n6 EFFECTS of HEAT 



On the 21 ft of April 1805, a fimilar experiment was made with 

 a new barrel, bored in a fquare bar of old fable, of about two 

 and a half inch in diameter, having its angles merely rounded ; 

 the inner tube being filled with chalk. The heat was main- 

 tained during feveral hours, and the furnace allowed to burn 

 out during the night. The barrel had the appearance of found- 

 nefs, but the metals came off quietly, and the carbonate was 

 entirely calcined, the pyrometer indicating 63 . On examina- 

 tion, and after beating off the fmooth and even fcale of oxide 

 peculiar to the old fable, the barrel was found to have yielded 

 in its peculiar manner ; that is, by the opening of the longi- 

 tudinal fibres. This experiment, notwithstanding the failure of 

 the barrel, was one of the moft interefting I had made, fince 

 it afforded proof of complete fufion. The carbonate had boil- 

 ed over the lips of the little tube, {landing, as juft defcribed J 

 with its mouth upwards, and had run down to within half an 

 inch of its lower end : moft of the fubftance was in a frothy 

 ftate, with large round cavities, and a fhining furface ; in 

 other parts, it was interfperfed with angular maffes, which 

 have evidently been furrounded by a liquid in which they 

 floated. It was harder, I thought, than marble ; giving no 

 effervefcence, and not turning red like quicklime in nitric 

 acid, which feemed to have no effect upon it in the lump. It 

 was probably a compound of quicklime with the fubftance of 

 the tube. 



With the fame barrel repaired, and with others like it, 

 many fimilar experiments were made at this time with great 

 fuccefs ', but to mention them in detail, would amount near- 

 ly to a repetition of what has been faid. I fhall take notice 

 of only four of them, which, when compared together, throw 

 much light on the theory of thefe operations, and likewife 

 feem to eftablifh a very important principle in geology. Thefe 



four 



