high Degrees of Heat in clofe Veffeh, 357 



pearcd, and the interior of the veflcl prefented a folitary fpot 

 of vitrid matter larger than that of No. I. by the additional 

 quantity of charcoal employed. 



E\p. III. was performed with 20 grains of charcoal, and 

 3, fimil ir remit with the former two was obtai'ned. 



Exp. IV. contained 30 grains of charcoal. This gilfo dif- 

 appeared. 



E p. V. was performed with 40 grains, when a few minute 

 flakes of charcoal remained. 



■ Exp. VI. was made with - - grs. 60 



After the ufual treatment and expofure, I found that a 

 eonfiderable portion or' the charcoal now remained, 

 which I found to weigh 35 



Not taken up 25 



The firft inference I was led to make from thefe experi- 

 ments was, that the charcoal was confumed by the air in- 

 cluded in the crucible when it was introduced. This feemed 

 plaufible enough where only five or ten grains were em- 

 ployed, and a eonfiderable fpace left unoccupied; but in the 

 two lad experiments.the charcoal was of luch bulk as nearly 

 to fill the crucible. 



Exp. VII. To determine this, I took a piece of well burnt 

 charcoal wood of 20 grains. This was introduced into a cru- 

 cible, and (hut up in a fimilar manner with the former. It 

 was placed, after the fame train of drving and preparation, 

 in the allay furnace, where for two hours it received the 

 utmoft heat that the pot was deemed capable of (landing. 

 When cold, I found the crucible verv entire, and inclofing 

 the piece of charcoal, apparently of its former dimenfions and 

 fhape ; but, on clofer examination, I found the angles com- 

 pletely rounded, and the furface covered with very minute 

 tranfparent globules of fait. The blaeknefs of the charcoal 

 had deepened into a degree of luftre and richnefs furpafling 

 any thing of the kind I had ever witneiTed. The mafs now 

 weighed 17 grains. 



From the refult of this experiment T inferred that tjie 

 quantity of included air was not adequate to explain the dif- 

 appearance of the charcoal powder of the former experiments. 

 I was now led to conceive that it might be materially a (lifted 

 by the expulfion of a certain quantity of water baked in the 

 clay, which, by a well known affinity, might be decompofed 

 on the charcoal at a high temperature, and carbonic acid gas 

 confequently formed. 



Exp. VIII. There were inclofed 20 grains of charcoal in 

 a crucible fimilar to the former. After ten weeks drying, in 



Z 3 a tern- 



