MODIFIED ty COMPRESSION. 95 
the whole, were fatisfactory, fince they feemed to eftablith fome 
of the effential points of this inquiry. 
_ THESE experiments prove, that, by mechanical conftraint, 
the carbonate of lime can be made to undergo ftrong heat, 
without-calcination, and to retain almoft the whole of its car- 
bonic acid, which, in an open fire, at the fame temperature, 
would have been entirely driven off: and that, in thefe circum- 
ftances, heat produces fome of the identical effe@s afcribed to 
it in the Huttonian Theory. 
By this joint ation of heat and preflure, the carbonate of 
lime which had been introduced in the ftate of the fineft 
powder, is agglutinated into a firm mafs, poffefling a degree of - 
hardnefs, compactnefs, and fpecific gravity *, nearly approach- 
ing to thefe qualities in a found limeftone; and fome of the 
refults, by their faline fracture, by their femitranfparency, and 
their fufceptibility of polith, deferve the name of marble. 
Tue fame trials have been made with all calcareous fub- 
ftances ; with, chalk, common limeftone, marble, f{par, and 
the fhells of fifh. All have fhewn the fame general. property, 
with fome varieties as to temperature. Thus, I found, that, 
in the fame circumftances, chalk was more fufceptible of .ag- 
glutination than {par ; the latter requiring a heat two degrees. 
higher than the former, to bring) it it to. the fame pitch of ag-- 
glutination. 
Tue chalk ufed in my firft experiments, always affumed the- 
* character of a yellow marble, owing probably to fome flight 
contamination of iron. When a folid piece of chalk, whofe 
bulk had been previoufly, meafured in the gage of Wedgwood’s. 
pyrometer was fubmitted to heat’ under compreffion, its con- 
traction was remarkable, proving the approach of the particles 
during their confolidation ; on thefe occafions, it was found. 
ta: 
* See’ Appendix, 
