vi PREFACE 



editors have contributed their services without personal 

 remuneration, and have done this as a welcome privilege 

 in helping to extend the achievements and underlying 

 truths of this most conspicuous field of modern thought. 

 Not all the lectures which were given in the course are 

 available; also changes which are advisable for publica- 

 tion have been made; and Dr. Kellogg and Dr. Williams 

 have kindly added chapters upon topics of wide interest 

 and importance. 



Why give such a course of lectures, and why publish 

 such a volume? Because the citizen of our day uses 

 modern science at each turn of his day's work. If he 

 is a thinking citizen, he is ambitious to benefit by what 

 he understands as scientific procedure in using facts, 

 principles, and occurrences. A manufacturer wants 

 his operators to possess whatever knowledge of ma- 

 terials and processes science has produced for the 

 improvement of quality and quantity of output. A 

 lawyer or preacher desires factual illustrative material 

 from the working world of science with which to make 

 his case clear and convincing. If this citizen is a teacher 

 of any subject or grade he deals with the biggest science 

 need of all, for those whom he teaches belong to an age 

 which science has made unlike any of its predecesssors. 

 To men in industry, commerce, and the professions, it is 

 of increasing importance that progressive workers shall 

 have knowledge not only of accomplishments of science, 

 but of the methods by which discoveries are made. 



Some thirty years ago Louis Pasteur said : 



In our century science is the soul of the prosperity of nations and 

 the living source of all progress. Undoubtedly, the tiring daily 



