THB DYNAMICAL THEORY OF OASBS. 



Sj*cijic Heat of Unit of Mass at Constant Pressure. 



By the addition of the heat dE the temperature was raised 30 and the 

 pressure 9p. Now, let the gas expand without communication of heat till the 

 pressure sinks to its former value, and let the final temperature be + V0. 

 The temperature will thus sink by a quantity dd-d'0, such that 



80-3*0 __ 2_ 3p 2 W_ 



~~e 2+3/s y = 2+30 e 





and the specific heat of unit of mass at constant pressure is 



8ff_2 + 3 p , . 



3-0- ~2~~ P 0- 



The ratio of the specific heat at constant pressure to that of constant volume 

 is known in several cases from experiment. We shall denote this ratio by 



whence = f ]- ................................. (115). 



The specific heat of unit of volume in ordinary measure is at constant volume 



and at constant pressure 



y 



_ 



T -l JQ" 

 where J is the mechanical equivalent of unit of heat. 



From these expressions Dr Rankine* has calculated the specific heat of air, 

 and has found the result to agree with the value afterwards determined ex- 

 perimentally by M. Regnaultt. 



* Transactions oflhe Royal Society of Edinburgh, Vol. XX. (1850). 

 f CompUt Rendtu, 1853. 



