Then the cam was installed. The time went by even slower then, because the cam must be lapped and polished to absolute perfection, not only of its own surface but to absolute concentricity to the shaft on which it turned. But eventually the job was finished, and the men stood back, their eyes expectantly upon Don Channing and Walt Franks. * * * * * Don spoke to the man chosen to control the beam. "You can start any time now. Keep her knifed clean, if you can." The man grinned at Channing. "If the devils that roam the void are with us we'll have no trouble. We should all pray for a phrase used by some characters in a magazine I read once: 'Clear ether!' We could use some right now." He applied his eyes to the telescope. He fiddled with the verniers for a brief time, made a major adjustment on a larger handwheel, and then said, without removing his eye from the 'scope, "That's it, Dr. Channing." Don answered: "O.K., Jim, but you can use the screen now. We aren't going to make you squint through that pipe for the next few hours straight." "That's all right. I'll use the screen as soon as we can prove we're right. Ready?" "Ready," said Channing. Franks closed a tiny switch. Below, in the transmitter room, relays clicked and heavy-duty contacts closed with blue fire. Meters began to climb upward across their scales, and the generators moaned in a descending whine. A shielded monitor began to glow, indicating that full power was vomiting from the mouth of the reflector. And out from the projector there went, like a spearhead, a wavefront of circularly polarized microwaves. Die-true they sped, crossing the void like a line of sight to an invisible spot above Mars and to the left. Out past the Sun, where they bent inward just enough to make Jim's job tough. Out across the open sky they sped at the velocity of light, and taking sixteen minutes to get there. Would it--or wouldn't it? A half-hour passed. "Now," said Channing. "Are we?" Ten minutes went by. The receiver was silent save for a constant crackle of cosmic static. Fifteen minutes passed. "Nuts," said Channing. "Could it be that we aren't quite hitting them?" "Could be," admitted Franks. "Jim, waggle that beam a bit, and slowly. When we hit 'em, we'll know it because we'll hear 'em a half-hour later. Take it easy and slowly. We've used up thirteen of our fifty-odd hours. We can use another thirty or so just in being sure." Jim began to make the beam roam around the invisible spot in the sky. He swept the beam in microscopic scans, up and down, and advancing the beam by one half of its apparent width at the receiver for each sweep. Two more hours went by. The receiver was still silent of reflected signals.