“It seems funny to me that the vacuum tube could have any use in radio,” put in Jimmy. “I never thought of it in any way but as being used for an electric light.”
“Neither did lots of other people,” replied the doctor, smiling. “Even Mr. Edison himself didn’t realize what its possibilities were. He did, though, discover some very curious things about it. In fact, he made the first step that led to its use for radio. He put a plate in one of his lamps. The plate didn’t touch the filament, but formed part of a circuit of its own with a current indicator attached. Then when he turned on the light and the filament began to glow, the needle of the indicator began to twitch. Since the filament and the plate weren’t touching, the movement of the needle indicated that the electricity must have jumped the gap between the two. But this simply showed that an invisible connection was established between the filament and the plate and nothing more came of it at the time.
“Now, it’s likely that even yet we shouldn’t have had that discovery of Edison’s used for the development of radio if it hadn’t been for the new theory of what electricity really is. That theory is that everything is electricity. This chair I’m sitting on, the railing to this porch, the hat that Jimmy is holding in his hand—all that is electricity.”
Jimmy gave a little jump at this, and held his hat rather gingerly at arm’s length and looked at it suspiciously.
The doctor joined in the laugh that followed.
“Oh, you needn’t be afraid that you’ll get a shock,” he said. “Electricity won’t hurt you as long as it’s at rest. It’s only when it gets stirred up that high jinks are apt to follow.”
Jimmy looked relieved.
“Now,” continued the doctor, “the theory is that all matter is composed of an infinite number of electrons. An electron is the smallest thing that can be conceived, smaller even than the atom which used to be thought of as the unit. There may be millions, billions, quadrillions of them in a thing as big as a hickory nut. And when these electrons get busy you can look out for things to happen.
“Every hot object sends out electrons. That’s the reason that the filament in the electric light tube sends them out.”
“I suppose a red-hot stove would send them out, too,” suggested Joe. “If that is so, I should think that people would have found out about them long ago.”