ON THK MATERIALITY OS CA10RIC 2(35' 



fceat by different bodies; On this theory, there is no active It ufually im- 

 principle or power inherent in bodies, and more active in but $ merc l«Ica- 

 fome than in others, — no tendency in the matter of heat to Hty. 

 attach itfelf, in preference to any one fubftance. The af- 

 figned caufe of the phenomena of heat is not, I apprehend, 

 adequate to produce the effects afcribed to it. 



On the theory of capacities, a change of form is, in certain By this theory 

 Initances, antecedent to the abforption of caloric. Thus, %^™*™ 

 when ether is converted into gas, on removing the prefliire precede the 

 of the atmofphere, according to this hypothefis, the capacity J^"' 011 of 

 ©f the ether is increafed by its volatilization ; and the change 

 of form is prior to, and the caufe of, the abforption of caloric. 

 The order of events, then, in the volatilization of ether, is 

 firft an alteration of form ; next a change of capacity ; and 

 laftly an abforption of caloric. On this hypothefis, ether may 

 exift in the (rate of gas, without containing a greater abfolute 

 quantity of caloric, than in a liquid form. But fuch an inter- 

 pretation of phenomena is directly contradictory to an efta- 

 bliflied principle, admitted, even by thofe who prefer the 

 doctrine of capacities, viz. that all bodies, during their con- 

 verfion from a fluid to a vaporous ftate, abforb caloric. It is 

 at variance, alfo, with obferved fa&s : for if a thermometer 

 be immerfed in a portion of ether, confined under the receiver 

 of an air pump, the temperature of the ether will be found to 

 (ink gradually, during the exhauftion of the air ; and the eva- 

 poration becomes proportionally flower, till, at laft, it is 

 fcarcely perceptible. We may, therefore, infer, that at a 

 certain point of diminiihed temperature, the volatilization of 

 ether would entirely ceafe, if the fupply of caloric, from fur- 

 rounding bodies, could be completely intercepted. But on 

 the theory of capacities, the evaporation fTiould proceed as 

 rapidly at the clofe, as at the commencement, of the procefs 

 — or, in other words, evaporation fhould be wholly indepen- 

 _dent of temperature, which every one knows is contrary to 

 faa. 



It may be confidered therefore, as extremely probable, that Whence It la 

 the tendency of ether to aiTume a gafeous form depends on its J?°* j^^., 

 chemical affinity for caloric. But, (it may be afked) how is arife from affi- 

 this affinity counteracted by an increafed preflure, and aug- mt y* 

 »ented by a diminiihed one ? 



A cir- 



