EXAMPLES. 117 



excess from (2) is equal to the quantity of heat /wr that is 

 disengaged when the gas is suddenly compressed into its 

 original volume. 



Sen. The value of A is found experimentally to be con- 

 stant for all simple gases, its value being approximately 

 1.408. (See Besant's Hydromechanics, p. 118.) 



EXAMPLES. 



1. A mass m of a substance of specific heat s t and tem- 

 perature t t , is mixed with a mass m z of a substance of spe- 

 cific heat s 2 an d temperature t z , the mixture being merely 

 mechanical, so that no heat is generated or absorbed by any 

 action between the substances, and all gain or loss of heat 

 from external sources is prevented. Find the resulting 

 temperature t of the mixture. 



Suppose the former body to be the warmer ; then it cools 

 down from t t to t, while the colder rises from t z to t. 

 Therefore we shall have 



m i*i (^i tne un its of heat lost by the 

 former body, 



and m^Sg (t t z ] = the units of heat gained by the 



latter body, 



and since the quantity of heat lost by the warmer body is 

 equal to that gained by the cooler, these two expressions 

 are equal ; therefore 



m l s l (#j t) = w 2 s 8 (t t z ) ; 



One of the methods of finding the specific heat of a sub- 

 stance is by immersing it in a given weight of water, and 

 observing the temperature attained by the two substances. 



