I cannot conclude this preface without thanking those who have assisted me in the preparation of this book--Sir William Osler, who read the first draft of the manuscript, and aided me with his counsel; Dr. Charles Singer, who read all the chapters in manuscript, and to whom I am indebted for advice in reference to the illustrations and for many other valuable suggestions; the officers of the Bodleian Library, whose courtesy was unfailing during the year I worked there; Professor Henry Crew, who helped in the revision of two of the chapters by his judicious criticism; Professor J. E. Rush, whose knowledge of bacteriology improved the chapter on Pasteur; Professor L. O. Grondahl, who read one of the chapters relating to the history of physics and suggested important emendations; and Dr. John A. Brashear, who contributed valuable information in reference to the activities of Samuel Pierpont Langley. I wish to express my gratitude also to Miss Florence Bonnet for aid in the correction of the manuscript. W. LIBBY. February 2, 1917. CONTENTS I. SCIENCE AND PRACTICAL NEEDS--EGYPT AND BABYLONIA 1 II. THE INFLUENCE OF ABSTRACT THOUGHT--GREECE: ARISTOTLE 15 III. SCIENTIFIC THEORY SUBORDINATED TO APPLICATION--ROME: VITRUVIUS 30 IV. THE CONTINUITY OF SCIENCE--THE MEDIEVAL CHURCH AND THE ARABS 43 V. THE CLASSIFICATION OF THE SCIENCES--FRANCIS BACON 57 VI. SCIENTIFIC METHOD--GILBERT, GALILEO, HARVEY, DESCARTES 72 VII. SCIENCE AS MEASUREMENT--TYCHO BRAHE, KEPLER, BOYLE 86 VIII. COÖPERATION IN SCIENCE--THE ROYAL SOCIETY 99 IX. SCIENCE AND THE STRUGGLE FOR LIBERTY--BENJAMIN FRANKLIN 114 X. THE INTERACTION OF THE SCIENCES--WERNER, HUTTON, BLACK, HALL, WILLIAM SMITH 129 XI. SCIENCE AND RELIGION--KANT, LAMBERT, LAPLACE, SIR WILLIAM HERSCHEL 142 XII. THE REIGN OF LAW--DALTON, JOULE 155 XIII. THE SCIENTIST--SIR HUMPHRY DAVY 170 XIV. SCIENTIFIC PREDICTION--THE DISCOVERY OF NEPTUNE 184 XV. SCIENCE AND TRAVEL--THE VOYAGE OF THE BEAGLE 197 XVI. SCIENCE AND WAR--PASTEUR, LISTER 213 XVII. SCIENCE AND INVENTION--LANGLEY'S AEROPLANE 231 XVIII. SCIENTIFIC HYPOTHESIS--RADIOACTIVE SUBSTANCES 245 XIX. THE SCIENTIFIC IMAGINATION 258 XX. SCIENCE AND DEMOCRATIC CULTURE 270 INDEX 283 ILLUSTRATIONS EARLIEST PICTURE KNOWN OF A SURGICAL OPERATION. EGYPT, 2500 B.C. 6