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XXII. W. H. WARREN. 
Holske works in Berlin, very similar to the last described, but 
still in the experimental stage. It is clear, therefore, that there 
is a general effort being made to find something better than the 
overhead wire and more in accordance with our notions of 
a permanent system, providing ample security against injury, 
but this cannot be done without increasing considerably the cost 
of electrical transmission. ; 
Motors.—An electric motor for street railway service differs 
from an ordinary electric motor for driving shafting, in that the 
power to be overcome is very variable. The large torque, OF . 
starting power, is the characteristic feature of the street railway 
motor, and it has been found that the average work is about 
20% of the maximum which occurs at starting. The electric motor 
has no dead centres like the steam engine, and can start equally 
well in al] positions of the revolution. 
Electric motors must be light and strong, must be completely 
protected from dirt and water; they should be capable of 
developing an emergency 100% more than their rated capacity 
without undue heating. All parts should be accessible and easily 
taken apart, and renewed or repaired when necessary. Motors 
are general series wound. The pole pieces are steel castings of a 
specially soft quality of metal, and in order to prevent losses from 
hysteresis, eddy currents, and friction, as well as to produce the 
large torque, a large number of windings of wire in the armature 
are necessary. A spur pinion on the motor drives a spur wheel 
on the axle, the reduction in speed is about one-fourth, and these 
are made with the greatest accuracy, by means of automatic 
wheel-cutting machinery. The armature is built up of a core 
consisting of thin soft iron disks, and these are punched out all 
round their circumference into notches, which form the slots for 
receiving the coils or winding, after the disks have been threaded 
upon the axle or shaft of the armature, and compres: 
hydraulic machinery. The coils are made up separately, being 
wound into form, carefully bound with several layers of insulating 
“material and treated with insulating compound. The completed 
