."

"A subterranean river?" asked the professor, at once interested.

"Yes, sir," rejoined Pete, "and not the only one in the West, either.
There's one in Californy that flows underground fer purty near fifty
miles, as I've heard tell."

"This is most remarkable," said the professor. "I, too, have heard of
subterranean rivers in this part of the world, but I have never had the
opportunity to explore one. Did this Indian you speak of ever tell you
where this river emerges?"

"He said it come out some place across the frontier in Chihuahua; I
don't jest rightly recollect where," said Pete carelessly, as if the
subject did not interest him much, as indeed it did not.

"I don't see what use a subterranean river is to anybody, anyhow," he
went on. "If it was on top, now, it might be some use."

"But this is most interesting," protested the professor, while the boys
lay about with their chins propped in their hands in intent attitudes.
"Then, too, if this river exists, perhaps it is even navigable."

"Why, professor!" exclaimed Jack. "Is it not possible that it was to
this river that those drawings of boats that interested and puzzled you
so much had reference?"

"Quite possible, my boy," agreed the man of science.

"I wish we could find some way of getting down into it," said Ralph
wistfully, poking at the ground, as if he thought he might force an
entrance that way.

"Thar you go," laughed Pete. "Giv' you boys a cayuse, an' you'll ride
him to death. I jes' mentioned that a lying, whisky-drinking old Injun
had sprung a pipe-dream about a lost river, and thar you go navagatin'
it in a Coney Island steamboat."

The boys could not help bursting into a laugh at the cow-puncher's
whimsical way of talking. The professor joined in, too, for none
realized better than he did that for a moment he, too, had been quite
carried away by the idea.

"I expect that it is as you say, Pete," he agreed. "These Indians are
most unreliable people. If anybody was to believe all the weird
legends an Indian tells him, he would spend the best part of his life
on wild-goose chases. Why, the Indians of the Mojave desert in
California can even tell a circumstantial story about a buried city of
Mojave. According to their contention, a great flood, occurring long
ago, wiped it out and buried it in the sands of the desert."

"Has any one ever tried to find it?" asked Jack.

"Many expeditions have been fitted out for the purpose,