
Total 110 2 12 Total 101 1 10
It is not worth while to insert any smaller peals of 8: indeed no peal of 8
with a tenor less than about 4 feet diameter, and 21 cwt., is worth having.
A nice peal of that size, by Warner, was hung at Hunslet Church, Leeds,
a few years ago, of the total weight of 85 cwt. There are plenty of peals
of 8 with E tenors weighing 17 cwt., and even less, made for foolish people
who insist on having bells of the deepest possible note and for the smallest
possible price, and lazy ringers like them better than the good old-fashioned
heavy bells, but they are miserable things.
I next give two new peals of 8 and 6, one unusually heavy for its size for
this reason. The three largest bells were made at first without the intention
of adding any others, and I determined to have them heavy for their size
to sound well alone. They were accordingly made even thicker than a 13th.
BELLS MAY BE TOO THICK OR THIN. 253
Afterwards the other three were added, and then a separate bell to make the
Cambridge andWestminster quarters (see p. 148), and then a treble to make
a ringing peal of 8 was given. That church at Headingley was also designed
and partly built by me. The Gainford peal is a particularly good one, made
by Taylor for a fine old church which has been admirably restored. I consider
that the model size for an ordinary peal of 6, and very nearly as small as
they will bear without running into objectionably high notes. There is a
very nice peal by Taylor at Coddington, near Malvern, half a note higher
than this, which is quite the smallest that will do:—
St. Chad’s, Headingley. Gainford, 1865.
in. cwt. qr. lb. in. cwt. qr. lb.
G 46 19 0 15 6 Afl. 401
2 12 0 11
A 41 14 0 0 5 Bfl. 36 8 3 18
B 371
2 10 0 11 4 C 321
2 8 0 18
C 36 9 3 24 3 Dfl. 31 8 0 0
D 34 9 0 9 2 Efl. 30 6 2 17
E 32 7 2 19 1 F 29 6 1 14
F sh. 30 7 0 21
G 29
Total 77 0 15 Total 50 0 22
The tenor of the beautiful little peal of 5 at Castle Camps, cast by
Dobson in 1828, is 40 in. and 11 cwt., and the treble 5 cwt. 1 qr.; but
nobody gets peals of 5 now, for they cost very little less than 6, and sound
much worse.
Although some very good old bells are thinner than that 13th of the
diameter which I have prescribed as the least thickness to be allowed, and
no such bells can be made of modern tin and copper, as I have already
said, yet the best modern bells on the 13 scale are better than any old ones
on the 15 scale. A fashion arose in the last century of making the trebles
enormously thick, even with the tenors thin, and some of the bell-founders
of the present time require constant repression to prevent them doing so. I
was assured that the trebles of the Doncaster peal would never be heard with
the large bells on my scale of thickness; but they are remarkably distinct.
The treble is on the d = 11t scale. In peals of 10 they may go up as high
as a 10th, but anything beyond that makes the bell too thick to ring—
I mean to sound, not to swing. I know a peal of which the middle bells
alone are good for anything, because the tenor is too thin and the treble
too thick to sound over the middle ones. The rule that I always adopt is
to prescribe the 13 scale for half the bells in the peal, and let the others
increase in proportionate thickness gradually up to some maximum, which
I usually define by limiting the diameter of the treble. And I have several
times advised people not to pay the founders for any weight due to excess
MAIDEN BELLS. 254
above the prescribed diameters, which is easy to calculate. There is not the
least difficulty in casting to any prescribed diameters.
The 4 largest bells at Doncaster were ‘maidens,’ i.e. they came out not
only of the prescribed diameter, but thickness too, so that they required no
tuning: the smaller ones were intentionally made just too thick, so that all
the tuning might fall on them, and they required very little. A good many
of the Worcester bells are also maiden; and every now and then, but very
rarely, a whole peal, for instance that of St. Andrew’s, Wells Street, is so;
but I always regard them with some suspicion that one or two bells have
been left a little out of tune for the sake of calling it a maiden peal.
Sizes of peals.—I have given the minimum for peals of 8 and 6. The
smallest tenor suitable for 10 bells is D flat, of 5 feet diameter and 42 cwt.,
or D at the very highest for the same reason that F, 48 in. of 21 cwt., is the
lightest tenor for a good peal of 8; viz. that if you go much higher you run into
a G sharp treble, which, for some reason that neither I nor the bell-founders
have discovered, though the fact is certain, never sounds well together with
large bells. At that point some change takes place in the character of the
sound, and bells above and below it do not sound homogeneous. Peals of 12 I
have already said I disapprove of altogether; and it is nothing but the vanity
of having them which induces ringers to cry out for them, and subscribers
to find money for them. It is almost impossible, with the very best ringing,
to distinguish the bells in them, and the best ringing is very difficult to get.
If you will have 12 bells the tenor should not be higher than C, for the same
reason as I gave just now, and even that makes the treble G, though that
is not quite so hopeless as G sharp. A B-bell would probably be the best
for such a peal, and anything below that, if of proper strength, roars over
the others in a way which does not produce a good effect. Perhaps even the
Bradford chimes would have been better without the A tenor, though no
bell is too big for a clock to strike on. The tenors of Exeter and St. Paul’s,
you see, are B flat; but both would be on a better scale of thickness if they
had been B with the same weight, or more like the B bell at Manchester,
which is not rung however. The Southwark B tenor is decidedly too thin.
I am speaking here only of ringing peals, in which the time of each round
is governed by the weight of the largest bell. The only limit to the number
of chiming bells, with as many notes as you please beyond the diatonic scale,
is that difficulty of getting small bells above C to mix well with the large
ones, which is painfully apparent both at Boston Church and Eaton Hall,
where alone it has been tried in England; and as both these peals are entirely
or chiefly Belgian, the defect cannot be attributed to any inferiority of the
English founders. The largest bells in both peals are good enough. (See
p. 282.)
Shape of bells.—Hitherto I have assumed that the bells are to be of the
well known and universal shape of church bells, as shown accurately enough
for this purpose at page 151. And I am convinced it is the right shape,
SHAPE OF BELLS. 255
notwithstanding the multitude of public and private assurances which we
had that it is wrong, and that the hemispherical form, or something like it,
is right. The persons who kept making these suggestions evidently did not
know that large and small bells require different shapes. Why it is so, I do
not pretend to explain. But the hemispherical form had been used for ages
in small clock and house bells up to the largest size at which it can properly
be used. I had tried myself for several years, and with several founders, to
get one made as large as 9 inches diameter that would sound well in a house
clock, and I was obliged to give it up and be content with one of 7 inches,
which seems to be the limit of their musical capacity. There was a very large
one in the 1851 Exhibition, but it was obliged to be struck with a muffled
hammer: otherwise the sound would have condemned it at once.
I know that bells of 3 or 4 cwt. of that shape are made for cemeteries,
for which their horribly doleful sound is appropriate enough; and as they
have the advantage of not being heard nearly so far as bells of the common
shape, it is perhaps still more appropriate. But those are not the qualities
usually sought for in either ringing bells or clock bells.
On the other hand, small bells of the usual church form, such as musical
hand bells, require to be thinner and straighter in the side, or more conical
than larger ones, which are bad if the sides are less hollow than at pp. 150
and 257. I exhibited a 6 in. bell-metal model of the Westminster bells
at the Royal Institution in 1857, and it sounded worse than a common
door bell, or a railway hand bell. But above 2 feet in diameter, all these
peculiarities vanish; and according to my observation and experience, and
the universal practice of the bell-founders of all ages the long-established
shape and proportion of church bells appears to be equally right for a bell
of 4 cwt. and of 220 tons, the probable weight of the largest Russian bell. I
may just mention here that the form of a very prolate hemispheroid, which
the Chinese and Indian bells have, is so manifestly bad, that no one need
hear them twice to know that that at any rate is wrong.
But when you have to design bells for construction it is necessary to go
somewhat farther than this general conclusion; inasmuch as what we may
fairly enough call the established form of bells, when speaking popularly, or
comparing it with a very different form, will be found to have considerable
variations of its own—considerable at least to the eye of a person who knows
what a great difference in tone may be produced by an apparently small
difference in shape. This, and the thickness, and the composition of the
metal, were the three great points to be settled in the experiments and
observations, which, as I have already said, were made before and during
the two years which were occupied in casting the Westminster bells. It
would be tedious and useless to describe the different variations that were
tried. They ended in our coming to the conclusion that the best shape was
something between the most common English pattern and the usual foreign
one. It is indeed a good deal nearer to the English than to the continental
RULE FOR CONSTRUCTION. 256
pattern, except the Russian, which I was surprised to find from a section
given in Lyall’s Russia, after the first Westminster bell was made, agrees
very nearly with that pattern.
After trying and observing the effect of a great many patterns, and
without any `a priori theory in favour of any particular curve, I saw that the
one which we all thought the best in effect was very like an ellipse in section,
though not the same ellipse as had been previously, and is still used by some
of the English founders. And after further experiments with slightly varying
shapes, I came to the conclusion that the following is the best for large bells
on the 13 scale of thickness. Thicker ones only require a slight modification
of the outside curve, and it is not worth while to complicate the description
by going into more details for them. (See next page, fig. 80.)
Consider the diameter of the bell mouth divided into 24 equal parts.
Then the inside sweep is simply the quadrant of an ellipse, whose semiaxis
major AC is 14, and minor BC, 6 ‘parts;’ in which I shall now give all the
measures. You see at once the arrangement and lengths of all the vertical
and horizontal lines in the figure. To draw this ellipse, mark B at 14 above
D, and with radius 14 from centre B mark S, and also H (beyond the size
of the page), in the line AC prolonged. S and H are the foci of the ellipse;
which is drawn in the well known way, by sticking pins in a table at S and
H, through the ends of a thread made just long enough to reach over SBH,
and running a pencil along it, keeping it stretched. The pencil will then
trace out the elliptic quadrant AP8B, the 8 indicating 8 parts from A, for a
purpose I shall mention presently.
The outside can obviously be made of no single curve, but must be
compounded of several curves in some empirical way to produce what we
find to be the best proportions of thickness throughout. As the thickness of
the waist of the bell is to be a third of the sound-bow PQ, which is a 13th
of the diameter, b must be a 39th, or practically 2 thirds of a ‘part,’ outside
of B. It is necessary to put the minor axis cb of this ellipse 1
2 p. below CB,
to make it come right below. From centre b with radius 11 mark s and h
for the foci of another ellipse, and then describe the quadrant aRb, in the
same way as before. The lower part aR is useless, and that part of the bell
curve is made up thus:—draw sQP4 to the point 4 in the base, and mark off
PQ = a 13th of the diameter. Then, with a radius of 31
2 or 4 (for there is
hardly any difference), draw the circular arc AQ, letting the centre K come
where it happens. The remaining little bit QR is easily filled up by hand.
This makes the thickness = 1 at 8 from A.
The lowest bells are somewhat taller than the elliptic quadrant which
forms the inside sweep, and the remainder is simply added as a cylinder.
The top is drawn as a circular arc with a radius = 161
2 to 18, from E the
centre of the base, small and thick bells being usually made taller than large
ones. This one is drawn with radius 17 for simplicity. I have drawn the
crown without canons, or ears for hanging in the old fashion, for a reason
RULE FOR CONSTRUCTION. 257
Fig. 80: ‘Sweep’ or Section of a Bell
RULE FOR CONSTRUCTION. 258
which I shall give afterwards; and have accordingly added two of the 4 or 6
bolts XX, for hanging the bell to the stock; and Y the larger bolt to which
the clapper is hung at T, which I have inserted to show its length, and to
remind people that the pit, or frame to hold a swinging bell, must be a good
deal longer than twice the height of the bell, as I have known it forgotten,
and the frame spoilt in consequence; and if the clapper catches the frame
the bell is almost sure to be cracked. The pit should be at least 5-3rds of
the diameter of the bell; and for tall bells, or bells hung long, or with the
gudgeons above the crown, the pit must be longer still. The clapper should
strike at the thickest part of the sound-bow. The tail F, called the flight,
is almost always requisite to make the clapper fly properly, and its axis, or
pivot at T, must be sensibly below the bell gudgeons, or the clapper will
not fly at all. This only has to be considered when the bell is tucked up in
the stock; for otherwise clapper axis cannot help being below the gudgeons.
Very thick bells require the sound-bow to be rather higher than in the
above figure, and therefore the lip to project a little more outwards, or it
becomes too lumpy. In that case, the bit of curve AQ requires drawing
with longer radius than 4. But minor details of this kind must be left to
the judgment of the bell-founder. I have given these fundamental rules,
because the time may come again, as it did when I undertook to design
the Westminster bells, that there may be no means of learning these things,
except by going through a course of experiments again, or else accepting
what the bell-founders call experience, which means nothing but the way
they happen to have been doing things for some time. The then existing
‘experience’ was manifestly wrong.
