638 Mr. J. H. Jeans on the 



It appears that the metal by its own attraction for the- 

 charge on the ion tends to neutralize the effect o£ the velocity 

 of impact ; so that,, with the current in the steady state, the 

 metal exerting the greater attraction for the charge it receives 

 possesses the smaller drop of potential. The series of metals 

 arranged according to the magnitude of the cathode drop 

 would be thus the reverse of that for the anode drop. 



We should expect the relatively large variation in both 

 cathode and anode drops when the electrodes become tar- 

 nished to be due to the same influences ; but here the results 

 are exactly the reverse of what we should predict from the 

 contact-potential series. According to Lord Kelvin*, "dry 

 oxide of copper is resinous to copper in contact with it, and 

 dry oxide of zinc is resinous to zinc in contact with it,, 

 just as copper is resinous to zinc in contact with it/' While 

 we would predict then, that, by tarnishing, the drop at the 

 anode should decrease, I have found by experiment (I. c.) 

 that there is invariably an increase in the drop at the anode, 

 Warburg (/. c.) having previously found that the drop at the 

 cathode decreases. 



Physical Laboratory, 

 University of Nebraska, Lincoln. 



LX. The Theoretical Evaluation of the Ratio of the Specific 

 Heats of a Gas. By J. H. Jeans, B. A., Fellow of Trinity 

 College, and Isaac Newton Student in the University of 

 Cambridge f. 



Introduction. 



§ 1. FT^HE Maxwell-Boltzmann theorem on the Partition 

 JL of Energy leads, as is well known, to a value of 7 

 which is not in accordance with observed values. In a 

 recently published paper % I have suggested that an escape 

 from the conclusions of this theorem might be found by taking 

 account of the interaction between matter and aether ; and it 

 was shown that even a small interaction might entirely modify 

 the conclusions of the theorem. In the present paper an 

 attempt is made to work out in greater detail the nature of 

 these modifications, and, in particular, to examine whether 

 it is possible, in this way, to obtain a theoretical evaluation o£ 

 7 which shall be in agreement with observed values. 



* Lord Kelvin, Phil. Mag. July 1898, p. 82. 

 f Communicated by Prof. J. J. Thomson, F.R.S. 

 % "The Distribution of Molecular Energy," Phil. Trans, cxcvi. 

 p. 897. 



