47^ Inquiry concerning the Sottrce of 



metallic dust, or, rather, scaly matter, which had been de- 

 tached from the bottom of the cylinder by the blunt 

 steel borer, in this experiment ; 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 113 lb. of 

 gun-metal at least 70 degrees of Fahrenheit's 'thermom- 

 eter, 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 incon- 

 siderable 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 -g^gth 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 i degree ; and consequently it must have 

 given off 66,2^0 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 

 supposition, we have only to recollect, that from the re- 

 sults of actual and decisive experiments, made for the ex- 

 press purpose of ascertaining 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. 



If the Heat, or any considerable part of it, were pro- 



