168 Combustibility of Wood. Ashes. 
of danger, while the box and its contents continued undisturbed? 
With this inquiry in my mind, I made a memorandum of the 
event in my common-place book, and left the subject for future 
reflection and research. Years passed, and the memorandum fre- 
quently met my eye as I occasionally turned over the leaves of 
my manuscripts; but it did not obtain any particular attention... 
4, A few months ago, however, I had cause, to congratulate 
myself for having made a careful record of the phenomenon re- 
ferred to. Our domestic informed me, perhaps two months since, 
that the ash-box, (a transverse section of. the trunk of a very 
large syecamore,) had “burnt through near the bottom.” The 
former occurrence of the same kind, presented itself vividly 
to mind, and I eagerly repaired to the late scene of combustion to 
pursue my original inquiry, believing the cause, whatever it might 
be, to be the same in both instances. The domestic. had poured 
a large quantity of water upon the ashes in the morning when 
she detected the fire, and she supposed every spark had been’ex- 
tinguished. I found, however, that the ashes were now, in the 
evening, insupportably hot ; and by means of.a spade, I ascer- 
tained that the heat oxiéntled throughout the mass; the blade 
when drawn out, hissed when spit upon. _ I thoroughly drench- 
ed the ashes, and then sat down to reflect upon the phenomenon. 
It soon occurred to me, as highly probable, that ashes, when 
taken from the fire-place, contain a considerable quantity of car- 
bonaceous matter in a state of minute division; that. ignition of 
these particles might exist without being apparent to the eye; 
that this ignition might be communicated very slowly to the ear- 
‘bonaceous powder in surrounding cold or extinguished ashes, and 
thus fire be conducted gradually to large coals, and to the wood- 
en vessel containing the ashes. 
To deter pine the correctness of my conjecture, I sifted through 
the finest Chine: e sieve I could procure, some ashes, which had 
been taken from the fire-place the day before, and weighing 642 
grs. subjected them to heat in a Hessian crucible. In a short 
time the crucible became red hot; but no redness. was visible im 
the ashes. At this stage of the process, I thrust a beech splinter 
into the ashes, (being careful not to touch the. crucible, ) and i 
Ht. fool fire. After allowing the crucible to onal a 
: ements; and found they had lost 12 grs. — 
quantity of © comminuted cark 
n no doubt varies in ee: a 
