on. It consists of means
by which the starting and stopping of the car, and changes, both in its
speed and direction, are placed under the control of the motorman. A
separate controller is placed on both platforms of the car. The
series-parallel controller consists essentially of a switch by means of
which the several motors, that are employed in all street cars, can
be variously connected with each other, or with different electric
resistances, or can be successively cut out or introduced into the
circuit, so that the speed of the car can be regulated at will, as the
handle of the controller is moved by the motorman to the various notches
on the top of the controller box. As generally arranged, the speed
increases from the first notch or starting position to the last notch,
movements in the opposite direction changing connections in the opposite
order of succession, and, therefore, slowing the car. There is, however,
no definite speed corresponding to each notch, for this will vary with
the load on each car, and with the gradient upon which it may
be running.

But there is another valuable gift received by the world as a result of
this great discovery of Faraday; namely, that most marvellous instrument
of modern times, the speaking telephone. This instrument was invented in
1861, by Philip Ries, and subsequently independently reinvented in 1876,
by Elisha Gray and Alexander Graham Bell.

As is well known, it is electric currents and not sound-waves that are
transmitted over a telephone circuit. The magneto-electric telephone in
its simplest form consists of a pair of instruments called respectively
the transmitter and the receiver. We talk into the transmitter and
listen at the receiver. Both transmitter and receiver consist of a
permanent magnet of hardened steel around one end of which is placed a
coil of insulated wire. In front of this coil a diaphragm, or thin
plate, of soft iron, is so supported as to be capable of freely
vibrating towards and from the magnet pole.

The operation of the transmitting instrument is readily understood in
the light of Faraday's discovery. It is simply a dynamo-electric machine
driven by the voice of the speaker. As the sound-waves from the
speaker's voice strike against the diaphragm, which has become magnetic
from its nearness to the magnet pole, electric currents are generated in
the coil of wire surrounding such pole, since the to-and-fro motions
cause the lines of electro-magn