104 EFFECTS of HEAT 



have refumed its original bulk, and by itfelf could have no 

 tendency to rufh out j the heat employed to open the barrel 

 being barely fufficient to foften the metal. Since, then, the 

 opening of the barrel was accompanied by the discharge of ela- 

 flic matter in great abundance, it is evident, that this muft have 

 proceeded from fomething fuperadded to the air originally in- 

 cluded, which could be nothing but the carbonic acid of the 

 carbonate. It follows, that the calcination had been, in part 

 at leaft, internal ; the feparation of the acid from the earthy 

 matter being complete where the heat was ftrongeft, and only 

 partial where the intensity was lefs. 



The chemical principles ftated in a former part of this 

 paper, authorifed us to expe6l a refult of this kind. As 

 heat, by increafing the volatility of the acid, tended to 

 feparate it from the earth, we had reafon to exped, that, 

 under the fame compreflion, but in different temperatures, 

 one portion of the carbonate might be calcined, and ano- 

 ther not : And that the leaft heated of the two, would be leaft 

 expofed to a change npt only from want of heat, but like- 

 wife in confequence of the calcination of the other mafs ; 

 for the carbonic acid difengaged by the calcination of the hot- 

 teft of the two, muft have added to the elafticity of the confined 

 elaftic fluid, fo as to produce an increafe of compreflion. By 

 this means, the calcination of the coldeft of the two might be 

 altogether prevented, and that of the hotteft might be hindered 

 from making any further advancement. This reafoning feemed 

 to explain the partial calcinations which had frequently occur- 

 red where there was no proof of leakage j and it opened fome 

 new practical views in thefe experiments, of which I availed 

 myfelf without lofs of time. If the internal calcination of one 

 part of an inclofed mafs, promotes the compreflion of other 

 manes included along with it, I conceived that we might for- 

 ward our views very much by placing a {mall quantity of carbo- 



nate> 



