knock
out our men?"

"The explanation is probably very simple," said the scientist. "There
must be, somewhere near the head of the defile we just left, a deposit
of the mineral or ore from which this gas I speak of is generated. It
is somewhat like carbon monoxide, but more powerful even in the open
air."

"Water, flowing over a bed of this mineral, liberates the gas in the
form of an almost invisible vapor. It is swept forward in a cloud by
the wind, some of it is carried along above the course of the
underground stream, and as soon as it reaches an opening in the earth,
like a fissure crack in the rock or ground, the gas rises and whoever
breathes it dies or is rendered unconscious for a time, according to
the strength of the vapor. At one time the underground stream may be
strongly impregnated with the dissolved chemicals that generate the
gas. At another time the emanations may be comparatively weak. That,
I think, is the explanation of happenings here in Death Valley, as you
call it."

"Then the men who thought they had a gold mine in the cave had nothing
to do with killing the cattle?" asked Nort.

"I can't say for sure, but I think not," the professor replied. "I am
inclined to believe that they got these tanks of gas to use in driving
away any who might try to get at their secret--a useless secret as it
proves now. But the accidental deaths, both of cattle and men, from
the underground gas must have been going on here a long time," the
scientist suggested.

"They have!" declared Old Billee. "Several years back. That's why I
quit here. But we didn't know what the cause was. Some said poisoned
water, others poison loco-weed. Some said it was the souls of Indians
who were driven out of this valley years ago."

"And all the while it was just a natural gas liberated by an
underground stream running over a bed of chemicals," stated Bud.

"That's what I think," said Professor Dodson. "It remains to be proved
conclusively, but that is what I think will be found."

"Then this means the end of Death Valley," went on Bud, gloomily. "We
can't afford to stay here and raise cattle to be killed off by gas."

"No," agreed Professor Dodson. "But do not form a hasty decision.
Science can do much these days. It may be possible to neutralize this
gas and so make your ranch safe. In that case it will be the end of
Death Valley but in a better way. It will be Life Valley then."

"Do you think it can be