284 Prof. J. J. Thomson. The Resistance of [Jan. 17, 



large, as would be case if the rate of propagation of the electro- 

 static potential were exceedingly small compared with that of electro- 

 dynamic action, the first term on the right hand side of equation (14) 

 would be very large, so that in this case again tan ml would be large 

 and ml = \TT approximately, and the same arguments would apply 

 as in the case when v 1 was finite. 



If v = 1 for all substances, then since the electromotive force 

 parallel to the axis of x is dY/dtdfi/dx, and since F = F' + d^dx, ip, 

 the x component of the electromotive force is dF'/dt. Similarly, the 

 y and z components are dG'/'dt, dUI'/dt. Thus the electromotive 

 force is propagated with the velocity of the transverse vibrations (see 

 " Report on Electrical Theories," ' Brit. Assoc. Report,' Aberdeen, 1885, 

 p. 138), and since F', G', H' satisfy the solenoidal condition, there is 

 no condensation. 



The rate of propagation of a disturbance through a conductor is 

 only equal to that of the electrodynamic action through a dielectric 

 when ff/Trpa? logp^^/n^v* is small, and though this will be so for the 

 rapid vibrations we are dealing with when the conductor is metallic, 

 it would not be so if the conductor were a dilute electrolyte or a 

 rarefied gas. In this case the rate of propagation of the disturbance 

 through the conductor would not be the same as that through the 

 dielectric. In this case the action propagated along the conductor, 

 and that propagated through the dielectric, would when they met 

 interfere and set up standing vibrations, so that along the conductor 

 there would be a series of stationary nodes at which the current 

 vanished, in other words, the current along the conductor would be 

 striated. In the discharge of electricity through rarefied gases we 

 have the current passing through a conductor of high resistance, and 

 it seems possible that the striations which are observed in the case 

 may be due to the interference of the disturbance propagated through 

 the conducting gas and that passing through the dielectric. The 

 widening of the striae on rarefaction, and on increasing the diameter 

 of the discharge tube, are consistent with this view. 



The resistances of the electrolytes to the very rapidly alternating 

 currents were compared in the following way : 



A, B, C are three coils, two of which (B and C) are approximately 

 of the same dimensions, and are nearly but not quite closed. Sphe- 

 rical balls are fastened to the ends of these coils. The two balls of 



