"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 n.o.body 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

THE END OF DEATH VALLEY

Hurrying along, some of the men in their saddles, others stumbling on foot, not having taken the time to mount, the whole party rushed out of the defile. It was not until they had reached open country, some distance removed from the entrance to Smugglers' Glen, that the older scientist thought it safe to call a halt. And he did not do this until he had looked around, with his a.s.sistant, to make sure there were no earth fissures near, and had also ascertained the direction of the wind. He tested the air by breathing deeply of it and said:

"We're safe for a time. But there's no telling how long. This is a most remarkable natural phenomenon--one of the most remarkable I have ever happened upon."

"Very remarkable," agreed Professor Snath.

"But what's it all about?" asked Bud. "We've seen those earth cracks before."

"And near the place where there were dead cattle," added Nort.

"We heard running water down below, too," was d.i.c.k's contribution to the general information.

"Those cracks go down to the bed of an underground stream," explained Professor Dodson. "The subterranean river, brook or whatever it is, must flow a long distance under this ranch," and he looked over the expanse of valley, hill and plain. "Now an ordinary underground stream is not dangerous. In fact where it comes to the surface, as many do, it provides valuable water. But the stream below here is impregnated with a deadly gas." He gave it a long Latin name. "At least if it is not always deadly," he went on, "and it may not be so at all times, owing to dilution, it is risky to breathe it. I think that is the explanation of the deaths of your cattle," he said to Bud. "And you men who were rendered unconscious," he indicated Sam and his guards, "you must have breathed a modified form of the gas."

"But those fellows had gas in tanks!" cried Nort.

"No question about that!" added Billee. "Did they bottle up this stuff you gave such a long name to, Professor, and shoot it out at us?"

"No," was the answer. "I am inclined to think these unknown men used a very different kind of gas against you--probably a comparatively harmless vapor discovered during the war activities. I think there are two puzzles here and that they are both in the way, now, of being solved."

"It looks so," murmured Bud. "But how is the poison gas generated and how does it come up out of cracks in the earth to kill cattle and 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 done?" eagerly Bud asked.

"I don't know. But it's worth trying. You say you have gas masks?

They will be needed I think."

"Plenty of 'em!" cried Bud. "Come on back to the ranch where we still have them. We may win yet!" he said to his cousins. "If the gold mine peters out, as it has done, we'll get rich raising cattle in one of the best valleys of the west--providing the poison gas can be done away with."

"There's always an _if_ in the road," murmured Nort.

But when, a little later, the scientists, the boy ranchers and some of the men, wearing gas masks, penetrated to the far end of the defile, they found conditions which were distinctly encouraging. Professor Dodson located the ma.s.s of mineral which, when wet, gave off the vapor that caused death or disablement according to its strength.

"All that needs to be done," he said, indicating the stream which ran for some distance in the open before plunging underground, "is to build a small dam, change the course of this little river and send it down _outside_ the defile, instead of _through_ it. Keep this stream entirely in the open and you will do away with the poison gas. It is really a not very difficult problem in engineering and irrigation. It will not cost much to do this."

"Then it's going to be done, and it means the end of Death Valley forever!" cried Bud. "I mean a happy ending," he added. "For we'll do away with all danger."

"Thanks to you gentlemen and to Old Tosh," said Nort. "For he helped, didn't he?"

"Indeed he did," agreed Professor Snath.

"And when the course of the stream is changed," went on his chief, "there is no reason why the old herb doctor cannot resume work in his cave if he wants to. It will be safe then."

"Guess he'll be glad to hear that!" chuckled Nort. "He's been like a lost dog these last few weeks. Then those fellows, with their gas tanks, didn't have anything to do with killing our cattle?" he suggested.

"Not a thing," declared Professor Dodson. "It was a war against nature you were fighting."

"We've only just begun to fight her!" cried Bud.

Mr. Merkel was not much disappointed when he learned that the cave mine had petered out.