is--though, of course, I might be wrong--that
there are two side passages, so to speak. Sometimes the water branches
off the main channel and fills the pool where we found Nort on the
rock. Then it may flow down another channel, farther on, but nearer to
the river end of the tunnel."

"But if the water came along the main channel, until it got here, and
then filled the pool to the limit, as was evidently the case,"
suggested Nort, "why wouldn't the water then back up and go on to our
reservoir--and it didn't do that."

"There may be some outlet from that pool and cavern where we were,"
said Bud.

They considered this for a moment, and agreed that he might be right.

"Then what we've got to look for," went on Bud, "is another side
passage where the water is shunted off, that is, providing it is not
cut off at the river pipe. And if there is such a passage it must be
on the right-hand side of the stream, as was the one where Nort fell
in. For we went all along the left-hand bank the other time, and
didn't discover anything."

"And suppose we find the second branch stream now--what will we do?"
asked Snake.

"Two of us will come back and work the lever, while the others stay at
the second stream to see what happens," was Bud's answer. "Come on;
let's go!"

They put out the fire, packed their belongings, and, making sure that
Nort was able to travel, they set out again. Nort's garments were
soaking wet, or, rather, they had been, but there was a current of warm
air in the tunnel, and soon he began to dry out, for which he was very
thankful.

They found the second branching stream sooner than they expected. It
was less than a quarter of a mile from the first, or the one into which
Nort had fallen, and it was almost of exactly the same character.

"Look out! Here it is!" cried Bud who saw it first, his lantern
gleaming on the swiftly-rushing water. "Go easy!"

And "easy" they went, reaching the edge of the ledge below which flowed
the mysterious, powerful current.

"We can go along here, just as we did before. Here's another branch
tunnel!" announced Dick, holding up his lantern, and showing a wide,
high passage, the bottom and middle part of which was occupied by the
stream.

"I wonder how many of them there are?" remarked Nort as he and the
others turned into the black opening, which seemed to slope as though
descending a hill. This gave greater force to this stream of water.

"And I wonder if