transmitted through a Metal of a Current in the Metal. 383 
If P were = 0, SIX = 0 and 
afX = V 2 {SI 2 . X - IXIX} = V 2 XSl 2 , 
so that op 2 = V 2 Sl 2 . 
Writing y = f> 
we have when P is not zero, 
a f 2 — Si 2 = c, 
where c is small. 
And then 
and 
cX=-lllX , 
cY— — m'ZlX — r ~(lY — mX), 
cZ — — nZlX + f ( nX - IZ), 
cL (Mm + Nn) - 12 LI 
and 
if L = 0 equations (2) give 
c + 1 = 0 or L = 0 : 
M (c + ?? /) = 0, 
N (c + ff 0 . 
Hence if c + 'fr i s not zero, M — 0 and N = 0, and there is 
no wave. 
yPl 
So if c 4- - y - — 0, a wave can be propagated in the metal ; 
the velocity and coefficient of absorption being determined by 
the equation 
yPl 
of 2 —l 2 — m 2 — n 2 + — 0 
.(3). 
