hed Tom. "You mean uranium pitchblende?"

"I mean uranium!" snapped Roger. "Uranium pitchblende isn't concentrated
enough to cause a reaction like that on the instruments. It would take a
big chunk of pure uranium to do the job."

"But if that were so," Astro protested, "wouldn't the instruments still
be acting up? In fact, wouldn't we start feeling the effects of the
radiation?"

"Not necessarily, Astro," said Tom. "I understand what Roger's getting
at. The uranium could be located in another sector of the satellite, on
the other side, maybe. It could be throwing radiation out into space
without affecting us here."

"You mean we're _under_ the effects?" asked Astro.

"Looks like it," replied Tom. "But on the other hand," he continued,
"why wasn't there some report of it when the first expedition came out
to look over the satellite?"

"I can't answer that question, Tom," answered Roger. "But I'd be willing
to bet my last credit that there's uranium on this space-forsaken rock.
And a whopping big deposit of it!"

They reached the air lock of the _Polaris_ and climbed wearily aboard.
At the end of the first day, on the new satellite, they were exhausted.
A few minutes after entering the giant cruiser they were all sound
asleep.

Dawn of the second day on Roald saw the vast plain crowded with men at
work. The first community objective was the construction of an
atmosphere station, and before the woman and children had finished
lunch, they were breathing synthetically produced air.

Working from a master plan that had been devised back at Space Academy
before the expedition blasted off, the colonists were divided into three
separate crews: the wreckers, those who would remove essential parts
from the spaceships as they were needed; the movers, those who would
haul the parts to construction sites; and the builders, those who would
take the parts and construct the community buildings.

The first and most difficult job was building a gigantic maneuverable
derrick and jet barge for removing, hauling, and installing the heavy
machinery.

Astro had been assigned to the crew responsible for the construction of
the jet barge. With many of the vital parts aboard the crashed
freighters still hot with radioactivity, the crew had to improvise. And
Astro, with his native talent for mechanics, soon became the unspoken
leader of the crew. Even the supervisor acknowledged the young cadet's
superior ability and allowed him a f