ARMY SURGEON AT POTSDAM 43 



disputes as to priority. While the memoir was enthusiasti- 

 cally welcomed by the younger physicists and physiologists 

 of Berlin, who were led by du Bois-Reymond, and Helmholtz 

 to his high delight was praised by the military authorities 

 ' for the splendid practical turn that he had given to his 

 studies ', the older scientists with hardly an exception rejected 

 the ideas which the work expressed, fearing, strangely enough, 

 that such speculations would revive the phantasm of Hegel's 

 'nature-philosophy', against which they had fought so long, 

 and in the end so successfully. There was but one, after 

 Johannes Mttller the most gifted scientific thinker of the day, 

 the mathematician Joh. Jac. Jacobi, who from his profound 

 studies of the principles of mechanics clearly recognized the 

 close connexion between the work of Helmholtz and that 

 of the great French mathematicians of the preceding century. 

 Notwithstanding the doubts of his distinguished colleagues 

 Lejeune-Dirichlet and Eisenstein, he unhesitatingly proclaimed 

 the significance of Helmholtz's work, and by this gave confi- 

 dence and self-assurance to its author. In the original 

 treatise Helmholtz had only attempted to give a critical 

 survey and arrangement of the facts in the interests of 

 physiology, expecting the physicists at most to reproach him 

 for having, as a young doctor, brought forward as new what 

 was well known to them, but he now realized from the general 

 opposition that he had been the first to set forth a universal 

 law of experimental science, and to purify and free it from 

 vague philosophical and speculative reflections. 



The elementary scientific discussions about perpetual motion 

 in his parents' house had never proved its impossibility con- 

 clusively for Helmholtz, and while still a student at the 

 Friedrich-Wilhelm Institute he resorted to the works of Daniel 

 Bernoulli, d'Alembert, and other mathematicians of the eigh- 

 teenth century which he found in its library. From these he 

 obtained the strictest and most convincing proof that a per- 

 petuum mobile cannot be produced by purely mechanical forces. 

 Just as the works of a clock have no energy of their own, and 

 can only distribute evenly, over a considerable period, what 

 is supplied to them from without, so, as these great thinkers 

 showed by rigid mathematical proof for all pure motive forces, 

 our machines and apparatus have no intrinsic energy, but 



