“Come in, come in, David and Jonathan,—­I mean William and Augustus!” greeted Professor Gray.  “Find chairs, boys.  I’m glad you’ve come.  Now, then, exactly in nine minutes the lecture starts and it will interest you.  The announcement, as sent out yesterday, makes the subject the life and labors of the great scientist and inventor, Thomas Alva Edison, and it begins with his boyhood.  Don’t you think that a fitting subject upon an occasion where electricity is the chief factor?  But before the time is up, let me say a few words concerning our little boxed instrument 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 aerial or antennas wires high in the air.  Thus sound is converted into waves, and the receiving station, as you see here, with its aerial 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 aerial and the assembling are all technicalities that may be mastered by a careful study of the subject and the result will be a simple and inexpensive set having a limited range.  With more highly perfected appliances, as a vacuum, or audion tube, and an aerial elevated from sixty to over a hundred feet, you may receive radio energy thousands of miles away.

“Now, this talk we are about to hear comes to us from the broadcasting station WUK at Wilmerding, a distance of three hundred miles, and this outfit of mine is such as to get the words loudly and clearly enough to be audible through a horn.  The talks are in series; there have been three on modern poets, two on the history of great railroad systems and now this will be the first of several on great inventors, beginning with Edison, in four parts.  The next will be on Friday and I want you all to be here.  Time is up; there will be a preliminary-ah, there it is:  a cornet solo by Drake.”