' XXXI 

 HERMANN VON HELMHOLTZ 



1821-1894 



Hermann von Helmholtz, horn at Potsdam, Prussia, August ji, 

 1821, studied medicine at the University of Berlin, from which he re- 

 ceived his degree in 1842. He then entered the German Army as sur- 

 geon and in 184/ published his paper on ''The Conservation of En- 

 ergy," zvhich summarized historically the development of the idea. 

 In 184P he was appointed professor of physiology and general 

 pathology at Konigsberg. In 1855 ^^ '^'^^ called to Bonn, and in 

 18 j8 was elected to the chair of physiology at Heidelberg, 



In 18^1 he invented the ophtJialmoscope and later at Heidelberg lie 

 continued his researches in the subject of sight, and also cleared up 

 the problem of the mechanical causes of sound. In 18/1 he was ap- 

 pointed professor of physics at the University of Berlin, where he re- 

 mained until his death, September 8, 18Q4. 



THE CONSERVATION OF ENERGY * 



A new conquest of very general interest has been recently made by 

 natural philosophy. In the following pages I will endeavour to give a 

 notion of the nature of this conquest. It has reference to a new and 

 universal natural law, which rules the action of natural forces in their 

 mutual relations towards each other, and is as influential on our theo- 

 retic views of natural processes as it is important in their technical 

 applications. 



Among the practical arts which owe their progress to the develop- 

 ment of the natural sciences, from the conclusion of the middle ages 

 downwards, practical mechanics, aided by the mathematical science 

 which bears the same name, was one of the most prominent. The 



* Translated from Vber die Erhaltung der Kraft (Berlin, 1847). 



273 



