On the Specific Heat of Gases and Vapours. 361 



y= cos pt\<j> l Ui + <l> 2 u 2 + ...}, 

 T = i jV (^tt, + <£ 2 w 2 +•...) Hx, 

 M = §P(K dx > 8 W = J fy> . i«J<te, 



§p uidx 



I do not stop to discuss the physical bearing of these results ; 

 enough has probably been said to enable the reader to judge of 

 the scope of the problem here considered, and of the simplicity 

 of the mathematical machinery by which the solution may be 

 obtained. 



September 23, 1873. 



XI V. On the Determination of the Specific Heat of Gases and 

 Vapours at Constant Volumes. By R. C. Nichols. 



[Continued from p. 290.] 



HE uncertainty of the ordinary method is sufficiently indi- 



T 



cated by the diverse results for the value of — obtained by 



different observers, namely 1*348, 1*375*, 1-419. The last, 

 however, that of Masson, does not greatly differ from the value 

 calculated by the independent method from the velocity of sound, 

 1-4122. 

 The value of c— c x may be expressed by the general equation 



a 



where a is the coefficient of expansion, fi the weight of a cubic 

 foot of the gas estimated in any given unit, at 32°, per unit of 

 pressure on the square foot, and H the mechanical equivalent of 

 heat. This expression will obtain equally if a, /Lt, and H are 

 taken for degrees Centigrade and metres. 



If the ratio — be represented by r, 



■(-9- 



which expresses a definite relation between the constants c, r, «, 



* Gay-Lussac. 



