hey? What depth was it?

Wilder took up a pebble and flung it down. They could hear it
descending, not at a single drop, but striking and ricochetting from
side to side.

It was long before it reached the bottom and lay silent. No matter for
that. The noise made in its descent told them of projecting points or
ledges that might give them a foothold.

They lost not a moment of time, but commenced letting themselves down
into the funnel-shaped shaft, the guide going first.

Slowly and silently they went down--like ghosts through the stage of a
theatre--soon disappearing in the gloom below, and leaving upon the
rock-strewn platform no trace to show that human foot had ever trodden
it.

CHAPTER TWELVE.

A STORM OF STONES.

Fortunately for the fugitives, the cavity into which they had crept was
a shaft of but slight diameter, otherwise they could not have gone down
without dropping far enough to cause death, for the echoes from the
pebbles betokened a vast vertical depth.

As it was, the void turned out to be somewhat like that of a stone-built
chimney with here and there a point left projecting. It was so narrow,
moreover, that they were able to use both hands and knees in the
descent, and by this means they accomplished it.

They went but slowly, and took care to proceed with caution. They knew
that a false step, the slipping of a foot or finger, or the breaking of
a fragment that gave hold to their hands, would precipitate them to an
unknown depth.

They did not go farther than was necessary for quick concealment. There
was noise made in their descent, and they knew that the Indians would
soon be above, and might hear them. Their only hope lay in their
pursuers believing them to have gone by the left hand path to the plain
above. In time the Indians would surely explore both branches of the
ravine, and if the cunning savages should suspect their presence in the
shaft there would be no hope for them. These thoughts decided them to
come to a stop as soon as they could find foothold.

About thirty feet from the top they found this, on a point of rock or
ledge that jutted horizontally. It was broad enough to give both
standing room, and as they were now in the midst of amorphous darkness,
they took stand upon it.

The Indians might at any moment arrive on the platform above. They felt
confident they could not be seen, but they might be heard. The
slightest sound borne upwards to the ears of th