He had subjected his muscles to such a tension that he was obliged to pause every few minutes and rest.

One of his feet was scarified and bleeding, and the other only a little better.
When he looked upward his heart sank, for a long distance still interposed between him and the ground above.
"I must have picked the place where the canyon is deepest," was his despairing conclusion; "I feel hardly able to hang on, and would not dare do what I did further below." He now yielded to a curious whim.

Instead of continually gazing at the sky, that he might measure the distance remaining to be traversed, he resolved not to look at it at all until he had climbed a long way.

He hoped by doing this to discover such a marked decrease in the space that it would reanimate him for the remaining work.
Accordingly he closed his eyes, and, depending on the sense of feeling alone, which in truth was his reliance from the first, he toiled steadily upward.

Sometimes he had to grope with his hands for a minute or two before daring to leave the support on which his feet rested, but one of his causes for astonishment and thankfulness was that such aids seemed never to be lacking.
He continued this blind progress until his wearied muscles refused to obey further.