ng only some ten feet standing up out of the ground.

A short distance farther on, as they were close in by the steep wall of
rock, they came to a slight projection, as if a huge piece had slipped
down from above, and turning sharply round this, the Beaver pointed to a
narrow rift just wide enough to allow of the passage of one man at a
time.

He signed to the Doctor to enter, and climbing over a few rough stones,
the latter passed in and out of sight.

"Bart! quick, my boy! quick!" he said directly after, and the lad sprang
in to help him, as he thought, in some perilous adventure, but only to
stop short and stare at the long sloping narrow passage fringed with
prickly cactus plants, which slope ran evidently up the side of the
mountain.

"Why, it's the way up to the top," cried Bart. "I wonder who made it."

"Dame Nature, I should say, my boy," said the Doctor. "We must explore
this. Why, what a natural fortification! One man could hold this
passage against hundreds."

Just then the chief appeared below them, for they had climbed up a few
yards, and signed to them to come down.

The Doctor hesitated, and then descended.

"Let's see what he has to show, Bart. I have seen no silver yet."

They followed the Beaver down, and he led them straight back, past the
camp, through the narrow ravine, once more to the shelf of rock
overlooking the canyon, and now, in the full glow of the sunny
afternoon, they were able to realise the grandeur of the scene where the
river ran swiftly down below, fully a thousand feet, in a bed of its
own, shut out from the upper world by the perpendicular walls of rock.

At the first glance it seemed that it would be impossible to descend,
but on farther examination there seemed in places to be rifts and
crevices and shelves, dotted with trees and plants of the richest
growth, where it might be likely that skilful climbers could make a way
down.

From where they stood the river looked enchanting, for while all up in
the plain was arid and grey, and the trees and shrubs that grew there
seemed parched and dry, and of a sickly green, all below was of the
richest verdant hues, and lovely groves of woodland were interspersed
with soft patches of waving grass that flourished where stormy winds
never reached, and moisture and heat were abundant.

Still this paradise-like river was not without signs of trouble visiting
it at times, and these remained in huge up-torn trees, dead branches,