This construction makes the sound-bow, and also the part above it,
rather fuller outside than had been usual. According to all the sections in
books, and in most of the bells that I have seen, you can lay a straight
edge against the lip and the top shoulder of the bell; but in the Westminster
pattern the straight edge would be thrown out a little beyond the lip, by the
protuberance of the sound-bow. I do not profess to give any reason why this
pattern should be any better than the more hollow ellipse, of major axis 12,
which was the more usual English pattern, instead of 14, or than the foreign
pattern, which is not an ellipse at all, but a very much less hollow curve, and
not ending horizontally at the mouth: all I can say is, that having tried them
all, both I and other people who examined them came to the conclusion that
this is the best in effect. The greater tallness of the foreign bells, beyond the
height of 18 ‘parts,’ at any rate, which has sometimes been copied in English
ones, appears to me to be a pure waste of metal in large bells, besides being
a serious incumbrance in the increased momentum and centrifugal force of
the bell in ringing; and I believe all the bell-founders are of that opinion
now. Among other experiments we tried making the ‘waist’ thinner than a
third of the sound-bow, but it produced an unpleasant whistling sound and
was plainly wrong.
COMPOSITION OF BELL-METAL. 259
Composition of bell-metal.—I exhibited in a lecture at the Royal
Institution, in 1857, a variety of small bells of different shapes, metals,
and alloys, and different proportions of copper and tin, which had been
suggested as possible improvements on the usual composition of old bells.
It was clear that none of them were improvements, and that something near
the proportion of 3 lbs. of copper to 1 of tin had been generally used by
the old founders. The tin was sometimes a little more than that, or tin
and antimony together, which both produce the same effect of making the
alloy brittle, and I understand are difficult to distinguish in the analysis.
But it was also clear from experiments that 3 to 1 with modern copper is
the turning point between safe and unsafe brittleness, although the sound
improves as you increase the tin up to that proportion, and even higher; and
that antimony is an inferior substitute for tin. I found it was the modern
practice to use much less than this. Accordingly we fixed on 22 to 7 for
the Westminster bells, and others made about the same time; none of which
have cracked, and we had great difficulty in breaking an experimental bell of
that composition. The specific gravity of the sound part of Mr. Mears’s bell,
as of the previous one, is 8.8, but of the unsound part only 8.32: some thin
pieces at the edge of the first bell were as high as 8.94, and very difficult to
break. There is no such test of good casting as a high specific gravity; but
unfortunately it cannot well be applied to large bells, as it involves weighing
them in water: for the specific gravity is the weight in air divided by the
difference between the weights in air and in water.
But I have since come to the conclusion, for chemical reasons, that the
proper composition for bells is 13 of copper to 4 of tin, though it is not
mentioned in any book, nor came out exactly on the analysis of any old
bell-metal. But in old times the doctrine of ‘chemical equivalents’ or atomic
weights was unknown; and the reason why 13 to 4 is the proper proportion
is, that it is the only one near 3 to 1 which is in atomic proportions. For
the ‘atomic weight’ of copper is 32, and of tin 59, and 13
4 × 59 = 6 × 32; or
the mixture of 13 to 4 by weight is a true chemical combination of 6 atoms
of copper to 1 of tin, and is written in chemical language Cu6Sn (Sn being
short for stannum, tin). (See p. 282.)
I am aware that some persons who know more of chemistry than I do
dispute the application of that theory to metallic alloys, on the ground
that the metals do not refuse to combine in other proportions, as gases
do and some other compositions. But the practical question is whether
those proportions do not combine more firmly and with less risk of the
alloy becoming unhomogeneous in cooling, or otherwise defective. And I
am convinced that they do. Without going into other metals, telescope
speculums only differ from bell-metal in containing rather more tin, and no
alloy has to undergo such severe tests as they have. Lord Rosse made all his
speculums as Cu4Sn, or 128 to 59 by weight, and a very little deviation from
that proportion runs great risk of spoiling the speculum. I have seen some
IMPURITIES OF BELL-METAL. 260
specimens intentionally varied a little, and certainly the difference between
the appearance of a fracture of the metal of atomic proportions, and of one
very slightly deviating from it, is remarkable. I was very near prescribing the
above-mentioned atomic proportion for the Westminster metal, and indeed
I published it as a suggestion in 1856; but it only differs about .01 from
the 22 to 7, which Mears told me agreed with his own practice, and it was
therefore inserted in his contract. Although not one bell in 1000 may fail in
casting to the extent that Mears’s bell did, and small ones probably not at
all, because they cool before the metals have time to separate, it is clear that
there is a tendency to do it; and indeed I find it is well known at Woolwich
as a thing to be provided against in casting large guns of gun-metal, which
is about 1 tin to 9.5 copper.
It seems to me at any rate imprudent not to avail ourselves of this undoubted
law of nature, especially as there is an atomic combination which
happens to be a particularly convenient proportion, being exactly a mean
between the 3 to 1 which is just too brittle to be safe, and the 31
2 to 1 which
the bell-founders like because it is easier to tune, but which is certainly softer
and less sonorous than it need be. I always now therefore require large bells
to be made of this 13 lbs. of copper to 4 of tin, or 76.5 and 23.5 of the whole
alloy; and they should be rejected as unhomogeneous if any part of the bell
is proved to be beyond the limits of 77 per cent. of copper or 23 of tin. It
must not be supposed however that this would have prevented the porosity
of Mr. Mears’s bell, which is a quite independent defect, and would have
made the bell a bad one, even if it had not also miscarried in composition.
The only other atomic combination within the range of bell metal is
Cu7Sn, or 19 copper to 5 tin by weight; but that is too soft, except for small
house bells, which are thinner and have clappers much larger in proportion
than church bells. Old Tom of Lincoln and the old York Minster bells of
1765, and probably the Bow bells, of nearly the same date and made from
the same patterns, contained .03 of antimony, which has a hardening effect
like tin. That is much too large a quantity to have got in by accident; but
there was certainly no improvement in the sound from introducing about
.03 of antimony into a small bell. The antimony diminishes the specific
gravity of the alloy, which tin does not, though so much lighter than copper
by itself. So far as I have an opinion on the point, it is at present against
the antimony, and the bell-founders have the same opinion. Very small
quantities of iron, lead, zinc, arsenic, and sulphur sometimes appear in the
analysis of bells; but they are mere impurities. I have indeed seen lead and
zinc in considerable quantities innocently put down in books as ingredients
of bell-metal; but they are mere adulterations; for both those metals are
injurious and have no business there at all, especially the lead: a little zinc
is sometimes put into small bells, I do not know for what reason.
Steel bells.—I have frequently been asked my opinion of these bells,
which are made both in Germany and at Sheffield. And I answer, as I did
SILVER IN BELLS USELESS. 261
to the makers who asked me for a testimonial, that if the object of bells
is to make the greatest noise for the least money, steel bells are very good
ones, but that the less they asked me to say about the quality of the noise
the better. It was remarked in the 1862 Exhibition that the sound of the
very large ones was rather less horrible than of the smaller ones; and that
was the best I heard anybody say of them. I have heard nothing of them
since 1862. Moreover they require hammers two or three times as heavy as
bell-metal bells: if so, there would be little saved in using them for large
clock bells, as the clocks would cost much more.
Silver.—The most inveterate of all popular delusions about bells is the
notion that old bells had silver in them, and that all bells would be improved
by it. There is not the slightest foundation for that belief. Nevertheless we
had some experiments made for the purpose of being quite sure that silver
was of no use, either with reference to sound or strength of the metal; several
different proportions were tried, beginning with sixpence in a bell of nearly
a pound weight, and it was clear that the silver rather did harm than good
in both respects. I suppose the delusion has arisen from the ring of shillings
and half-crowns, which justifies no such inference, any more than in the case
of aluminium, which some people fancied would make very fine bells, until I
exhibited one at the Royal Institution, which M. St. Claire Deville of Paris
was good enough to cast for the purpose, and the sound was worse than of
cast iron. A bell of copper and aluminium was also bad, though the bronze
of 9 copper to 1 aluminium is in other respects a very superior metal to
either brass or any alloy of copper and tin. No composition for bells has
yet been discovered equal to copper and tin in the proportions I have given.
There was a large bell of iron and tin in the 1851 Exhibition; but that also
was very inferior indeed to bell-metal; and it required an enormous blow to
bring out the sound, though it was thin, and was at last cracked thereby.
Moulding.—There are two different ways of making the moulds for
bells. As to the internal mould or core they are nearly identical, that being
made by covering a cone either of brickwork or of cast iron with moulding
clay, which is swept over into the shape of the inside of the bell by a piece
of wood called a sweep or crook fixed to an axis or spindle set up in the
middle of the core. The advantage of the iron core is that it can be lifted
up and put into a furnace to dry, instead of lighting a fire inside it. At this
point the difference between the two methods begins. The old method is to
make a clay bell on the core by means of another crook, and when that is
dry to make the outside mould or cope on the top of that. The cope has
hair and hay-bands, and in large ones, iron bands worked into it, to make
it hold together and lift off when it is dry; then the clay bell or thickness is
knocked to pieces, the cope dropped down again and weighted with earth in
the pit where the bells are cast, and the metal poured in at the top through
one hole, another being left for the air to come out at.
In the other way there is no thickness made, but the cope is an iron
MODES OF CASTING. 262
case lined with clay, and swept out by an internal sweep to the shape of
the outside of the bell. The wires, or ornamental rings round the bell, are
made in both cases by the second sweep, and the letters, and any other
ornament are pressed by stamps into the clay of the cope while it is soft.
These iron copes can be bolted down to a plate under the core, and therefore
do not require to be sunk so deep in the ground, provided only proper care is
taken to get a high enough head of melted metal above the bell, or else it is
certain to be of bad specific gravity, and probably porous in a casting of any
considerable size, as in the top of the first Westminster bell, where the metal
ran short. I was told by an old bell-founder that the core should not be strong
enough to resist the contraction of the bell in cooling, or the strain injures the
tone. Small bells are generally cast in sand, like iron, from models, and not
in loam moulds made by sweeps. Bells are always cast mouth downwards,
so that the sound-bow, which is by far the most important part, may have
the best chance of being sound by having the greatest pressure of metal on
it. The importance of this was illustrated by Lord Rosse’s experiments with
large cast iron crucibles for melting speculum metal in, which were always
porous in the bottom, which is their most important part, until he had them
cast with their mouths upwards.
Bell-metal melts at a temperature far below that of the copper, as is
usual with the alloys of one easy-melting metal. Small bits will melt in
a common house fire. It is melted in a reverberatory furnace, in which
the fire is at one end of a long shallow trough which holds the metal, and
the flame is drawn over it to reach the chimney at the other end, and is
reverberated down upon it from a ‘bridge’ or a low roof over the trough. The
different founders use different fuel as well as different ways of moulding.
At Whitechapel they confessed that they still use wood. I suppose the
old founders used charcoal, as I understand they do in Russia, which is
probably far better, because wood contains so much moisture that it takes
much longer to get the requisite heat up with it, and it is notoriously a bad
thing to keep the metal long melted getting up the heat. At Woolwich they
have given up using wood for that reason, and use coal or coke in melting
gun-metal, which is bell-metal with much less tin in it. Warner and Taylor
use coal. In order to test this as far as possible, I gave to Warner and
Mears the same pattern for a bell of about 12 cwt. for the two new churches
at Doncaster; and the result was very decidedly in favour of the coal-cast
bell; but whether from that cause or some other difference in the general
management of the casting, of course I cannot say. Most of the metal of
Mears’s Westminster bell was nine times as long in the furnace as Warner’s
(which however I suspect was run too soon), and was also much longer
running into the mould than either that bell or Great Paul. I have no doubt
that that slow running contributed to its unsoundness. Lord Rosse specially
mentions the importance of quick running of large speculums, which again
are bell-metal with a higher quantity of tin.
MENDING CRACKS IMPOSSIBLE. 263
Mending cracked bells.—Whenever a bell of any importance cracks,
there invariably follows a flood of suggestions, public and private, for mending
it: generally by ‘cutting out the crack’ in some way or other. And as
there exists in some persons what is called colour-blindness by the world
at large, so there are persons to whom a bell so divided, and others apparently
to whom a bell with a deep crack in it, sounds (at least, they say it
does) no worse than when it was whole, though to other people’s ears the
tone is generally altered several notes, or is made otherwise intolerably bad.
Another way of mending, which is continually being reinvented, is by what
is called burning the parts together; i.e. cutting the crack wide enough to
let hot metal be poured in and through, which is done until the constant
application of it partially melts the faces of the division, and then the running
is stopped and left to cool. This may perhaps answer in very thin bells,
though the cracking of one of Sir C. Barry’s gun-metal hands which were put
together in that way is not very encouraging even for much thinner castings;
and the contraction, and consequent tension of the metal, would most likely
crack the bell again as soon as it is rung. There is no evidence that I can
learn, of any bell as large as a common church bell having been successfully
treated in this way yet. And if the bell has cracked from any radical defect,
as both the Westminster bells did, it is absurd to think of mending it, even
if it were otherwise possible; for the same defect would make it crack again.
