It continued up and up, and finally seemed to end in the face of a precipitous wall of rock.

Thor's trail led him directly to a great crevice, hardly wider than his body, and through this he went, emerging at the edge of the wildest and roughest slide of rock that Muskwa had ever seen.

It looked like a huge quarry, and it broke through the timber far below them, and reached almost to the top of the mountain above.
For Muskwa to make his way over the thousand pitfalls of that chaotic upheaval was an impossibility, and as Thor began to climb over the first rocks the cub stopped and whined.

It was the first time he had given up, and when he saw that Thor gave no attention to his whine, terror seized upon him and he cried for help as loudly as he could while he hunted frantically for a path up through the rocks.
Utterly oblivious of Muskwa's predicament, Thor continued until he was fully thirty yards away.

Then he stopped, faced about deliberately, and waited.
This gave Muskwa courage, and he scratched and clawed and even used his chin and teeth in his efforts to follow.