. PREFACE vii 



seventeen to twenty-two years of age (and their in- 

 tellectual compeers) in order to direct their atten- 

 tion to the story of the development of the sciences. 

 It makes no claim to be in any sense complete or 

 comprehensive. It is, therefore, a psychological in- 

 troduction, having the mental capacity of a certain 

 class of readers always in view, rather than a logical 

 introduction, which would presuppose in all readers 

 both full maturity of intellect and considerable ini- 

 tial interest in the history of science. 



I cannot conclude this preface without thanking 

 those who have assisted me in the preparation of 

 this book Sir William Osier, who read the first 

 draft of the manuscript, and aided me with his coun- 

 sel ; 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 Li- 

 brary, 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 chap- 

 ters 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. 



February 2, 1917. 



