PREFACE ix 



pies is gradually laid down, upon which in its turn a coherent architec- 

 ture of theory can be built, and finally this passes over into a period of 

 maturity, in which the position is consolidated, the scope of the prin- 

 ciples widened, their bases more finally tested, and their consequences 

 worked out in fullest detail. Naturally, each stage lasts for a con- 

 siderable time, and in many cases a science which thought itself se- 

 curely embarked upon the third phase is reminded by some funda- 

 mental discovery that it is still only in the second." ^ 



These movements of science have produced a copious literature 

 which has not enjoyed the same attention and reading as imaginative 

 books, because, once the ideas are known and incorporated into the 

 existing body of scientific knowledge, these scientific writings tend to 

 acquire chiefly an historical interest. Yet they are monuments of the 

 advance of civilization, and deserve a better fate. Many of them are 

 still interesting to read as human documents because they illustrate 

 how painfully and slowly man's exact knowledge of verifiable pheno- 

 mena has been accumulated. No one outside of the small company of 

 highly trained scientists can read all of them through, yet most of 

 them have sections which are as readable and as exciting as any mod- 

 ern novel. It is the purpose of this book to present to the young col- 

 lege student and to the general reader some of the more representative 

 of these classics in the literature of science, bringing together in this 

 convenient form at least some reminders of a vast field of reading 

 where one may browse for a lifetime with interest and profit. If it 

 be used in conjunction with a history of science it will readily supply 

 a vivid sense of the movement of the mind of western civilization, in- 

 creasing in us a respect for the effort of our ancestors, and inspire us 

 to encourage and to forward the work of contemporary scientists, 

 and restrain us at least from hindering them in their efforts. 



Although the selections may be used as a textbook in courses like 

 Introduction to Modern Civilization, Philosophy, and The History of 

 Science now given in the more progressive colleges and universities, 

 it may also profitably be used as a text for freshman or sophomore 

 readings in English courses given in colleges predominantly technical 

 or scientific, like Engineering, Agricultural, and Forestry Colleges. 

 In those English courses where emphasis upon ideas is made to pro- 

 vide the inspiration for writing, these selections will be found, as I 



* Julian Huxley, in Harper's Magazine for April, 1926. 



