it also runs into a cavern, with a rock and a copper
lever in the middle!" voiced Dick.

"Hope we find out soon," spoke Bud. "This is getting more and more
queer all the while."

They tramped on in the blackness that was relieved only by their
swaying lanterns. They walked beside the strange, underground stream,
and they had progressed farther than along the other branching body of
water when Old Billee, who was ahead just then, suddenly halted and
uttered a warning.

"Listen!"

"What is it?" asked Yellin' Kid, in his usual tones, but Billee reached
back and gave him such a dig in the ribs that Kid subsided with a grunt.

"I hear talkin'!" whispered Billee. "Voices! There's some one else in
this place than us! Listen!"

They stopped and strained their sense of hearing. And then, above the
slithering murmur of the water, they all distinctly heard a voice say:

"I think we've fixed 'em this time! They won't steal any more water
from Pocut River!"

The boy ranchers looked at each other.

"Del Pinzo!" whispered Nort.

"As sure as Zip Foster ever ate ham and eggs!" agreed Bud.

"Hush!" begged Old Billee.

And as they became quiet again they heard another voice say:

"I guess it's all up with 'em now. We might as well light out and
touch off the fuse!"

"Whew!" softly whistled Bud.

Together the party of searchers moved softly forward. Suddenly the
passage along the bank of the mysterious stream turned sharply, almost
at a right angle.

And there, in what appeared to be a small cave, excavation or cavern,
high in the upper wall was disclosed a roughly circular opening, like a
window or port hole. Through this port hole a light showed, and
outlined in the light were several rough-appearing men, leaning
together over what might have been a table.

"Del Pinzo!" murmured Dick.

"Conspirators!" exclaimed Bud. "They're the ones that's been turning
this water on and off! We're on the track of the mystery now!"

Whether he spoke loudly enough to be heard, or whether some other sound
made by the searchers alarmed the men in the upper niche, was not
disclosed just then.

But the light suddenly went out, and confused sounds followed.

And chief among these sounds was the rushing, roaring noise, the
blowing as of a mighty wind, and the water near the boy ranchers and
their companions was strangely agitated.

CHAPTER XXIV

A POWERFUL STREAM

"Better look out!" came the high-pitched voice