H, Helmholtz on the Interaction of Natural Forces. 199 



I myself, without being acquainted with either Mayer or Cold- 

 ingj and having first made the acquaintance of Joule's experi- 

 ments at the end of my investigation, followed the same path. 

 I endeavored to ascertain all the relations between the different 

 natural processes, which followed from our regarding them from 

 the above point of view. My inquiry was made public in 1847, 

 in a small pamphlet bearino; the title, ^' On the Conservation of 

 Force."* 



Since that time the interest of the scientific public for this 

 subject has gradually augmented, particularly in England, of 

 which I had an opportunity of convincing myself during a visit 

 last summer. A great number of the essential consequences of 

 the above manner of viewing the subject, the proof of which 

 was wanting w^hen the first theoretic notions were published, 

 have since been confirmed by experiment, particularly by those 

 of Joule ; and during the last year the most eminent physicist 

 of France, Regnault, has adopted the new mode of regarding 

 the question, and by fresh investigations on the specific heat of 

 gases has contributed much to its support. For some important 

 consequences the experimental proof is still w^anting, but the 

 number of confirmations is so predominant, that I have not 



. deemed it too early to bring the subject before even a non-scien- 



' tific audience. 



How the question has been decided you may already infer 

 from what has been stated. In the series of natural processes 

 there is no circuit to be found, by which mechanical force can 

 be gained without a corresponding consumption. The perpetual 

 motion remains impossible. Our reflections, however, gain there- 

 by a higher interest. 



We have thus far regarded the development of force by nat- 

 ^^'al processes, only in its relation to its usefulness to man, as 

 mechaiiical force. You now see that we have arrived at a gene- 

 ral law, which holds good wholly independent of the application 

 ^vhich man makes of natural forces; we must therefore make 

 the expression of our law correspond to this more general sig- 

 nificance. It is in the first place clear, that the woi'k which, by 

 any natural process whatever, is performed under favorable con- 



ience ; we are totally unacquainted with the generating power of each and all of 

 them, and probably shall ever remain so : we can only ascertain the normal of their 

 action : we must humbly refer their causation to one omnipresent influence, and con- 

 tent ourselves with studying their effects, and developing by experiment then- 

 mutual relations." 



"I have long held an opinion," eays 5Ir. Faraday in 18i5, "almost amounting to 

 conviction, in common I believe with mnny other lovers of natural knowledge, that 

 tlie various forms under which the forces of matter are made manifest have a com- 

 mon origin, or in other words, are so directly related aiid mutuaUy dependent, tliat 

 they are convertible one into another.'*— Te, . .£ ai 



* A translation of this most important essay appears in the Scientific Memoirs, 



new series, p. 114.— J. t. 



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