“All is well.  The heat begins, but it will not endure for long.”

I nodded and glanced over the edge of the stone at Bastin’s lantern which was sailing alongside of us, till presently we passed it.  Bastin had lit it before we started, I think in a moment of aberration, and it burned for quite a long while, showing like a star when the shaft grew darker as it did by degrees, a circumstance that testifies to the excellence of the make, which is one advertised not to go out in any wind.  Not that we felt wind, or even draught, perhaps because we were travelling with it.

Then we entered the heat zone.  About this there was no doubt, for the perspiration burst out all over me and the burning air scorched my lungs.  Also Tommy thrust his head from beneath the cloak with his tongue hanging out and his mouth wide open.

“Hold your breaths!” cried Yva, and we obeyed until we nearly burst.  At least I did, but what happened to the others I do not know.

Fortunately it was soon over and the air began to grow cool again.  By now we had travelled an enormous distance, it seemed to be miles on miles, and I noticed that our terrific speed was slackening, also that the shaft grew more narrow, till at length there were only a few feet between the edge of the stone and its walls.  The result of this, or so I supposed, was that the compressed air acted as a buffer, lessening our momentum, till at length the huge stone moved but very slowly.

“Be ready to follow me,” cried Yva again, and we rose to our feet, that is, Bickley and I did, but poor Bastin was semi-comatose.  The stone stopped and Yva sprang from it to a rock platform level with which it lay.  We followed, dragging Bastin between us.  As we did so something hit me gently on the head.  It was Bastin’s lamp, which I seized.

“We are safe.  Sit down and rest,” said Yva, leading us a few paces away.

We obeyed and presently by the dim light saw the stone begin to stir again, this time upwards.  In another twenty seconds it was away on its never-ending journey.

“Does it always go on like that?” said Bastin, sitting up and staring after it.

“Tens of thousands of years ago it was journeying thus, and tens of thousands of years hence it will still be journeying, or so I think,” she replied.  “Why not, since the strength of the draught never changes and there is nothing to wear it except the air?”

Somehow the vision of this huge stone, first loosed and set in motion by heaven knows what agency, travelling from aeon to aeon up and down that shaft in obedience to some law I did not understand, impressed my imagination like a nightmare.  Indeed I often dream of it to this day.