87 
the Source of the Heat excited by Friction . 
Having taken away the borer, I now removed, the metallic 
dust, or rather scaly matter, which had been detached from the 
bottom of the cylinder by the blunt steel borer, in this experi- 
ment ; and, having carefully weighed it, I found its weight to 
be 837 grains Troy. 
Is it possible that the very considerable quantity of heat that 
was produced in this experiment (a quantity which actually 
raised the temperature of above 1131b. of gun-metal at least 
70 degrees of Fahrenheit’s thermometer, and which, of course, 
would have been capable of melting 6^-lb. of ice, or of causing 
near 5 lb. of ice-cold water to boil,) could have been furnished 
by so inconsiderable a quantity of metallic dust ? and this merely 
in consequence of a change of its capacity for heat ? 
As the weight of this dust (837 grains Troy) amounted to 
no more than ^-^th part of that of the cylinder, it must have 
lost no less than 948 degrees of heat, to have been able to have 
raised the temperature of the cylinder 1 degree; and conse- 
quently it must have given off 66360 degrees of heat, to have 
produced the effects which were actually found to have been 
produced in the experiment ! 
But, without insisting on the improbability of this supposi- 
tion, we have only to recollect, that from the results of actual 
and decisive experiments, made for the express purpose of as- 
certaining that fact, the capacity for heat, of the metal of which 
great guns are cast, is not sensibly changed by being reduced to 
the form of metallic chips, in the operation of boring cannon ; 
and there does not seem to be any reason to think that it can 
be much changed, if it be changed at all, in being reduced to 
much smaller pieces, by means of a borer that is less sharp. 
