12 HIST'ORT of the SOCIETr. 



The cylinder being then placed in a Heffian crucible, and fur- 

 rounded with a mixture of dry fand and clay, was fubjected to 

 the fire of a fmith's forge for an hour. When taken out, the 

 pyrometer indicated 151 ° ; the upper, part of the iron appeared 

 to have been melted, and feveral bright metallic globules were 

 feen adhering to the compacted mafs of fand and clay next the 

 iron. The lower part of the cylinder retained its fhape, but 

 was bliftered on the furface, except at the bottom, which remain- 

 ed fmooth. When the ends were polifhed and touched with 

 diluted nitric acid, they exhibited the fpot characteristic of fleel, 

 that on the end which had been fufed being confiderably* dark- 

 er than the other. The part which had remained fmooth after 

 being cut off, was heated red hot, and plunged into cold water, 

 when it became fo hard, that it received no imprefhon from a 

 file. Several cavities were found within the cylinder, but the 

 diamonds had totally difappeared. 



The whole cylinder of foft iron was thus converted into 

 fteel ; one end of it having been melted, was in the ftate of call 

 fleel ; the other end, having remained folid, was of the kind of 

 fteel produced by cementation. 



A gentleman of the ClydeTronworks having about that 

 time been led, by fome experiments, to doubt of the; conclufive- 

 nefs of thofe made by Guyton, and to fufpect that the dia- 

 mond had contributed nothing to the converlion of the iron 

 into fleel, Sir George Mackenzie thought it, necefTary to 

 direct fome experiments to the folution of this queftion. 



In one of thefe a piece of foft iron, in all refpects fimilar.to 

 that ufed in the laft experiment, was expofed to the fame degree 

 of heat as in that experiment, and with all the circumftances 

 alike, except that the diamonds were, wanting. The refult was, 

 -that the. iron was not altered in its mape or qualities. It had 

 been expofed to the heat an hour, antf the pyrometer marked 



- % - I 5 2 ° 



