HISTORY of the SOCIETT. 13 



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

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

 the action 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 diflblved in caloric penetrates the crucibles, 

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

 the teil of experience, it was thought proper to expo fe the foft 

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

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

 ftance which, by being interpofed between the iron and the 

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

 the white felfpar or adularia y Dr Kennedy, in an analyfis of 

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

 heat of 90°, fo that there was reafon 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 alio 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 higheft pitch, after which the crucible was 

 withdrawn.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

 The iron retained its fhape and all its properties unchanged. 

 The felfpar was reduced to a glafs, tranfparent and colourfefs» 

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

 contact, with the iron. 



Several other experiments were mad^e with the fame view 

 as this, kit, but with the circumitances varied as much as poifi- 

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

 the prefence of the diamond, was never converted into fteel; fo 



that 



