POPULAR LECTURES 



ON 



SCIENTIFIC SUBJECTS, 



BY 



H. HELMHOLTZ, 



IT 



PROFESSOR OF PHYSICS IX THE UNIVERSITY OF BERLIN 



TRANSLATED BY 



E. ATKINSON, PH.D. F.C.S. 



PROFESSOR OF EXPERIMENTAL SCIENCE, STAFF COLLEGE. 



B U A II Y 



^Y OF | 



CAL1FOUN1A. 



LONDON : 

 LONGMANS, GKEEN, AND CO. 



1881. 



All rights reserved. 



