58 POWER DISTRIBUTION FOR ELECTRIC RAILROADS. 
rather prone to break. Both the trolley wire and the 
principal feeder are continuous and of uniform cross sec- 
tion. 'This continuity is useful in case of the crowding of 
cars at one or more points on the line since it brings to the 
rescue the full conductivity of the system. Itis bad how- 
ever in case of short circuits in that the main circuit 
breaker at the station is quite likely to open and stop 
every car on the line. 
As a real feeding system it hardly deserves the name, 
since electrically it is nothing more than a continuous 
working conductor of uniform area. ‘The properties of 
such a conductor have already been fully considered in 
Chap. 1. The only additional fact that has to be taken 
into account in the ladder system is the limited conductivity 
of the trolley wire between the subfeeders. ‘The drop in 
voltage at a car located at any point is practically the drop 
A B 
G Bl T e 
Street Ry. Journal D 
FIG. 38. 
in the principal feeder up to that point plus the drop in the 
trolley wire from the car to the nearest subfeeders, which 
are virtually in parallel, inasmuch as current flowsinto the 
trolley in both directions along the trolley wire. 
2. A system similar in some respects to Fig. 38 is 
shown in Fig. 39. Here there is as before a principal 
feeder A B. ’'The trolley wire C D is not however contin- 
uous, but is broken by insulating joints into separate 
sections of approximately equal length each with its own 
subfeeder a, b, ¢, etc. ‘The added conductivity of the con- 
tinuous trolley wire is, of course, sacrificed by this arrange- 
ment. Both the trolley and feeder are generally of uniform 
area throughout their respective lengths and the system is 
electrically, to all intents and purposes, a uniform linear 
conductor save for the abrupt change in conductivity in 
passing from the principal feeder to any subfeeder and.its 
section of trolley wire. As regardsa load at any point