MODIFIED by COMPRESSION. 95 



the whole, were fatisfaclory, lince they feemed to eftablifh fome 

 of the elTential points of this inquiry. 



These experiments prove, that, by mechanical conflraint, 

 the carbonate of lime can be made to undergo flrong heat, 

 without calcination, and to retain almofl 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 a&ion of heat and prefliire, the carbonate of 

 lime which had been introduced in the ftate of the fineft 

 powder, is agglutinated into a firm mafs, poiTefling a degree of 

 hardnefs, compa&nefs, and fpeeific 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 poliiTi, deferve the "name of marble. 



The fame trials have been made with all calcareous fub- 

 fiances ; with chalk, common limeftone, marble, fpar, 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 cireumftances, chalk was more fufceptible of .ag- 

 glutination than fpar ', the latter requiring a heat two degrees 

 higher than the former, to bring it to the fame pitch of ag- 

 glutination. 



The chalk ufed in my firft experiments, always aflumed the 

 ehara&er of a yellow marble, owing probably to fome flight 

 contamination of iron. When a folid piece of chalk, whofe 

 bulk had been previouily meafured in the gage of Wedgwood's 

 pyrometer was fubmitted to heat under compreilion, its con- 

 traction was remarkable, proving the approach of the particles 

 during their, confolidation ; on thefe occafions, it was found 



to 



* See Appendix. 



