HISTORT of the SOCIETr. 13 



152°. Hence it was natural to conclude, that the converfion 

 into fteel in the former experiment, is folely to be attributed to 

 the aflion of the diamond. It had been fuggefted by the gen- 

 tleman above alluded to, that when foft iron is expofed to a high 

 temperature, carbon difTolved in caloric penetrates the crucibles, 

 and converts the iron into fteel. To bring this hypothefis to 

 the teft of experience, it was thought proper to expofe the foft 

 iron to a ftrong heat in an apparatus which muft exclude all 

 carbonaceous matter, except fuch as was fo difTolved. The fub- 

 {lance which, by being interpofed between the iron and the 

 crucibles, feemed to be inofl likely to anfwer this purpofe, was 

 the white felfpar or adularia ; Dr Kennedy, in an analylis of 

 this fubftance, having found that it began to be vitrified in a 

 heat of go °, fo that there was reafou-to think, that before the 

 heat was intenfe enough to melt the iron, the iron would be 

 furrounded by a mafs free from carbonaceous matter, and im- 

 pervious alfo to carbon coming from without. 



Into a fmall crucible, made of the porcelain clay of Corn- 

 wall, was put fome felfpar in fine powder, and upon this a 

 fmall cylinder of foft iron, after which the crucible was filled 

 with the felfpar, which therefore furrounded the iron on all 

 fides. The crucible was then placed in an air furnace, in which 

 the heat was gradually raifed for an hour, and continued for 

 another hour at its highcft pitch, after which the crucible was 

 withdrawn. The heat marked by the pyrometer was' 152°. 

 |Thi^. iron retained its fliape and all its properties unchanged. 

 The felfpar was, reduced to a glafs, .tranfparent and colourlefs) 

 except that it had received a greenifh tinge where it was in 

 conta<5t. with the iron. 



Several other experiments were madie with the fame view 



j^_tjl^isj\aft,, but .with the circumflances varied as much as polfi- 



ble, and in all the refult was the fame ; that is, the iron, without 



;h^ pyefence of the diamoad, ,was.nev;«;r;(;<)ftyer!Ce.d into Heel; fo 



■'-■ ■• • - v'^^'•^^N-=K that 



