“Cover,” whispered Cavor, and I turned towards the bushes.

At that instant came a thud like the thud of a gun, and then a thing happened—­it still haunts me in my dreams.  I had turned my head to look at Cavor’s face, and thrust out my hand in front of me as I did so.  And my hand met nothing!  I plunged suddenly into a bottomless hole!

My chest hit something hard, and I found myself with my chin on the edge of an unfathomable abyss that had suddenly opened beneath me, my hand extended stiffly into the void.  The whole of that flat circular area was no more than a gigantic lid, that was now sliding sideways from off the pit it had covered into a slot prepared for it.

Had it not been for Cavor I think I should have remained rigid, hanging over this margin and staring into the enormous gulf below, until at last the edges of the slot scraped me off and hurled me into its depths.  But Cavor had not received the shock that had paralysed me.  He had been a little distance from the edge when the lid had first opened, and perceiving the peril that held me helpless, gripped my legs and pulled me backward.  I came into a sitting position, crawled away from the edge for a space on all fours, then staggered up and ran after him across the thundering, quivering sheet of metal.  It seemed to be swinging open with a steadily accelerated velocity, and the bushes in front of me shifted sideways as I ran.

I was none too soon.  Cavor’s back vanished amidst the bristling thicket, and as I scrambled up after him, the monstrous valve came into its position with a clang.  For a long time we lay panting, not daring to approach the pit.

But at last very cautiously and bit by bit we crept into a position from which we could peer down.  The bushes about us creaked and waved with the force of a breeze that was blowing down the shaft.  We could see nothing at first except smooth vertical walls descending at last into an impenetrable black.  And then very gradually we became aware of a number of very faint and little lights going to and fro.

For a time that stupendous gulf of mystery held us so that we forgot even our sphere.  In time, as we grew more accustomed to the darkness, we could make out very small, dim, elusive shapes moving about among those needle-point illuminations.  We peered amazed and incredulous, understanding so little that we could find no words to say.  We could distinguish nothing that would give us a clue to the meaning of the faint shapes we saw.

“What can it be?” I asked; “what can it be?”

“The engineering!...  They must live in these caverns during the night, and come out during the day.”

“Cavor!” I said.  “Can they be—­that—­it was something like—­men?”

“That was not a man.”

“We dare risk nothing!”

“We dare do nothing until we find the sphere!”

“We can do nothing until we find the sphere.”