here, out of which will come the words we hope to hear. Some of you, I
think, have become pretty familiar with this subject, but for those who
have not given much attention to radio, I will briefly outline the
principles upon which these sounds we shall hear are made possible.

"It would seem that our earth and atmosphere," continued the Professor,
"and all of the universe, probably, is surcharged with electrical energy
that may be readily set in motion through the mechanical vibrations of a
sensitive diaphragm much as when one speaks into a telephone. This
motion is transmitted in waves of varying intensity and frequency which
are sent into space by the mechanism of the broadcasting station, which
consists of a sound conducting apparatus induced by strong electrical
currents from generators or batteries and extensive aërial or antennas
wires high in the air. Thus sound is converted into waves, and the
receiving station, as you see here, with its aërial on the roof, its
detector, its 'phone and its tuner, gets these waves and turns them
again into sound. That is the outline of the thing, which you will
understand better 'after' than 'before using.'

"The technical construction of the radio receiving set is neither
difficult nor expensive; it is described fully in several books on the
subject and I shall be glad to give any of you hints on the making and
the operation of a receiving set. The 'phone receivers and the crystal
detector will have to be purchased as well as some of the accessories,
such as the copper wire, pulleys, battery, switches, binding posts, the
buzzer tester and so forth. With proper tools and much ingenuity some of
these appliances may be home-made.

"The making of the tuner, the wiring, the aërial and the assembling are
all technicalities that may be mastered by a careful study of the