104 EFFECTS: of HEAT 
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have ref{umed its original bulk, and by itfelf could have no 
tendency to rufh out; 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 ditcharge of ela- 
{tic 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 f{trongeft, and only 
partial where the intenfity was leis. 
Tue chemical principles ftated in a former part of this 
paper, authorifed us to expect 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 expect, 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 not 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 compreffion. 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 ; 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 
maffes included along with it, I conceived that we might for- _ 
ward our views very much by placing a {mall quantity of carbo- 
nate, 
