Whether Heat be Matter ei- Motion, 



89f 



advanced is, I think, fufficlent to (hew that Dr. Pearfon's explanation of the fubje£l in 

 queition is neither philofophical nor admiflible ; and, for the credit of the dodtrine which 

 he efpoufes, fome more fatisfa£lory explanation fhould be given. With. refpe61: to Dr. 

 Parr's theory, that light and fire repel each other, when difengaged from matter, it appears 

 to me too fanciful to be folid, and too inconfiftent to be fupported. If light and fire repel 

 each other when difengaged from matter, by its decompofition, it is not an eafy matter to 

 fhew how they, when in ftates of freedom and confequent repulfion, were brought to- 

 gether on the fame fubftance at its formation : and, if oxygen and light repel each other, 

 as he contends, why doee light combine at once with the oxygen of nitric acid, and form 

 oxygen gas, by merely placing the acid in its way ? But this is not the hypothefis I have 

 undertaken to combat. , 



I offer this letter for your perufal, and confefs that I wifli to fee the fubje£l: impartially 

 attended to. It is painful and humiliating to fee how readily the mod glaring abfurdhies 

 are overlooked, nay, even adopted as principles, and employed as indifputable fa£ts ; and 

 po further proof is necefiary to point out the confufion and abfurdity to vi'hich fuch erro- 

 neous principles tend, than the refult of Count Rumford's experiments and reafonings on 

 the produtSlion of heat by fri£llon *; which is, that as heat thus produced by friftlon can- 

 4iot be accounted for upon the adopted principles of chemiftry, he feems inclinable to con- 

 ■clude, that it cannot be a material fubflance, and is moft probably nothing but motion !!! 

 Surely this is facrificing too much to hypothefis, to give up the convlftion of reafon, and 

 the teftimony of the fenfes, rather than fuppofe it pofiible that a favourite theory may be 

 falfe. The produflion of heat by friftion, is, no doubt, inexplicable upon the principles 

 of M. Lavoifier, which ought to excite the fufpicion of thofe who have embraced them ; 

 for, if fo fimple a fa£l cannot be explained by thofe principles, it is, at leaft, probable, that 

 they are not deferving of that confidence which is fo generally and implicitly placed ia 

 them. The production of heat, ad libitum, by fridion or percuffion between folid bodies, 

 does, however, admit of an eafy explanation, without being driven to the neceffity of 

 making caloric a non-entity, or heat a particular kind of motion t, propagated in fuch a 



particular 

 • Philof. Journal, 11. lOG. 



f The prodigious quantity of heat which follows from an apparently rainute aftion, has always been con- 

 fidered as a ftrong argument againft the hypothefis, that heat is mere motion ; but, upon clofe examination, it r» 

 found to apply to both theories. If a very minlite portion of a large mafs-of oxygen gas and carbon be ^a/is/od 

 Jlnle of •vibration (or heated), and the combination of this firft portion be fucceeded by vibrations nnd combina- 

 tions of the remaining parts of the mafs, we fhall be led to inveftigate the attraflive and repulfive powers con- 

 c?nied in the phenomena, and fhall in all probability find the tafk by no means eafy. But will our difficulties" 

 be alleviated or removed by fuppofing the prefence of a third fubftance (caloric) in previous combination with 

 the oxygen, which will certainly demand, an exhibition of fimilar powers to account for its tranfition ? What- 

 ever may be the fuppofcd play of the affinities or powers tottb caloric, it feems probable tliat the mere theory 

 might be conftrufted as well ( I do not fay better) ivilhout it. 



It has been faid that latent motion (or heat) is an abfurdity, as in terms indeed it is ; but this might be ex- 

 plained in a variety of ways. Caloric is abforbed, or motion is accumulated, in certain procef&s. Slight inci- 

 dents, not commenfiirate to the clFefl, fet them free. He who fcts the catch of the pile-engine at liberty, or dif- 

 charges a crofs-bow, or breaks the tail of Prince Rupert's drop, or communicates a fpark to a powder-maga- 

 zine, may be faid to give effeft to latent motion, or rather to deftroy the equilibrium of forces generated by 

 £Qrm<:r clForts, far fuperior to that employed to fet thdm at liberty. 



3 F a - Though 



