78 POWER DISTRIBUTIQN FOR ELECTRIC RAILROADS. 
tion apart. eand & (Fig. 48) have this position. No load 
can therefore be more than 2500 ft. from a feeder. Now 
consider the maximum load of 300 amperes at A. Sup- 
pose first that the feeder H a is to give five per cent drop, 
twenty-five volts at average load. 'This average (half the 
total average load) is seventy-five amperes. The distance 
A H is 4500 ft., the wire therefore must be of area, 
13 X 75 X 4500 
25 
G = == 175,500, 
This is best met by a No. ooo wire, which is the nearest 
size (167,000 c. m.) and will give less than one per cent 
more drop. 
With 300 amperes at A the drop in the trolley wires 
for 2500 ft. would be thirty six volts. ‘The drop in the 
feeder would obviously be a little over a hundred volts, 
making a total quite too great, since the overcompound- 
ing, unless a special generator be devoted to the feeder in 
question responds to the total load on the system and not 
fully to the load at A. FEven the gain from the current 
path along H B @ will not relieve matters quite enough. 
Now we might use a much larger feeder and thus reduce 
the drop, but a simpler and cheaper way is to cross tie 
both feeders into the trolley lines at ¢. ‘T'his, assuming 
both feeders to be of the same size, puts at our disposal from 
@ to ¢ no less than 433,000 c. m., with 334,000 c. m. for the 
1000 ft. between H and C. 'The total drop will then be 
36 + 31 + 12 = 79 less whatever has been gained from 
the overcompounding. ‘T'his last depends on the total 
load on the system and is consequently indeterminate, It 
could hardly however be less than half the full overcom- 
pounding, say twenty-five volts, thus giving a net drop of 
fifty-four volts at A. 
This cross connecting process is a very useful safe- 
guard against extreme terminal loads, though if the whole 
line is likely to have a heavy distributed load at the same 
time, it is better to take a different step as will presently be 
shown.