30 BELL SYSTEM TECHNICAL JOURNAL 



= iV^V + 2(^)Ho g (1+ ^^ VI + 72)4 



(/+Vi+5 2 +/ 2 ) 4 



+ 8 (4 a) (vT+^+T 2 +l- Vl+5 2 



-Vl+i 2 ),i{A'B'b'a' is a horizontal 

 rectangle at the distance Z = t{Aa) 

 below the earth and A B = s(A a), (39) 



= A^r-v - 2Z [log Ki + Vi+7 2 ) - VT+^+ 1 +*], 



if A'B'b'a' is a vertical rectangle with 

 one edge at the surface of the earth and 

 AB = ab = s(A'a)=sZ, (40) 



Nw-£)(u-.)=Njr*' + P'p'Yp> p ,-2Pp'Ypp—&r P > + 2bp p .-£i Pp . (41) 



