~ Judging by the remarks of Prof. Hubbard, accompanying two 
cases of combustion in wood ashes, reported by him in a late 
number of this Journal,* it appears to be his opinion that the ca- 
loric in question was generated within and near the bottom of the 
heap, by aspontaneous but unknown process. I conceive that 
the following experiments render this opinion highly improbable, 
and they goto sustain the view taken by the present writer, so 
far as it respects the origin of the caloric, and perhaps measura- 
bly as it regards the means by which the heat is diffused through- 
out the ashes. They show that the heat-retaining power is net 
peculiar to ashes, but is common to various pulverulent substan- 
ees ; that this residue of combustion contains an appreciable quan+ 
tity of charcoal in a state of minute division; and, as formerly 
"stated, that it is unsafe to deposit hot ashes upon, perhaps, the 
largest heaps of cold ashes. I shall marshall these aap tamente 
under the head of 
Lgnitibility of Wood Ashes—1. A pint of sifted ashes was 
made into a conical heap four inches high, upon a folded news- 
paper, and a coal lighted at one corner only, was laid upon the 
summit and very slightly covered. In seventeen minutes the 
coal was examined and found to be wholly ignited. It was again 
covered, and in eleven minutes afterward, that part of the paper 
on which the ashes rested became quite warm, and also the board 
pe it. in aichitig the paper nearly off the board, and gen- 
tly bendi ran | anceeoded i in- producing a fis 
sure, dixindling from the ‘fipex-oftha'e one a con- 
siderable depth.” oy this means I ‘enabled to see the interior 
& Le ee D ee! Pare Se: 1 “a ee ae Ts 
of my 
3 r a : 
ia res sites - ss the eg Rae 
trssure ex- 
were pee hot, if not i 
tended. After this peep, I PER He er by sliding-the 
paper back upon the board, and waited an hour from the begin- 
ning of the experiment. At the expiration of this period, the 
coal was not wholly consumed, and the ashes were still quite 
warm. 
-» The coal used ‘in the foregoing instance was of sugar-tree wood, 
and at the time it was placed upon the ashes, two other coals, one 
of sugar-tree and WE. ome of seas were sag 8 ignited and 
eee 
sich 
