SPECIAIL, METHODS OF DISTRIBUTION. IOl 
ples already laid down. The distance, A B, being ten miles 
we have already seen that to deliver an assumed maximum 
of 500 amperes at B would require at 150 volts total drop, 
about 2,000,000 c. m. of copper, costing about $45,000. 
This we will assume to be based on a dynamo giving at 
full load with its overcompounding 550 volts in accordance 
with ordinary practice. The voltage at the motors will 
then occasionally drop to 400 volts, certainly the extreme 
drop that could be tolerated. We have already seen that 
by boosting to 750 volts and doubling the loss in the line, 
the copper can be reduced by one-half. At the same time 
the minimum voltage is raised to about 450, which is much 
more satisfactory. 
Now suppose that instead of doing either of these 
things we say to ourselves, ‘‘’These standard motors of 
ours are intended to operate on 500 to 550 volts like the 
generators, let us make them do it.”” In fact these stand- 
ar® railway motors will operate beautifully at 550 volts. 
Gear them so as to get the full advantage of this voltage 
and keep down the current. Without any allowance for 
increased efficiency at the higher voltage the mere change 
of the running voltage at thaximum load from 400 to 550, 
leaving other things the same, reduces the current to be 
transmitted for the sameenergy from 500 amperes to 364 
amperes. Now install a boosting dynamo as before, auto- 
matically holding the voltage at B at or near 550 volts. 
Using a 200 volt booster as before, we can allow 200 volts 
drop, and figuring the copper on this basis it appears that 
1,183,000 c. m. will do the work. As a matter of fact 
there would be an additional gain of nearly ten per cent 
owing to higher motor efficiency. 
The net result is that the copper needed for the work 
at 500 voltsis cut in half while the loss in voltage at full 
load is twenty-six per cent instead of forty as in the orig- 
inal booster system and the boosting dynamo itself is for 
seventy-five kilowatts instead of crie hundred kilowatts. 
As to the actual arrangement of the feeders, for a 
system likely to involve the use of large motor units and