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. I wish that you could start out slow and
take it easy."

"In a way, so do I, but she wasn't designed to 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 as much of us as
anybody else does--maybe more--and we aren't committing suicide 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. Goodbye!"

"Goodbye, 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 valley
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 push the
switch-button--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 disappeared utterly and instantaneously. But almost as