SUGGESTIONS TO TEACHERS vii 



Company, Riehle Brothers, National Carbon Company, 

 Inc., Southern Pine Sales Corporation, Worthington Pump 

 and Machinery Company, Western Electric Company, 

 Greenfield Tap and Die Corporation. 



Acknowledgment is also made of indebtedness to those 

 teachers who have kindly read the manuscript arid offered 

 valuable suggestions. 



The author will be pleased to receive any constructive 

 criticism of the book. 



WILLIAM H. DOOLEY. 



NEW YORK CITY, 

 August 15, 1919. 



SUGGESTIONS TO TEACHERS 



The arrangement of this book is such that it may be 

 used equally well by science teachers in the regular secondary 

 and technical schools and by science teachers in vocational 

 schools. When used in connection with a year's course in in- 

 dustrial science in the technical, industrial, or manual training 

 courses of regular secondary schools, it will aid in correlat- 

 ing the principles of science with shop observation and 

 experience. 



The method of presenting the subject of industrial science 

 in a vocational school should be different from the method 

 used in the regular high school, since there is a wide difference 

 both in the aims of the courses and in the types of pupils. In 

 the vocational school it is well to consider first the practices 

 of the trades and industries as based on practical shop ex- 