Fig. 81: New Bell Crown
New bell crown.—Church bells used always to be hung by 6 long ears,
called ‘canons,’ which cut a large piece out of the stock, and weakened it
very much. They were not set radially, and the iron bolt which carries the
clapper was cast into the bell. Consequently when a bell got worn in one
place it could not be turned without a new stock and a great deal of trouble.
Several plans to cure this had been proposed, but none of them were satisfactory;
and I had the Westminster bells and some others made with a top like
TUCKING-UP OF BELLS. 264
a mushroom or button embraced by a collar in two pieces, or by bolts with
heads of proper shape surrounded by a ring, which may advantageously be
connected with the gudgeons or pivots. But the founders complained (unduly,
I think) of this ironwork being expensive, and so I invented another
crown, with 4 short and thick canons, which will be understood from figure
81. It has been generally adopted by Messrs. Warner. Mr. Taylor uses
6 very short canons, and in many cases, with my approval, none at all, but
only a thick crown with 6 bolt-holes through it, as at p. 257. I believe canons
are of no use. In all these plans the clapper bolt goes through a round hole
in the bell, but a square or octagonal hole in the stock. By placing the bolts
(of my plan) each with one leg in the stock, or two of them inside and the
other two outside of the stock, you may get 4 different pairs of places for
the clapper to strike, with the same stock and without any cutting of it, and
the stock itself is far less cut into and weakened than by the usual canons,
which are necessarily taller. The Doncaster bells were the first peal made
in this way.
On the old plan too, the clapper bolt is always cast into the bell, and
must be cut off and a new one stuck on in some way, to turn the bell at all,
which is an awkward job, and postpones the turning of bells for years after
it ought to be done. And in connexion with that, it is another advantage of
this plan, that it enables the clapper bolt to be adjusted both for length and
position, which cannot be done when they are cast in. The length of that
bolt ought to be more or less according as the bell is hung more or less high
in the stock, in order to bring the point of suspension of the clapper below
the gudgeons or pivots of the bell, without which it will not swing or strike
properly; and again, if the bolt is cast in a little on one side, the clapper will
not strike true, and the time between the blows will be unequal, which makes
it impossible to ring the bells truly. If some such plan as this had existed in
old times, whereby a bell could easily be turned in the stock, many a fine
old bell would now be alive which got cracked from being constantly struck
in one place, and so worn too thin. These four short and thick canons are
moreover much stronger and less liable to crack than the usual six thinner
and longer ones.
Opinions differ whether large bells should be what is called ‘tucked up in
the stock,’ or the top of the bell made higher than the ‘pivots or gudgeons.’
The advantage of it evidently is that it diminishes the centrifugal force, or
sideway strain of the bell on the frame; and if friction were out of the way
it would of course make the bell easier to raise and ring. But friction is
not out of the question; and as a bell in swing is in effect a pendulum,
and not (as I have even heard bell-founders represent it) a body lifted by
a steady pull like a lever, it may very easily happen that a certain amount
of friction on the pivots may make it impossible to make the bell pendulum
swing through 360 by any practicable force that can be applied to it at the
beginning of its motion, which is the only time when the rope acts upon
FRICTION ROLLERS PROPOSED. 265
it. The Rev. Mr. Taylor told me, that a bell of about 52 cwt. at Hereford,
which he and some other boys used to raise and set (i.e. ring till it stands
mouth upwards) was made unraisable by them by being re-hung, and at the
same time ‘tucked up;’ and so confident was he of the mistake of this mode
of hanging, that he offered to fill Mears’s great bad bell at York with beer if
any number of men could set it, and they never could, as Browne’s History
of York Minster also testifies.
There is moreover a remarkable difference in the facility of tolling, according
as the bell is hung low or high. I can toll the two largest bells of
Doncaster Church together, weighing 21
2 tons, one with each hand, whereas
it is difficult to make a high-hung bell toll at all. At the same time, it is true
that the largest bells of a peal, where the tenor is above 30 cwt., can hardly
be rung with the others, unless they are somewhat tucked up, though it
makes them ‘rise false,’ or with the clapper striking the low side of the bell
and lying on it, and the men have to go up and set them right before ringing
(and they will keep so), otherwise there is a risk of cracking the bells, and
they do not sound so well. The reason why heavy bells in peals must be
rather tucked up is that otherwise their momentum is so great that no man
can check them, so as to keep time; but this would not apply to a single
bell.
I am surprised that very large bells, say above 2 tons, are not hung on
friction rollers—i.e. so much of the circumference of a friction wheel as =
the circumference of the gudgeon or pivot of the bell. Of course brasses must
be put to keep the gudgeons in their place, against the side swing. And, by
the way, let me say a word here to warn those whom it may concern, that if
the smaller bells of a peal jump out of their brasses when they are new, it is
because the gudgeons are not sunk deep enough. I have known that happen
several times. Of course the founders denied that that was the reason, but
as I cured it by getting deeper brasses, the denial was worth nothing.
I recommended rollers of about 21
2 in. diameter in annular bushes round
the 6 inch pivots of Great Paul, like bicycle bearings on balls. Swinging
that bell through only 60 from the vertical (the most that is proposed) is
equivalent to sliding 18 tons 6 inches rapidly at every swing. Even tolling it
is equivalent to sliding that weight an inch forwards and an inch backwards
at every pull. Tolling consequently takes three men now. (See p. 282.)
Tolling-levers.—The great Worcester bell is hung, by my advice, on
wedge-shaped rolling gudgeons, only round instead of sharp, to enable it to
be tolled almost without friction, by a long lever; for the tower would not
bear it in full swing; and it went so easily that the Rev. H. T. Ellacombe,
then 80 years old, tolled it with one hand. But for all practical purposes it
answers equally well to toll it by a short lever, or shank, projecting from the
top of the clapper, and pulled by a slight rope; which is a very good plan for
all bells which the tower is either too small or too weak to bear swinging.
If a double lever is used with two ropes one for each hand, you may ring as
BELL-ROPES GENERALLY TOO THICK. 266
rapidly as the bell itself would sound when swinging about ‘frame-high,’ or
half-way up. See such a lever at p. 257 for one side.
A few years ago I introduced a mode of hanging chapel and school bells,
i.e. single bells from 1 to 4 cwt., or 18 to 28 in. wide, so as to swing lengthways
in the plane of the wall, instead of across it. A bell of very moderate
weight will soon pull an ordinary wall to pieces if rung in full swing across it.
The bells in ‘bell gables’ can hardly ever be safely rung for that reason, but
only tolled. Mr. Taylor has introduced an ingenious plan for ringing small
school bells without the risk of the rope being carried over, by putting it to
a crank in the iron axis which serves for the stock of such small bells: you
may then ring the bell ‘over’ as often as you like, and the rope always keeps
right.
Bell-ropes.—I said just now that some people fancy a bell is hauled up
like a dead weight on a lever, and not swung up as a pendulum; and they
forget still more, that the measure of the strength required for a rope is that
of the man who has to pull it, and has nothing to do with the weight of
the bell. A small bell can be ‘raised’ in a few pulls, while a large one takes
many, but in either case the ringer may be exerting his full strength, though
in fact no man does in raising small bells; and therefore some difference
in thickness of the ropes should be allowed. But experienced ringers know
too well that inexperienced rope-makers always make the ropes much too
thick, though probably not many ringers have reflected on the proposition
that it is their force used in pulling, and not the weight of the bells, that
determines the thickness of the ropes—allowing reasonably for wear, and for
some greater force being used upon the large bells.
The great superiority of tone of bells ringing in full swing over tolling,
and even of tolling over striking by a clock hammer, has been often noticed,
but never yet accounted for. I think the explanation is this. It is now well
known that the note of an approaching source of sound like a railway whistle
is sharper than when it is receding, because the velocity of transit is added
to, or subtracted from, the velocity of vibration which fixes the notes. (The
analogy of light to this has been made use of by Mr. Huggins, in one of
the greatest astronomical discoveries of late, to determine the velocity of
approach or recession of the stars, as is explained in my Astronomy.) The
bell in full swing, while it also vibrates from the blow, is always sending out
vibrations of slightly different velocity in each direction, and so varying its
own note a little. I remember a gentleman trying to persuade the Institute of
Architects that bells sound as well stationary as swinging, and he illustrated
it with a common dinner bell; which by the way a servant of experience
always swings as far as he can. Everybody exclaimed immediately that he
had refuted himself. The motion in tolling is probably too small to vary
the note sensibly, but the inevitable variation of a man’s pull makes it less
monotonous than the unvarying lift of a clock hammer, or of any chiming
machinery, a melancholy and miserable substitute for a set of ringers, only
CHIMING AND RINGING. 267
justifiable as a precaution against strikes—of the men, I mean. Even that
hardly justifies it.
Ellacombe’s chiming hammers.—There is however a less objectionable
mode of chiming by one man, with a set of separate clappers fixed
below the bells, temporarily tied up very near them, so that a small pull
of the rope makes the clapper strike. This was invented by Mr. Ellacombe,
and is fully described in his large book on bells, and in some smaller ones.
Not that even this is to be compared to genuine chiming by tolling the bells
themselves, for they are stationary, and those clappers are necessarily too
small to bring out the full tone. In this way however, a skilful man can
play tunes, whereas in ordinary chiming or ringing a bell can only change
one place at a time: e.g. the greatest change that can follow 1 2 3 4 5 6
7 8 is 2 1 4 3 6 5 8 7. I do not profess to teach the art of ringing, or to
deal with the interesting and complicated subject of change-ringing, which
is quite enough to have a book to itself; and there are several, by Captain
J. E. Acland Troyte, and by Mr. Jasper Snowdon, of Old Bank Chambers,
Leeds. I will only say that ringing ‘the tenor behind,’ i.e. ringing the changes
only on the other bells, always sounds much better than ringing the tenor
in the changes, though ringers think more of it as a feat. One man can ring
a very heavy bell ‘behind,’ which would require two to ring in, as its time
has then to be altered continually. Also, when two men are required, it tries
their wind much less, and it requires only one rope, for one to take the ‘fore
stroke’ only, and the other the ‘back stroke’ only, though it is hardly ever
done.
Stays and sliders.—The stay is a strong piece of wood, about as long
as the radius of the wheel, bolted to the stock and pointing upwards, so that
when the bell is swung right up, the stay points downwards and rests against
a stop there. But if that stop were fixed, the bell could not reach quite the
vertical position, at least in one direction of the swing. Therefore the stop
is a sliding bar, which lies low enough to clear the wheel and clapper, and
it has play enough in its own bed near the stay to allow the bell to go just
beyond the vertical both ways; and so a small portion of its weight is borne
by the stay and slider when it is ‘set,’ or so resting, until it is pulled off again
by the rope and swung the other way. Sometimes the stay has to be put by
the wheel, on account of clock hammers at the other side, but generally it
is at the other end of the stock.
After a long struggle with bell-founders and their hangers, I got the
practice introduced of striking the bed or board in which the slider runs
as an arc of a circle from the gudgeon as a centre, instead of leaving it
flat, which the smallest knowledge of mechanics will show anybody must
produce a grinding action between the stay and the slider. Moreover, sliders
were generally much too heavy, which increased the friction and the cost
of breaking. A slider need be little more than a common stick, and can be
replaced almost for nothing in a few minutes, whereas the breaking of a stay
THE GUDGEONS. 268
is a more serious matter, as many a learner of bell-ringing knows. At the
lower end (away from the stay) it need only lie loosely in a hole; its weight
and slope will keep it there without a pin. Stays can hardly be too strong,
and should always go through a strong iron loop, and not be merely bolted
to the stock, which weakens them, and gives more leverage for breaking.
Boards should be put over the sliders to keep the grease off, which increases
rather than diminishes their friction; black lead is the thing to diminish it
on wood.
The Gudgeons, or pivots on which the bells swing, are often made
too short, under an erroneous idea that that diminishes the friction, which
it does not, and may in fact increase it, because if the pressure on each
particle of surface is too great, it squeezes out the oil, and the metals come
in contact, which it is the object of oil or grease to prevent. Besides that,
short gudgeons tend to twist the beams. They should not be less than 2 in.
long and 1 in. thick for the smallest bells in a peal, and rather longer and
much thicker for the large ones. I think they should be of steel. And it
should be specified that the ‘brasses’ in which they run are to be 19 copper
to 5 tin, for the reason given at p. 260. The brasses should be large, to
allow for wearing down, and for firm fixing in the beams. All the ironwork
should be well painted, except the gudgeons; and the woodwork too, though
it hardly ever is, which is very bad economy in the long run. But oak should
not be painted very soon.
