"I'm afraid to take the chances of keeping on any further. It may be a long run to the next broken wall, that offers us a chance to climb. Some places the sides go up as smooth as glass. Have you see an opening here, Bob?"
"Yes, yes, right on the left, Frank!" exclaimed Bob, eagerly. "I couldn't see so very far up, but it looks good to me."
Frank turned his gaze up to where his comrade pointed.
"I think it's rough as far as that ledge," he said; "and let us hope that will be out of the reach of the water. Come on, Bob; let's see how you can climb; but be careful, boy, be mighty careful!"
"Frank, that roaring sound didn't seem like the others we've been hearing; d'ye think it means anything has happened?" Bob called, as he started to clamber up the rough face of the wall, taking advantage of every jutting rock, and showing a nimbleness 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.