212 POWER DISTRIBUTION FOR ELECTRIC RAILROADS.
elsewhere on the section at the same time, calling perhaps
for one hundred amperes.
The joint load can be best taken care of by a pair of
feeders, one to B of, say, 500,000 ¢. m., the other out, say,
four miles from F, of about 250,000 c. m. The function of
the latter is to handle cars within that distance of ¥ and
also to improve the conditions at B. These are shown
with the rest in Fig. 112. ‘The weight of the main feeder
here would be 60,000 1lbs., that of the small feeder, say,
15,000 1bs.
We can now take account of stock and find the total
cost of copper for the feeding system. We may tabulate
as follows:
Section. Wt.
AE 48,000
E G (main) 80,000
(adjunct) 20,000
G’ F (long main) 80,000
adjunct 18,000
F B (main) 60,000
adjunct 15,000
321,000
This would cost at fifteen cents per pound about $48,000,
a very different figure from that previously found by the
assumption that the maximum load may be taken at the
middle point of the proposed line to be fed.
The existence of this excess and the causes that pro-
duce it must be carefully examined. In the first place
20,000 1bs. of copper, the section of feeder G’G belonging
to station F, is directly chargeable to safety precautions,
and is for the purpose of enabling the two stations to be of
some material assistance to each other in case of accident
to one of them.
The large refnaining discrepancy is almost wholly due
to the fact that the load on an electric railway is a shifting
one. Instead of being able to assume a uniform distribu-
tion of the maximum load, it must be treated as a concen-
trated load, perhaps even at the most unfavorable point of
the line. In fact, it often happens that the maximum load