wires it would seem, on first thought, to be an easy matter to
telephone without wires, but not so, for the electric spark sets up
damped and periodic oscillations and these cannot be used for
transmitting speech. Instead, the oscillations must be of constant
amplitude and continuous. That a direct current arc light transforms a
part of its energy into electric oscillations was shown by Firth and
Rogers, of England, in 1893.

The author was the first to connect an arc lamp with an aerial and a
ground, and to use a microphone transmitter to modulate the sustained
oscillations so set up. The receiving apparatus consisted of a
variable contact, known as a _pill-box_ detector, which Sir Oliver
Lodge had devised, and to this was connected an Ericsson telephone
receiver, then the most sensitive made. A later improvement for
setting up sustained oscillations was the author's _rotating
oscillation arc_.

Since those memorable days of more than two decades ago, wonderful
advances have been made in both of these methods of transmitting
intelligence, and the end is as yet nowhere in sight. Twelve or
fifteen years ago the boys began to get fun out of listening-in to
what the ship and shore stations were sending and, further, they began
to do a little sending on their own account. These youngsters, who
caused the professional operators many a pang, were the first wireless
amateurs, and among them experts were developed who are foremost in
the practice of the art today.

Away back there, the spark coil and the arc lamp were the only known
means for setting up oscillations at the sending end, while the
electrolytic and crystal detectors were the only available means for