"We'll have some more selections later on in the evening," he
continued, "but now I want to explain to you how this thing is done.
I can't hope to do much more than touch the surface of the subject
to-night, for I don't want to tire you out, and there'll be plenty of
other nights and days when I hope you boys will call upon me for any
information that you want and I can give.

"Of course the whole thing is based on electricity, the most wonderful
thing that perhaps there is in the whole physical world. Nobody knows
what electricity is--Mr. Edison himself doesn't know. We only know
that it is a wonderful fluid and that the ether is full of it. But
though we don't know what it is, scientific men have learned how to
develop and use its energy, and among other things they have harnessed
it in the service of the wireless telephone.

"Take for instance a quiet lake. It may seem absolutely still, but
if you throw a stone in it you start a number of ripples that keep
spreading further and further out until they break on the shore. So
if you hit a drum with a stick, sound waves are stirred up that keep
spreading out very much like the ripples on the lake.

"Now electricity is something like that. It doesn't begin to act until
you do something to it. The impulse to ripple is in the quiet lake all
the time, but it doesn't ripple until you throw the stone in it. The
sound quality is in the drum, but you don't hear it until you hit the
drum with a stick. So you've got to put into the ether something that
disturbs the electricity in it, something that stirs it up, and then
this disturbance makes waves that travel on, just as the waves on the
lake follow one another and just as the sound waves from the drum keep
pushing each other along.