98 EFFECTS of HEAT 



A curious circumflance 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 2 8° was 

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

 the carbonic acid had efcaped through its pores. When bro- 

 ken, 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- 

 llance, which proved to be quicklime ; the fphericles being 

 interfperfed through the flag, as fpar and agates appear in 

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

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

 rical form of the quicklime feems to fhew, that the carbonate 

 had been in fufion 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 publifhed 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 

 poffible to eftablifh, by experiment, the truth of all that was 

 hypothetically aflumed in the Huttonian Theory. 



The principal object was now to accomplifh the entire fu- 

 fion of the carbonate, and to obtain fpar as the refult of that 

 fufion, in imitation of what we conceive to have taken place 

 in nature. 



It was likewife important to acquire the power of retaining 

 all the carbonic acid of the carbonate, both on account of the 

 fact itfelf, and on account of its confequences ; the refult be- 

 ing vifibly improved by every approach towards complete fa- 

 turation. I therefore became anxious to inveftigate the caufe 

 of the partial calcinations which had always taken place, to 



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