286 Mr. J. Rose-Innes on the Ratio of 



existing in electrical discharges and those of the electrodes of 

 an ordinary voltaic cell. The electrical density on the ter- 

 minals of a condenser is proportional to the strength of 

 the current which the charging battery is capable of 

 producing. 



3. The electrostatic field diminishing much more rapidly 

 with the distance than the electromagnetic field doubtless has 

 its energy consumed in molecular movements. 



Jefferson Physical Laboratory, 

 Harvard University. 



XXX. On the Ratio of the Specific Heats of Air. 



To the Editors of the Philosophical Magazine. 

 \/ Gentlemen, 



IN the July number of the Philosophical Magazine there is 

 an article by Mr. E. F. J. Love on " The Joule-Thomson 

 Thermal Effect ; its Connexion with the Characteristic Equa- 

 tion, and some of its Thermodynamical Consequences." In 

 that article Mr. Love endeavours to calculate the increase in 

 tr 



~} which takes place when we take into account the deviation 

 iv v 



of the behaviour of air from the laws of a perfect gas. His 



method in the main appears to be correct ; but he appears to 



me to have fallen in one place into a mistake of algebra which 



may vitiate his final numerical result. He says : — 



" We obtain 





.K, 



p + 



a 



V 2 



2a 



' J 



} v ~ 



■b 



V 6 



'/■l- 







n 



R 



v-b 



(WW rH 



" Since — is in general small compared with p, and b and 



H/9 v 



Yr- are both small compared with v, we have 



Granting, for the sake of argument, the correctness of the 

 first equation here quoted, it dees not seem possible to me to 



