THE CONSERVATION OF ENERGY 



was yet another road which led just as surely and 

 even more readily to the same goal. This was the 

 road furnished by the phenomena of heat, and the 

 men who travelled it were destined to outstrip their 

 fellow-workers ; though, as we have seen, wayfarers on 

 other roads were within hailing distance when the 

 leaders passed the mark. 



In order to do even approximate justice to the men 

 who entered into the great achievement, we must recall 

 that just at the close of the eighteenth century Count 

 Rumford and Humphry Davy independently showed 

 that labor may be transformed into heat ; and correctly 

 interpreted this fact as meaning the transformation of 

 molar into molecular motion. We can hardly doubt 

 that each of these men of genius realized vaguely, at 

 any rate that there must be a close correspondence 

 between the amount of the molar and the molecular 

 motions; hence that each of them was in sight of the 

 law of the mechanical equivalent of heat. But neither 

 of them quite grasped or explicitly stated what each 

 must vaguely have seen; and for just a quarter of a 

 century no one else even came abreast their line of 

 thought, let alone passing it. 



But then, in 1824, a French philosopher, Sadi Car- 

 not, caught step with the great Englishmen, and took a 

 long leap ahead by explicitly stating his belief that a 

 UTinite quantity of work could be transformed into a 

 lite quantity of heat, no more, no less. Carnot did 

 not, indeed, reach the clear view of his predecessors as 

 to the nature of heat, for he still thought it a form of 

 "imponderable" fluid; but he reasoned none the less 

 clearly as to its mutual convertibility with mechanical 



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