the Heat excited by Friction. 489 



faces, and given off in a constant stream or flux in all di- 

 rections without interruption or intermission, and with- 

 out any signs of diminution or exhaustion. 



From whence came the Heat which was continually 

 given off in this manner in the foregoing experiments? 

 Was it furnished by the small particles of metal, de- 

 tached from the larger solid masses, on their being 

 rubbed together ? This, as we have already seen, could 

 not possibly have been the case. 



Was it furnished by the air? This could not have 

 been the case ; for, in three of the experiments, the ma- 

 chinery being kept immersed in water, the access of the 

 air of the atmosphere was completely prevented. 



Was it furnished by the water which surrounded the 

 machinery ? That this could not have been the case is 

 evident : jirst^ because this water was continually receiv- 

 ing Heat from the machinery, and could not at the same 

 time be giving to, and receiving Heat from, the same body ; 

 and, secondly, because there was no chemical decomposi- 

 tion of any part of this water. Had any such decompo- 

 sition taken place (which, indeed, could not reasonably 

 have been expected), one of its component elastic fluids 

 (most probably inflammable air) must at the same time 

 have been set at liberty, and, in making its escape into 

 the atmosphere, would have been detected; but though 

 I frequently examined the water to see if any air-bubbles 

 rose up through it, and had even made preparations for 

 catching them, in order to examine them, if any should 

 appear, I could perceive none; nor was there any sign 

 of decomposition of any kind whatever, or other chemi- 

 cal process, going on in the water. 



Is it possible that the Heat could have been supplied 

 by me:ins of the iron bar to the end of which the blunt 



