146 



Mr Glazebrooh, On the general equations [April 28, 



Now let 



and 



1 2A, sin e 

 etc., 



d&. AlLl+Mm + NnS . 6 



— 5- 1 = i = sin 6 



dt sm e 



Zcos8 (22), 



.(23). 



These values of u 1} v 1} w 1 and ^ satisfy 



a\ 

 dc 



we may therefore put 



du, dv, dw, 1 od^>. 

 doc dy dz 4nr dt 



where 



Substituting in (21) we have 



u = u t + u 2 , etc. 



du„ , dv„ dw 2 1 2 J<3>„ 

 efoc cfa/ cfo 47r eft 



•(24), 



1 d® B 



2 47r dxdt ' 



Thus the magnetic force gives rise to an electric current whose 

 components are u x ,v lt w x and direction cosines L, M, N, while there 

 may at the same time exist an additional current u 2 , v 2 , w 2 inde- 

 pendent of the magnetic force. Hence if we are given a wave 

 of magnetic force defined by 



a = A%smS (25), 



where S is written for 



— (Ice + my + nz — Vt), 



we obtain the waves denned by 

 A 



/= 



47rFsin e 



Lsmo+ -. r^ 



47T dx 



d% 



F= _J^ LcosB + 



Z7T sin e dx 



, AX (Ll+Mm + Nn) ~ , 

 <E> = — s^~- : cos S + <E> 



2ttF 



sm e 



.(26). 



The quantity <J> 2 disappears from the equations which connect the 

 displacement and the magnetic force and is independent therefore 



