Febeuaey 7, 1896.] 



SCIENCE. 



191 



a living directed his professional studies 

 towards medicine and he became a military 

 surgeon. As a physiologist he was led to 

 the study of 'vital force'; his taste for math- 

 ematics and physics forced him to the dy- 

 namical point of view, and his first great 

 paper, prepared before he was twenty-six 

 years of age, was on the Conservation of 

 Energy. It is now nearly fifty years since 

 this essay was presented to the Physical So- 

 ciety of Berlin, and doubtless quite fifty 

 years since it was actually worked out. 

 Its excellence is shown b}^ the fact that if 

 rewritten to-day it would be changed only 

 a little in its nomenclature. Fifty years 

 ago the great law of the Conservation of 

 Energy, which will ever be regarded as the 

 anost pregnant and far-reaching generaliza- 

 tion of this century, was so far from being 

 known or recognized that many of the 

 ablest men of the time either regarded it as 

 a ' fanciful speculation' — or did not regard 

 it at all. 



As a matter of ordinary mechanics, it had 

 long been admitted that no machine could 

 create power and, as a part of that applied 

 was always lost or frittered away in friction, 

 the work coming out of a machine rnust al- 

 ways be less than that put into it. The 

 first great advance had been made by an 

 American, Benjamin Thompson, afterwards 

 Count Eumford, when he asked what be- 

 came of that part lost in friction and found 

 his answer in the heat generated thereby, 

 thus proving that ' heat was a mode of mo- 

 tion,' ' rather than an imponderable agent,' 

 as it was rather ambiguously designated up 

 to nearly the middle of this century, but 

 that all of the forces of nature were so re- 

 lated to each other as to be interconvertible 

 and that the sum total of all the energies 

 of the universe was always the same, en- 

 ergy being no more capable of creation or 

 destruction than matter ; these were great 

 facts, mere glimpses of which had been per- 

 mitted to the physicists of the early part of 



the century. Helmholtz was certainly one 

 of the first to completely grasp this splendid 

 generalization, and not more than two or 

 three others stand with him in the credit 

 which is due for its complete proof and gen- 

 eral acceptance. His first contribution had 

 the merit of being quite original in concep- 

 tion and execution, for he then knew almost 

 nothing of what others had done ; he was 

 entirely ignorant of the important paper of 

 his fellow countryman, Mayer, and knew 

 only a little of Joule's earlier work. The 

 principle of the conservation of energy, 

 which for a quarter of a century has been 

 the open-sesame to every important advance 

 in phj'sical science, was not then, to say 

 the least, a popular topic. But for five or 

 six years a young Englishman named Joule, 

 not yet thirty years old, had been engaged 

 with it and, from the point of view of the 

 engineer, had made it his own. On the 

 28th of April, 1847, he gave a popular lec- 

 ture in Manchester, where he lived and 

 died, which was the first full exposition of 

 the theory. A few weeks later Helmholtz 

 read his paper in Berlin. In England even 

 the local press refused, to publish Joule's 

 address, but finally the Manchester Courier, 

 moved by the family influence (the elder 

 Joule being a wealthy brewer) , promised to 

 insert the whole, as a special favor. In 

 Germany the subject met with only a little 

 more favorable reception, and the leading 

 scientific journal, Poggendorfs Annalen, de- 

 clined to publish Helmholtz 's paper. Even 

 at the meeting of the British Association at 

 Oxford a few months after the Manchester 

 address, when Joule again undertook the 

 exposition of his theory and his experi- 

 mental proofs of it, before what ought to 

 have been a more friendly audience, he was 

 advised by the Chairman to be brief, and 

 no discussion of his paper was invited. As 

 Joule himself relates, his presentation of 

 the subject would have again proved a 

 failure, ' if a young man had not risen in 