Clappers should be hung by or on wooden blocks, and not with a mere
piece of leather inside an iron strap, which soon wears away, and leaves the
two irons in contact, and they are sure to be rusty by that time. Thick bells
of course require heavier clappers than thin ones. I remember a very good
bell of Warner’s remained unsold in the 1851 Exhibition, and long after,
merely because it was very thick (copied from the 3rd Bow bell) and had
too small a clapper. I happened to try it with a large one which was lying
loose, and bought it immediately for a chapel for which I had been asked to
get one. All nuts connected with clappers should be either double or keyed
on with wire, or they will shake loose and come off.
Iron stocks and frames are now coming into general use, especially
for heavy bells. They have great advantage in point of durability, if kept
properly painted; and the bells are much easier to ring, owing to the ironwork
not being subject, like wood, to constant swelling or shrinking with every
atmospheric change. They are made in two shapes—A frames and H frames:
the former being preferable for light peals, and the latter for heavy bells.
The weight and rigidity of these massive frames of iron and steel cause
them to absorb, as it were, nearly all the vibration, if the bells are properly
hung; and when built into the walls they form excellent crop-braces for the
strengthening of the tower.
The iron frames, etc., at Beverley and Exeter are excellent examples.
Frames constructed partly of iron and partly of oak are to be avoided.
BELL-FRAMES. 269
Bell-frames, like most other things nowadays, are generally starved of
proper bulk. I do not see my way to laying down any rule for the thicknesses
of the beams, as they must vary so much according to the weights of the
bells. The beams of the smallest bells ought never to be less than 5 in. wide,
and 10 in. deep, and of the large ones for a peal with a tenor about 30 cwt.,
not less than 9 × 12, and the lower beams should be always a little wider
than the upper ones. It is also specially important to have the diagonal
trusses very deep, particularly under the heavy bells. Dove-tailing and any
cutting away of the beams should be avoided as much as possible, by using
‘bed-bolts’ and iron T pieces bolted on at all weak corners. The upper beams
should also be bolted to the lower by long diagonal bolts, set the opposite
way to the trusses.
And now I have to correct one of the most common errors about framefixing.
It is quite true that the upper beams should not touch the walls,
unless the walls are very thick and strong. But if they must touch anywhere,
for want of room, they should touch close, and in fact tight, all along
the beam, so as to avoid anything like battering. The lower beams should
always do so, or be somehow connected with the walls as firmly as possible.
The notion that they should not is an extraordinary piece of architectural
ignorance. Either the whole frame must float about on the floor under the
swing of the bells, or it must be fixed to the floor; and if it is fixed, the
horizontal thrust must ultimately go to the walls, pulling the floor or its
beams against them anyhow; and it is much better to make this connection
firm at once, and avoid all chance of battering.
All the elasticity takes place between the upper frame and the lower,
and it acts like carriage springs, and the pressure is diffused over the walls
as well as it can be, if the lower frame is tight. The oscillation of towers
under ringing is merely due to the elasticity of the whole mass of stonework;
and though they sometimes move enough to make the little call-bell from
the church into the belfry almost ring by accumulated vibrations, the actual
motion of the tower is too small to see, except perhaps with a fixed telescope.
The idea of preventing it by building up a frame from the ground
within the tower is ludicrous, though some architects do not know it, or
that such frames have always at last to be wedged against the walls of the
bell-chamber.
Another ‘vulgar error’ about bell-frames is that bells swinging at right
angles to each other tend to correct each other’s swinging thrust upon the
frame and tower; whereas every mathematician knows that that is exactly
the position in which the thrusts cannot the least neutralise each other.
Besides that, it has the effect of making the ends of some beams thrust
against the gudgeons of other bells, and so occasionally binds them tight. I
was assured by a bell-founder’s foreman, before making the first frame on
the parallel plan (for the cathedral at Fredericton, which also had the first
gravity escapement clock), that ‘all experience was against such a plan.’
BELLS CRACKED BY CLAPPERING. 270
I said, I should like to be referred to some frames of that kind which were
proved by experience not to answer. His reply was, ‘O, nobody ever thought
of making such a frame.’ That total absence of experience of the very thing
in question is what so-called practical men mean by experience—and many
other people too.
The following is the plan which I prescribed for Doncaster and the others
mentioned at p. 252. All the bells swing north and south: 2, 1, 8, 7, are on
the south side, and 3, 4, 5, 6, on the north; all the beams going through,
except the one on the west side of 8 and 5, which is divided, and overlapped
and bolted together, so as to make the tenor pit wider than the 5th by the
thickness of that beam, and the treble pit as much narrower than the 4th.
The east and west beams are only notched on to the others and bolted, not
halved or cut away as usual. There should always be long bolts nearly vertical,
but oblique, holding the upper and lower beams together the opposite
way to the diagonal struts which carry the weight, because the mortices
always get loose, but the bolts can be tightened from time to time. In this
frame the ropes can fall in a very good and wide circle, in one or two ways
which will be obvious; and in large towers such as those, there is also room
for the entrance; indeed in all but Croydon you can go all round the frame.
But when the tower is only just large enough to hold the frame, it is
expedient to adopt some other and inferior plan, in which the bells cannot
all swing parallel, in order to avoid having the ropes too close to the walls for
the men to stand behind them; for leading them down obliquely in troughs
increases the friction and labour of ringing. It may be taken as a rule that a
peal of 8 bells hung properly on beams of proper thickness requires a frame
nearly 4 times the width of the tenor, both ways; and one of 6 bells requires
rather more than 3 times the width of the tenor. In hanging 10 or 12, some
space may be saved by making a few of the smaller bells swing at right
angles to the others; but it should only be the small ones. When the large
ones all swing parallel, they are sure never to be thrusting all one way twice
together; and as it is only an accumulation of similar vibrations that could
affect the tower, they are certain on the whole to escape that effect, and in
a great measure to neutralise each other, though of course not completely.
Clappering.—It is still necessary to warn clergymen and churchwardens
against allowing the lazy and pernicious practice of ‘clappering,’ i.e. tying
the bell-rope to the clapper, and pulling it instead of the bell. More bells
have been cracked in that way than by all other causes together, and there
is not the least excuse for it, as any man may learn to toll a bell in one
lesson, and the work of doing it is nothing, for the bell moves so little that
it seems wonderful that the clapper should strike it; but they both act as
pendulums which a very small impulse will keep up, and the blow being
elastic loses very little of the force. Bells are consequently much easier to
toll when they are not tucked up in the stock, because they act more like
a pendulum and less like a grindstone; in fact, it is difficult to set a much
SPECIFICATION FOR A PEAL OF LARGE BELLS. 271
tucked-up bell tolling, though easy to keep it up afterwards. The only safe
way of allowing bells to be clappered is to fix a separate pulley in the floor
under the bell with a thin rope, in such a position that no pulling of the
rope over the pulley can hold the clapper against or very near the bell, so
that it must depend entirely on the swing given to it by the rope.
Specifications.—As I gave a specification for large clocks, I will do the
same for bells, so far as any one model can serve for a variety of cases. I add
however some variations and notes to explain them, which will enable anybody
with the least understanding of such things to make out a specification
for the peal he wants. And first, I remark that specifications should always
be silent about notes, and stick to diameters and weights. Most of the bad
peals in the kingdom, except those by utterly bad bell-founders, are greatly
due to people demanding low notes for low prices; and besides that, there
are so many uncertainties about notes, even with bells of very nearly the
same dimensions, that it leads to nothing but confusion to specify anything
about them. Suppose then a specification is wanted for a peal of ten bells,
intended to be as good as possible, and of no unusual weight: it should be
as follows:—
1. The founder to make, and hang complete for ringing, a peal of 10 bells
in perfect tune; the tenor to be 60 inches wide (or more, if you like, up
to 67 or 68). The 4 or 5 largest bells to be a 13th of the diameter in
thickness; and the smaller ones to increase gradually up to the treble,
which is not to exceed a 10th of its diameter in thickness.
For 8 bells, the 4 largest to be a 13th, increasing up to an 11th in the
treble; and for 6 bells, the 3 largest to be a 13th, and the treble may
be an 11th, or a 12th.
2. The bells are to be of the shape described in this book as to their
‘sweep,’ and all to have independent clapper bolts going through a
round hole in the crown, and through the stock. The larger bells to
have no canons, and the smaller bells low canons, if any. The bells
are all to consist of pure copper and tin only, in the proportions of
13 to 4, and are to be guaranteed as perfect castings, homogeneous,
and free from porosity or other defects. (I should mention that those
superficial marks called seams are of no consequence, though of course
a casting looks better without them; but the slightest visible porosity
in the smoothest bell is a fatal mark of unsound casting, though a
bell-founder should find any number of brass-founders and engineers
to swear that it is not, as I know that Mears was prepared to do about
Big Ben, before Dr. Percy’s examination of the ‘taster’ cut out of it
(see p. 192). Also an inequality in thickness round the bell, such as
Great Peter of York has, is equally fatal, and is not a ‘perfect casting.’)
SPECIFICATION FOR A PEAL OF LARGE BELLS. 272
3. The clappers to be hung with wooden blocks, not iron and leather (for
the leather soon wears out). The tenor clapper to be a 90th of the
weight of the bell, and the others to increase upwards, to about a 30th
for a treble a 10th of its diameter thick, and a 36th for an 11th, and a
40th for a 12th. All nuts connected with the clappers to be keyed on,
or else double nuts (or they will shake loose).
4. The brasses to be of 19 copper to 5 tin, and none to have less than
11
2 in. of metal on each side of the hole, and the holes to be deep
enough to prevent the small bells from jumping, and to have at least
2 inches of metal below the hole. They are to be boxed over with wood
to keep out dust. [Metal tops always get torn off and stolen.]
5. The gudgeons to be of steel, and to run from 2 in. to 21
2 in. long in
the brass, and 11
2 in. thick for a bell of 30 to 35 cwt. (It is difficult to
define the thickness farther, and the fault is more generally in making
them too short than too thin.) They are to be fixed so that they will
keep themselves quite true in the stock. (The founders have different
ways of doing this, and I do not like to prescribe any one absolutely,
but I must say that Taylor’s plan is the best I have yet seen. The old
one is very rough indeed, and cannot be relied on to keep them either
true or firm.)
6. The stays to go through iron loops bolted to the stocks, the bottom
only of the stay having a bolt through it, and to be so strong that the
slider may break rather than the stay. The sliders to run in circular
beds, traced from the gudgeon, which are to be covered over to protect
them from grease dropping (which makes wood stick, though it makes
metals run).
7. The wheels are all to have at least 4 side stays to keep them true.
(The founders will never put more than two unless they are made, and
others have always to be added in a year or two.) The wheels to be wide
enough and deep enough to prevent the ropes from slipping (a source
of frequent accidents, and always arising from bad or untrue wheels;
in fact wheels, like everything else now, are generally made too flimsy;
but I do not see how to define their dimensions in a specification, nor
indeed many other things which can only be judged of by a competent
eye when they are done).
8. The frame to be of English oak,15 and the founders to state the dimensions
of the beams. (This will at any rate be useful in comparing
tenders, which otherwise are deceptive.) The wood must be perfectly
dry before using, and if joints get loose afterwards, the founder will be
15See, however, what is said about iron frames on p. 268.
ARCHITECTS DESTROY BELFRIES. 273
held responsible for all expense incurred in consequence. The beams
are to be cut into by mortices as little as possible, and iron T pieces,
and bed-bolts to be used instead, or in addition. The diagonal struts
especially are to be deep, and diagonal bolts inclined the other way
are to be used also.
9. The bottom of the frame to fit tight against the walls, if it is about
the width of the tower (see p. 269), and if not, to be strongly bolted
to the great beams below; the position of which the architect should
be made to settle with the bell-founder beforehand, if the tower or
the floor is new; and also to arrange for having two floors between the
ringers and the bells, with gravel or small stones on the lower one, if
they are very close together (see p. 274). All the large bells, as far as
possible, to swing either north and south or east and west, and not
across each other.
10. The tender to state the probable weight of each bell, and maximum
of the whole peal (the word ‘about’ not to be allowed there), and the
founder will be paid for no excess beyond that maximum. The tender
also to state the cost of frame and hangings separately, besides the
price per cwt. for the bells, and all other expenses, as far as they can
be estimated. (Recasting of old bells is always charged at two guineas
a cwt. whatever is the price of new metal, see p. 243.)
11. The whole of the work to be subject to the approval of some competent
person or persons, not being in the trade, to be appointed by the
[committee], who may require any experiments to be made which they
may think fit for testing the bells.
12. All the iron and woodwork to be painted twice, and the frame also
after a year, with Carson’s anticorrosive paint. (It is very odd that
nothing will induce people to paint their bell-frames. They leave them
exposed to damp, and frost, and heat, and see them cracking all over
worse and worse yearly, and then they are surprised at having to spend
three times as much as the painting would have cost, in repairs after
a few years. It is said not to be expedient to paint oak immediately,
and for that reason only I have allowed the year for it.)
