“Of course you know about the waves of the sea,” began Joe. “Well, the air, or more properly the ether, is full of just such waves. But they are not set in motion till a disturbing element answering to a storm or a wind at sea is set loose among them. For instance, when I depress this key, I set loose an electric shock that agitates the ether and sends out waves. These waves may be long or short as I desire, according to the power of the shock sent out.
“In 1888 a Professor Hertz began the first attempts to utilize these waves to send messages through the air. In a crude way he succeeded, and paved the way for his followers along these lines. Hertz found that heat and light are all electric waves. The waves that he set in motion from his apparatus bear his name, Hertzian waves.”
“Then all the air is full of waves?” asked Hank, looking about him in a rather scared sort of way, as if he rather expected to be engulfed in some atmospheric disturbance at any time and was preparing to swim for his life.
“That’s it, Hank, you’re catching on fine. But understand, the waves require some force to agitate them. It’s like a mill pond, the air is, quite smooth till you chuck a stone into it, and then waves begin spreading out in all directions.”
Hank nodded as if he quite understood this homely illustration.
“Heave ahead,” he said, settling back in his seat.
“All right,” smiled Joe. “Now you see my detector here,—quite an elaborate bit of mechanism, isn’t it?”
“Yep, that’s what bit me,” muttered Hank, rubbing his arm once more at the recollection.
“Well, Hertz had to make his detector just out of a circle of wire with a gap in it. A screw adjustment lengthened or shortened the distance between the ends of the wire, making the gap larger or smaller. The waves, as they came in, were registered on this detector in the form of minute sparks. Is this all clear to you?”
“Oh, as clear as mud,” was the non-committal reply, with a wave of the hand.