88 POWER DISTRIBUTION FOR ELECTRIC RAILROADS. 
conveniently overcome by ordinary compounding, boosting 
is eminently useful. 
If the line A B (Fig. 50), when designed for a certain 
drop at average load, say, five per cent, gives no more 
than fifteen per cent or so at maximum load ordinary over- 
compounding will answer admirably. If, however, the 
maximum load rises to five or six times the average 
for which the line was designed boosting is by far the 
simplest way out of the difficulty. 
Suppose now A B to be fifteen or twenty miles long 
and to have a heavy and fast interurban traffic. Could it 
be worked to advantage by supplying current directly to 
that part of the line comfortably near the power station 
and feeding the rest of the line by boosting, in sections 
using boosters of different voltage if necessary? At first 
thought one might be tempted to say ‘‘ Yes’’, for in such 
case each section would be in full action for but a short 
part of the day. On the other hand it should be noted 
that a// the energy supplied to the distant sections, be it 
little or much, is supplied under very wasteful conditions, 
and while such an arrangement would allow a very long 
line to be served there is generally no excuse in the pres- 
ent state of the art for a device so clumsy and wasteful. 
It must not be understood from this that there are no 
cases in which direct transmission at more than usual line 
loss is to be preferred to indirect transmission with recon- 
version. Such certainly exist, but since at the present 
time it is possible to transmit power at high voltage and 
reconvert to direct current with a loss not exceeding fif- 
teen to twenty per cent, the field for direct ‘ransmission at 
much greater lossis very limited. 
Boosting is preferable to heavy overcompounding, 
when unusually long feeders are exposed to great changes 
of load, for the reasons already suggested, and it must not 
be forgotten that when the only loss is that in the line 
which varies inversely as the load, the all-day efficiency 
of the system may be fairly high. ‘This matter will 
be taken up again in connection with the application of the