f the canyon and
the water ceased just before him. Beyond the steep and bare rocks ran
directly downward into the stream.

"That settles it," he muttered, in great disappointment. "All this
traveling for nothing. And it's getting night over head, too! It's a
shame!"

Allen paused to rest, for in his weak condition the walk had tired him
greatly. Then he started to retrace his steps.

Hardly had he taken a yard's advance, when his left foot slipped upon a
round stone. He was thrown over on his side, and before he could save
himself went plunging headlong into the stream!

He essayed by every means in his power to regain the bank, but in vain.
The current of the river was extra strong at this point--the width of
the course having narrowed down--and before he could clutch the first
thing he was carried to where nothing but the steep and slippery rocks
presented themselves.

Vainly he put out his hands to stay his progress, vainly he tried by
every means in his power to obtain some sort of hold on the rocks.

[Illustration: VAINLY HE PUT OUT HIS HANDS TO STAY HIS PROGRESS]

And now the surface of the river grew blacker as the rocks on both sides
began, seemingly, to close in over his head.

He was almost tempted to cry out for help, and took a breath for that
purpose, but the sound was not uttered. What would be the use? Not a
soul would hear him.

On and on went the young ranchman, the waters growing more cold each
instant and the prospects more gloomy. He was half tempted to give
himself up for lost.

It was an easy matter to keep himself on the surface, for he was really
a good swimmer, but now the current was so strong that he could scarcely
touch either side of its rocky confines as he was swept along, he knew
not where. Allen had never explored this stream, and this to him made
the immediate future look blacker than ever.

"If it ends in some sort of a sink hole, I'm a goner sure," he thought.
"But I never heard of such a hole up here among the mountains, so I
won't give up just yet."

Hardly had the thought occupied his mind when, on looking up, he saw the
last trace of evening fade from sight. The river had entered a cavern!
He was now underground!

It may well be imagined with what dismay Allen, stout-hearted as he was,
viewed the turn of the situation. Here he was being borne swiftly along
on an underground river, he knew not where. It was a situation
calculated to chill the bravest of hearts.