Dynamical Theory of Heat. 373 



a work published in 1839, and devoted more to political economy 

 than to physics, has presented considerations regarding the 

 steam-engine which closely resemble those by which I endea- 

 voured, in our first lecture, to make you comprehend the trans- 

 formation of heat into mechanical power." 



I should deem it probable that M. Verdet knows as much 

 about the labours of M. Seguin as you do, and he certainly 

 knows more about those of Mayer. But he does not see in the 

 former the annihilation of the latter. He proceeds thus : — 

 "I now come to the researches which from 1842 to 1849 defi- 

 nitely founded the science, These researches are the exclusive 

 work of three men, who without concert, and even without know- 

 ing each other, arrived simultaneously in almost the same manner 

 at the same ideas. The priority in the order of publication 

 belongs without any doubt to the German physician Jules Robert 

 Mayer, whose name has occurred so often in these lectures ; aud 

 it is interesting to know that it was by reflecting on certain ob- 

 servations in his medical practice that he perceived the necessity 



of an equivalence between work and heat He perceived in 



the act of respiration the origin of the motive power of animals ; 

 and the comparison of animals with thermic engines afterwards 

 suggested to him the important principle with which his name 



will be connected for ever We also find," continues M. 



Verdet, "in the same memoir (Liebig's Annalen, 1842) a first 

 determination of the mechanical equivalent of heat, deduced 

 from the properties of gases, which is perfectly exact in prin- 

 ciple*." You see then that I am not the only person who has 

 failed to arrive at your remarkable conclusion that " Mayer's 

 paper has no claims to novelty or correctness at all. }} 



After referring to M. Colding, M. Verdet passes on to Mr. 

 Joule. " The third inventor," he says, " of whom it remains for 

 me to speak is Mr. Joule, who perhaps has done most for the 

 demonstration of the principle and for its final adoption. His 

 first investigation, published only in 1843, is incontestably poste- 

 rior by some months to the first publications of Mayer and 

 Coldingt- All this is certainly very much at variance with your 

 statement in e Good Woods/ " Curiously enough," you there say, 

 " although similar coincidences are common, while Joule was pur- 

 suing and publishing his investigations, there appeared in Ger- 



* Page 116. 



t Though the history of the subject compels him to write thus, M. 

 Verdet recognizes in the most explicit manner the merits of Mr. Joule. 

 After giving an account of Joule's experiments, he thus addresses his 

 audience : — " Vous nerefuserez pas a voir dans le travail aujourd'hui clas- 

 sique de M. Joule le preuve experimentale de l'exactitude des nouveaux 

 pnncipes." (P. 20.) 



Phil Mag. S. 4. Vol. 25. No. 169. May 1863. 2C 



