A crimson forest of
the heat-rays flashed up behind us, and flamed upon the black walls
and roof of the cavern until glistening lava became incandescent,
cracked and fused.

We were below the line of the rays. Quickly we made the bend in the
cavern and followed at a halting run up the path beside the shimmering
river of opalescent light. Before us the torrent of fire fell in a
magnificent flaming arc from the roof.

We rounded the pool of lambent milk of flame, passed the roaring
torrent of coruscating liquid radiance and reached the ladder in the
square, metal shaft. "If we can get to the top before they can get up
here, we're safe," Ray said. "If we don't, this shaft will be a
chimney of fire."

In the haste of desperation, we attacked the thousand-foot climb. I
went first, Mildred below me, and Ray, with the rifle, in the rear.
Our heavy packs were a terrible impediment, but we dared not attempt
to go on without them. The metal rungs were four feet apart; it was no
easy task to scramble from one to the next, again and again, for
hundreds of times.

* * * * *

It must have taken us an hour to make it. We should have been caught
long before we reached the top, but the giant crabs were slow in their
lumbering movements. Despite their evident intelligence, they seemed
to lack anything like our railways and automobiles.

The cold gray light of the polar sky came about us; a dull,
purple-blue square grew larger above. I clambered over the last rung,
flung myself across the top of the metal shaft. Looking down at the
tiny fleck of white light so far below, I saw a bit of red move in it.

"A crab!" I shouted. "Hurry!"

Mildred was just below me. I took her pack and helped her over the
edge.

Red flame flared up the shaft.

We reached over, seized Ray's arms and fairly jerked him out of the
ruby ray.

The bitterly cold wind struck our hot, perspiring bodies as we
scrambled down the rungs outside the square metal shaft. Mildred
shivered in her thin attire.

"Out of the frying pan into the ice box!" Ray jested grimly as we
dropped, to the frozen plain.

Quickly we tore open our packs. Ray and I snatched out clothing and
wrapped up the trembling girl. In a few minutes we had her snugly
dressed in the fur garments that had been Major Meriden's. Then we got
into the quilted garments we had made for ourselves.

The intensely red heat-beam still flared up the shaft. Ray looked at