148 Mr Glazebrook, On the general equations [April 28 



L, M, N", the same as that of the first part of F, G, H. There may 

 however be additional terms in the values of f, g, h depending on 

 <I> , that part of <E> which does not arise from the given wave of 

 magnetic force. 



According to Maxwell <I> is necessarily zero everywhere. More- 

 over (§ 616) he neglects the terms in %, i.e. puts J=Q also. As 

 was shewn in the previous paper Helmholtz' theory becomes 

 Maxwell's by putting <J> = 0, while at the same time J is zero and 

 &may have any finite value, for in that case the terms in k all dis- 

 appear from the equations. 



One other point may here be noticed, the values given for 

 u, v, w and <E> agree with those found by Lorentz, equations 37, 39 

 of the paper referred to. According to him if 



2-7T . 2-7T / Ix + my + nz 

 u = --7jrPas m ^j T [t y— p 



-*. c*rr,TT, t \ • ^W, lx + my + nz \ 

 <£> = — 2TV(pl + qm + rn) asm-^ \t ^ — pj. 



To consider the case of a crystalline medium we have, following 

 the methods and notation of my paper on " Some equations 

 connected with the electromagnetic theory of light " (Camb. Phil. 

 Proc. iv. Pt. iii.). 



4<7r ( 1 dg _ 1 dh\ _ da. . . 



-JWJz K 3 dy]~dt W- 



d'f^du^ 1 d (d 2 ® dy d/3 

 df dt 4*irdt\dxdt dy dz 



dfV terdx) 



= ^ + ^-& 2 ^-c 2 -^ (30), 



\dy 2 dz 1 j dxdy dzdx 



etc 



These give us the equations satisfied by/, g, h. 



Also 

 d 2 a _ 47r f 1 dv _ 1 dw 



df fi \K 2 dz K 3 dy 



l_d_ (d<x _ dy\ 1_ d^ fdfi _ da\ 



fj,K 2 dz Kdz dxJ fiK 3 dy \dx dy) 



, d*$> [\ \\^**+v*± 



dtdydzlpK^ fiK 3 ) dz 2 dy' 1 



dzdx dxdy dtdydz 



