JQQ ON THE MATERIALITY OF CALORIC. 



fchool foine forcible arguments have lately been advanced by 



Count Rumford and by Mr. Davy, both of whom have ado.pt T 



ed that theory refpeciing heat, which affigns, as its caufe, a 



motion among the particles of bodies, 



Mr. Davy's op- The method of reafoning, employed by Mr. Davy, in 



mallTofhe^t is Paving the immateriality of the caufe of heat, is the reduBia 



hyreduftioadab-iid abfurdum, i. e. the oppugned theory is afmme:l as true, 



furdum. together with its applications ; and facts are adduced, dire&ly 



contradictory of the afllimed principles. I flip.ll take the liberty 



of offering a ftatement of the argument, rather different from 



that of Mr. Davy ; though I trull without mifreprefentation, 



or any material omiffion. 



Another ftate- Let heat be confidered as matter ; and let it be granted, 



ment: Ailum- ^ t ^ temperature of bodies depends on the pretence of un- 

 ing the exiftence .«" .„, , r i . i • 



•f caloric, &c. combined caloric. Now, if the temperature of a body be in- 



creafed, the free caloric, occasioning that elevation, muft 

 proceed from one of two fources ; either, \J}ly> It may be 

 communicated by furrounding fubfiances; or, 2<%, It may 

 proceed from an internal fource, i. e. from a difengagement 

 of what before exifted in the body, latent or combined. But 

 the temperature of bodies is uniformly increafed by friction and 

 percuflion, and, neceilarily, in one of the foregoing modes. 

 Heat by friction & Mr. Davy found, by experiment, that a thin metallic plat« 

 in vacuo, was heated by friction in the exhaufted receiver of an air- 



pump, even when the apparatus was infulated from bodies 

 capable of fupplying caloric, by being placed on ice. This 

 experiment he confiders as demonftrating, that the evolved 

 caloriccould not be communicated by furrounding bodies, 

 does not exclude To the inference deduced from this experiment it may be 

 caloric, objected, that the mode of inhalation was by no means perfect. 



Admitting the vacuum produced by the air-pump to have been 

 complete, Hill the fupply of caloric could not thus be intirely 

 becaufe a vacu- cut off} fince it has been (hewn by Count Rumford, that ca- 

 ura conducts. i or i c pailes even through a torricellian vacuum. If, therefore, 

 friction produce in bodies fome change, which enables them 

 to attract caloric from furrounding fubftances, this attraction 

 may be equally efficient in an exhaufted receiver, as in one 

 containing an atmofphere of mean denfity. It would be an 

 interefting fubject of experiment, to determine the influence of 

 atmofpheres of various denh* ties, as conductors of caloric ; for, 

 fince effects are proportionate to their caufe?, ancl.it is afcer- 

 3 tained 



