210 POWER DISTRIBUTION FOR ELECTRIC RAILROADS. 
vantageously approximated by a 600,000 c. m. cable plus 
the trolley wire. If this cable is tied into the trolley wire 
at frequent intervals, say, every 1000 ft., for a mile or two 
near A, the drop in the trolley wire as such becomes 
trifling, and the drop saved here may be transferred to 
the feeder account. Nearer E the taps need not be so fre- 
quent, and the trolley wire should be directly connected to 
the station. We may then arrange thissection as shown in 
Fig. 112 by the dotted lines. Under this arrangement the 
drop at normal full load, with one car at A, a second nearly 
midway between E and A, and another near E, assuming 
for current 100 amperes per car would be pretty near the 
required fifteen per cent, although, as we have pre- 
viously seen, the conditions of extreme load must in the 
last resort determine the amount of feeder copper. 
A feeder of 600,000 c.m., uninsulated, weighs 1800 1bs. 
per thousand feet (threetimes the circular mils in thous- 
ands, as we have already seen), hence we must write down 
against this section about 48,000 1bs. of copper. 
Next comes the long section E G. - On this three or 
four cars may normally be operated. About the worst 
that can be expected is a couple of cars near G 
calling for perhaps 150 amperes together and a similar 
pair fairly near K. As to drop we may here take rather 
extreme measures and allow, so far as station E is 
concerned, a maximum drop of 150 volts. This calls for 
770,000 c. m. which we can again make up of a 600,000 
c. m. cable plus the trolley, the two being frequently tied 
together. But even this does not properly take account of 
the second pair of cars. These at worst cannot be ex- 
pected to be more than five miles from E. Hence under 
the same conditions of drop the total area of copper re- 
quired would be 385,000 c. m. In connection with the 
trolley wire a 250,000 c. m. cable would be rather more 
than enough to do the work. 'This feeder should be tied 
to the trolley perhaps every 1000 ft., and should cover the 
first half of E G. 'This pair of feeders, as shown in Fig. 
112, complete the distribution system for the station E. The 
o s s S 
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