"You say that you think that it's safe, and yet you won't take a crew," Samms argued. "In that case it isn't safe enough for you men, either. We need you too badly to permit you to take such chances."

"You've got to let us go; because we are the only ones who are thoroughly familiar with her theory," Rodebush insisted. "I said, and still say, that I think it is safe. I can't prove it, however, except mathematically; because she's altogether too full of too many new and untried mechanisms, too many extrapolations beyond all existing or possible data. Theoretically, she is sound, but you know that theory can go only so far, and that mathematically negligible factors may become operative at those velocities. We do not need a crew for a short trip. We can take care of any minor mishaps, and if our fundamental theories are wrong, all the crews between here and Jupiter wouldn't do any good. Therefore we two are going--alone."

"Well, be very careful, anyway. Start out slow and take it easy."

"Start out slow? We can't! We can't neutralize half of gravity, nor half of the inertia of matter--it's got to be everything or nothing, as soon as the neutralizers go on. We could start out on the projectors, of course, instead of on the neutralizers, but that wouldn't prove anything and would only prolong the agony."

"Well, then, be as careful as you can."

"We'll do that, Chief," Cleveland put in. "We think a lot of us, and we aren't committing suicide just yet if we can help it. And remember about everybody staying inside when we take off--it's barely possible that we'll take up a lot of room. Good-bye to all of you."

"Good-bye, fellows!"

The massive insulating doors were shut, the metal side of the mountain opened, and huge, squat caterpillar tractors came roaring and clanking into the room. Chains and cables were made fast and, mighty steel rails groaning under the load, the space-ship upon her rolling ways was dragged out of the Hill and far out upon the level floor of the surface before the tractors cast off and returned to the fortress.

"Everybody is under cover." Samms informed Rodebush. The chief was staring intently into his plate, upon which was revealed the control room of the untried super-ship. He heard Rodebush speak to Cleveland; heard the observer's brief reply; saw the navigator throw his switches--then the communicator plate went blank. Not the ordinary blankness of a cut-off, but a peculiarly disquieting fading out into darkness. And where the great space-ship had rested there was for an instant nothing. Exactly nothing--a vacuum. Vessel, falsework, rollers, trucks, the enormous steel I-beams of the tracks, even the deep-set concrete piers and foundations and a vast hemisphere of the solid ground; all had disappeared utterly and instantaneously. But almost as suddenly as it had been formed the vacuum was filled by a cyclonic rush of air. There was a detonation as of a hundred vicious thunderclaps made one, and, through the howling, shrieking blasts of wind, there rained down upon the valley, plain and metaled mountain a veritable avalanche of debris: bent, twisted, and broken rails and beams, splintered timbers, masses of concrete, and thousands of cubic yards of soil and rock. For inertia and gravitation had not been neutralized at precisely the same instant, and for a moment everything within the radius of action of the iron-driven gravity nullifiers of the Boise had continued its absolute motion with inertia unimpaired. Then, left behind immediately by the almost infinite velocity of the cruiser, all this material had again become subject to all of Nature's everyday laws and had crashed back to the ground.

"Could you hold your beam, Randolph?" Samm's voice cut sharply through the daze of stupefaction which held spellbound most of the denizens of the Hill. But all were not so held--no conceivable emergency could take the attention of the chief ultra-wave operator from his instruments.

"No, sir," Radio Center shot back. "It faded out and I couldn't recover it. I put everything I've got behind a tracer on that beam, but haven't been able to lift a single needle off the pin."