The chasm was short.

Sunlight burst upon them suddenly, and a few minutes later MacDonald waited for them again.
Even Aldous could not restrain an exclamation of surprise when he rode up with Joanne.

Under them was another valley, a wide-sweeping valley between two rugged ranges that ran to the southwest.

Up out of it there came to their ears a steady, rumbling roar; the air was filled with that roar; the earth seemed to tremble with it under their feet--and yet it was not loud.
It came sullenly, as if from a great distance.
And then they saw that MacDonald was not looking out over the sweep of the valley, but down.

Half a mile under them there was a dip--a valley within a valley--and through it ran the silver sheen of a stream.