“You mean that my nature doesn’t correspond?”

He was just considering his reply, when their talk was abruptly broken off by a huge and terrifying, but not very loud sound rising up from the gulf directly underneath them.  It was a low, grinding, roaring thunder.

“The ground is rising under us!” cried Oceaxe.

“Shall we escape?”

She made no answer, but urged the shrowk’s flight upward, at such a steep gradient that they retained their seats with difficulty.  The floor of the canyon, upheaved by some mighty subterranean force, could be heard, and almost felt, coming up after them, like a gigantic landslip in the wrong direction.  The cliffs cracked, and fragments began to fall.  A hundred awful noises filled the air, growing louder and louder each second—­splitting, hissing, cracking, grinding, booming, exploding, roaring.  When they had still fifty feet or so to go, to reach the top, a sort of dark, indefinite sea of broken rocks and soil appeared under their feet, ascending rapidly, with irresistible might, accompanied by the most horrible noises.  The canal was filled up for two hundred yards, before and behind them.  Millions of tons of solid matter seemed to be raised.  The shrowk in its ascent was caught by the uplifted debris.  Beast and riders experienced in that moment all the horrors of an earthquake—­ they were rolled violently over, and thrown among the rocks and dirt.  All was thunder, instability, motion, confusion.

Before they had time to realise their position, they were in the sunlight.  The upheaval still continued.  In another minute or two the valley floor had formed a new mountain, a hundred feet or more higher than the old.  Then its movement ceased suddenly.  Every noise stopped, as if by magic; not a rock moved.  Oceaxe and Maskull picked themselves up and examined themselves for cuts and bruises.  The shrowk lay on its side, panting violently, and sweating with fright.

“That was a nasty affair,” said Maskull, flicking the dirt off his person.

Oceaxe staunched a cut on her chin with a corner of her robe.

“It might have been far worse....  I mean, it’s bad enough to come up, but it’s death to go down, and that happens just as often.”

“Whatever induces you to live in such a country?”

“I don’t know, Maskull.  Habit, I suppose.  I have often thought of moving out of it.”

“A good deal must be forgiven you for having to spend your life in a place like this, where one is obviously never safe from one minute to another.”

“You will learn by degrees,” she answered, smiling.

She looked hard at the monster, and it got heavily to its feet.

“Get on again, Maskull!” she directed, climbing back to her perch.  “We haven’t too much time to waste.”

He obeyed.  They resumed their interrupted flight, this time over the mountains, and in full sunlight.  Maskull settled down again to his thoughts.  The peculiar atmosphere of the country continued to soak into his brain.  His will became so restless and uneasy that merely to sit there in inactivity was a torture.  He could scarcely endure not to be doing something.