Belt cities, they had soon learned that, physically speaking, the
stuff of life was _not_ bread. And no matter how carefully oxygen is
conserved, no process is one hundred per cent efficient. There will be
leakage into space, and that which is lost must be replaced.

There is plenty of oxygen locked up in those silicates; the problem is
towing them to the processing plants where the stuff can be extracted.

Captain St. Simon's job was simple. All he had to do was sink an anchor
into the asteroid so that the space tugs could get a grip on it. Once he
had done that, the rest of the job was up to the tug crew.

He crawled across the face of the floating mountain. At the spot where
the North Pole was, he braced himself and then took a quick look around
at the _Nancy Bell_. She wasn't moving very fast, he had plenty of time.
He took a steel piton out of his tool pack, transferred it to his left
hand, and took out a hammer. Then, working carefully, he hammered the
piton into a narrow cleft in the rock. Three more of the steel spikes
were hammered into the surface, forming a rough quadrilateral around the
Pole.

"That looks good enough to me, Jules," he said when he had finished.
"Now that we have our little anchors, we can put the monster in."

Then he grabbed his safety line, and pulled himself back to the _Nancy
Bell_.

* * * * *

The small craft had floated away from the asteroid a little, but not
much. He repositioned it after he got the rocket drill out of the
storage compartment.

"Make way for the stovepipe!" he said as he pushed the drill ahead of
him, out the door. This time, he pulled himself back to his drilling
site by means of a cable which he had attached to one of the pitons.

The setting up of the drill didn't take much time, but it was done with
a great deal of care. He set the four-foot tube in the center of the
quadrilateral formed by the pitons and braced it in position by
attaching lines to the eyes on a detachable collar that encircled the
drill. Once the drill started working, it wouldn't need bracing, but
until it did, it had to be held down.

All the time he worked, he kept his eyes on his lines and on his ship.
The planetoid was turning under him, which made the ship appear to be
circling slowly around his worksite. He had to make sure that his lines
didn't get tangled or twisted while he was working.

As he set up the bracing on the six-inch diameter drill