"A man named Hertz discovered a way of stirring up this energy,
snapping it, you might say, as a man snaps a whip. It was found that
these waves could be made long enough and strong enough to go all
the way across the Atlantic Ocean, in fact to go around the world.

"Around the world!" murmured Jimmy, and again he was tempted to ask
somebody to pinch him, but remembered his previous experience and
stopped just in time.

"Now," continued the doctor, "you may ask what this has to do with
the voice, for it is with the voice that one talks over the 'phone.
The whole principle of the wireless telephone is based on the fact
that sound can be transformed into electricity and then can be
transformed back into sound again. I know," he said, with a smile,
"that that sounds very much like saying that you can make eggs into
an omelet and then get the omelet back into separate eggs again"
--here there was an audible snicker from the boys--"but that is very
much like what is done by the wireless, although it doesn't exactly
fit the case.

"Now see what a wonderful increase in power you get the moment the
sound waves are changed into electric waves. Sound goes at the rate
of one thousand and ninety feet a second. Electrical energy travels
at the rate of one hundred and eighty-six thousand miles a second.
In other words it could go around the world more than seven times
in a single second.

"When you speak into a telephone, unless you are greatly excited,
you don't use more than a fiftieth part of the power of your voice.