e up! Don't rub it in
on your old dad. I admit that folks did laugh at those inventors,
with their seemingly impossible schemes, but they made good. And
you've made good lots of times where I thought you wouldn't. But
just stop to consider for a moment. This thing of sending a
picture over a telephone wire is totally out of the question, and
entirely opposed to all the principles of science."

"What do I care for principles of science?" cried Tom, and he
strode about the room so rapidly that Eradicate, the old colored
servant, who came in with the mail, skipped out of the library
with the remark:

"Deed, an' Massa Tom must be pow'fully preragitated dis mawnin'!"

"Some of the scientists said it was totally opposed to all natural
laws when I planned my electric rifle," went on Tom. "But I made
it, and it shot. They said my air glider would never stay up, but
she did."

"But, Tom, this is different. You are talking of sending light
waves--one of the most delicate forms of motion in the world--over
a material wire. It can't be done!"

"Look here, Dad!" exclaimed Tom, coming to a halt in front of his
parent. "What is light, anyhow? Merely another form of motion;
isn't it?"

"Well, yes, Tom, I suppose it is."

"Of course it is," said Tom. "With vibrations of a certain length
and rapidity we get sound--the faster the vibration per second the
higher the sound note. Now, then, we have sound waves, or
vibrations, traveling at the rate of a mile in a little less than
five seconds; that is, with the air at a temperature of sixty
degrees. With each increase of a degree of temperature we get an
increase of about a foot per second in the rapidity with which
sound travels."

"Now, then, light shoots along at the rate of 186,000,000 miles a
second. That is more than many times around the earth in a second
of time. So we have sound, one kind of wave motion, or energy; we
have light, a higher degree of vibration or wave motion, and then
we come to electricity--and nobody has ever yet exactly measured
the intensity or speed of the electric vibrations."

"But what I'm getting at is this--that electricity must travel
pretty nearly as fast as light--if not faster. So I believe that
electricity and light have about the same kind of vibrations, or
wave motion."

"Now, then, if they do have--and I admit it's up to me to prove
it," went on Tom, earnestly--"why can't I send light-waves over a
wire, as well as electrical waves?"