2 POWER DISTRIBUTION FOR ELECTRIC RAILROADS. 
equal resistance. ‘They may therefore be treated alike as 
parts of the working circuit. The ordinary return circuit 
calls for special investigation, because it is a heterogeneous 
conductor, unequal in resistance to the working conductor, 
and involving unusual complications. 
The feeding system in railway work serves the doubie 
purpose of reinforcing the conductivity of the working con- 
  
  
  
  
  
  
A B 
Ap 
o 
An \ 
E, 
FIG. I. 
ductor and equalizing the voltage at various parts of the 
system. It therefore must be deferred asa practical matter 
until the working system, which it supplements, has been 
considered. 
Three classes of working systems are common, making 
the classification according to the nature of the distribution. 
F 
t 
D 
FIG. 2. 
The first class isillustrated by the linear system, shown 
in Fig. 1. Ideally it is a straight line, A B, near some 
point at which the power station is generally situated. It 
may be modified by bends or curves, as in A;B, and