of Electrons, and the Sjiectrum of Canal Rays. 661 



the meridian (0) and parallel ((f)), (I, m, n), (V, m' , ri), and 

 (/", m", n"), these forming a right-handed system. 



Let the components o£ E', H' in these directions be 

 (R', T' 3 P'), (?', 0', <£') respectively. In virtue of the 

 third of equations (3) we find for a distant point 



R'=P'=0, ^ 



^/T'wa'WHO, I ; (5) 



T' = <£>'=- 



P'=-0' = 



i a 



^-,d"F'-{-m"G' + ?i"R'). I 

 of v 



These equations show that at a great distance from the 

 system the electric and magnetic forces are perpendicular to 

 the radius vector and to each other. Since equations (4) do 

 not explicitly involve U, the distant field of (20 is calculated 

 exactly in the same way as if U were zero. It differs from 

 that of the system (2), when at rest, in so far as the motion 

 changes the relative configuration and velocities of the 

 electrons of the system from those existing in the system 

 at rest. 



§ 7. The electric and magnetic forces in the system (2) are 

 given in terms of the forces T', P' by the following equations, 

 which follow at once from (1) . 



VT'+i"?', L=Z"T'-Z'P'. ) 



= (m'+gn^T'+ (m"-J? *')p', «M=(m"-5 »')T'- (m'+ ?»")p'. ! 



.... (6) 

 Let the Poynting vector, — [EH] , be denoted bv P, 



(P,Q,R)- " . i77 



Equations (6) give 



^4^ W ( 1 + Z ?) (r2+P ' 2) ' I 



(7) 



J 



The equations (6), (7) have a simple geometric inter- 

 pretation. 



