[ 222 ] 
i. e. lefs inflammable air, was expelled j and there- 
fore I fuppofe that more of it was fixed. I could 
never afterwards, by equal degrees of heat, make 
this coal to weigh as little as another that was firft 
coaled by a fudden heat. 
I took two pieces of dry oak, the contiguous 
parts of the fame flick, each weighing exactly 14 
grains. One of thefe 1 heated fuddenly. It yielded 
8 ounce meafures of inflammable air, and then 
weighed 2 grains. The other I heated flowly, but 
as vehemently, at the laft, as the other. It yielded 
only i \ ounce meafures, and weighed 3 grains. 
I repeated the fame experiment feveral times, and 
always with nearly the fame refult. 
Examining the conducing power of the pieces of 
charcoal, made with thefe different circumftances in 
the procefs, I could not diftinguifh which were better. 
Perhaps a more accurate method of trying them 
might fhow, that thofe which were coaled flowly 
were the better conductors ; unlefs, which is not 
improbable, the goodnefs of the conducting power 
confift in the completenefs of the union that is pro- 
duced between the inflammable principle and its bafe, 
which will depend upon the degree of heat only, 
and not on the quantity of phlogifton thus united to 
the earth. 
N. B. To catch the inflammable air, fet Ioofe in 
making charcoal, I put the fubflances into a gun 
barrel, to which I luted a long glafs tube, and to the 
tube I faftened a bladder, out of which the air was 
carefully prefled. 
As metals and charcoal agree in confiding of phlo- 
gifton united to an earthly bafe, and alfo in condudt- 
1 ing 
