Properties of Wood Ashes. 81 



Judging by the remarks of Prof. Hubbard, accompan^'-ing 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 a spontaneous but unknown process. I conceive that 

 the following experiments render this opinion highly improbable, 

 and they go to 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 not 

 peculiar to ashes, but is common to various pulverulent substan- 

 ces ; 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 experiments 

 under the head of 



Ignitibility 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 

 beneath it. On sliding the paper nearly off the board, and gen- 

 tly bending it convexly upwards, I succeeded in producing a fis- 

 sure, extending from the apex of the cone downward to a con- 

 siderable depth. By this means I was enabled to see the interior 

 of my diminutive volcano, and to discover that the ashes within 

 were red hot^ if not incandescent, as far down as the fissure ex- 

 tended. After this peep, I closed up the crater 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 the other of beech, were thoroughly ignited and 



* Vol. xLii, p. 165, et seq. 

 Vol. XLiii, No. 1.— April-June, 1842. 11 



