390 Mr. 0. Heaviside on Electromagnetic Waves, and the 

 comparing which with (139), we see that 



E=,»H + £{«-«- ,£(l-i) + «-— £(l + i) }/, (145 



We have, therefore, only to develop the second part, which is 

 not in the same phase with H. It is, in the same manner as 

 before, 



f lV g /A 2 A 3 \ , /iw /A 2 , A 8 \ / Uf A 



only operating when «rfj=trf— r + a, and rt 2 — vt—r — a are 

 positive. Or, 



1 and 2 referring to the two waves. So, when irt > (?• + a), 

 and the two are coincident, we have the sum 



■-^j& ( 147 ) 



which is the tangential component of the steady electric field 

 left behind. 



The radial component F is, by (137), 



(out) F = ^{ e -,,-.,(I + ^_^-^) + . ..}/,, (J 



where the unwritten term . . . may be obtained from the pre- 

 ceding by changing the sign of a. Or, 



where vt { = vt + a—r. Or, 



„ /iOCOS ( a 2 a a 1 



F= — p— { 3r + 2 + 27- (t ^-^-^^-^ 



so that, when both waves coincide, we have their sum, 



F _ 2/i« 3 cos0 n - n 



1 - 3 r s ' t 101 J 



which is the radial component of the steady field left behind 

 by the part of the primary wave whose magnetic field is 

 wholly cancelled. 



