a mountain goat might
almost have envied.

"I reckon it does, Bob," replied the other. "Get along as fast as you
can with all caution."

"Has the cloudburst arrived?" demanded Bob, who was already ten feet
from the floor of the canyon.

"Either that, or else with that last shock the geyser burst its bonds,
and the flood Smith expected is rushing out from all the passages into
this same channel! Perhaps both things have happened at the same
time," Frank replied.

"Wow! then we'd better be climbing some, I reckon, if that's the case!"
cried the Kentucky boy, as he increased his efforts to ascend to the
ledge.

CHAPTER XXI

A CLOSE CALL

"It's sure coming down on us, Frank!" cried Bob, shortly, as he caught
a strange mixture of terrifying sounds.

"Climb!" shouted back the other; for he knew they would have about all
they could do to reach the shelf of rock before the mighty wave swept
through that narrow channel between the high walls of the canyon, with
a force utterly irresistible.

Bob was doing his best. He realized that the ledge was just above his
head now, and also how necessary it was that they reach it before the
rushing flood arrived to fill the gap.

Now his eager fingers clutched the edge, and he strove to pull himself
up higher. But his breath was exhausted from his violent efforts, and
the excitement attending the occasion.

Bob realized that the torrent was very close at hand. Its roar dinned
in his ears so that he could hear nothing else. The rocks seemed to be
quivering under the impact of the released forces. He felt a cold
shiver pass over him as he was seized with a dreadful fear that the
rock to which he clung was giving way.

Then something seized him by the back of the neck, and Bob found
himself being helped up to a firm foundation. Frank had succeeded in
gaining the ledge ahead of his chum; and naturally enough his first
thought was to assist Bob.

Panting, and completely exhausted, Bob lay there on the shelf of rock.
He could look down, and when the lightning played, see the oncoming of
that foam-crested bank of mad waters that rushed pell mell down the
canyon.

Now it was speeding past them, rising higher and higher with each
second, until a new fear began to grip at Bob's anxious heart. He
dreaded lest the wave might attain such a height that he and his chum
would be swept from their perch, to be carried away, helpless victims
on the crest of the flood.

It