HISTORY OF THERMOTICS. 



liquids, the attraction of the particles for the caloric, 

 in airs, the repulsion of the caloric. But the doc- 

 trine of latent heat again modifies 7 the hypothesis, 

 and makes it necessary to include latent heat in the 

 calculation; yet there is not, as we might hope 

 there would be if the theory were the true one, any 

 confirmation of the hypothesis resulting from the 

 new class of laws thus referred to. Nor does it 

 appear that the hypothesis accounts for the rela- 

 tion between the elasticity and the temperature of 

 steam. 



It will be observed that Laplace's hypothesis 

 goes entirely upon the materiality of heat, and is 

 inconsistent with any vibratory theory ; for, as 

 Ampere remarks, " It is clear that if we admit heat 

 to consist in vibrations, it is a contradiction to attri- 

 bute to heat (or caloric) a repulsive force of the 

 particles which would be a cause of vibration." 



An unfavourable judgment of Laplace's theory 

 of gases is suggested by looking for that which, in 

 speaking of optics, was mentioned as the great cha- 

 racteristic of a true theory ; namely, that the hypo- 

 theses, which were assumed in order to account for 

 one class of facts, are found to explain another class 

 of a different nature : the consilience of inductions. 

 Thus, in thermotics, the law of an intensity of radia- 

 tion proportional to the sine of the angle of the ray 

 with the surface, which is founded on direct experi- 

 ments of radiation, is found to be necessary in order 

 1 Mtc. Ctl. t. v. p. 93. 



