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?"