came to a long swell of naked stone that led down to a narrow green
split. This one had straight walls and wound away out of sight. It was
the head of a canyon.

"Nonnezoshe Boco," said the Indian.

This then was the Canyon of the Rainbow Bridge. When we got down into
it we were a happy crowd. The mode of travel here was a selection of
the best levels, the best places to cross the brook, the best places
to climb, and it was a process of continual repetition. There was no
trail ahead of us, but we certainly left one behind. And as Wetherill
picked out the course and the mustangs followed him I had all freedom
to see and feel the beauty, color, wildness and changing character of
Nonnezoshe Boco.

My experiences in the desert did not count much in the trip down this
strange, beautiful lost canyon. All canyons are not alike. This one
did not widen, though the walls grew higher. They began to lean and
bulge, and the narrow strip of sky above resembled a flowing blue
river. Huge caverns had been hollowed out by water or wind. And when
the brook ran close under one of these overhanging places the running
water made a singular indescribable sound. A crack from a hoof on a
stone rang like a hollow bell and echoed from wall to wall. And the
croak of a frog--the only living creature I noted in the canyon--was a
weird and melancholy thing.

"We're sure gettin' deep down," said Joe Lee.

"How do you know?" I asked.