solved the mystery."

"Right!" cried Bud. "So let's get at them. In the first place some of
us will go back and shift the lever on the big rock in the first cave,
while some of us stay here to see what happens."

The party was divided and when watches had been adjusted to mark the
same time, so it might be known how many minutes elapsed between the
shifting of the lever and any noticeable effect, Dick, Old Billee and
Snake went to the first cave--that of the huge boulder.

It did not take long to demonstrate that when the water flowed from the
main stream into that side branch, the stream nearer the river end of
the tunnel went dry. But even with that no water passed along the main
tunnel so that it would flow into the reservoir of Flume Valley.

"The water must flow out of the first big cave by some outlet we know
nothing about," decided Bud. "Now we'll look for the second water
gate."

They found the lever that controlled this in a corner of the upper,
rocky room where Del Pinzo and his conspirators had been plotting when
discovered. And when this lever was pulled from the position in which
the seekers found it after the Mexican half-breed fled, the second
stream (by which I mean the one nearest the river end of the tunnel)
filled with water. But this did not affect the first.

And not until both levers were set at positions which caused the branch
streams to empty, did any water fill the end of the tunnel near Bud's
ranch.

But when this had been done; when the secret of working the levers was
discovered, and water was once again flowing along the valley end of
the tunnel, where the stream bed had been dry for two days, then Bud
cried:

"The fight is over and we've won!"

"I wouldn't say that yet," spoke Old Billee cautiously, "Del Pinzo an'
Hank Fisher are still around an' above ground. But I guess you've put
a crimp in 'em, boys!"

"I reckon!" shouted Yellin' Kid. "But are we sure that the water now
goes to Flume Valley?"

"We'll soon find out," declared Bud. "We're almost out of the tunnel
now, and we can 'phone back and ask."

And a little later they did emerge from the mysterious underground
tunnel, with its still stranger water courses. But what was their
surprise to find that night had fallen--in fact it was not exactly
night, but nearly morning of the next day.

For a moment coming out into the dark night bewildered them. And then,
as they stood at the mouth of the mysterious tunne