• MUTUAL IMPEDANCE OF GROUNDED WIRES 



177 



dZs, = — ds\_Ex cos € -\- Ey sin e} 



dSds 



iccP{r) cos e 



dx^ 



cos 6 



dxdy 



sin e 



(28) 



= I ^^ + ^■'^^('') cos 6 1 dSds. 



Integration over the two wires 5' and s extending from A io B and 

 from a to b, respectively, gives their mutual impedance: 



Zss = r r I '-—J + io:P{r) cos e } dSds. (29) 



With Xo = 0, the expressions following (27) for P(r) and Q(r) 

 reduce to those given in Part I for wires on the surface of the earth. 

 The expressions given in Part I for wires in the plane of separation at 

 the depth b below the earth's surface are obtained by putting X2 = 

 and changing Xo to X2 in the resulting expression. 



We are indebted to Mr. R. M. Foster for evaluation of some of the 

 integrals as well as for general suggestions and counsel. 



