of the Laxvs of Elastic Fluids. 65 



variance with pheenomena almost whatever form we may 

 give to the function <p. It is however not my intention to pur- 

 sue them. My object has been merely to show, that M. La- 

 place's principal and fundamental equations are erroneously 

 deduced from his principles ; and consequently that his sub- 

 sequent conclusions are not consequences of what he first as- 

 sumes. 



It appears to me to be evident that the equations he 

 has produced are more the offspring of a previous know- 

 ledge of what they should be from the pluenomena, than of 

 that sound reason which his other works usually manifest. 

 Had the principles he sets out with been given him, 

 namely, that there is such a thing as caloric, which, while 

 strongly repulsive of its own, attracts and is attracted by all 

 other matter; which by some means radiates in extremely 

 minute portions with a great velocity; which attaching itself in 

 considerable quantities to particles of matter overcomes their 

 mutual attraction, and occasions them to stand at the greatest 

 distance the envelope admits from each other; — had, I say, 

 these things only been given him withoutv any knowledge of 

 what the phajnomena require, I would enture to appeal to 

 himself, whether, with his mind so unacquainted, unbiassed, 

 and unprejudiced with the facts in question, his results would 

 not have been very different to what they are. Now, so far from 

 this having been the case with myself, I was not even acquainted 

 with any other law of airs than that of Mariotte, when my 

 theories of collision and of aeriform bodies were first laid down. 

 It was not until some time afterwards that I knew any thing of 

 MM. Gay Lussac and Dalton's law ; which, from the awkward 

 synthetical course I pursued, I had some difficulty in demon- 

 stratinjT, Nor was I acquainted with the law that the pressure 

 of a mixture is equal to the sum of the pressures of the compo- 

 nent airs, until after my theory had been published; when I acci- 

 dentally met with it in Biot's Traitc de Physique while look- 

 ing over the theory of vapours. The theory of latent heat, and 

 particularly that of evaporation, was investigated under cir- 

 cumstances hicomparably more disadvantageous. Examples 

 such as these of correct fertility are, I belie\e, never to be met 

 with where nature and dieory are at variance. 



It is rather curious that M. Laplace has in effect brought 

 out the same point of absolute cold that I had. lie says that 

 all the caloric in a mass of any air at the centigrade zero, is 

 equal to 2G6| centigrade degrees, or to 266| X ^ = 480^ Fahr. ; 

 the precise quantity that I had given. 



With respect however to the Marquis de Laplace's theory 

 and mine, there are cases by which the liUe of bolh may be 



Vol. G2. No. 3013. Jidij 1K2:}. I decided 