Bell-towers.—I proceed to notice a few things relating to bells which
are more the business of architects than bell-founders, except that architects
nowadays rather think it their business to ignore everything that has to be
done in a building after they have left it. I have known plenty of cases
where they knew perfectly well that it was intended to have peals of bells
and clocks, and yet have built costly towers without condescending to learn,
either by reading or inquiry, what provisions should be made, or even what
dimensions were required. That they may have the less excuse, and that
ARCHITECTS DESTROY BELFRIES. 274
those who want church bells may have some idea of what their architects
ought to do, I will give the following information as the result of my own
experience; and I am probably the only person living who has the experience
of designing both bells and clocks, and the towers in which they are to be
placed.
It follows from what I said before about bell-frames, that the smallest
tower fit for even a small peal of 6 bells, should be 11 ft. square inside;
and the smallest for a very moderate peal of 8 should be 16. Even these
sizes make the ropes hang closer to the walls than they ought to do, and
therefore they are much better somewhat larger. Very few old towers with
8 bells are so small as 16 ft.; they are much more frequently 20, and those
with 6 bells at least 14. In what is called A Book on Building, I have shown
how much narrower modern towers generally are than old ones; but I am
only now dealing with them as campaniles, which in fact they always are,
without reference to architectural reasons in the same direction. Of course
when 10 or 12 bells are intended, the towers should be larger still, certainly
not less than 22 and 24 ft. square inside.
There is also another reason for it. Bells sound much better in a large
chamber than a small one. Anyone who has heard the Doncaster bells will
hardly believe that the three bells in All Saints’ Church, Margaret Street,
are repetitions by the same founders of the 1st, 4th, and tenor of Doncaster.
But the Doncaster bell-chamber is 23 ft. square, and Margaret Street not
more than 14, or just two-fifths of the area. And the same at All Saints,
Halifax, with a spire 240 feet high. The bells, a smaller peal than Burton,
could not be got into it on one level.
Another important consideration is the windows. I have known two
cases, both in Leeds as it happened, where clock bells had to be re-hung
some feet higher up than the architects had provided, because they did not
know that the bells ought to be above the sills of the windows. Louvres
again are a frequent source of trouble, by being put too close or too much
overlapping, even if they are on that ugly and now fashionable foreign plan
of having a few enormously wide or deep boards sticking out beyond the
face of the mullions, which never were in genuine English architecture. It
is no use trying to keep out snow, or even small driving rain, and it does
no harm if bell hangings are kept painted, and the floor is made waterproof
and drained. Louvres just overlapping will keep out ordinary rain, and I
am afraid cannot be dispensed with in church towers, though they are at
Westminster, where the floor under the bells is flagged. It is the custom in
the eastern counties to put small clock bells quite open on the tops of the
church tower’s, instead of making the clock strike on the tenor of the peal,
and they are generally heard farther; in fact, a clock bell (if only a clock
bell) cannot be too open, as it has no hangings that will spoil with rain if
the hammer gudgeons are occasionally oiled—or even if they are not, for a
long time.
ARCHITECTS DESTROY BELFRIES. 275
There must be two floors between the ringers and the bells, or they
cannot hear for the noise. In most towers of good size this can easily be done,
but in low central towers it is sometimes difficult. The plan to be adopted
then is to lay a strong floor about a foot below the bell-floor by straps from
the great beams, and cover it a few inches thick with large gravel, or broken
stones (not sand), or else to fill up the whole space between the floors with
shavings, including a box full of them for the trap door which must be left
under the great bell. I need hardly say that the great floor beams ought to
come under the beams of the bell-frame as much as possible, and should rest
on large corbels, and for heavy peals should be strutted also from corbels
lower down This too is often neglected, and a floor made at random, and
then the bell-founder is expected to fix a firm bell-frame on a floor not fit
to carry it.
But the worst abomination of all, committed by architects and church
restorers, is the destroying of the belfry (i.e. ringing chamber) floor for the
sake of making a ‘lantern’ of the tower. This has been done, at Hereford
Cathedral, Ludlow and Boston churches, Merton College Chapel, St. Alban’s
Abbey, and divers other places. At St. Alban’s, where the space is
abundant, they have lately re-hung the bells higher up, and so regained a
ringing chamber, but not so at the others. At Howden the ringing is done
inconveniently and dangerously from a narrow gallery round the tower, and
so it is at Merton Chapel—unless they ring from the ground now, as the
tower is practically in the ante-chapel. At Pershore Sir G. Scott did a better
thing than a gallery, by the converse of it, a sort of insulated floor, leaving
an open space round it except where there is a bridge to reach it. Mr. Cattley
and I did much the same at Worcester Cathedral, which has probably
the best belfry in England on account of the great width of the tower, 32 ft.
inside. The much larger central towers of York and Lincoln do not contain
the peals of bells; they are in the smaller western towers. In the central
tower which I designed for Mr. Bass, at Burton: there are small spandril
windows to light the space under it, as in the grand old church of Hedon, so
that the belfry floor can still be at the natural place, about the level of the
roofs of the four limbs of the church; and it is 22 feet high. At Doncaster
there was height enough above the lower windows of the tower.
But this lanterning mania has destroyed some belfries irreparably, and
ringers will not ring long in dark holes about 8 feet high, which were only
intended for the intermediate chamber or clock room. That demon of church
destruction, under the name of restoration, Wyatt, in the last century and
early in this, pulled down the old campanile of Salisbury, and the bells had
to be sold because nobody dared ring them in the great overloaded steeple of
the cathedral. Well might Pugin say of him, in one of his ‘restored’ churches,
‘Yes, the monster has been here!’
Where it has become impossible to ring bells properly, the best thing to
do is at once to fit them up for chiming only, i.e. tolling with levers. Though
THE GREAT BELLS OF EUROPE. 276
inferior to ringing in some respects, and much less interesting to ringers, it
has a sweeter sound, but feebler. The clappers ought to be heavier for it, as
they strike much softer: especially when there are only 3 or 4 bells, chiming
sounds much better than ringing. The tolling of 3 large bells has a very
grand sound, and the ringing of two bells only frame high, i.e. swinging up
to horizontal, so that they strike quickly, has a pleasant and lively sound. I
always admire it at New College Chapel when I visit Oxford.
The windows of bell-chambers, and of every opening in the tower or spire
above them, should be completely covered with strong wire netting, which
must also be kept in repair, to keep out birds, which otherwise fill the place
with sticks and dirt, which caused the second fire at York Minster, and the
destruction of the bells. The netting should be of about 18 gauge woven in
squares of half an inch, not in long openings tied with thin wire, which soon
perishes.
The well-known story of St. Paul’s clock being heard at Windsor striking
13 by a sentinel who was charged with being asleep, is often regarded as
fabulous; and so it would be in the present feeble condition of the striking.
But Reid says, in his book on clocks, that he heard it there himself and
I have heard an officer quartered there say the same The Doncaster clock
striking on a bell of only 30 cwt. has been heard 11 miles in a very flat
country. Nobody has yet solved the problem why a wind which you can
hardly feel will make the difference of your hearing bells half a mile or ten
miles, according as the wind is with you or against.
The great bells of Europe are all that remains to notice, by which I
mean those above any ordinary weight of the tenor of a peal, which may be
called 3 tons; for there is none except Exeter and St. Paul’s which exceeds or
even reaches that weight.16 There are clock bells of 3 tons at the town halls
of Hull (W) and Halifax (T), and one lately made from my specification,
with 4 quarter bells, for the post office at Adelaide (T). I cannot vouch for
the accuracy of the whole of the following list; indeed I am sure that some
of the figures cannot be correct, and I must warn people against newspaper
statistics of such things. For instance even in London, the St. Paul’s clock
bell still figures in sundry books as 9 ft. wide instead of 6 ft. 9 in., and I have
seen the York bell credited with a greater weight than Westminster; and if
such exaggerations as these take place about bells whose sizes and weights
have been correctly published for years in this and other books, it is evident
that little reliance can be placed on others where the weights and sizes are
plainly inconsistent. Most of the foreign ones are taken from the small
German book on bells by Otte, before noticed. But I satisfied myself that
he sometimes uses the measures of one country and sometimes of another. I
have received sections and measures of some bells from architects and others
16I will use the letters M, T, W, to denote the only three English founders who have
made large bells in this century, viz.: Mears, Taylor, and Warner.
CHARACTER OF SOME GREAT BELLS. 277
who had measured them, and I shall be thankful for any more, of really large
bells. I give the weights of the two great Russian ones by calculation from
their size and thickness, which is easily done, from their similarity to the
Westminster pattern. I have seen even a larger weight than 8 cwt. given
for the clapper of the Paris bell; but the 8 cwt. agrees pretty well with the
drawing; but if the drawing I have of the Erfurt clapper is right it cannot
be so heavy as Otte gives it. Our clappers are of a better shape than the
foreign ones, though generally too light.
I have no doubt that some of these bells are bad ones, or they would have
a greater reputation than they have. The Erfurt bell is the most famous of
all the very large ones, and probably that of Paris next, though there are
two opinions about that; the old Cologne and Lucerne bells I have heard
well spoken of. The new and larger Cologne one was cast three times. I
have never heard it praised. On the other hand the new Great Paul was
cast successfully at once, and it seems to me as good as possible. We have
ample proof at home that large bells may be thought not worth ringing
after costing a great sum of money, or may sound no distinct note, or may
be supposed to be cracked because they are so bad. I heard the Montreal
bell before it went out, and thought it quite as bad as York. I am told
that the bell of St. Peter’s at Rome sounds as ill as it ought to do from
its extremely bad flower-pot shape; I have a model of it, and it is loaded
also with ornaments in high relief, which are sure to injure the sound; but
the shape is such that it is of very little consequence what the decoration
is. The Canterbury bell is struck so feebly by a good-for-nothing modern
clock that no one would suppose it had any business in this list: nor Tom of
Oxford either, if judged only by his weak and abominable sound. See List,
over the page.
LIST OF GREAT BELLS. 278
Great Bells of Date. Diameter. Weight. Note. Thick- Clapper or
ness. Hammer.
ft. in. tns. cwts. in. lbs.
Moscow (broken) 1734 22 8 220 0 . . . 23 . . .
Another 1817 18 0 110 0 . . . 18 . . .
Another 1878 . . . . . . 28 13 . . . . . . . . .
Novogorod . . . . . . . . . 31 0 . . . . . . . . .
Cologne 1874 11 3 25 10 D flat . . . 1530
Rouen (was) 1501 10 8 17 6 . . . . . . . . .
Olmutz . . . . . . . . . 17 18 . . . . . . . . .
Paris, Montmartre 1898 9 111
2 18 10 C 9 . . .
Vienna 1711 9 10 17 14 . . . . . . 1600?
St. Paul’s, T. 1882 9 61
2 16 14 E flat 83
4 730
Westminster, M. 1858 9 0 13 11 E . . . 766
Paris, Notre Dame 1680 8 8 12 0 F to 71
2 900
F sharp
Montreal, M. 1847 8 7 11 11 . . . 81
2 413
Sens . . . 8 7 11 0 . . . . . . . . .
Frankfort 1868 8 61
2 10 0 E . . . . . .
Frankfort (2nd) 1868 6 5 4 8 A flat . . . . . .
Erfurt 1497 8 53
4 10 0 E 71
2 1120?
Erfurt (2nd) 1720 6 5 4 8 A flat . . . . . .
York, M. 1845 8 4 10 15 F sharp 8 405
Rheims 1570 8 21
2 9 0 F . . . . . .
Rheims (2nd) 1849 . . . . . . 7 0 G . . . . . .
Vienna (2nd) . . . . . . . . . 10 0? . . . . . . . . .
Magdeburg 1702 8 11
2 8 16 E . . . . . .
Magdeburg (2nd) 1590 6 5 5 0 B flat . . . . . .
Schaffhausen 1486 . . . . . . 9 0? . . . . . . . . .
Lyons . . . . . . . . . 8 0? . . . . . . . . .
Cologne (2nd) 1448 7 11 8 0 G . . . . . .
Tournai 1843 7 9 8 10 . . . . . . . . .
Tournai (Beffroi) 1393 6 53
4 . . . . . . . . . . . . . . .
Breslau 1507 . . . . . . 9 0? . . . . . . . . .
Breslau (2nd) 1721 . . . . . . 5 0? . . . . . . . . .
Amiens 1748 . . . . . . 9 0? . . . . . . . . .
Amiens (2nd) 1736 6 0 5 0? . . . . . . . . .
Rennes . . . 7 74
4 7 8 F to . . . . . .
F sharp
Rennes (2nd) . . . 5 111
2 4 2 A . . . . . .
Marseilles . . . . . . . . . 8 0? . . . . . . . . .
Manchester, T. 1882 7 71
2 8 3 G 7 458
Manchester (2nd), T. 1882 6 8 5 2 . . . . . . . . .
Gorlitz 1516 . . . . . . 8 0? . . . . . . . . .
LIST OF GREAT BELLS. 279
Great Bells of Date. Diameter. Weight. Note. Thick- Clapper or
ness. Hammer.
ft. in. tns. cwts. in. lbs.
