d sat down,
wiping his forehead with a huge blue handkerchief.

There was a roar. A pushpot had started its motor. Another roar.
Another. One by one, the multitude of clustering objects added to the
din. In the open a single jet was appalling. Here, the noise became a
sound which was no longer a sound. It became a tumult which by pure
volume ceased to be anything one's ears could understand. It reached a
peak and held there. Then, abruptly, all the motors slackened in unison,
and then roared more loudly. The group controls within the Platform were
being tested. Three--four--five times the tumult faded to the merely
unbearable and went up to full volume again.

Joe felt Sally plucking at his arm. He turned, and saw a jet plane's
underbelly, very close, and its swept-back wings. It was climbing
straight up. Then he saw another jet plane streaking for the great
dome's open door. It moved with incredible velocity. It jerked upward
and climbed over the Shed's curve and was gone. But there were others
and others and others.

These were the fighter ships of the jet-plane guard. For months on end
they had flown above the Shed, protecting it. Now they were going aloft
to relieve the present watchers. They were rising to spread out as an
interceptor screen for hundreds of miles in every direction, in case
somebody should be so foolish as to try again the exploit of the night
before. They would not see the monster in the Shed again. So in a single
line which reached to the horizon, they made this roaring run for the
one last glimpse which was their right. Joe saw tiny specks come
streaking down out of the sky to queue up for this privileged view of
the Platform before it rose.

Suddenly they were gone, and Joe felt that tingling sense of pride which
never comes from the sensation of sharing in mere power or splendor or
pompous might, but is so certain when the human touch modifies
magnificence.

And then the roaring of the pushpot engines achieved an utterly
impossible volume. The whole interior of the Shed was misty now, but
shining in the morning light.

And the Platform moved.

At first it was a mere stirring. It turned ever so slightly to one side,
pivoting on the ways that had supported it during building. It turned
back and to the other side. The vapor thickened. From each jet motor a
blast of blue-white flame poured down, and the moisture in the earth was
turning into steam and stray wood-blocks into acrid smoke. T