But by the time that sound has been caught up and churned, as it
were, into electrical energy it is more than a hundred thousand
times as loud and strong.

"Suppose now, just as an illustration, that you were going to
telephone to Europe. You'd pick up the 'phone and give your message.
That sound would go in the form of a tiny electrical impulse into one
of the great sending stations on the Atlantic Coast, we'll say, and
there it would be caught up by a powerful lot of electrical machines,
amplifiers, alternators, and others, that would keep making it
stronger and stronger until finally it was flung out into space from
the ends of the great wires or antennae. Out and out it would go until
it struck a lot of wires on the other side of the ocean. Then it would
go through another process that would gradually change the electrical
impulse back into sound again, and the man at the other end of the
telephone would hear your voice, just as one does now when you 'phone
to any one in this town."

He paused for a moment, and there was a long drawn breath on the part
of his auditors that testified to the rapt attention with which they
had followed him into this fairyland of science.

"So much for the theory and principle of the wireless," resumed the
doctor. "Of course I've only scratched the surface, and if I talked
to you all night there'd be still lots left to say. But we only need
to know a little about it to put it to practical use. And it is the
practical use of the wireless telephone that I'm especially interested
in for the sake of you boys. I'm satisfied that there's hardly
anything that could give you more pleasure or more benefit than for
each of you to have one of these contrivances in your own home. It's