378 Mr. Joule on the Chavges of Temperature produced by 



water had been produced in the jrj~ 5^ 



receiver from which the air had 

 expanded, while 2°*38 of heat had 

 been produced in the other re- 

 ceiver, and 0°'31 of heat also in 

 the can in which the connecting 

 piece was immersed ; the sum of 

 the whole amounting nearly to 

 zero. The slight redundance of 

 heat was owing to the loss of 

 cold during the passage of the 



air from the charged receiver to the stop-cocks, through a 

 part of the pipe which could not be immersed in water. 



A series of experiments was now made in the following 

 manner: —The receiver was filled with dry compressed air, 

 and a coiled leaden pipe, ^ of an inch in internal diameter and 

 12 yards long, was screwed tightly upon the nozle, as repre- 

 sented in fig. 6. The whole was then immersed into an oval 



Fiff. 6. 



can, which was constructed as before described, and was also 

 covered at top as perfectly as possible. Having ascertained 

 the temperature of the water by means of the sensible ther- 

 mometer before used, the stop-cock was opened and the air 

 made to pass from the receiver through a pneumatic trough 

 into ajar, by which it was carefully measured. After the air 

 in the receiver had been reduced to the atmospherical press- 

 ure, the water was again well-stirred and its temperature 

 noted. An interpolation was made after each of these expe- 

 riments, in order to eliminate the effects of stirring, &c. 



