ither side, and, of course, was much deeper in the
centre. But as the tunnel sloped from either wall, in a sort of V
shape to the centre channel, naturally the parts nearest the side walls
were less covered by water than the others.

It was because of this that Bud, Nort and Dick were enabled to maintain
a footing, though they were knee-deep in water in an instant, and the
one remaining lantern had to be held up to prevent it from being
engulfed and extinguished in the sudden flood.

"Climb up! Climb up!" shouted Bud. "Isn't there some place--some
rocky ledge--where you can find a footing? The water's getting deeper!"

And this was true. Either the flood was growing at its source (a place
as yet unknown to the boys) or it was running too rapidly, and in too
great a volume, to accommodate itself to the tunnel channel, and was
thus piling up in the vicinity of the boys.

"What happened? What caused it?" cried Nort.

"Never mind that--now!" shouted Bud. "Find the highest place you can,
and stick!"

"Suppose the whole tunnel fills?" asked Dick, trying to pierce the
semi-gloom, and look for a refuge on the rocky wall.

"If it does we'll have to swim for it," grimly said Bud. "But isn't
there some place where you can climb up?"

"This looks like a ledge," Dick answered, as he caught sight of a
darker shadow on the rocky wall of the tunnel, above his head, when his
brother swung the lantern.

"Just what we need!" exclaimed Bud, as he waded through the
ever-deepening water to the side of his cousins. "Up with you! Here,
Nort, I'll hold the lantern until you make it!"

Thus, again, Bud was seeing that his cousins reached a place of
comparative safety before he looked to himself. For they found the
ledge, once they had scrambled up to it, well above the water, and wide
enough to give shelter and a safe perch for all three.

"Whew! That was touch and go!" murmured Bud, as he leaned back, half
exhausted, against the rocky wall at the rear of the ledge.

"I should say so!" gasped Dick. "It all happened so suddenly that I
don't know yet what it was all about."

"The stream suddenly started flowing again," spoke Bud. "That's all
there was to it. Must have been dammed up some place, and suddenly
released. It's still rising, too," he added, as he leaned forward and
held the lantern down over the ledge where he and his cousins had taken
refuge.

"Rising?" sharply inquired Nort, and there was a tone of anx