Passage of Electric Wave-trains through Electrolyte, 531 



molecules that can be explained by representing the molecules 

 as smooth spheres, but there are others which cannot be so 

 explained, the best known of the latter being the specific heat. 

 It is well to see how far a simplifying hypothesis such as that 

 of smooth spherical molecules can lead us ; but it is also well 

 to recognize when the hypothesis has got to the end of its 

 tether. Van der Waals's theoretical equation agrees closely 

 with experiment for the element gases only through an acci- 

 dental compensation in the effects of two neglected causes, 

 namely, the effect of molecular force on the number of col- 

 lisions of molecules and the effect of a difference between the 

 forces called into play in the collision of molecules and of 

 smooth spheres. It must also be remembered that the empi- 

 rical equation given for compound gases in my paper on the 

 " Laws of Molecular Force " is quite different in form from 

 that for elements, and that a theoretical explanation of it must 

 involve considerations beyond the range of the spherical 

 molecule. Indeed it appears to me that a combined and col- 

 lated study of specific heat, characteristic equation, and thermal 

 conductivity of gases might now be expected to yield some of 

 that knowledge of the internal dynamics of molecules which 

 is absolutely necessary for the advancement of the kinetic 

 theory in the most interesting directions. 



Melbourne, June 1893. 



LIII. On the Passage of Electric Wave-trains through Layers 

 of Electrolyte, By G. Udny Yule*. 



Introduction, 



THE attempt to compare the resistances of electrolytes with 

 rapidly alternating currents, by utilizing for that pur- 

 pose electric radiation, was first made by Prof. J. J. Thomson 

 in 1888 f. The method he used was as follows : — Between a 

 circular oscillator and a resonator was placed a large shallow 

 dish, into which an electrolyte was poured, forming an absorbent 

 layer which greatlj r weakened the resonator-sparks and finally 

 extinguished them. So long as the layer be thin, the thick- 

 ness of liquid necessary to just extinguish the sparks is 

 inversely proportional to its conductivity. In this way the 

 conductivities of several different solutions were compared, 

 and the ratios found were approximately those of the conduc- 



* Communicated by the Author. A preliminary note was published, 

 Proc. Roy. Soc. liv. p. 96, May 1893. 

 f Proc. Roy. Soc. xlv. p. 269 (1889). 



2 N2 



