r of a mile from each other. Telephonic
communication was established between them, and thus he had attained
wireless telephony by induction. In 1887, another Englishman, A.W.
Heaviside, laid circuits over two miles long on the surface and other
circuits in the galleries of a coal-mine three hundred and fifty feet
below, and established communication between the circuits. Working
together, Preece and Heaviside extended the distances over which
they could communicate. Preece finally decided that a combination of
conduction and induction was the best means of wireless communication.
He grounded the wire of his circuit at two points and raised it to a
considerable height between these points. Preece's work was to put the
theories of Professor Trowbridge to practical use and thus bring the
final achievement a step nearer.

But conduction and induction combined would not carry messages to a
distance that would enable extensive communication. A new medium had
yet to be found, and this was the work of Heinrich Hertz, a young
German scientist. He was experimenting with two flat coils of wire,
as had many others before him, but one of the coils had a small gap
in it. Passing the discharge from a condenser into this coil, Hertz
discovered that the spark caused when the current jumped the gap set
up electrical vibrations that excited powerful currents in the other
coil. These currents were noticeable, though the coils were a very
considerable distance apart. Thus Hertz had found out how to send out
electrical waves that would travel to a considerable distance.

What was the medium that carried these waves? This was the question
that Hertz asked himself, and the answer was, the ether. We know that
light will pass through a vacuum, and these electric waves would do
likewise. It was evident that they did not pass through the air. The
answer, as evolved by Hertz and approved by other scientists, is that
they travel through the ether, a strange substance which pervades all
space. Hertz discovered that light and his electrical waves traveled
at the same speed, and so deduced that light consists of electrical
vibrations in the ether.

With the knowledge that this all-pervading ether would carry electric
waves at the speed of light, that the waves could be set up by the
discharge of a spark across a spark-gap in a coil, and that they
could be received in another coil in resonance with the first, the
establishment of a practical wireles