i.o8 ExperUnents on Iron at elevated Temperatures., is^c. 



at the end of which I found the outer crucible vitrified, but the interior ones intlrc. The 

 pyrometer mcafured 153°, and the iron remained unchanged. 



Finding that under the circumftances above-mentioned no carbon penetrated to the iron, 

 I now refolved to repeat Mr. Muftiet's firft experiment, following exa£lly the procefs which 

 he has defcribed ; and as he does not inform us what kind of crucibles he ufed, I took 

 Englifli crucibles, which are lefs compaft than the Heffian. 



Mr. Mufhet fays, that he ufed fand, obtained by pounding the (tone of which the fur- 

 nace hearths at Clyde Iron Works are made. I am unacquainted with this particular flone ; 

 but it is well known, that many fand-ftones contain coaly matter. I therefore made ufe of 

 Lynn fand. 



Into an Englifli crucible I put three fmall cylinders of foft iron, and on this luted a lid 

 made of fand, with a very fmall proportion of clay. I placed this in a larger crucible con- 

 taining fome fand, and covered it up with the fand, till the outer crucible was almoft full. 

 Having adjufted a lid to it, I placed the whole in the air furnace. The fire was managed 

 as in the former experiments, and the greatell heat continued for one hour and a half, 

 when the crucibles were taken out entire. • 



Part of the interior crucible, and the oxide of the iron, occafioned by the included air 

 had entered into fufion, and formed a fmall quantity of brownifh glafs. The three pieces 

 of iron adhered flightly together, and on thofe parts which had not been in conta£t with 

 the glafs, there was a thin film of oxide, which eafily fcaled off: but the fliape of the cy- 

 linders was not altered. On feparating them, I found that they retained all the qualities 

 of foft iron. Their foftnefs muft therefore have been fuch as to unite them by a procefs 

 fimilar to that of welding. 



As Mr. Mufliet informs us, that in one of his experiments his crucible was cracked, I 

 conceived that carbon might have found acccfs to the iron through the aperture in the form 

 of carbonic acid, of flame, or of fmoke. In order, therefore, to afcertain how far the 

 procefs was affefted by this circumftance, I followed the detail of his experiment precifely ; 

 uCng a cracked crucible, and fand pounded from a fand flone, in which, however, I could 

 difcover no traces of coaly matter. The heat in this experiment was continued for an hour 

 and a half. The iron remained unchanged. 



With the fame view I made a fecond experiment, which I imagined would be ftill more 

 decifive. A fmall (hallow crucible containing a cylinder of foft iron, fimilar to thofe for- 

 merly ufed, was placed in a larger one, through the fides of which I had bored three holes. 

 In this inftance, no fand was introduced into either of them. Having adjufted a lid to the 

 outer crucible, I expofed the whole to the greateft heat that the forge could produce for 

 forty-five minutes 5 after which the iron was found not to have received any alteration ia 

 its qualities. 



In the experiments already defcribed, the heat generally exceeded 150, but was not of 

 fufficient intenfity to melt the iron, and the refults would fcarcely have fatisfied me, had I 



not 



