, and it was not easy to
scramble down from one to another; certainly not easy for one who was
cold, hungry, thirsty, worn out with a week of exhausting marches, and
suffering the torture of frozen feet.

"You know, this thing was not built by men," Ray observed.

"Not built by men? What do you mean?"

"Men would have put the steps closer together. Jim, I'm afraid we are
up against something--well--that we aren't used to."

"If men didn't build this, what did?" I was astounded.

"Search me! This continent has been cut off from the rest of the world
for geologic ages. Such life as has been found here is not common to
the rest of the earth. It is not impossible that some form of life,
isolated here, has developed intelligence and acquired the power to
erect that cone of light--and to burn the wing off a metal airplane."

My thoughts whirled madly as we clambered down the shaft.

* * * * *

It must have taken us an hour to reach the bottom. I did not count the
steps, but it must have been at least a thousand feet. The air grew
rapidly warmer as we descended. We both took off most of our heavy fur
garments, and left them hanging on the rungs.

I was rather nervous. I felt the nearness of an intelligent, hostile
power. I had a great fear that the owners of those steps would use
them to find us, and then crush us ruthlessly as they had brought down
Meriden's plane.

The little square of white light below grew larger. Finally I saw Ray
swing off and stand on his feet in a flood of white radiance below me.
The air was warm, moist, laden with a subtle unfamiliar fragrance that
suggested growing things. Then I stood beside Ray.

We stood on the bare stone floor of a huge cavern. It must have been
of volcanic origin. The walls glistened with the sparkling smoothness
of volcanic glass. It was a huge space. The black roof was a hundred
feet high, or more; the cave was some hundreds of feet wide. And it
sloped away from us into dim distance as though leading into huger
cavities below.

The light that shone upon us came from an amazing thing--a fall of
liquid fire. From the roof plunged a sheer torrent of white
brilliantly luminous fluid, falling a hundred feet into a shimmering
pool of moon-flame. Shining opalescent mists swirled about it, and the
ceaseless roar of it filled the cave with sound. It seemed that a
stream of the phosphorescent stuff ran off down the cave from the
pool, to li