180 THOMSON ON CARNOT'S 



any temperature is known, certain information 

 may be derived with reference to the saturated 

 vapor of any liquid whatever, and, with reference 

 to any gaseous mass, without the necessity of ex- 

 perimenting upon the specific medium considered. 

 Nothing in the whole range of Natural Philosophy 

 is more remarkable than the establishment of gen- 

 eral laws by such a process of reasoning. We have 

 seen, however, that doubt may exist with reference 

 to the truth of the axiom on which the entire the- 

 ory is founded, and it therefore becomes more than 

 a matter of mere curiosity to put the inferences 

 deduced from it to the test of experience. The 

 importance of- doing so was clearly appreciated by 

 Carnot ; and, with such data as he had from the 

 researches of various experimenters, he tried his 

 conclusions. Some very remarkable propositions 

 which he derives from his theory coincide with 

 Dulongand Petit's subsequently discovered experi- 

 mental laws with reference to the heat developed 

 by the compression of a gas ; and the experimen- 

 tal verification is therefore in this case (so far as 

 its accuracy could be depended upon) decisive. 

 In other respects, the data from experiment were 

 insufficient, although, so far as they were available 

 as tests, they were confirmatory of the theory. 

 42. The recent researches of Regnault add im- 



