HELMHOLTZ IN BERLIN 



scientific value of Helmholtz's little essay on the 

 Conservation of Force, we should have to ask those 

 to whom we owe the greatest discoveries in thermo- 

 dynamics and other branches of modern physics, how 

 many times they have read it over, and how often 

 during their researches they felt the weighty state- 

 ments of Helmholtz acting on their minds like an 

 irresistible driving power ? ' I 



The essay was read to the Physical Society of 

 Berlin on the 23rd of July 1847, an( ^ ^ created much 

 excitement in the distinguished band of youthful 

 workers. The author showed himself, at one stroke, 

 to be a mathematician of the first order, but he also 

 enunciated as a fundamental principle of physics the 

 conservation of force, just as Lavoisier, seventy years 

 before, had made that of the persistence of matter the 

 fundamental principle of chemistry. He showed that 

 ' if the forces acting between material bodies were equi- 

 valent to attractions or repulsions between the particles 

 of these bodies, the intensity of which depends only on 

 the distance, then the configuration and motion of 

 any material system would be subject to a certain 

 equation, which, when expressed in words, is the 

 principle of the conservation of energy.' 2 In less 

 technical language, he established mathematically that 

 'force' (Kraft), or, as it is now termed, energy, is 

 indestructible, and he shows that this principle 'con- 

 tradicts no known parts of science, while it is con- 



1 Nature, op. cit. 2 Clerk Maxwell, Nature, of, clt. 

 41 



