On the evening of the fourth day I came up to the laboratory about ten o’clock, and found Tom making some last adjustments, while Dorothy and Jones looked on.
“We think we have it,” said Dorothy, as she greeted me. “This is the last connection.”
“Now that you have it all set up, tell me how it works,” I said. “You’ve been so tied up in the thing, that I’ve hardly heard a word from you in a week.”
“Too bad,” answered Dorothy, laughing. “We’ll tell you enough about it to show you what to expect.”
I leaned over curiously to examine the wave-measuring machine. It stood on a round table ten or twelve feet in diameter looking not unlike some fortressed town, such as rises on the banks of many a river in southern Europe. A belt of broad, shining metal a foot high encircled it as the gray walls of stone surround the town. Within the belt stood polished cones and hemispheres, which rose for a height of some two feet, bringing to mind round towers of fortalice and dwelling within battlemented walls. Wires, ranged with mathematical preciseness, completed the comparison by their similarity to streets surmounted by telegraph wires. The surrounding belt seemed solid, but, as Jones threw the reflector of a powerful incandescent on it, I could see it was lined with millions of tiny seams. Tom threw a switch and, to my surprise, the belt began slowly to revolve about the central portion.
“What’s that belt for?” I asked.
“That’s where the wave of electrical energy enters. It goes into the interior of the machine through one of those tiny slits which you see. Once inside, the wave strikes a magnetic coil about a mirror, which swings when the energy acts upon it, and throws a beam of light down that scale.” He pointed to the opposite wall.
There, extending from one side to the other of the room, some fifty feet in all, stretched a scale like a foot rule suddenly grown gigantic. Its space was covered with divisions, a big zero in the middle and numbers running up from zero into the hundreds of thousands and millions on either side. Just at the zero point rested a long narrow beam of light.
“You see that beam,” Tom went on. “When the waves come into the machine, they go through as I explained, the machine stops, and the light goes up or down the scale. The distance that it goes shows how far away the wave started. The slit through which the wave comes shows the exact direction from which it comes, and we can get that easily because the machine stops as the wave goes through. Then, by means of a certain amount of mathematics, we hope to be able to find just where a wave comes from. We can adjust the machine so that it will register anything from a wireless telegraph message through a radium discharge to the enormously powerful waves which ‘the man’ uses. We have it adjusted now for the waves which ‘the man’ uses in destroying battleships. We know something of them from the way in which they charged the reflectoscopes. That’s the whole thing.”
“One thing more,” I said inquiringly. “If ‘the man’ destroys a battleship, does the machine stop and the beam of light run down the scale.”