FOR 



SECONDARY SCHOOLS 



BY FRANCIS M. WALTERS, A.M. 



PROFESSOR OF PHYSIOLOGY, STATE NORMAL 

 SCHOOL, WARRENSBURG, MO. 



" It is quite possible to give instruction in this subject in 

 such a manner as not only to confer knowledge which is 

 useful in itself, but to serve the purpose of a training in 

 accurate observation, and in the methods of reasoning of 

 physical science." Huxley. 



D. C. HEATH & CO., PUBLISHERS 



BOSTON NEW YORK CHICAGO 



