On Conduct) cities of certain Media for a Steady Flux. 221 



On an average it was estimated that the proportion of oxygen 

 would be about 37 per cent, of the whole. The total quantity 

 of diffused gas reckoned at atmospheric pressure was about 

 300 c.c. per twenty-four hours. 



On removal from the pump the gas was introduced into an 

 inverted flask standing over alkali, and with addition of 

 oxygen as required was treated with the electrical discharge 

 from a transformer in connexion with the public supply of 

 alternating current. In this way the nitrogen was gradually 

 oxidized and absorbed. Towards the close of operations the 

 gas was transferred to a smaller vessel, where it was further 

 sparked until no further contraction occurred, and the lines 

 of nitrogen had disappeared from the spectrum. The excess 

 of oxygen was then removed by phosphorus. 



It remains only to record the final figures. The residue, 

 free of oxygen and nitrogen, from 3205 c.c. of diffused gas 

 was 39 c.c. The most instructive way of stating the result 

 is perhaps to reckon the argon as a percentage, not of the 

 whole, but of the nitrogen and argon only. Of the 3205 c.c. 

 total, 2020 c.c. would be nitrogen and argon, and of this the 

 39 c.c. argon would be 1'93 per cent. Since, according to 

 Kellas (Proc. Roy. Soc. vol. lix. p. 67, 1895), 100 c.c. of 

 mixed atmospheric nitrogen and argon contains 1*19 per 

 cent, of argon, we see that in the diffused gas the proportion 

 of argon is about half as great again as in the atmosphere. 

 Argon then passes the indiarubber film more readily than 

 nitrogen, but not in such a degree as to render the diffusion 

 process a useful one for the concentration of argon from the 

 atmosphere. 



XVI. On the Conductivities of certain Heterogeneous Media 

 for a Steady Flax having a Potential. By Charles H. 



Lees, D.Sc* 



IN the chapter on " Conduction through heterogeneous 

 media," in his ' Electricity and Magnetism,' Maxwell 

 works out the conductivity of a compound medium formed 

 by embedding in a medium of conductivity 7c 2 a number of 

 small spheres of a medium of conductivity k x , for the case in 

 which the total volume of the spheres bears only a small pro- 

 portion to that of the medium k 2 , and the distances of the 

 spheres apart are so great that they have no mutual effect on 

 one another. He also works out the conductivities for two 

 other cases of compound media : in the first the two media 

 are separated by planes either parallel or perpendicular to 

 * Communicated by the Physical Society : read November 24, 1899. 



