50 PROCEEDINGS OP THE AMERICAN ACADEMY 



have now been placed in the hands of two students of mechanical 

 engineering in a well known Professional School, and I look for 

 interesting results from their work. 



For indispensable assistance in the work which this article de- 

 scribes I am indebted to Messrs. Barron, Curtis, Hale, Kendrick, 

 and Page, members of a class at Harvard College engaged in a 

 study of the steam-engine. 



