64 POWER DISTRIBUTION FOR ELECTRIC RAILROADS. 
cent, the proper distance between feeders would be virtu- - 
ally doubled, rising to about 8ooo ft.—a mile and a half. 
For long roads, then, one may use with advantage 
such an arrangement of feeders as is shown in Fig. 43. 
Here a continuous heavy trolley wire is divided into 
sections of, say, a mile to a mile and a half in length, each 
with a junction to the feeding system. This, as shown, 
consists of three main feeders, each supplying two sections 
of trolley wire. ‘The number of these main feeders and 
the number of sections each supplies is regulated by con- 
venience and local conditions, as is too the length of each 
section. ‘The sketch (Fig. 43) shows merely the principle, 
which is well suited to roads up to a dozen miles in length 
fed from somewhere near the middle. Such roads are apt 
| 
Street Ry. Journal 
  
  
  
  
  
  
H1G. 43, 
to require rather large units of loads, due to well loaded 
trains and high speed, but the number of trains to be oper- 
ated at any one time is usually small. A rather nice 
question sometimes arises as to the relative cross section of 
copper to be put in the trolley wire and in the feeders. In 
the large work that we are just now considering, the trolley 
wire must be in any event large enough to give sufficient 
contact with the trolley. And this is apt to indicate about 
as large a working conductor as can conveniently and se- 
curely be supported. ‘Therefore the feeders will be rela- 
tively smaller than in ordinary street railway practice, and 
it is not advantageous to separate permanently the sections 
of trolley wire, thus throwing away the conductivity of its 
large cross section. Whenever double tracks are used it 
goes quite without saying that the whole system of con- 
ductors should be united, each trolley wire serving as a 
feeder to the other.