3 56 Effects of Heal modified by Compression. 



air-tube was used, and, the heats being low, the air lodged 

 in interstices had been sufficient to secure the barrels from 

 destruction by the expansion of the liquid metal. In this 

 view, likewise, I often used lead, whose expansion in such 

 low heats I expected, to be less than that of the fusible metal. 

 And the lead requiring to melt it a beat very near to that of 

 redness, the subject of experiment was thus, on removing 

 the cradle, exposed in freedom to a temperature which was 

 comparatively high. But_, observing that a great loss was 

 thus occasioned, I returned to the use of the fusible metal, 

 together with my former method of melting it, by plunging 

 the barrel, when removed from the furnace, into a solution 

 of muriate of lime, by which it could only receive a heat of 

 250° of Fahrenheit. 



The effect was remarkable in the few experiments tried its 

 this way. The horn did not, as in the other experiments, 

 change to a hard black substance, but acquired a semi-fluid 

 and viscid consistency, with a yellow red colour, and a very 

 offensive smell. This shows that the substances which here 

 occasioned both the colour and smell of the results, had been 

 driven off" in the other experiments by the too great heat ap- 

 plied to the substance when free from compression. 



I found that the organization of animal substance was 

 entirely obliterated by a slight action of heat, but that a 

 stronger heat was required to perform the entire fusion of 

 vegetable matter. This, however, was accomplished ; and 

 in several experiments pieces of wood were changed to a jet 

 black and inflammable substance, generally very porous, in 

 which no trace could be discovered of the original organiza- 

 tion. In others, the vegetable fibres were still visible, and 

 are forced asunder by large and shining air-bubbles. 



Since the publication of the sketch of my experiments I 

 have had the pleasure to read Mr. Hatchett's very interesting 

 account of various natural substances nearly allied to coal, 

 and I could not help being struck with the resemblance 

 which my results bear to them, through all their varitii'-s, 

 as brought into view by that able chemist ; that resemblance 

 affording a presumption, that the changes which, with true 

 scientific modesty, he ascribes to an unknown cause, may 



have 



