Jo6 Convtrfion of Iron inia Steel by the Diamond. 



fire, and allowed to cool, I found that one end of the cylinder was (lightly bliftered ; but 

 otherwife had retained its fliape and original qualities. The temperature was 152°. 



I may here once for all obferve, that I took care to examine whether the iron made ufe 

 of was real foft iron, before it was fubje£led to experiment. I likewife, in every inftance, 

 referved a part of the iron, as a ftandard with which I compared that on which the expe- 

 riment had been made. In this I was aflifted by a fkilful workman, who in my prefence 

 made trials of the hardnefs and malleability of the metal when heated to various degrees of 

 temperatnrej and alfo when cold, after having beeti ignited and plunged into water. When- 

 ever therefore, in future, I mention foft iron as remaining unaltered after an experiment, 

 I wifti it to be underftood, that it was fubjefted to thefe proofs of its malleability, and that 

 it had the fame qualities with the portion of foft iron that had been referved. 



This refult affords a proof, that iron expofed to a heat of 150° during one hour, cannot 

 be converted into fteel without the aid of carbon ; and that in the firft experiment, the 

 converfion into fteel was folely to be attributed to the a£lion of the diamond. 



Mr. Mufhel's doubt, " whether the diamond afforded even one particle of carbon to the 

 iron," is thus clearly removed. In the paper above-mentioned, he ftates it as his opinion, 

 founded on his own experiments, that when foft iron is expofed to a high temperature, 

 carbon diflblved in caloric penetrates the crucibles, and the reft of the apparatus in which 

 it is enclofsd, and converts the iron ifito fteel. In order to determine how far this opinion 

 was well founded, I made the following experiments : 



My firft objedl was to expofe foft iron to ftrong heat, in an apparatus which might abfo- 

 lutely exclude all carbonaceous matter, except fuch as might be fo dlfTolved. This I hoped 

 to accomplifh by making ufe of compa£t crucibles, and, for greater fecurity by the inter- 

 pofition of fome fubftance between the iron and the crucibles. 



On confidering vcith Dr. Kennedy what fubftance would moft efFeftually anfwer this 

 puj-pofe, we agreed that pure white felfpar (adularia) would be the beft ; for Dr. 

 Kennedy, in the courfe of an analyfis of this fubftance, having found that it began to pafs 

 into the ftate of glafs about 90°, we concluded, that before the heat was of fufficient in- 

 tcnfity to melt the iron, it would be furrounded by a vitreous mafs perfe£tly free from car- 

 bonaceous matter ; and, as we prefumed, impervious to the a£lion of carbon from with- 

 out. Another reafon for ufing adularia was, that its aftion on crucibles is but flight, 

 which would prevent any rifk of the experiment failing by their being melted. 



For the procefles next to be defcribed, I made fome fmall crucibles of the porcelain 

 clay of Cornwall, and baked them in a ftrong heat. Into one of thefe I put fome felfpar 

 in fine powder, upon which having placed a fmall cylinder of foft iron, the crucible was 

 filled with the felfpar, fo that the iron was completely furrounded with it. On this cru- 

 cible I luted a lid of the fame clay, and placed it in a HelEan crucible, which was filled up 

 with powdered felfpar. Having alfo luted a lid on the HefTian crucible, I attached to its 

 outfide a fmall clay cafe containing a pyrometer piece, and covered the whole with a coat- 

 ing of Stourbridge clay and quartzylfand. The crucible and its contents were then placed 



in 



