the Heat excited by Friction. 479 



duced in consequence of a change in the capacity for 

 Heat of a part of the metal of the cylinder, as such 

 change could only be superficial, the cylinder would by 

 degrees be exhausted; or the quantities of Heat pro- 

 duced in any given short space of time would be found 

 to diminish gradually in successive experiments. To 

 find out if this really happened or not, I repeated the 

 last-mentioned experiment several times with the utmost 

 care; but I did not discover the smallest sign of exhaus- 

 tion in the metal, notwithstanding the large quantities 

 of Heat actually given off. 



Finding so much reason to conclude that the Heat 



o 



generated in these experiments, or excited^ as I would 

 rather choose to express it, was not furnished at the ex- 

 pense of the latent Heat or combined caloric of the metal, I 

 pushed my inquiries a step farther, and endeavoured to 

 find out whether the air did, or did not, contribute any- 

 thing in the generation of it. 



Experiment No. 2. 



As the bore of the cylinder was cylindrical, and as the 

 iron bar (m\ to the end of which the blunt steel borer 

 was fixed, was square, the air had free access to the in- 

 side of the bore, and even to the bottom of it, where 

 the friction took place by which the Heat was excited. 



As neither the metallic chips produced in the ordinary 

 course of the operation of boring brass cannon, nor the 

 finer scaly particles produced in the last-mentioned ex- 

 periments by the friction of the blunt borer, showed any 

 signs of calcination, I did not see how the air could pos- 

 sibly have been the cause of the Heat that was produced ; 

 but, in an investigation of this kind, I thought that no 

 pains should be spared to clear away the rubbish, and 



