There were tangled thickets of wild plum-trees and other thorny growths that made passage extremely laborsome.

He found innumerable tracks of wildcats and foxes.

Rustlings in the thick undergrowth told him of stealthy movements of these animals.

At length his further advance appeared futile, for the reason that the stream disappeared in a split at the base of immense rocks over which he could not climb.

To his relief he concluded that though beaver might work their way up the narrow chasm where the water rushed, it would be impossible for men to enter the valley there.
This western curve was the only part of the valley where the walls had been split asunder, and it was a wildly rough and inaccessible corner.
Going back a little way, he leaped the stream and headed toward the southern wall.