etic force to pass through the wire on
the moving coil. The operation of the receiving instrument is also
readily understood. It acts as an electric motor driven by the
to-and-fro currents generated by the transmitter. As these currents are
transmitted over the wire, they pass through the coil of wire on the
receiving instrument, and reproduce therein the exact movements of the
transmitting diaphragm, since, as they strengthen or weaken the
magnetism of the pole, they cause similar motions in the diaphragm
placed before it. Consequently, one listening at the receiving diaphragm
will hear all that is uttered into the transmitting diaphragm. It was
thus, by the combination of the dynamo and motor, both of which were
given by Faraday to the world, that we have received this priceless
instrument, which has been so potent in its effects on the civilization
of the Twentieth century.

The electric telegraph had its beginnings long before Faraday's time. As
early as 1847, Watson had erected a line some two miles in length,
extending over the housetops in London, and operated it by means of
discharges from an ordinary frictional electric machine. In 1774, Lesage
had erected in Geneva an electric telegraph consisting of a number of
metallic wires, one for each letter of the alphabet. These wires were
carefully insulated from each other. When a message was to be sent over
this early telegraphic line an electric discharge was passed through the
particular wire representing the letter of the alphabet to be sent; this
discharge, reaching the other end, caused a pithball to be repelled and
thus laboriously, letter by letter, the message was transmitted. How
ludicrously cumbersome was such an instrument when contrasted with the
Morse electro-magnetic telegraph of to-day, which requires but a single
wire; or with the harmonic telegraph of Gray, which permits the
simultaneous transmission of eight or more separate messages over a
single wire; or with the wonderful quadruplex telegraphic system of
Edison which permits the simultaneous transmission of four separate and
distinct messages over a single wire, two in one direction, and two in
the opposite direction at the same time; or with the still more
wonderful multiplex telegraph of Delaney, which is able to
simultaneously transmit as many as seventy-two separate messages over a
single wire, thirty-six in one direction and thirty-six in the opposite
direction. These achievements have been