PREFACE vii 



discussions of politics that seem to be our guide are empty appear- 

 ances. What really leads us forward are a few scientific discoveries 

 and their applications. 



And the following is quoted from a recent statement 

 by President James R. Angell: 



Nothing can be more certain than that the character and rapidity 

 of our national development in all matters which relate to industry, 

 agriculture, public health and the preservation of the physical 

 framework of our civilization will be dependent upon the quantity 

 and quality of sound research which is carried on. The truth of 

 this assertion becomes even more apparent when one recognizes the 

 fact that every modern nation stands in relation of industrial and 

 commercial competition with other nations, and, in the measure in 

 which this is true, to fall behind the others in scientific development 

 is to precipitate a trend of events which spells national depression 

 and disaster. In other words, the price of a sound, comprehensive 

 national life is, in these times, widespread and intelligent scientific 

 research. 



Men need and desire a genuine interpretation of 

 modern science as it appears in the home, street, and 

 factory. They want to know its meaning in public 

 health, in industry, in social relations, and above all 

 in the adjustment of their philosophy to the scientific 

 truths of the modern world. 



This volume is especially designed to assist the 

 teacher of courses in general science or the special 

 sciences by bringing textbooks up to date and suggest- 

 ing possible occupations to young people who really 

 need guidance in finding callings which appeal to them 

 as fields of opportunity and usefulness. 



It is expected also that the public will find this volume 

 a convenient and engaging means of catching up with 



