With my last flickering ray of consciousness I turned mechanically toward the distance meter.  It stood at exactly five hundred miles from the earth’s surface—­and then of a sudden the huge thing that bore us came to a stop.  The rattle of hurtling rock through the hollow jacket ceased.  The wild racing of the giant drill betokened that it was running loose in air—­and then another truth flashed upon me.  The point of the prospector was above us.  Slowly it dawned on me that since passing through the ice strata it had been above.  We had turned in the ice and sped upward toward the earth’s crust.  Thank God!  We were safe!

I put my nose to the intake pipe through which samples were to have been taken during the passage of the prospector through the earth, and my fondest hopes were realized—­a flood of fresh air was pouring into the iron cabin.  The reaction left me in a state of collapse, and I lost consciousness.

II

A STRANGE WORLD

I was unconscious little more than an instant, for as I lunged forward from the crossbeam to which I had been clinging, and fell with a crash to the floor of the cabin, the shock brought me to myself.

My first concern was with Perry.  I was horrified at the thought that upon the very threshold of salvation he might be dead.  Tearing open his shirt I placed my ear to his breast.  I could have cried with relief—­his heart was beating quite regularly.

At the water tank I wetted my handkerchief, slapping it smartly across his forehead and face several times.  In a moment I was rewarded by the raising of his lids.  For a time he lay wide-eyed and quite uncomprehending.  Then his scattered wits slowly foregathered, and he sat up sniffing the air with an expression of wonderment upon his face.

“Why, David,” he cried at last, “it’s air, as sure as I live.  Why—­why what does it mean?  Where in the world are we?  What has happened?”

“It means that we’re back at the surface all right, Perry,” I cried; “but where, I don’t know.  I haven’t opened her up yet.  Been too busy reviving you.  Lord, man, but you had a close squeak!”

“You say we’re back at the surface, David?  How can that be?  How long have I been unconscious?”

“Not long.  We turned in the ice stratum.  Don’t you recall the sudden whirling of our seats?  After that the drill was above you instead of below.  We didn’t notice it at the time; but I recall it now.”

“You mean to say that we turned back in the ice stratum, David?  That is not possible.  The prospector cannot turn unless its nose is deflected from the outside—­by some external force or resistance—­the steering wheel within would have moved in response.  The steering wheel has not budged, David, since we started.  You know that.”

I did know it; but here we were with our drill racing in pure air, and copious volumes of it pouring into the cabin.