154 EFFECTS of HEAT 



dom ; and I find that, in the open fire, horn yields a charcoal 

 equal to 20 per cent, of the original weight. But more expe- 

 riments mull be made on this fubject. 



Another caufe of the lofs of weight, lay undoubtedly in the 

 excefs of heat employed in mofl of them, to remove the cradle 

 from the barrel. With inflammable fubftances, no air-tube 

 was ufed, and the heats being low, the air lodged in inter- 

 faces had been fufficient to fecure the barrels from deftruction, 

 by the expanfion of the liquid metal. In this view, likewife, I 

 often ufed lead, whofe expanfion in fuch low heats, I expe&ed 

 to be lefs than that of the fufible metal. And the lead requir- 

 ing to melt it, a heat very near to that of rednefs, the fubject 

 of experiment was thus, on removing the cradle, expofed in 

 freedom to a temperature which was comparatively high. But, 

 obferving that a great lofs was thus occafioned, I returned to 

 the ufe of the fufible metal, together with my former method 

 of melting it, by plunging the barrel, when removed from the 

 furnace, into a folution 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 in 

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

 change to a hard black fubftance, but acquired a femifluid and 

 vifcid confiftency, with a yellow-red colour, and a very orTen- 

 ffve fmell. This ftiews, that the fubftances which here occa- 

 fioned both the colour and fmell of the refults, had been dri- 

 ven off in the other experiments, by the too great heat applied 

 to the fubftance, when free from compreffion. 



I found that the organization of animal fubftance was en- 

 tirely obliterated by a flight action of heat, but that a ftronger 

 heat was required to perform the entire fufion of vegetable 

 matter. This, however, was accomplifhed ; and in feveral 

 experiments, pieces of wood were changed to a jet-black and 

 inflammable fubftance, generally very porous, in which no 



trace 



