[ ] 
it in an open fire doth not aft'eCt the remainder, as 
I obferved in the account of my former experi- 
ments. ■ • 
I had imagined, that the folidity of fubdances con- 
verted into charcoal would have had a very conf.der- 
able efFeCt on their conducting power afterwards ; 
but the conjedture was not confirmed by experiment. 
Coals made of the lighted; woods conduced, as far 
as I could perceive, as well as thofe that were made* 
from the moft folid, if they had been expofed to the 
lame degree of heat in the procefs. Fine fhavings 
of fir, the thin coats of an onion, the lighted; font, 
and every other vegetable fubftance that I tried, con- 
ducted equally with coals made of oak or ebony. 
I had imagined, alfo, that the moment a piece of 
wood was become black with heat, it was, to 
all intents and purpofes, a real charcoal, and, along 
with other properties of charcoal, would conduCt 
electricity, more or lefs : but I found, by coaling 
feveral pieces very dowly, that they would not con- 
duct in the lead degree, not only when they were 
made fuperficially black, but likewife when they 
were black quite through, and had remained a long 
time in the heat that made them fo ; fo that no eye 
could didinguifh them from the mod; perfeCt char- 
coal. 
I have fometimes found charcoal in fuch a date, 
that it would afiid the pafiage of an explofion along 
its furface, when it would not conduCt a fhock any 
other way. 
In order to fatisfy myfelf in what proportions the 
diminution of weight, the decreafe of bulk, and the 
conducing power of wood and charcoal, correfponded 
to 
