kind used in the war, to
fight 'em. But we drove 'em out."

"And a lot of good it did us," said Bud gloomingly, "if there isn't any
gold in there."

"No, the evidence is too plain to be mistaken," said Professor Snath.
"It does not even require a laboratory test to prove that the cave is
rich in iron sulphid, but not gold."

"Maybe it will turn out to be an iron mine instead of a gold mine!" put
in Billee, with new hope showing on his face. "Iron's valuable. Not
worth as much as gold, of course, but a good iron mine--say, boys,
maybe I'll get that self-playin' piano yet."

But again his hopes were dashed.

"It wouldn't pay to work this section even for iron," said Professor
Dodson, and his assistant nodded his agreement.

"Well, then," remarked Nort, "we'll have to keep on raising cattle."

"But we can't do that if these fellows are going to let loose a flood
of poison gas and kill them off every now and then!" bitterly cried
Bud. "We're beat either way you look at it. Just as you said, Billee,
this is Death Valley."

"Tell me more about this!" suddenly suggested the older scientist.
"What is all this about poison gas in tanks killing cattle?"

"I can tell you!" came from Old Tosh. "I know all about it but nobody
would ever listen to me. They said I was crazy. But I know! Look
here!"

He pointed to a crack, or fissure in the rocky floor of the glen, not
far from the cave entrance. It was just such a crack as Bud and his
cousins had noticed one day near the place where they had found some
dead cattle.

"Listen to that! It's rising!" cried Old Tosh, bending over the crack.

The two professors, the boy ranchers and some of the punchers leaned
over and listened. From somewhere down in the depths of the earth came
the rustle and swish of running water.

"An underground stream," said Professor Dodson. "They are not uncommon
in this region. But----"

Suddenly he started back and withdrew his face quickly from above the
crack in the earth.

"Hurry away from here!" he cried. "The gas is rising. I begin to
understand now. It is the secret you have been trying to solve. Hurry
away! It may not be deadly, but it will overcome all of us in a short
time."

He ran down the defile, away from the long fissure, followed by the
others, Billee and his men driving the ponies before them. Professor
Dodson had made a strange discovery, after Old Tosh had put him on the
track of it.

CHAPTER XXV