272 



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



There will be equations of exactly similar form connecting the D 

 coefficients. 



Equation (2) may be written 



and if the plate is so thin that ha' is small, this may be written 



(6). 



Now the transverse disturbances satisfy in the dielectric equations 

 of the form 



where v is the velocity of propagation of the electrodynamic action ; in 

 the plate they satisfy equations of the form 



dt 



_ 

 dx* dy* dz* 



where a is the specific resistance of the substance of which the plate is 

 made. 



From these equations we see that 



and 



Now if the primary system is a circular coil whose plane is parallel 

 to the plane of the plate, b and c will be of the order sr/R, where B is 

 the radius of the coil ; hence if as in our experiments 4nripja is large 

 compared with 7r 2 /B 3 , we may put 



a ' 8 = Z^E. 



<7 



Since p 2 /-y 2 was small compared with 6 2 -}-c 2 for the vibrations used, 

 we have approximately 



and, therefore, a 2 is small compared with a' 2 ; hence from equation (6) 

 we get 