St. Peter’s, Rome 1786 7 6 7 0? . . . . . . . . .
Beverley, T. 1901 7 3 7 1 G 61
2 360
Sneeberg . . . 7 6 7 10? . . . . . . . . .
Cambrai . . . . . . . . . 7 15? . . . . . . . . .
Hamburgh (St. Nic.) 1876 7 6 6 7 . . . . . . . . .
Nuremberg 1392 . . . . . . 7 16? . . . . . . . . .
Malines 1844 7 71
4 7 0 G flat . . . . . .
Malines (2nd) 1696 6 3 4 18 A flat . . . . . .
Le Mans . . . 7 3 5 16 F . . . . . .
Lucerne 1636 . . . . . . 6 0? . . . . . . . . .
Halberstadt 1457 . . . . . . 6 0? . . . . . . . . .
Bale . . . 7 11
2 5 14 F sharp . . . . . .
Middleburg . . . 7 11
2 5 8 F sharp . . . . . .
to G
Rouen (Cathedral) 1852 7 01
2 6 0 A flat . . . . . .
Rouen (Bons`ecours) 1892 6 91
2 . . . . . . G . . . . . .
Rouen (St. Hilaire) . . . 5 113
4 . . . . . . . . . . . . . . .
Rouen (St. Ouen) . . . 5 11 3 10? A flat . . . . . .
Antwerp 1655 7 0 5 12 A flat . . . . . .
Antwerp (2nd) 1310 6 5 4 18 A . . . . . .
Oxford 1680 7 0 5 15? . . . . . . . . .
Newcastle, T. 1891 6 111
2 5 18 A flat . . . . . .
Halle 1480 6 0 . . . . . . . . . . . . . . .
Munich 1493 7 3 6 0 . . . . . . . . .
Tourcoing . . . . . . . . . 6 0 . . . . . . . . .
Ghent . . . 6 111
2 5 10 G to G . . . . . .
flat
Ghent (2nd) . . . 6 3 5 0 A to A . . . . . .
flat
Lincoln, M. 1835 6 10 5 8 A 6 224
F´ecamp 1878 6 10 . . . . . . G . . . . . .
St. Paul’s (Old) 1716 6 91
2 5 2 A and C 180 . . .
Bruges 1680 6 91
4 5 0 G . . . . . .
Leipsic 1634 7 73
4 5 4 A . . . . . .
Brussells . . . . . . . . . 7 0 . . . . . . . . .
Brussells (2nd) . . . . . . . . . 5 1 . . . . . . . . .
Coire (Protestant) . . . 6 53
4 4 10 A flat . . . . . .
Coire (R. C.) . . . 6 13
4 4 0 A flat . . . . . .
Bradford, T. 1873 6 51
4 4 7 A 6 . . .
Courtrai . . . 6 4 4 12 B flat . . . . . .
Dantzic 1453 . . . . . . 5 0? . . . . . . . . .
Cologne (3d) 1449 5 0 4 10? . . . . . . . . .
LIST OF GREAT BELLS. 280
Great Bells of Date. Diameter. Weight. Note. Thick- Clapper or
ness. Hammer.
ft. in. tns. cwts. in. lbs.
Batisbon 1325 . . . . . . 5 0? . . . . . . . . .
Brunn 1515 . . . . . . 5 0? . . . . . . . . .
Rodiz 1814 . . . . . . 5 0? . . . . . . . . .
Chalons . . . . . . . . . 5 0? . . . . . . . . .
Mariazell 1830 . . . . . . 5 0? . . . . . . . . .
Dresden 1787 . . . . . . 5 0? . . . . . . . . .
Worcester, T. 1868 6 41
4 4 10 B flat 6 246
Exeter (Peter) 1675 6 21
4 4 0 A . . . . . .
Exeter (Tenor).T 1902 6 0 3 12 B flat 5 . . .
Lille (St. Andr`e) . . . . . . . . . 4 8 . . . . . . . . .
Lille (N. D. de la Treille) . . . . . . . . . 3 103
4 . . . . . . . . .
Sydney, T. . . . . . . . . . 4 18 . . . . . . . . .
Merville . . . . . . . . . 4 71
2 . . . . . . . . .
Preston, T. 1868 6 3 4 16 B flat 6 227
Bolton, W. 1872 6 2 4 2 B 6 200
Leeds, W. 1859 6 2 4 1 B 6 200
Valetta . . . 6 1 . . . . . . B flat . . . . . .
Boulogne 1800 . . . . . . 4 0 . . . . . . . . .
Westminster(4th) 1857 6 0 3 18 B 57
8 175
” (all W.)3rd qur. 1858 4 6 1 131
2 E 41
2 80
” (all W.)2nd qur. 1857 4 0 1 6 F sharp 37
8 60
” (all W.)1st qur. 1857 3 9 1 1 G sharp 33
4 56
Chichester, T. 1877 5 101
2 3 14 B flat . . . 142
Hˆotel de Ville, Paris . . . . . . . . . 3 10 . . . . . . . . .
Canterbury 1762 5 9 3 10 C 51
2 . . .
Gloucester 1400 5 81
2 3 5 C . . . . . .
N.B.—Many of the above weights have been calculated from measurements
taken by an experienced English bell-founder on the spot.
ADDENDA.
Addendum to p. 142.—A powerful clock, by Messrs. Smith of Derby,
was fixed at Beverley Minster in 1902, which is the only clock in the world
striking upon bells in two towers. The quarters chime upon the peal of 10
bells (tenor 411
2 cwt.) in the N.W. tower (in strains of 12, 20, 32, and 41
notes, at the 1st, and, 3rd, and 4th quarters respectively), and the hour is
struck upon the bell, “Great John” (7 tons, 1 cwt.) in the S.W. tower, which
is exactly in tune with the peal. For this purpose, the clock is divided; the
going part, and the chiming machine, being in the N. tower (on the north
face of which there is a Gothic skeleton dial 14 feet in diameter), and the
striking train in the S. tower. The connection is made by a rod through the
“tympanum,” or chamber between the towers.
Addendum to p. 142.—I designed the clock at St. Paul’s Cathedral
to strike the hour on “Great Paul,” but objection was taken to altering the
striking from the very inferior old “Phelps” bell.
Addendum to p. 245.—Since 1896, a revolution has been brought
about in the tuning of bells, inaugurated by the late Rev. A. B. Simpson,
Rector of Fittleworth and Prebendary of Chichester. Every bell gives
out several notes, but, while the old Belgian founders (Hemony, Van den
Gheyn, etc.) endeavoured to bring these more or less nearly into tune with
each other, the task has never been achieved, and but rarely attempted, in
England or any other country, for the past three centuries. Elaborate experiments,
however, have demonstrated its possibility, and modern science and
improved machinery enable the old methods to be applied with greater exactness
than ever before. There is no reason now why every bell should not
give out a true and harmonious chord instead of a collection of discords. The
tone of properly tuned bells is incomparably fuller and richer; and ordinary
bells sound so thin and poor (as well as inharmonious) by comparison, that
more than one fair average peal has already been sent to Loughborough to
be recast—Messrs. Taylor being as yet the only founders who have taken up
the discovery. The principal examples are the new peals of the Minster and
St. Mary’s, Beverley; St. Patrick’s Cathedral, Dublin; Holy Trinity, Hull;
and Loughborough Church, and the tenor of Exeter Cathedral. In the N.
281
ADDENDA. 282
tower of Beverley Minster hangs a peal of 10 bells (1901), the tenor of which
(411
2 cwt. in C) was described by Mr. W. W. Starmer, a.r.a.m., when lecturing
on bells before the Incorporated Society of Musicians, in February,
1903, as an ideal example of a perfectly tuned bell. In the S. tower is a
Bourdon (“Great John”) of 7 tons, 3 cwt. in G, which has been tuned an
exact octave below the sixth bell of the peal, thus satisfying the most exacting
ear, both when it is rang as a service-bell on the ceasing of the peal,
or when it follows the chimes as an hour-bell for the clock (v. Addendum to
p. 142). During the visit of the Yorkshire Association of Change Ringers to
Beverley in September, 1902, it was rung as a bass accompaniment to the
peal, with fine effect.
Addendum to p. 254.—It is now, however, asserted that this difficulty
has been entirely overcome by the new method of tuning, to prove which, a
very small set of six bells, the largest only a little over 4 cwt., was exhibited
at the Ecclesiastical Art Exhibition in the Imperial Institute in connection
with the London Church Congress of 1899. Canon Simpson called attention
to the subject in a letter to the Times (Oct. 8, 1899), in which he said, “This
little chime shows that the difficulty of small bells has been mastered, and
there can be no reason why carillons of any size should not now be made in
perfect tune.” Messrs. Taylor have placed a similar miniature peal of eight
in their tower at the Loughborough Foundry.
Addendum to p. 259.—Persons who want large bells or peals should
be informed that Messrs. Taylor of Loughborough still use my composition
of 13 of copper to 4 of tin which I prescribed for the Westminster bells as
mentioned in this book.
Addendum to p. 265.—This recommendation has now been carried
out with great success. Two out of the three largest church bells in this
country, “Great Paul” of London, and “Great John” of Beverley, have been
hung in roller-bearings, and in steel headstocks of horseshoe shape, so that
there is a very considerable counterpoise above the gudgeons. They can be
easily rung “frame-high,” or higher, if desired, without any strain to the
towers.
APPENDIX.
Weathercocks (see also p. 161).—Weathercocks are so much expected
on steeples and other high roofs, and so much within the competence of
public clockmakers, and so universally made wrong, that I add a few lines
about them and their universal defects of sticking fast (and so pointing
wrong) by day and squeaking by night, and swallowing damp and dust,
which decay them prematurely.
The only way to make them, and avoid all this, is to join the meeting
narrower ends of two oblong sheets of copper by copper rivets, so as to form
a tube that will ride loosely on the usual spike, and then stop the upper
end of the tube with a bell-metal plug or disc, pushed tight into the tube
and fixed with common solder, or only the edges of the tube hammered over
it, so that it will ride and spin on the top of the spike—which is better
rounded than sharp. The other end of the double plate may be cut into
any shape you like, as pointer to the point of the compass from which it is
called E. W. N. S., as usual. I have had successive cocks of this construction
in use, and perfectly successful, for years. Two of my best makers of large
clocks—viz. Joyce of Whitchurch, and Smith and Sons of Derby, who made
the new St. Paul’s clock under my direction in 1893—have offered to make
them, and a firm of coppersmiths wrote to me to the same effect, intimating
that they did so already. But my building foreman could find nothing of
the kind in shops that sell weathercocks of the usual badness, and I have
a similar complaint from a friend with a large country house. The spike
should be slightly oiled occasionally, but not greased thickly.
Chimney-cowls may evidently be made in the same way.
283
INDEX.
Air
barometric effect of, 48
resistance of to pendulum, 30,
48
Air-tight clock-case, 50
Airy, Sir G. B., 7
conditions forWestminster clock,
188
failure of his alteration of the
striking work, 192
for gravity escapements, 77
his calculations for dead escapements,
55, 57, 59
his detached escapement, 73
his report on the Westminster
bells, 192
maintaining power, 107
on wheel teeth, 193
spring remontoire, 166
Alarums, 126
Aluminium bronze, 65
bad for bell metal, 261
balance springs, 215
American clocks, 94, 109
mainspring barrel, 208
watch factories, 240
watches, 208
Anchor pallets, 52
Antimony in some bells, 260
Arbors, or axes, of wheels, 14
Architects
ignore bells and clocks, 130,
273
often destroy belfries, 274, 275
their ignorance of requirements,
154
Arcs of vibration in clocks, 25, 49,
64
watches, 226
Arsenic in bell metal, 260
Astronomical clocks, 57, 89
dial work of, 96
Greenwich clock, 73
‘Astronomy without Mathematics’
referred to, 1, 3, 266
Austrian clocks, 110
Baily, F.
his mistake on pendulum compensation,
45
on barometric compensation,
49
Bain’s electrical clocks, 111
Balance spring, 212
glass, 215
Balance springs of watches, 212,
215
Balance-wheel clock escapements,
19
Balances, compensation of, 217, 224
Barometric compensation, 48
Barrels, going, 104
Barry, Sir C.
his Westminster clock hands,
156, 157, 182, 263
Beat
adjustment of, 54
284
INDEX. 285
self acting in French clocks, 110
single-beat escapements, 75, 230
Beat pins
eccentric, 70
ivory and wooden, 92
spring, 72
Beckett, Sir E.
