112 Mi: W. J. M. Raiikiue on the Mechanical Action of Heat, 

 gas, it has already been stated (equation 7) that 

 dV ^ ^-0 



dT~ T^' dV ' 



and because the volume of unity of weight is directly as the 

 absohitc temperature and inversely as the pressure, 



Y dr ~ r V dr ^ ''' 



Hence the following are the values of the apparent specific 

 heats of unity of weight of a theoretically perfect gas under dif- 

 ferent circumstances. 



General value of the total apparent specific heat : — 



1 ri . Jk; , 1 dv\\ 



Apparent specific heat at constant volume : — 



x'lpparent specific beat under constant pressure: — 

 „ _ 1 /I , K^\ 



=.{i+n(i-5)}. 



The ratio of the apparent specific heat under constant pressure 

 to the apparent specific heat at constant volume is the following: — 



(18) 



Kp 

 Kv 



1 + 



K-^') 



1 



= 1 + N- 



1 + N 



(^7:) 



(19) 



i+n(-.--,) 



The value of k is unknown ; and, as yet, no experimental data 

 exist from which it can be determined. I have found, however, 

 that practically, results of sufiicient accuracy are obtained by 



regarding k as so small in comparison with t, that -, and afo7-- 



tiori -g, may be neglected in calculation*. 



* The mean value of k, as coniputed from experiments made by Mr. Joule 

 and Professor William Thomson in 1 B52, is about 2°- 1 Centigrade ; but 



