220 Historical Review of Experiments 



mained in the same condition throughout the entire 

 experiment, it is evident that it could contribute in no 

 measure to the effect produced. 



We will now inquire how much heat would have been 

 developed if the experiment had been carried on without 

 cessation, until the whole mass of metal had been re- 

 duced to powder by the friction. 



After the experiment had lasted an hour and a half, 

 there were 4145 grains (Troy) of the metallic dust, and 

 during that time an amount of heat was produced by 

 the friction sufficient to raise 26.58 pounds of ice-cold 

 water to the boiling-point. 



Since the mass of metal weighed 113.13 pounds, or 

 791,910 grains, all this metal would have been reduced to 

 powder if the experiment had lasted uninterruptedly, day 

 and night, for 477^ hours, or for 19 days 2i| hours, 

 and during this time an amount of heat would have 

 been produced sufficient to have raised 5078 pounds 

 of water to the boiling-point. 



Since the metal used in this experiment showed a 

 capacity for heat which was to that of water as o.n to 

 i, it is evident that this amount of heat would have 

 been sufficient to raise a mass of the same metal 46,165 

 pounds in weight through 180 degrees of Fahrenheit's 

 scale, or from the temperature of melting ice to that of 

 boiling water. 



This amount of heat would be sufficient to melt a 

 mass of metal sixteen times heavier than that which I 

 used in the experiment.* 



* Brass melts at a temperature of 3807 Fahrenheit ; copper at 4587; bell- 

 metal melts more easily than copper ; if, however, we suppose that it requires the 

 same heat for fusion, we find by a very simple calculation, that the amount of heat 

 necessary to raise the temperature of 46,165 pounds bell-metal through 180 degrees 

 would be sufficient to raise the temperature of i8ii pounds through 4587 



