the Heat excited by Friction. 485 



grains heated 180 degrees, with the Heat generated in 

 the combustion of i grain of wax. 



The quantity of ice-cold water which might have been 

 heated 180 degrees with the Heat generated by friction 

 in the before-mentioned experiment was found to be 

 26.58 lb. J avoirdupois, = 188,060 grains ; and, as 

 81.631 grains of ice-cold water require the Heat gener- 

 ated in the combustion of i grain of wax to heat it 180 

 degrees, the former quantity of ice-cold water, namely, 

 188,060 grains, would require the combustion of no less 

 than 2303.8 grains (:^ 4^^^ oz., Troy) of wax to heat it 

 180 degrees. 



As the experiment (No. 3) in which the given quan- 

 tity of Heat was generated by friction lasted 2 hours 

 and 30 minutes, = 150 minutes, it is necessary, for the 

 purpose of ascertaining how many wax 'candles of any 

 given size must burn together, in order that in the com- 

 bustion of them the given quantity of Heat may be 

 generated in the given time, and consequently with the 

 same celerity as that with which the Heat was generated 

 by friction in the experiment, that the size of the candles 

 should be determined, and the quantity of wax consumed 

 in a given time by each candle in burning equably should 

 be known. 



Now I found, by an experiment made on purpose to 

 finish these computations, that when a good wax candle, 

 of a moderate size, | of an inch in diameter, burns with 

 a clear flame, just 49 grains of wax are consumed in 30 

 minutes. Hence it appears that 245 grains of wax would 

 be consumed by such a candle in 150 minutes ; and 

 that, to burn the quantity of wax (^ 2303.8 grains) ne- 

 cessary to produce the quantity of Heat actually ob- 

 tained by friction in the experiment in question, and in 



