of rocket fumes from the side of the Platform.
Something went foaming away toward Earth. It dwindled with incredible
rapidity. Then Joe said:

"Chief, I think we'd better go down and meet that rocket. We'll learn to
handle these wagons on the way. I think we're going to have a fight on
our hands. Whoever's in that rocket isn't coming up just to shake hands
with us."

He steadied the small red vehicle and pointed it for Earth. He added:

"I'm firing a six-two solid-fuel job, Chief. Counting three.
Three--two--one."

His mount vanished in rocket fumes. But after six seconds at two
gravities acceleration the rocket burned out. The Chief had fired a
matching rocket. They were miles apart, but speeding Earthward on very
nearly identical courses.

The Platform grew smaller. That was their only proof of motion.

A very, very long time passed. The Chief fired his steering rockets to
bring him closer to Joe. It did not work. He had to aim for Joe and fire
a blast to move noticeably nearer. Presently he would have to blast
again to keep from passing.

Joe made calculations in his head. He worried. He and the Chief were
speeding Earthward--away from the Platform--at more than four miles a
minute, but it was not enough. The manned rocket was accelerating at a
great deal more than that rate. And if the Platform's enemies down on
Earth had sent a manned rocket up to destroy the Platform, the man in it
would have ways of defending himself. He would expect guided
missiles--but he probably wouldn't expect to be attacked by space
wagons.

Joe said suddenly:

"Chief! I'm going to burn a twelve-two. We've got to match velocities
coming back. Join me? Three--two--one."

He fired a twelve-two. Twelve seconds burning, two gravities
acceleration. It built up his speed away from the Platform to a rate
which would have been breathless, on Earth. But here there was no
sensation of motion, and the distances were enormous. Things which
happen in space happen with insensate violence and incredible swiftness.
But long, long, long intervals elapse between events. The twelve-two
rocket burned out. The Chief had matched that also.

Brown's voice in the headphones said, "_The rocket's cut acceleration.
It's floating up, now. It should reach our orbit fifty miles behind us.
But our missile should hit it in forty seconds._"

"I wouldn't bet on that," said Joe coldly. "Figure interception data for
the Chief and me. Make it fast!"

He spott