the alternating-current motor first same into general use, it was
employed, in connection with the alternating-current generator, in
electric transmission systems; but such motors also possess the
inconvenience of not readily starting from a state of rest, with their
full turning power, or torque, and of therefore being unsuitable where
the motor requires to be frequently stopped or started. Had these
difficulties remained unsolved, long-distance electric transmission of
power, so successful in operation to-day, and which bids fair to be
still more successful in the near future, would have been impossible.
Fortunately, these difficulties were overcome by the genius of Nikola
Tesla, in the invention of the multiphase alternating-current motor, or
the induction motor, as it is now generally called. Although Baily,
Deprez, and Ferraris had accomplished much before Tesla's time, yet it
was practically to the investigations and discoveries made by Tesla,
between 1887 and 1891, that the induction motor of to-day is due.

Another requirement of our twentieth-century civilization is rapid
transit, either urban or inter-urban, and this is afforded by various
systems of electric street railways or electric traction generally,
including electric locomotives and electric automobiles. The wonderful
growth in this direction which has been witnessed in the last few
decades would have been impossible without the electric generator and
motor, both gifts of Faraday to the world. Their application in this
direction must, therefore, go to swell the debt our civilization owes to
the labors of this great investigator.

In the system of electric street-car propulsion very generally employed
to-day, a single trolley wheel is employed for taking the driving
current from an overhead conductor, suspended above the street. The
trolley wheel is supported by a trolley pole, and is maintained in good
electric contact with the trolley wire, or overhead conductor. By this
means the current passes from the wire down the conductor connected with
the trolley pole, thence through the motors placed below the body of the
car, and from them, through the track or ground-return, back to the
power station. A small portion of the current is employed for lighting
the electric lamps in the car. In some systems an underground trolley
is employed.

An important device, called the series-parallel controller, is employed
in all systems of electric street-car propulsi