She had half an hour's start of them when they reached the mouth of the gorge, and not until they had travelled another half-hour up the rough bed of the break between the two mountains, and MacDonald pointed ahead, and said: "There's the cavern!" did he breathe easier.
They could see the mouth of the cavern when they were yet a couple of hundred yards from it.

It was a wide, low cleft in the north face of the chasm wall, and in front of it, spreading out like the flow of a stream, was a great spatter of white sand, like a huge rug that had been spread out in a space cleared of its chaotic litter of rock and broken slate.

At first glance Aldous guessed that the cavern had once been the exit of a subterranean stream.

The sand deadened the sound of their footsteps as they approached.

At the mouth of the cave they paused.