dred and fifty-four miles to be exact."

"_Exact_ only as far as my sun sight told me," said Roger.

"Do you think it's right?" asked Tom.

"I'll answer you this way," Roger replied. "I took that sight six times
in a half hour and got a mean average on all of them that came out
within a few miles of each other. If I'm wrong, I'm very wrong, but if
I'm right, we're within three to five miles of the position I gave you."

"That's good enough for me," said Astro. "If we're going out there"--he
pointed toward the desert--"instead of sitting around here waiting for
Strong or someone to show up, then I'd just as soon go now!"

"Wait a minute, fellas. Let's get this straight," said Tom. "We're all
agreed that the odds on Captain Strong's showing up here before our
water runs out are too great to risk it, and that we'll try to reach the
nearest canal. The most important thing in this place is water. If we
stay and the water we have runs out, we're done for. If we go, we might
not reach the canal--and the chance of being spotted in the desert is
even smaller than if we wait here at the ship." He paused. "So we move
on?" He looked at the others. Astro nodded and looked at Roger, who
bobbed his head in agreement.

"O.K., then," said Tom, "it's settled. We'll move at night when it's
cool, and try to rest during the day when it's the hottest."

Roger looked up at the blazing white sphere in the pale-blue sky that
burned down relentlessly. "I figure we have about six hours before she
drops for the day," he said.

"Then let's go back inside the ship and get some rest," he said.

Without another word, the three cadets climbed back inside the ship and
made places for themselves amid the littered deck of the control room. A
hot wind blew out of the New Sahara through the open port like a breath
of fire. Stripped to their shorts, the three boys lay around the deck
unable to sleep, each thinking quietly about the task ahead, each
remembering stories of the early pioneers who first reached Mars. In the
mad rush for the uranium-yielding pitchblende, they had swarmed over the
deserts toward the dwarf mountains by the thousands. Greedy, thinking
only of the fortunes that could be torn from the rugged little
mountains, they had come unprepared for the heat of the Martian deserts
and nine out of ten had never returned.

Each boy thought, too, of the dangers they had just faced. This new
danger was different. This was something that cou