518 



immersed in a large quantity of water, the changes in the tempe- 

 rature of which were ascertained by a thermometer of extreme sen- 

 sibility. By comparing the amount of force expended in condensing 

 air in the receiver with the quantity of heat evolved, after deducting 

 that which was the effect of friction, it was found that a mechanical 

 force, capable of raising 823 pounds to the height of one foot, must 

 be applied in the condensation of air, in order to raise the tempe- 

 rature of one pound of water one degree of Fahrenheit's scale. In 

 another experiment, when air condensed in one vessel was allowed 

 to pass into another vessel from which the air had been exhausted, 

 both vessels being immersed in a large receiver full of water, no 

 change of temperature took place, no mechanical power having been 

 developed. The author considers these results as strongly corro- 

 borating the dynamical theory of the nature of heat, in opposition 

 to that which ascribes to it materiality ; but he reserves the further 

 discussion of this question to a future communication, which he 

 hopes soon to present to the Royal Society. 



The Society then adjourned over the long vacation, to meet again 

 on the 21st Nov. next. 



