198 H. Ilehnholtz on the hiteraction of Natural Forces. 



net of reciprocal actions, a track throngli chemical, electrical, 

 magnetical, and thermic processes, back to mechanical actions, 

 Avhich might be followed with a final gain of mechanical work : 

 thus wonkl the perpetvial motion be found. 



Butj warned by the futility of former experiments, the public 

 had become \viser. On the whole, people did not seek much 

 after combinations which promised to furnish a perpetual motion, 

 but the question was inverted. It was no more asked, how can 

 I make use of the known and unknoAvn relations of natural 

 forces so as to construct a perpetual motion ? but it was asked, 

 if a perpetual motion be impossible, what are the relations which 

 must subsist between natural forces ? Everything was gained 

 by this inversion of the question. The relations of natural 

 forces rendered necessary by the above assumption, might be 

 easily and completely stated. It was found that all known rela- 

 tions of forces harmonize with the consequences of that assump- 

 tion, and a series of unknown relations were discovered at the 

 same time, the correctness of which remained to be proved- If 

 at single one of them could be proved false, then a perpetual 

 motion would be possible. 



The first who endeavored to travel this way was a Frenchman 

 named Carnot, in the year 1824. In spite of a too limited con- 

 ception of his subject, and an incorrect view as to the nature of 

 heat, which led him to some erroneous conclusions, his experi- 

 ment was not quite unsuccessful. He discovered a law which 

 now bears his name, and to which I will return further on. 



His labors remained for a long time without notice, and it was 

 not till eighteen 3'ears afterwards, that is, in 1842, that different 

 investigators in different countries, and independent of Carnot, 

 laid hold of the same thought. The first who saw truly the 

 general law here referred to^ and expressed it correctly, was a 

 rnian physician, J. R Mayer of Ileilbronn, in the year 1842. 

 little later, in 1843, a Dane named Colding, presented a me- 

 moir to the Academy of Copenhagen, in which the same law 

 found utterance, and some experiments were described for its 

 further corroboration. In England, Joule began about the same 

 time to make experiments having reference to the same subject 

 We often find, in the case of questions to the solution of which 

 the development of science points, that several heads, quite inde- 

 pendent of each other, generate exactly the same series of re- 

 flections,* 



* The following extract is taken from a lecture by Mr. Grove, delivered at the 

 LoniJon Institution on the I9th of January, 1842: — " 



'• Light, heat, electricity, maarnetisni, motion, and chemicnl affinity, nre all convert- 

 ible juateriiil affections; assujuing any one aa a cause, one of tlie others will be the 

 effect. Thus heat may be said to produce electricity, electricity to produce heat; 

 magnetism to produce electricity, electricity magnetism; and ?*> of thf re^^t. Cause 

 and effect, therefore, in their relation to such forces, are words solely of couveri- 



A 



