PHYSICAL SCIENCE. 49 



attained in animal and vegetable physiology at large, and 

 very especially in the great department of Human Phy- 

 siology, that not even the briefest summary could bring the 

 subject within our present limits ; and we must postpone to 

 another time the notice of these eminent discoveries, and of 

 the works which best describe and illustrate them. 



What has been derived, however, from other branches of 

 physical science will, we trust, adequately fulfill our intention 

 of showing in what spirit all such science has been recently 

 pursued ; and what signal success it has obtained in com- 

 passing and expounding the great phenomena of the natural 

 world. Happy those who can work tranquilly amidst these 

 wonders of nature, animated by the love of knowledge for its 

 own sake, and undisturbed by the storms which are ever 

 agitating and vexing the world without.* 



* It is always interesting, as well as important, to learn the different methods 

 by which men of genius arrive at a common truth. When the first edition of 

 this volume was published, I knew but by name only the remarkable writings 

 of Dr. Mayer of Heilbronn (appearing under various dates from 1842 to 1851), 

 in which the doctrine of the mutual convertibility of certain of the physical 

 forces is maintained by bold and ingenious argument; anticipating in part 

 those inductive proofs, which have now given it the character of a great phy- 

 sical law. His earlier views chiefly appertain to the equivalent relations of 

 Heat and Mechanical Force ; but in later memoirs he extends his argument to 

 other forces, including those which act in the phenomena of organic life. 



