On the Origin of Species: or, the Causes of the Phenomena of Organic Nature By: Thomas Henry Huxley

On the Reception of the 'Origin of Species' By: Thomas Henry Huxley

On the Relations of Man to the Lower Animals By: Thomas Henry Huxley

On the Significance of Science and Art By: Leo Tolstoy

On the Study of Zoology By: Thomas Henry Huxley

On the uncertainty of the signs of murder in the case of bastard children By: William Hunter

On War By: Carl von Clausewitz

One Hundred Proofs That the Earth Is Not a Globe By: William Carpenter

One Martian Afternoon By: Tom Leahy

One Out of Ten By: J. Anthony Ferlaine

One-Shot By: James Blish

Oneness By: James H. Schmitz

Ontario Teachers' Manuals: Nature Study By: Ontario. Ministry of Education

Operation Earthworm By: Joe Archibald

Operation Haystack By: Frank Herbert

Operation Lorelie By: William P. Salton

Operation R.S.V.P. By: H. Beam Piper

Optical Projection Part 1: Projection of Lantern Slides By: Russell S. Wright

Organic Syntheses By: James Bryant Conant

Origin and Nature of Emotions By: George W. (Washington) Crile

Origin of Species By: Thomas Henry Huxley

Other Worlds Their Nature, Possibilities and Habitability in the Light of the Latest Discoveries By: Garrett Putman Serviss

Our Atomic World: The Story of Atomic Energy By: C. Jackson Craven

Our Bird Comrades By: Leander S. Keyser

Our Common Insects A Popular Account of the Insects of Our Fields, Forests, Gardens and Houses By: Alpheus S. Packard

Our Feathered Friends By: Elizabeth Grinnell

Our Friend the Dog By: Maurice Maeterlinck

Out Around Rigel By: Robert H. Wilson

Out Like a Light By: Randall Garrett

Out of This World Convention By: Forrest J. Ackerman

Outlines of a Mechanical Theory of Storms Containing the True Law of Lunar Influence By: Thomas Bassnett

Outlines of Dairy Bacteriology, 8th edition A Concise Manual for the Use of Students in Dairying By: H. L. (Harry Luman) Russell

Outlines of Greek and Roman Medicine By: James Elliott

Outlines of Lessons in Botany, Part I; from Seed to Leaf By: Jane H. Newell

Pandemic By: Jesse F. Bone

Papers on Health By: John Kirk

Passages from the Life of a Philosopher By: Charles Babbage

Personal Experience of a Physician By: John Ellis

Personal Recollections, from Early Life to Old Age, of Mary Somerville By: Mary Somerville

Peter Cooper The Riverside Biographical Series, Number 4 By: Rossiter W. (Rossiter Worthington) Raymond

Pharaoh's Broker Being the Very Remarkable Experiences in Another World of Isidor Werner By: Ellsworth Douglass

Philosophical Transactions of the Royal Society - Vol 1 - 1666 Giving some Accompt of the present Undertakings, Studies, and Labours of the Ingenious in many considerable parts of the World By: Various

Philosophy of Osteopathy By: A. T. (Andrew Taylor) Still

Physics and Politics, or, Thoughts on the application of the principles of "natural selection" and "inheritance" to political society By: Walter Bagehot

Pioneer Surgery in Kentucky A Sketch By: David Wendel Yandell

Pioneer Work in Opening the Medical Profession to Women By: Elizabeth Blackwell

Pipe of Peace By: James McKimmey

Pirates of the Gorm By: Nathan Schachner

Plain Facts for Old and Young By: John Harvey Kellogg

Planet of Dreams By: James McKimmey

Pleasant Journey By: Richard F. Thieme

Pleasures of the telescope An Illustrated Guide for Amateur Astronomers and a Popular Description of the Chief Wonders of the Heavens for General Readers By: Garrett Putman Serviss

Pleistocene Bats from San Josecito Cave, Nuevo Leon, Mexico By: J. Knox Jones

Poisoned Air By: Sterner S. Meek

Police Your Planet By: Lester del Rey

Policing the Plains Being the Real-Life Record of the Famous North-West Mounted Police By: R. G. (Roderick George) MacBeth

Politics: A Treatise on Government By: Unknown

Popular Lectures on Zoonomia Or The Laws of Animal Life, in Health and Disease By: Thomas Garnett

Popular Science Monthly Oct, Nov, Dec, 1915 — Volume 86 By: Anonymous

Popular Superstitions, and the Truths Contained Therein By: Herbert Mayo