Mr. J. P. Joule on the Mechanical Equivalent of Heat. 175 



and the tin casing and cover 19396 grs., the whole capacity 

 of the vessel and its contents was estimated at 77617 + 2319 

 + 1056-4-363 = 81355 grs. of water. Therefore the quantity 

 of heat evolved in the experiments, referred to a pound of 

 water, was 7°-7636. 



The equivalent of a degree of heat in a pound of water was 

 therefore found to be 781-5 lbs. raised to the height of one 

 foot. 



I now made a series of experiments in which sperm oil was 

 substituted for the water in the can. This liquid, being that 

 employed by engineers as the best for diminishing the friction 

 of their machinery, appeared to me well-calculated to afford 

 another and even more decisive proof of the principles con- 

 tended for. 



Table II. — Friction of Sperm Oil. 



