It is easy to understand the wonders of wireless telegraphy when we
consider that electric waves transverse space in exactly the same
manner as light waves. When energy is transmitted with finite velocity
we can think of its transference only in two ways: first by the actual
transference of matter as when a stone is hurled from one place to
another; second, by the propagation of energy from point to point
through a medium which fills the space between two bodies. The body
sending out energy disturbs the medium contiguous to it, which
disturbance is communicated to adjacent parts of the medium and so the
movement is propagated outward from the sending body through the medium
until some other body is affected.

A vibrating body sets up vibrations in another body, as for instance,
when one tuning fork responds to the vibrations of another when both
have the same note or are in tune.

The transmission of messages by wireless telegraphy is effected in a
similar way. The apparatus at the sending station sends out waves of
a certain period through the ether and these waves are detected at the
receiving station, by apparatus attuned to this wave length or period.

The term electric radiation was first employed by Hertz to designate
waves emitted by a Leyden jar or oscillator system of an induction
coil, but since that time these radiations have been known as Hertzian
waves. These waves are the underlying principles in wireless telegraphy.

It was found that certain metal filings offered great resistance to
the passage of an electric current through them but that this resistance
was very materially reduced when electric waves fell upon the filings