Titan of Chasms. The Grand Canyon of Arizona

We measured the length of the Grand Canyon by the length of the river running through it, but the running extent of wall can not be measured in this manner. In the black gneiss, which is at the bottom, the wall may stand above the river for a few hundred yards or a mile or two; then to follow the foot of the wall you must pass into a lateral canyon for a long distance, perhaps miles, and then back again on the other side of the lateral canyon; then along by the river until another lateral canyon is reached, which must be headed in the black gneiss. So for a dozen miles of river through the gneiss there may be a hundred miles of wall on either side. Climbing to the summit of the black gneiss and following the wall in the variegated quartzite, it is found to be stretched out to a still greater length, for it is cut with more lateral gorges.

In like manner there is yet greater length of the mottled (or alcove) sandstone wall, and the red wall is still farther stretched out in ever-branching gorges.