We can't just break up the enemy installations--we've got to learn from
them, we must find out how they do it and how we can use it." This was
Lockhart speaking. "You'd better start the job," he added to Haines.
"Are you ready?"

Haines nodded reluctantly. "Yep," and turning to the three who would
accompany him, he ordered, "let's go."

The four explorers gathered near the exit port. They had put on space
suits and strapped on various items of equipment, weapons and work
tools. They passed through the airlock into the cargo section of the
ship. Communicating through the helmet radios, Haines directed each what
to do, and also directed Lockhart where to bring the ship for the
landing.

Burl heard Lockhart's voice warn them that he did not want to hold the
ship too long over the sunny hot side. "We've already noticed a buildup
of heat from the solar radiation on the skin. And the heat radiating
from Mercury is accumulating too fast. We can't get rid of it if _both_
sides of this ship are going to be heated up. As soon as you make your
landing, I'm taking the ship back to the cold side."

"Uh huh," came Haines's voice. "We don't want to hang around here any
too long, either."

Then the four, as prearranged, unlimbered the work rocket they had
picked. There were several sizes of small exploration craft. They had at
first thought of the tractor--an enclosed, airtight truck on tractor
wheels which could crawl up to the station while the men inside it were
protected by air conditioning. But a quick survey showed that it would
overheat too fast and might easily bog down in one of the many soft
spots. So they took the four-man, rocket-propelled cargo plane instead.

The ship was airtight and pressurized. They had taken every precaution.
The four piled in with their supplies. Then, as the _Magellan_ swooped
momentarily lower, the escape hatch opened and, with Ferrati at the
controls, the rocket plane shot out with a roar of its exhausts.

They raced low over the burning landscape, and before them the wide,
dark, forbidding canyon cut its way through the plain. It was into this
canyon that the rocket plunged.

The precipitous rocky sides rose above them, and suddenly they were in
darkness. Immediately, the plane's cooling system became more effective
as Ferrati guided the rocket through the shadowy depths away from the
blazing sunbeams. Burl saw, by means of the radar, that the bottom of
the heat crack was many miles do