"What are they?" asked "Nort.
"One is, what effect has the turning of that lever we worked on the main stream? The other is, where is the lever that Del Pinzo and his gang shifted to cause this second branch stream to stop running?"
"And when we find answers to those two questions," said Dick, "I think we'll have 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: