MODIFIED by COMPRESSION. 125 



On the 2d of January 1804, I made an experiment with 

 marble and chalk, with the addition of 1.1 grain of water. I 

 aimed at a low heat, and the pyrometer, though a little bro- 

 ken, feemed clearly to indicate 2 2°. Unluckily, the muzzle 

 of the large tube, which was clofed as ufual with chalk, was 

 placed uppermoft, and expofed to the ftrongeft heat. I found 

 it rounded by fufion, and in a frothy ftate. The little tube came 

 out very clean, and was fo nearly of the fame weight as when 

 put in, that its contents had loft but 0.07 4 per cent, of the weight 

 of the original carbonate. The marble was but feebly aggluti- 

 nated, but the chalk was in a ftate of firm limeftone, though it 

 muft have undergone a heat under 2 2°, or that of melting fil- 

 ver. This experiment is certainly a moft remarkable one, fince 

 a heat has been applied, in which the chalk has been chan- 

 ged to hard limeftone, with a lofs lefs than the iooodth par 

 of its weight, (exactly tjtt) \ while, under the fame circum* 

 ftances of preflure, though probably with more heat, fome of 

 the fame fubftance had been brought to fufion. What lofs of 

 weight this fufed part fuftained, cannot be known. 



On the 4th of January, a fimilar experiment was made, like- 

 wife with 1 . 1 grain of water. The difcharge of the metal 

 was accompanied with a flafh of flame. The pyrometer in- 

 dicated 2 6°. The little tube came out quite clean. Its con- 

 tents had been reduced from 14.53 to I 4*4^? difference 0.07 

 grains, being 0.47 per cent, on the original carbonate, lefs 

 than one two-hundredth part of the original weight, (exactly 

 T 4- T ). The chalk was in a ftate of firm faline marble, but with 

 no unufual qualities. 



These two laft experiments are rendered ftill more intereft- 

 ing, by another fet which I made foon after, which mewed, 

 that one efiential precaution in a point of fuch nicety 

 had been neglected, in not previoufly drying the carbonate. 

 In feveraL trials made in the latter end of the fame month, 



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