bolt and shutter, 107
concave dials, 156
detached escapement, 74
‘drop bushes’ for turret clocks,
135
experiments for the Westminster
bells, 244
four and three legged gravity
escapements, 85, 91
general plans for turret clocks,
131, 138, 140
half-hour striking, 120
improved stays and sliders, 267
meridian dial, 8
new bell-crown, 263
on ‘Clocks’ &c., in the Encyclopædia
Britannica, 14
plan for bell frames, 270
plan for Great Paul, 265
plan for hanging small bells,
266
plan for theWestminster clock,
188–190
rules for bell construction, 256
rules for composition of bell
metal, 259
spring remontoire, 168
three-legged dead escapements,
71, 73
Belfries, their destruction by architects,
275
Bell frames, 269
bottom should fit tight to walls,
269
their arrangement, 269
Bell ropes, 266
generally too thick, 266
Bell-crown
common, 263
mushroom-shape, 264
Sir E. Beckett’s, 263
Taylor’s, 264
Bell-founders
foreign, 243
some celebrated ones, 242
Bell-hanging, 265
for clocks, 150, 151
stays and sliders for, 267
Bell-metal
impurities of, 260
its composition, 243, 244, 259–
260
its specific gravity, 259
melting point of, 262
silver useless in, 261
Bell-moulding
different methods of, 261
Bell-ringing
books on, 267
Bell-tolling, 265
Bell-towers, 273
construction and size for bells,
274
windows should be caged, 276
windows should have louvres,
274
Bells
clappers, 268
Cologne, cast three times, 277
cracked, incurable, 263
frames, 269
great bells of Europe, 276
list of their weights and sizes,
278–280
hemispherical, bad, 255
history of famous ones, and their
makers, 241
notes, 245
Oxford and York very bad, 242
price for casting and re-casting,
243
INDEX. 286
proper shape for, 254
rule for construction of large
bells, 256
scale of weights, 246, 248
sound best swinging, 266
specifications for, 271
St. Peter’s, and Montreal, and
Great Paul, 265, 277
stocks, 268
thickness of sound bow, 247,
258
‘tucking up’, 258, 264
tuning, 245
Bells in peals
Beverley, 282
Boston and Eaton Hall, 148,
243, 254
Bow Church, 248
Bradford, 250
Burton, 252
Doncaster, 252
Exeter, 248
Gainford, 253
Great Paul, 265
Headingley, 253
large and small together, bad,
148, 254, 282
Manchester, 250
Ossett, 252
Rochdale, 249
sizes, &c., 248
Southwark, 248
St. Paul’s, 250
St. Paul’s, 249
Worcester, 249, 250
York Minster, 248
Bells, Chinese and Indian, 255
Bells, gudgeons, 268
Bells, Oxford and York very bad,
243
Berthoud on escapements, 63, 225
Bevelled wheels, 201
Beverley
bells, 282
clock, 141, 281
Big Ben of Westminster
the first and second, 191, 192
Bloxam
corrected Sir G. Airy, 45, 83
his escapements, 45, 57, 79, 83
invented the dipleidoscope, 9
on barometric error, 49
Bobs for pendulums, 22, 30, 37, 40
Bolt and shutter, 104
Sir E. Beckett’s improved, 107
Bond’s telescope-driving clock, 165
Bottle-jack escapement, 21
Bow Church bells and York, 248
Box chronometer, 209
Bradford Town Hall tower and bells,
154, 251
Brass-work destroyed by town atmosphere,
171
Brasses for bell gudgeons, 265, 268,
272
Breguet’s tipsy key, 208
Bryant, bell founder and clockmaker,
243
Buffers for large hammers, 151
Burton and Ossett bells, 252
Bushes, various kinds of, 135, 136
Cambridge andWestminster chimes,
143, 145
Cams, 202
for large clocks, 133
in the Westminster clock, 183
proper form of, 202
Candles graduated, for marking time,
12
Canons of bells, 263
Cast iron
for clock wheels, 170
for steel pinions, 171, 200
Cast iron jars best for mercurial
pendulums, 47
Casting of bells, test for good, 259
Cattley, Rev. R.
INDEX. 287
lifting off hammers, 146
Worcester chimes, 144
Cemetery bells, 255
Centre of oscillation of pendulums,
26
Chance’s glass for dials, 157
Chester cathedral chimes, 144
Chime-tunes, 124, 147
Boston and Eaton Hall, 148
improvements
by Gillett and Bland, 148
by Lund and Blockley, 148
Chimes (quarter)
Cambridge and Westminster,
143, 145
Chester and Worcester cathedrals,
144
Doncaster and Scarborough, 144,
145
Headingley, 145
interval between each quarter,
145
peculiar, on two bells at York
Minster, 146
Royal Exchange, 144, 145
St. Alban’s cathedral, 147
Chiming hammers
by machinery, 242
Ellacombe’s, 267
Chimney-piece clocks, 217
Chinese
bells, 255
gongs, 241
‘Chords’ in chime-tunes bad, 148
Chronograph at Greenwich, 18
Chronometer escapement, 230
secondary compensation, 219
trials at Greenwich, 220
trials at Liverpool, 220
Chronometers, 209, 216
rate of, 224
Chronometrical thermometer, 219
Chronoscopic dials, 100, 101
Church clocks, see Turret clocks
Church towers and architects, 273,
275
Circular error of pendulum, 24, 33,
79
‘Clappering’ cracks bells, 270
Clappers, 258, 268
Cleaning watches, 240
Clepsydræ of Greeks and Romans,
11
Clock out of beat, to regulate, 54
Clock time, all regulated by sidereal
time, 1
Clock-cases, 97
Clock-room, ventilation of, 161
Clocks
American, 94, 109
ancient clocks in England, 13
arrangement of common, 95
astronomical, 57, 89, 96
Austrian, 110
construction of, 14
cuckoo, 109
day of the month, 98
electrical, 111
equation of time, 102
French, 109
German, 109
going part of, 93
influence one another, 31
invention of, 12
musical, 127
regulate by sidereal observations,
4
self-winding, 110
silent beat, 68
spring, 108
striking, 116
English or repeating striking
work, 117
foreign or locking-plate method,
119
half-hour striking, 120
strike and silent, 119
striking one at the hour, 116
INDEX. 288
striking quarters, 123
various mechanisms for striking
work, 126
tell-tale, 127
year, 97
Clocks with dials for many places,
7
Cologne bell cast three times, 277
Compensation of balances
common, 217
Dent’s, 221
Dent’s prismatic, 223
Eiffe’s, 220
Kullberg’s, 223
Loseby’s, 222
secondary, 219
Compensation of pendulums, 36,
128
Baily’s mistake on, 45
barometric, 48
compound bar, 42
Ellicott’s, 44
homogeneous, 43
mercurial, 45
Smeaton’s, 42
wood and lead, 40
wood, zinc, and lead, 41
zinc and steel, 37
Composition of bell-metal, 243, 244,
259–261
Concave dials for large clocks, 156
Conical pendulum, 17
its uses, 18
Construction of bells
rule for, 256
Construction of dials, 153, 155
Continuous motion clocks, 17, 164
Cooke
clock and telescope maker, 172
his telescope-driving clock, 164
Copper for bell-making, 244, 261
Counterpoises for clock hands, 157
Crab, double-barrelled, 176
Cracked bells
cannot be mended, 263
clappering causes, 270
Cranks, different forms of, 152
Cubit of Pyramid, and Jewish, 28
Cuckoo clocks, 109
Cumming’s escapement, 81
Cycloidal
cheeks useless, 24
theory, 23
Day
sidereal, 1
solar, 2
Day of the month dials, 98
Dead escapements, 55
Beckett’s three-legged, 70
effects of friction on, 57
Graham’s, 55
large and small arcs, 63
length and arrangement of pallets,
66
Macdowall’s, 68
mathematical theory of, 59
pin-wheel, 67
various materials for pallets,
64
Degree plate for a pendulum, 33
Dennison, A. L., of America
his improved Geneva stop, 211
keyless watch, 237
lever escapement bridge, 226
Dent, E. J.
compensation balance, 221
Exhibition clock, 129, 168
prismatic balance, 223
regulation of watches, 214
Royal Exchange clock, 165
Westminster clock, 188–190
‘Depthing’ tool described, 200
Detached escapements
for clocks, 73
for watches, 230
G. B. Airy’s, 73
Sir E. Beckett’s, 74
INDEX. 289
De la Rue’s telescope-driving clocks,
164
De Vick’s clock escapement, 19, 21
Dial wheels, 158
of watches, 212
Dial work
of house clocks, 94, 96
of large clocks, 153
Dials
chronoscopic, 101
colour and materials for, 155–
156
convex and concave, 156
figures of, 154
hands of, 156
illuminated, 157
moon, 98
of public clocks, 153
of the Westminster clock, 155
Dials of watches, 239
Dipleidoscope,the, 9–11
Doncaster
bells, 244, 253
quarter chimes, 144
Double three-legged gravity escapement,
90
Double-barrelled crab, 176
Driving and running teeth, 197
‘Drop bushes’ for large clocks, 136
Duplex escapement, 230
Dutch clocks, 109
Eaton Hall bells, 148, 243, 254
Eiffe’s compensation balance, 220
Electrical clocks, 111
Bain’s, 111
Jones’s, 112
Ritchie’s, 112
Shepherd’s, 111
Ellacombe, Rev. H. T.
his chiming hammers, 267
on the bells of Devon, 242
Ellicott’s compensation pendulum,
44
Elliptical section of a bell, 257
English fusee watch, 209
Epicycloidal teeth, 195
Equation of time, 3
table of the, 5
Equation of time clocks, 102
Equatorial telescope at Greenwich,
its driving apparatus, 19
Escapements of clocks, 19, 51
dead, 55
detached, 73
half-dead, 63
pin-wheel, 67
recoil, 52
remontoire, 75
silent, 68
single beat, 75, 230
single pin, 68
three-legged dead, 70
Escapements of watches, 224
chronometer or detached, 230
duplex, 230
Gray’s, 225
horizontal or cylinder, 228
vertical, 224
virgule, 229
Escapements, gravity
Beckett’s, 85–93
Bloxam’s, 83
Cumming’s, 81
Gannery’s, 82
Gowland’s, 82
Hardy’s, 81
Kater’s, 82
theory of, 75
Europe, the great bells of, 276, 278–
280
Exchange, Royal
chimes, 144, 145, 147
clock, 129, 159, 165
alterations of, 170
Exeter Cathedral bells, 248, 249
Figures on dials useless, and proper
INDEX. 290
size of, 154
‘Finishing’ too much undesirable,
66, 171, 232
Fly, remontoire, 163, 169
Fly, striking
for gravity escapements, 87, 90
for turret clocks, 137
Fly-wheel clocks, earliest, 17
Foreign
bell-founding, 243
churches, chimes in some, 147
Forks of pendulums, 32
with springs, 72
Four-legged gravity escapement, 85
Four-wheeled trains, 135
Frames
for bells, and fixing, 269
for turret clocks, 129, 130
French clocks, 108
improved kind of, 109, 122, 129
Friction
in dead escapements, 57
in turret clocks, 127, 130
Friction rollers
for bells, 265, 282
for clock barrel, 54, 58
Fusee of watches, 209
often dispensed with, 208
Gainford peal of bells, 253
Gannery’s escapement, 82
Geneva stop, 211
German clocks, 109
Gillett and Bland’s
chime machinery, 148
clocks and bells, 129, 242
Gimbals, chronometer, 216
Glass balance springs, 215
Gnomon, its position on sundials,
8
Going barrels, see Maintaining power
Going part of clocks, 93
Gongs, 241
Gowland’s escapement, 82
Graham’s
dead escapement, 55
horizontal watch escapement,
228
Gravity escapements, 75
Beckett’s four-legged, 85
best for large clocks, 90, 170
double-three-legged, 90
in the Westminster clock, 180
Mudge’s, 76
rate of some, 92, 129, 187
require heavy weights, 88
theory of, 76
Gravity, specific, of metals, 36
Gray’s vertical watch escapement,
225
Great Paul of London, 247, 265,
277
Great Tom of Oxford, 242, 243
Great wheel, striking from, 133
Greenwich
barometric pendulum compensation
at, 51
equatorial driving clock, 19
mean time and local time, 4
table for forty-two towns, 6
revolving pendulum, 19
sidereal clock escapement, Airy’s,
73
trials of chronometers at, 220
Gridiron pendulum, 36
Gudgeons of bells, 268
Gun metal, 262
for clock wheels, 171
its composition, 171
Half-dead escapements, 63
Berthoud’s, 63
Half-hour striking, 120
Half-hours with rack movement, 122
‘Half-hunting’ watches, 240
Hammers, clock, 150
fixing, 150
lifting off, 146
INDEX. 291
shape, 150
weight, 152, 174
Hand-bells, 255
Hands of clocks and watches
counterpoises, 157
for large clocks, 156
of the Westminster clock, 182
proper construction and fixing,
156
the best colours for, 96, 101
Hanging bells, 265
chapel and schools bells, 266
on friction rollers, 265
Hardy’s escapement, 81
Harrison
going barrel, 104
gridiron pendulum, 36
