40 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



worked to zero-potential plane, so that the current-strength in the 

 circuit is the same with either method of computation. 



The above conditions are illustrated in Figure 4, where ABB'A repre- 



A B A t = S-.89S8 l*tr.ir.ib- 1^ B 



ia|«-z. --- --- -g A5a....HJy -ff-W 



^73^967»5f.f)--»j 



4 lfO-74f\tWir 2+0-7* pfs-oy j 7 - p 



o 



G 



g-fO-747 \45-oyir 2j 0-747 Wr^y, 



o 



z* 



A 2W47\<F3nr rwfW^- B' 



Figure 4. Equivalent circuits of lines with ground return and 

 metallic return. 



sents a simple metallic-return telephone circuit with a transmitter 

 induction coil of impedance Z s at A, and a receiver of impedance Z r at 

 B. One half of this circuit, with only one wire and ground return, is 

 indicated at AB on the right hand. The length of the circuit has been 

 taken as L = 50 km. (31.068 statute miles), and the following linear 

 constants have been assumed: 



