712 herma:nn von helmholtz. 



of course depends n]>on whether the premises are admitted to be axi- 

 omatic; but it was followed by an appeal to experiment. The greater 

 part of the memoir was occupied with an elaborate discussion as to 

 whether the law of the couservation of energy was consistent with the 

 facts then known. This involved a survey of the api)li<'ation of the law 

 to mechanics, heat, electricity, magnetism, and electro-magnetics. A 

 number of most interesting calculations and suggestions were made, 

 and the conclusion arrived at was ''that the law of the conservation of 

 energy does not contradict any known fact in natural science, but in a 

 great number of cases is, on the contrary, corroborated in a striking- 

 manner." 



The author was acquainted with the earlier experiments of Joule 

 only, and, while employing the idea of a mechanical equivalent of heat 

 and using symbols to represent it, dismisses the results of observation 

 as having but ^-little claim to accuracy." It need hardly be said that 

 this opinion was not afterwards extended to the later investigations, 

 which were only just then becoming known. 



In a note appended, when the essay was republished in 1881, Von 

 Helmholtz expressly disclaimed any right to priority as an originator 

 of the doctrine of conservation of energy, but his essay is the more 

 remarkable on account of his slight acquaintance with the Avork of his 

 predecessors. lie knew nothing of Mayer, and his information as to 

 Joule's experiments Avas only gained after his own work was far 

 advanced. 



Enough has, perhaps, been said to show that he must, as Professor 

 Tait asserts, "be classed as one of the most successful of the early pro- 

 moters of the science of energy on legitimate principles." 



The ])aper on the Conservation of Energy was only the third or 

 fourth which Helmholtz had published, but his remarkable abilities 

 were now fully recognized. 



His connectiou Avith the army was scA'ered in 1848. For some mouths 

 he was an assistant in the Anatomical Museum of Berlin, and also 

 teacher of anatomy at the Academy of Arts. After this he held in 

 succession the professorships of physiology in the universities of 

 Konigsberg, Bonn, and Heidelberg, and in 1871 he Avas appointed pro- 

 fessor of natural philosoi^hy in the ITniversity of Berlin. 



Honors of all sorts were showered upon him. Late in life he was 

 ennobled by the German Emperor, and the esteem in Avhich he was held 

 in this country Avas proA^ed by the aAvard of the Copley medal, the high- 

 est distinction in the gift of the Eoyal Society. 



It would be impossible to follow in chronological order the work 

 which Yon Helmholtz gaA^e to the Avorld during these long years. The 

 most that can be attempted is to convey some idea of its importance. 

 He was great as a mathematician and i^hysicist, but the direction of 

 his most characteristic efforts Avas probably determined by the early 

 necessity for seeking a livlihood by the practice of medicine. On the 



