"And near the place where there were dead cattle," added Nort.
"We heard running water down below, too," was Dick'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.