--“ MODIFIED ly COMPRESSION. 119 
rometer gave 25°, anditheunder one 169 :. The loweft mafles 
of carbonate were featcely affected by the heat : The contents 
of the little tube had loft 2.9 percent. ; both the lump and the 
pounded chalk were in a fine faline ftate, and, in feveral places 
had run and fpread upon the infide of the tube, which I had 
not expected to fee in fuch a low heat. On the upper furface 
of the chalk rammed into the little tube, which, after its in- 
~-trodudion had been wiped fmooth, were a fet of white cryf 
tals, with fhiming facettes, large enough to be diftinguifhed by 
the naked eye, and feeming to rife out of the mafs of car-- 
bonate. I likewife obferved, that the folid mafs on which 
thefe cryftals ftood, was uncommonly tran{parent. 
In thefe four experiments, the bulk of the included air was 
fucceflively diminifhed, and by that means its elafticity in- 
‘creafed. The confequence was, that in the firft experiment, 
ewhere that elafticity was the leaft, the carbonic acid was 
allowed to feparate from the lime, in an early ftage of the 
-rifing heat, lower than the fufing point of the carbonate, and 
complete internal calcination was effefted. In the fecond 
experiment, the elaftic force being much greater, calcina- 
tion was prevented, till the heat» rofe fo high as to occa- 
fion the entire fufion of the carbonate, and its action on 
the tube, before the carbonic acid was fet at liberty by 
the failure of the barrel. In the third experiment, with {till 
greater elaftic force, the carbonate was partly conftrained, 
and its fufion accomplifhed, in a heat between 41° and 15°. 
In the laft experiment, where the force was ftrongeft of all, 
the carbonate was almoft completely protected from) decom- 
pofition by heat, in confequence of which it cryftallized and 
acted on the tube, in a temperature between 25° and 16°. 
On the other hand, the eflicacy of the carbonic acid as a 
flux on the lime, and in enabling the carbonate to a@ as a. 
flux on other bodies, was clearly evinced.; fince the firft ex- 
Ut i periment. 