his clock escapement, 54
inventor of watch compensation,
217
the chronometer maker, 36
Headingley, St. Chad’s chimes and
peal, 145, 253
Helix teeth, 194
Hemispherical bells, 255
Henderson’s sidereal and mean time
clocks combined, 6
Holmes, an old clockmaker, 42, 100
Homogeneous compensation, 43
Hooke, inventor of the balance-spring
of watches, 22, 52, 206
Horizontal or cylinder escapement,
228
House clock, common, 95
‘Howard Clock Company,’ of America,
208
Huyghens
endless chain, 104
theory of balance-spring for watches,
206
theory of the pendulum, 22
Hypocycloid and epicycloid, 195
Illuminated dials, 157
Indian bells
bad shape, 255
Iron in bell-metal wrong, 260–261
Iron stocks and frames for bells,
268
Isochronal spring, Loseby’s, 63
Jewelled pallets, 65, 226
Jobbing in contracts for public clocks,
172, 173
Jones’s electrical clocks, 112
Joyce’s turret clocks, 129
Kater
his escapement, 82
his mercurial pendulum, 46
Key
best watch, 209
for clocks, 97
Keyless watches, 236
Dennison’s, 237
Kullberg’s, 236
Keys, winding, 97
King’s Cross clock, 68, 168
Kullberg’s
compensation balance, 223
keyless watch, 236
Lantern pinions for clocks, 94, 198–
200
Lantern towers difficult for bellringing,
275
Large and small arcs, 49, 64
Large and small clocks, difference
between, 127
Large turret clocks, 139
Lead
adulteration in bells, 260
decay of, on church roofs &c.,
244
Leap-year, how it affects the equation
of time, 3
Leaved pinions, 200
Lepaute’s pin-wheel escapement, 68
Lever escapement, 225
INDEX. 292
chronometer escapement, 230
Light-house clocks, 18
Lincoln Minster clock, 129, 141
Lines and pulleys for winding up
large clocks, 135
Local time, clocks for, 7
Locking-plate movement, 119, 123
Loseby’s
balance for watches, 222
isochronal spring, 63
Lunar clocks, 98
Lund & Blockley’s
chime machinery, 148
stop watches, 238
Lutz of Geneva, his balance springs,
215
Macdowall’s
single-pin escapement, 68
spiral drill, &c., 68
Magnet used for regulating clocks,
35, 51
Maiden bells, 254
Mainspring of watches, 206
Maintaining powers of clocks or going
barrels, 104
bold and shutter
Beckett’s improved, 107
bolt and shutter, 104
endless chain, 104
going-barrel in watches, 206
Harrison’s, 104
‘sun and planet’ power, 108
Westminster clock plan, 142,
181
Manchester Town Hall clock and
bells, 129, 251
Marine chronometer, 216
Mean time, 2
how got from sidereal observations,
4
Mears, bell-founders, 191, 242, 244,
259
Montreal and York, 276, 277
Royal Exchange and York, 191,
244
their Westminster bell, 260
Mending cracked bells impossible,
263
Mercurial compensation, 45
Barometric, 48
Cast-iron jars for, 47
Kater’s and Beckett’s, 46
Meridian dial, 8
method of constructing one, 8
Metre, the French, a bad measure,
28
Metronome, the, 29
Moon dials, 98
Moore, Holmes, and Mackenzie, bellfounders,
242, 268
Morrison’s universal joint, 160
Moulding bells, 261
Mudge
his gravity escapement, 76
invented the lever escapement
for watches, 209
Musical
clocks, 127
hand-bells, 255
New bell-crown, Sir E. Beckett’s,
263
Notes of bells, 245, 252
should not be prescribed, 271
Oil for clocks, 204
Old bell-founders, 242
Old Tom of Lincoln, 260
Oscillation, centre of, 26
Painting
all ironwork of large clocks, 171
bell frames and wheels, 273
Pallets, 19
anchor, 52
length of, 66
pin, 68
silent, 68
INDEX. 293
steel, 65
various materials for, 65
Peal of large bells, specification for,
271
Peals of bells, some of the largest,
249
Pedometer, the, 237
Pendulum
bobs, 22, 30, 37
cocks, 31
springs, 31
Pendulum
conical or revolving, 17, 18
of the Westminster clock, 31,
180
Pendulums
centre of oscillation of, 26
circular error of, 24, 33
compensation, 36
homogeneous, 43
mercurial, 45
wood and lead, 40
wood, zinc, and lead, 41
cycloidal theory, 23–24
for church clocks, 128
heaviest in England, 39
importance of firm fixing, 31,
64
invented, 21
lengths of, 25
regulation of, 34
relation to gravity, 26
shape of, 29
short and slow, 29
springs of, 33
standard lengths, 27
suspension, 30
temporary regulation, 35
Percy, Dr., his report on the Westminster
bell, 191
Phelps & Co., old bell founders,
242
Pin pallets, 68
Pin-wheel escapement, 67
Pinions of clocks, 14
lantern, 198
leaved, 200
Potts, maker of Lincoln Minster
clock and others, 129, 141
Pulleys, 15, 104, 135
Quarter chimes, see Chimes
of Westminster clock, 183
on two bells, 142, 146
rack and repeating movements
in small clocks, 124
should be independent of hour
in large clocks, 146
Radius of oscillation of pendulums,
26
Ratchet wheels, 16, 104
Rate
of 1851 Exhibition Clock, 168
of some other gravity escapement
clocks, 92, 129
of the Westminster clock, 187
of watches, 224
Recoil
anchor pallets, 52
escapements, 52
Harrison’s, 54
Regulation
of pendulums, 31, 34
of watches, 213
the old plan, 214, 215
Reid on train remontoires, 162
Remontoire
bevelled wheel, 162
continuous motion, 164
internal wheel, 165
spring, 166, 169
train, 161
Remontoire escapements, 75, 235
Repeaters, 235
Repeating striking work, 117
Ritchie’s electrical clocks, 112, 113
their pendulums, 114
INDEX. 294
Robinson, Dr., on barometric compensation
of pendulums, 50
Rochdale chimes and tower, 249,
252
Rollers, friction, 265
Ropes, wire
best for turret clocks, 133
in the Westminster one, 183
Rosse, Lord, his water clock, 12
Rudhalls, famous bell-founders formerly,
242
Sam Slick was Eli Terry, 109
Sand clocks, 12
Scape wheels
a very small one, 71
bad weight of, 65
Secondary compensation
inventions for, 220–224
theory of, 219
Self-winding
clocks, 110
watch, 237
Shape
of bells, 254
of pendulums, 29
Shepherd’s electrical clocks, 111
Ship time-pieces, 216
Siddons and Meese’s clocks, 101
Sidereal
day, 1
time, 1, 2
Silver, none in bell-metal, 261
Single-beat escapements, 75
Single-pin escapement, 68
Skew-bevelled wheels, 201
Smeaton’s glass pendulums, 42
Snowdon’s books on bell-ringing,
267
Solar day
defined, 2
why it varies, 2
Sound-bow of bells, 258
Specific gravity
of bells, 259
of metals, &c., 36
Specifications
for bells, 271
for public clocks, 172
Spring
clocks, 108
remontoires, 166, 169
St. Alban’s cathedral chimes, 147
St. Paul’s
clock heard at Windsor striking
thirteen, 276
peal of bells, 249, 250
the great bell, 247, 277
Stays and sliders of bells, 267
Steel
bells, bad, 260
pallets, 65
Stop, Geneva, 211
Stop, winding, of watches, 210
Stop-watches, 238
Stops for weights, 134, 187
Strike and silent, 119, 126
Striking clocks, 116
accuracy of discharge, 132, 141,
146, 184
half-hours, 120
Striking part
of house clocks, 116
of turret clocks, 133, 174
of Westminster clock, 183
‘Sun and planet’ maintaining power,
107, 108
Sundials, 8
Suspension of pendulums, 30, 64
Sweep or section of bells, 256, 257,
261
Swinging, effect of, on the sound
of bells, 266
Swiss watches, 108
Table
difference of forty-two towns
from Greenwich mean time,
INDEX. 295
6
equation of time, 5
expansion for compensated pendulums,
36
great bells of Europe, 278–280
sizes of public dials, 155
various quarter-chimes, 145
weights and sizes and notes of
bells, 246, 248–253
Taylor, bell-founder, 242, 252, 253
Taylor, Rev. W.
and the Westminster bell, 190
and the York bell, 265
Teeth of wheels, 193
bevelled wheels, 201
cams, 202
construction of, 202
epicycloidal teeth, 195, 196
helix teeth, 194
internal wheels, 201
lantern pinions, 198
leaved pinions, 200
Telescope-driving clocks, 12, 18
Cooke’s, Bond’s, and De la Rue’s,
164
Tell-tale clocks, 127
Tenor bell in a peal, proper proportions
of, 247, 248
Thermometer, chronometrical, 219
Thickness of bells, 247
Three-legged
dead escapement, 70, 71
gravity escapement, 90, 91
Three-quarter plate watches, 210
Time balls and guns, 115
Time of striking (quarters), 146
Time, measures of, see mean, sidereal,
local
dipleidoscope, 9
graduated candles, 12
meridian dials, 8
sand clocks, 12
sun-dials, 8
water clocks, 11, 111
Timepieces, ship, 216
Timing screws, 213
timing for position, 216
Tin in bell-metal, 244, 260, 261
Tipsy winding-key, 208
Tolling levers, 265
Tolling of bells, 265
Tom of Oxford, a very bad bell,
242
Tourbillon escapement, 234
Tractrix curve, to describe for cams,
203
Train of wheels
in clocks, 14, 15
in watches, 209
Train remontoires, 161
bevelled wheel, 162
continuous motion, 164
internal wheel, 165
Reid’s, 162
spring, 166, 169
Transit instrument, 1
Troughton’s pendulum, 37
Troyte on bell-ringing, 267
Trumpet and cuckoo clocks, 109
‘Tucking-up’ of bells, 264
Tunes, chime, 124, 147
on church bells, 147
Tuning of bells, 281–282
Turret and church clock makers,
129
Turret clocks, 127
Batch-wood clock, 131
best position for, 128
counterpoises for the hands, 157
dials, 153
illumination of, 157
frame for, 129
its construction, 130
hammers of, 133
iron barrels, 130
larger ones, 137
lifting off hammers for ringing,
146
INDEX. 296
position of fly, 137
regulating and setting the hands,
156
smaller ones, 137
specification for, 172
stops against overwinding, 134,
187
striking part, 141
three-wheeled trains, 130
wire ropes for, 133
Universal joints, 159
new American, 160
‘Up and down’ dial, 211
Ventilation of clock-rooms, 161
Vertical watch escapement, 20
Gray’s, 224
Virgule escapement, 229
Vulliamy, Mr., 63, 65, 129, 144
and theWestminster clock, 188,
189
Wagner’s continuous motion remontoire,
164
Warners, bell-founders, 191, 242,
252
Watch
cases, 239
dials, 239
escapements, 224–236
Watch keys, best kind of, 209
Watches
American factories, 240
balance-spring, 212
compensation of balances, 217
secondary, 219
dial wheels, 212
fusee, 209
general construction, 210
glass balance springs for, 215
keyless, 236
mainspring, 206
regulation, 213
repeaters, 235
self-winding, 237
stop, 238
their early history, 206
timing for position, 216
winding-stops, 210
Water clocks, 11, 111
Lord Rosse’s, 12
the one at Greenwich, 12
used by the Greeks and Romans,
11
Weathercocks, 161, 283
Weights and sizes of bells, 246, 248,
278–280
Weights, stops
for falling, 134
for winding, 134, 187
Westminster bells, the, 244, 246,
259
their cost, 193
their history, 190
Westminster clock
construction, 176
cost, 193
dials, 181
gravity escapement, 180
hands, 182
has no barometric error, 49
history, 188
maintaining power, 181
rate, 187
regulation of the pendulum, 180
striking parts, 183
curious suggestions for winding,
186
winding of, 186
Wheatstone’s electrical clocks, 112
Wheels for clocks, 65
aluminium bronze for, 65
bevelled, 201
cast iron, 170
skew-bevelled, 201
train of, 14
Wheels, numbers of teeth, 16, 94,
130, 141, see Teeth
INDEX. 297
for dials, 158, 212
in watches, 209
Whitaker’s almanack, sidereal time
of noon in, 4
White’s gearing, 194
Willis, Prof., his table of wheelwork,
196
Winding keys
for clocks, 97
for watches, 209
should be long, 97
Winding stops
for clocks, 134, 186
for watches, 210
Windows of bell-chambers, 276
Wire ropes best for large clocks,
133
Wooden
beat pins, 92
pendulums, 40–41
Worcester cathedral
bells, 250, 254
chimes, peculiar, 144
clock, 129, 146
Year clocks, 97
York Minster
bells, 248, 260
great bell, a bad one, 243
quarter chimes, peculiar, 146
Zinc
in bell-metal, 260
zinc and steel pendulums, 37
better than mercurial, 48
INDEX. 298
THE END.
PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, LONDON
AND BECCLES.


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