[ 2I 5 ] 
the ftrongeft conduQing power, by repeating the 
proceis of coaling, either in a crucible, or a gun 
barrel, covered with fand, and kept in an intenfe 
heat. 
I could - not find that the mere continuance of the 
fame degree of heat had any effect with refped to 
the conducting power of charcoal. 
Macquer and other chemifts define charcoal to be 
‘wood burned, without being buffered to flame • but 
with refped to its conduding power, and, I make no 
doubt, with, refped to all other effential properties 
alio, it makes no difference whether it flame or not 
I have coaled pieces of wood, both in gun barrels* 
and in crucibles, flightly covered with fand, and have 
let the inflammable vapour that exhaled from them 
take fire, at various difiances from the fubfiances • 
and 1 have alfo put pieces of wood in an open fire’ 
and urged the heat applied to them, with a pair of 
bellows ; and in all thefe cafes have found the char- 
Coal equally good. In the lafi method, indeed, very 
little of the fubftance is preferved ; but the little that 
doth remain, after it has ceafed to flame, whether it 
oe quenched immediately, or not, conduds as well 
as any charcoal whatever. But one can hardly' be 
fure that the fame degree of heat is given to every 
part of a piece of wood, except it be expofed to it 
for fome time ; and in an open fire, urged with a pair 
or bellows, the wood waftes as fa ft as" it is red hot 
before the center of it is much affeded with die 
heat. 
.' When once an y degree of conduding power is 
given to a piece of charcoal, .1 never found that it 
was afterwards leffened. A partial confuming of 
3 if 
