Very many 

 Were durable 

 garble. 



Remarkable 

 faft. 



381^ ACTION OF HEAT MODIflEB 



fpeclmen produced on the 3d of March, 1801, though a frefh 

 fradure has reftored it. 



A fpecimen, too, of marble, formed from pounded fpar, on the 

 I5th of May, 1 801 , was fo complete as to deceive the workman 

 employed to pohai it, who declared, that, were the fubftance 

 a little whiter, the quarry from which it was taken would be 

 of great value, if it lay within reach of a market. Yet, in a 

 few weeks after its formation, it fell to duft. 



Numberlefs fpecimens, however, have been obtained, which 

 reiift the air, and retain their polifti as well as any marble. 

 Some of them continue in a perfed flate, though they have 

 beffa kept without any precaution during four or five years. 

 That fet, in particular, remain perfectly entire, which were 

 fliewn laft year in this Society, though fome of them were 

 made in 1799, fome in 1801 and 1802, and though the firfl 

 eleven were long foaked in water, in the trials made of their 

 fpecific gravity. 



A curious circumftance occurred in one of thefe experi- 

 ments, which may hereafter lead to important confequences. 

 Some ruft of iron had accidentally found its way into the 

 tube : 10 grains of carbonate were ufed, and a heat of 28*^ was 

 applied. The tube had no flaw ; but there was a certainty 

 iliat the carbonic acid had efcaped through its pores. When 

 broken, the place of the carbonate was found occupied, partly 

 by a black flaggy matter, and partly by fphericles of various 

 fizes, from that of a fmall pea downwards, of a white fub- 

 fiance, which proved to be quicklime; the fphericles being 

 interfperfed through the flag, as fpar and agates appear in 

 whinflone. The flag had certainly been produced by a mix- 

 ture of the iron with the fubftance of the tube ; and the fphe- 

 rical form of the quicklime fecms to fliew, that the carbonate 

 had been in fuflon along with the flag, and that they had 

 feparated on the efcape of the carbonic acid. 



The fubject was carried thus far in 1803, when I fliould 

 probably have publiflied my experiments, had I not been in- 

 duced to profecute the inquiry by certain indications, and 

 « accidental refults, of a nature too irregular and uncertain to 



meet the public eye, but which convinced me, that it was 

 poflible to eftablifli by experiment the truth of all that was 

 bypothetically aflumed in the Huttonian theory. 

 Endeavour to The principal objed was now to accomplifli the entire fu- 



mprove Che ex- f^^jj q[ jj^g gftrbonate, and to obtain f^^ar as the refuU of that 



peiiments by 



fufion 



