.

Far below them was a plateau, stretching endlessly like the one they had
left behind them. But the chasm dominated all else. It was a gigantic,
sheer-walled valley, a hundred miles long by forty miles wide, sunk deep
in the plateau with the tops of its mile-high walls level with the floor
of the plateau. The mountain under them dropped swiftly away, sloping
down and down to the level of the plateau and then on, down and down
again, to the bottom of the chasm that was so deep its floor was half
hidden by the morning shadows.

"My God!" Barber said. "It must be over three miles under us to the
bottom, on the vertical. Ten miles of thirty-three per cent grade--if we
go down we'll never get out again."

"You can turn back here if you want to," Humbolt said.

"Turn back?" Barber's red whiskers seemed to bristle. "Who in hell said
anything about turning back?"

"Nobody," Humbolt said, smiling a little at Barber's quick flash of
anger.

He studied the chasm, wishing that they could have some way of cutting
the quartz crystals and making binoculars. It was a long way to look
with the naked eye....

Here and there the chasm thrust out arms into the plateau. All the arms
were short, however, and even at their heads the cliffs were vertical.
The morning shadows prevented a clear view of much of the chasm and he
could see no sign of the red-stained strata that they were searching
for.

In the southwest corner of the chasm, far away and almost imperceptible,
he saw a faint cloud rising up from the chasm's floor. It was impossible
to tell what it was and it faded away as he watched.

Barber saw it, too, and said, "It looked like smoke. Do you suppose
there could be people--or some kind of intelligent things--living down
there?"

"It might have been the vapor from hot springs, condensed by the cool
morning air," he said. "Whatever it was, we'll look into it when we get
there."

The climb down the steep slope into the chasm was swifter than that up
the canyon but no more pleasant. Carrying a heavy pack down such a grade
exerted a torturous strain upon the backs of the legs.

The heat increased steadily as they descended. They reached the floor of
the valley the next day and the noonday heat was so great that Humbolt
wondered if they might not have trapped themselves into what the summer
would soon transform into a monstrous oven where no life at all could
exist. There could never be any choice, of course--the mountai