192 POWER DISTRIBUTION FOR ELECTRIC RAILROADS.
class are liable to poor power factors when starting, though
when running the power factors are uniformly high.
The induction motors for monophase circuits are still
in an early stage of development as regards application to
such severe service as is mecessary on electric railways.
The most promising of them are those supplied with de-
rived polyphase currents even if this advantage involves
the use of condensers, since they can be made to give high
starting torque and a gcod power factor. ‘Thestarting de-
vices applied to all existing strictly monophase motors are
entirely insufficient for railway purposes unless a clutch
connection is used in which rather unmechanical case syn-
chronous motors would be generally preferable.
With derived polyphase circuits, at least for starting, it
is, in the author’s opinion, entirely practicable to produce
even now a motor for monophase circuits entirely capable
of doing railway work successfully and economically.
It does not follow from this that all classes of electric
railway work can now, or ever, be acccmplished best by
the use of alternating motors of any sort. But the same
logic of circumstances that has brought alternating sys-
tems into increasing use for lighting and general power
purposes applies to railway work with ominous force. It
is altogether probable that for a vast amount of strictly
street railway work the continuous current motor is here
to stay. In its present state of development it is, at least
as a motor, as good as any alternating current motor is
likely to be. But the question of voltage presses hard,
and as the distances to be reached continually grow the
time comes when a distribution that can be used for con-
tinuous current motors becomes outrageously costly in ma-
terial or in loss of energy. ‘The economic value of alter-
nating motors - depends on their adaptation to a very
economical method of distribution. In many cases they
not only meet this condition, but can be applied with ad-
vantage irrespective of the distribution system.
For urban work they possess few intrinsic advantages
over continuous current motors. For much interurban
