Science

On the Origin of Species
or, The Preservation of Favoured Races in the Struggle for Life.
Charles Darwin

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

On the Significance of Science and Art
Leo Tolstoy

On the Study of Zoology
Thomas Henry Huxley

On the Variation of Species, with Especial Reference to the Insecta
Followed by an inquiry into the nature of genera
Thomas Vernon Wollaston

One Thousand Questions in California Agriculture Answered
Anonymous

Ontario Normal School Manuals: Science of Education
Ontario Ministry of Education

Opuscula Selecta Neerlandicorum
Nederlandsch Tijdschrift voor Geneeskunde
Various Authors

Organic Gardener's Composting
Steve Solomon

Organic Syntheses
James Bryant Conant (editor)

The Origin and Nature of Emotions
Miscellaneous Papers
George W. Crile

The Origin of Finger-Printing
William J. Herschel

The Origin of Species by means of Natural Selection (6th ed)
or, The Preservation of Favoured Races in the Struggle for Life.
Charles Darwin

The Origin of Species
Thomas Henry Huxley

Other Worlds
Their Nature, Possibilities and Habitability in the Light of the Latest Discoveries
Garrett P. Serviss

Our Nervous Friends
Illustrating the Mastery of Nervousness
Robert S. Carroll

The Outline of Science, Vol. 1
A Plain Story Simply Told
J. Arthur Thomson

Outlines of a Mechanical Theory of Storms
Containing the True Law of Lunar Influence
T. Bassnett

Outlines of the Earth's History
A Popular Study in Physiography
Nathaniel Southgate Shaler

Parent and Child Vol. III.
Child Study and Training
Mosiah Hall