mething
that'll float us on the canal."

Single file, wearing the space cloths once more as protection against
the sun, they walked along the bank of the canal. When the heat became
unbearable, they dipped the squares of space cloths into the water and
wrapped themselves in them. When they began to dry out, they would
repeat the process. At noon, when the sun dried the fabric nearly as
fast as they could wet it, they stopped and slipped over the edge of the
bank into the cool water. Covering their heads with the cloths they
remained partly submerged until the late afternoon. When the sun had
lost some of its power, again they climbed out and continued walking.

Marching late into the night, they made camp beside the canal, finished
the last container of food, and, for the first time since leaving the
ship, slept during the night. By the time Deimos had risen in the sky,
they were sound asleep.

[Illustration]

CHAPTER 22

"Eeeeeeoooooooow!" Astro's bull-like roar shattered the silence of the
desert. "There--up ahead, Tom--Roger--a building!"

Tom and Roger stopped and strained their eyes in the bright sunshine.

"I think you're right," said Tom at last. "But I doubt if anyone's
there. Looks like an abandoned mining shack to me."

"Who wants to stand here and debate the question?" asked Roger, and
started off down the side of the canal at a lope, with Astro and Tom
right behind him.

During the last three days the boys had been living off the contents of
the last remaining food container and the few lichens they found growing
along the canal. Their strength was weakening, but with an abundant
supply of water near at hand and able to combat the sun's heat with
frequent swims, they were still in fair condition.

Tom was the first to reach the building, a one-story structure made of
dried mud from the canal. The shutters and the door had long since been
torn away by countless sandstorms.

The three boys entered the one-room building cautiously. The floor was
covered with sand, and sand was piled in heaping drifts in front of the
open windows and door.

"Nothing--not a thing," said Roger disgustedly. "This place must be at
least a hundred and fifty years old."

"Probably built by a miner," commented Tom.

"What do you mean 'nothing'?" said Astro. "Look!"

They followed Astro's pointing finger to the ceiling. Crisscrossed, from
wall to wall, were heavy wooden beams.

"Raft!" Tom cried.

"That's