d Tom's warning.

"Forget about the time!" snapped Connel. "By the blessed rings of
Saturn, we'll finish this job if it's the last thing we do!"

Connel went to each of the working figures and adjusted the valve,
regulating the air-cooling humidity control on their space suits.
"Getting pretty hot, eh, boys?" he joked, as he stopped one and then the
other to make the delicate adjustment counteracting the heat that was
increasing each second they remained on the satellite.

"How hot do you think it is, sir?" asked Roger.

"Never mind the heat," said Connel. "These suits were designed to
withstand the temperature of the light side of Mercury! It gets boiling
there, so I guess we can stand it here for a while."

One by one, Alfie, Shinny, Roger, and Astro completed their assigned
roles, digging the holes, placing the reactors inside, setting the fuse,
covering it up, then quickly gathering the equipment, piling back into
the three jet boats, and heading for the next point. Landing, they would
tumble out of the small space craft almost before the rocket had stopped
firing and begin their frantic digging in the hard surface.

[Illustration: _Landing, they would tumble out of the jet boat and begin
their frantic digging_]

Over and over, they heard Tom's crisp clear count of time. Five minutes
passed, then ten, and before they knew it, a full half-hour of the
precious time had vanished. They completed the installation of the
second unit and climbed back into the jet boats. The first two units
had been buried at points protected from the sun by cliffs, and they had
been sheltered from the burning rays.

But, approaching the position for the third reactor unit, Connel
searched in vain for some shade. He wasted five precious minutes,
scouting an area of several miles, but he could find nothing to protect
them on the flat plain.

"Better put in the ultraviolet glass shields in our helmets, boys," he
called into the jet-boat communicator. "It's going to be mighty hot, and
dangerous."

"Aye, aye, sir," came the replies from the other two jet boats soaring
close by.

Roger began refitting their space helmets with the dark glass that would
shield them from the strong rays of the enlarging sun.

"Ever been outside in the direct path of the sun with no protection,
Roger?" asked Astro.

"No," replied Roger. "Have you?"

"Once," said Astro softly. "On the second moon of Mars, Phobos. I was
bucking rockets on the old che