'284 PHILOSOPHICAL TRANSACTIONS. [ANNO 1798. 



might have been heated 180°, with the heat generated by friction in the before- 

 mentioned experiment, was found to be 26.58 lb. avoirdupois, = 188060grs.; 

 and, as 81.631 grs. of ice-cold water require the heat generated in the combustion 

 of 1 gr. of wax, to heat it 180°, the former quantity of ice-cold water, namely 

 188o60grs., would require the combustion of no less than 2303.8 grs. = 4^ oz. 

 Troy, of wax, to heat it 180°. 



As the experiment, N° 3, in which the given quantity of heat was generated 

 by friction, lasted 2 h 30 m , = 150 m , it is necessary, for the purpose of ascertaining 

 how many wax candles of any given size must burn together, in order that in the 

 combustion 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, 4- of an inch in diameter, burns with a clear flame, just 49 grs. of wax are 

 consumed in 30 m . Hence it appears, that 245 grs. of wax would be consumed by 

 such a candle in 150 m : and that, to burn the quantity of wax, = 2303.8 grs., 

 necessary to produce the quantity of heat actually obtained by friction in the expe- 

 riment in question, and in the given time, I50 m , 9 candles, burning at once, 

 would not be sufficient; for, 9 multiplied into 245, the number of grains con- 

 sumed by each candle in 150 m , amounts to no more than 2205 grs.; whereas the 

 quantity of wax necessary to be burnt, in order to produce the given quantity of 

 heat, was found to be 2303.8 grs. 



From the result of these computations it appears, that the quantity of heat pro- 

 duced equably, or in a continual stream, by the friction of the blunt steel borer 

 against the bottom of the hollow metallic cylinder, in the experiment under con- 

 sideration, was greater than that produced equably in the combustion of 9 wax 

 candles, each -f- of an inch in diameter, all burning together, or at the same time, 

 with clear bright flames. As the machinery used in this experiment could easily be 

 carried round by the force of one horse, (though, to render the work lighter, two 

 horses were actually employed in doing it), these computations show further how 

 large a quantity of heat might be produced, by proper mechanical contrivance, 

 merely by the strength of a horse, without either fire, light, combustion, or che- 

 mical decomposition; and, in a case of necessity, the heat thus produced might be 

 used in cooking victuals. But no circumstances can be imagined, in which this 

 method of procuring heat would not be disadvantageous; for, more heat might be 

 obtained by using the fodder necessary for the support of a horse, as fuel. 



As soon as the last-mentioned experiment, N° 3, was finished, the water in the 

 wooden box was let off, and the box removed; and the borer being taken out of 

 the cylinder, the scaly metallic powder, which had been produced by the friction 

 of the borer against the bottom of the cylinder, was collected, and, being carefully 



