But there were plain evidences of the fact that the men they had seen had fled in a hurry, as, indeed, they had practically witnessed.

Playing cards, cigarettes, tobacco and bottles were scattered on a rude wooden table, and there were several candle-ends stuck in the necks of flasks. The smell of the extinguished candles was heavy on the air.

"But where did they go?" asked Bud, when a hasty glance around the rocky room disclosed no occupants.

"What's that?" asked d.i.c.k, pointing to what seemed to be a hole in the floor at one corner.

"It's a pa.s.sage!" cried Billee, holding his lantern above it. "An' big enough, even for me! I'm going down!"

"Will it be safe?" asked Nort. "It may lead into the stream, or to where they have planted a mine--they spoke of a fuse----"

"You've got to take chances in times like these!" declared Old Billee.

"I guess if they went down it will suit us."

"Unless they can close it up, or turn water in," suggested Snake, dubiously.

"Git out! I'm going down!" stoutly declared the rather fleshy veteran cow puncher, and when he let himself down the hole the others followed.

There was a natural stairway, or what served the same purpose, leading down out of the stone room where the conspirators had been evidently plotting so far underground. The pa.s.sage went down, at first, like a flight of steep, cellar stairs. Then it straightened out, and, after twists and turns, led upward.

"Where are we going?" asked Nort.

"n.o.body knows!" grimly answered Bud. "But it's safe so far!"

"And we're right on their trail!" added Snake.

"How do you know?" asked Billee.

For answer Snake paused and pointed to a smouldering cigarette stub on the rocky floor of the pa.s.sage that had led out of the conspirators'

niche.

"That wasn't dropped many minutes ago," declared the cowboy. "They came along here."

This was evident, but it was also evident that Del Pinzo and his conspirators were sufficiently in advance to escape. For, with another sudden turn, the pa.s.sage led to another natural, rocky stairway, and when this had been mounted the boy ranchers found themselves again in the main tunnel.

"What's this?" cried Bud, when it was evident that they had come back to the place whence they had started, but farther on, and nearer to the river end of the tunnel. "This is a regular maze!"

"But where is Del Pinzo?" asked d.i.c.k.

"Out there, I fancy," and Nort pointed to where the main tunnel extended under the mountain and beyond, to the dam in Pocut River.

"They've gotten away!"

"And about time, too!" added Snake, "or they'd be trapped as we may be!"

"Trapped!" cried Old Billee. "What do you mean?"

"I mean there's a mine set here, somewhere! Don't you smell powder smoke?"

A sharp, acrid odor, once smelled never forgotten, came to the nostrils of all as they stood there in the tunnel, while the stream flowed beside them. Whatever the conspirators had done, they had, evidently, not shut off all the water.

"There it is!" cried d.i.c.k, and he pointed to where, in the light of the lanterns, there could be seen, slowly ascending, a thin wisp of smoke.

"Look out!" yelled Old Billee as d.i.c.k dashed forward. "It may explode!"

Then, as d.i.c.k rushed up with his lantern, they saw trailing over the floor of the tunnel, and on the same side of the stream as themselves, a thin white fuse, like a sinister snake. It was this burning fuse which caused the smoke.

It was the work of but an instant for d.i.c.k to step on it, and extinguish the smouldering spark, while it yet had some distance to travel before the fuse lost itself in a ma.s.s of rocks.

"Whew! That was a close call!" exclaimed. Bud, when the fuse was entirely out.

"Let's see where it leads to," suggested Snake.

They followed it up, and discovered a hidden mine of explosives, tamped down into a hole that had been drilled in the rocky floor. Iron bars, hammers and other mining implements showed that the perpetrators of the dastardly deed had evidently fled in a hurry.

"They were going to blow up the tunnel!" cried Nort.

"And when that collapsed it would mean the end of Flume Valley," spoke Bud soberly.

"We never could have opened the tunnel again, with all these strange, branching streams playing around inside."

"But we reached here just in time!" declared Old Billee. "Now let's get t' th' bottom of this. We know there's a main stream, an' two branching streams. One of th' branching streams is controlled by th'

water gate with th' copper handle."

"And there must be another gate here, or else Del Pinzo and his crowd couldn't have shut off the water as they did before they ran away,"

went on Bud. "There must be a whole maze of water-courses in this old tunnel. Probably the Aztecs dug 'em to save their gold and other valuables. But I'd like to know what that roaring is?" and as Bud and the others listened they could hear a subdued murmur, a rumbling and roaring sound, that seemed to shake the whole tunnel near where they stood.

"Maybe this leads to it," suggested d.i.c.k, as he walked along and suddenly flashed his lantern across another opening--a natural stairway leading down into black depths.

"Let's try it," said Bud.

Down it they went, one at a time, carrying their lanterns. And as they advanced, descending until they came to a level pa.s.sage, the murmur and roaring became louder.

"Would you look at that!" suddenly cried. Bud, in an awe-stricken voice, as he came to a stop and pointed ahead.

And then, as the others gathered about him and looked, they saw a wondrous sight.

They had entered a cavern, similar to the one where Nort had been found, but not so large. And from the very centre, it appeared, of the uneven rocky floor of the cave there spouted out a stream of water about three inches in diameter.

Solid white was this stream of water, like a bar of gla.s.s, and it shot out of a round hole in the floor as a stream comes from the nozzle of a fire hose. It was inclined at an angle of about forty-five degrees, was this strange stream of water, and whence it came and whither it went to the boys and their friends could only guess.

It was this powerful, rushing stream, under immense head and power it seemed, that caused the rumbling, roaring sound. It appeared to strike against some rocky wall a long distance off, so far that the light of the lanterns could not penetrate to it, and the searchers did not feel like venturing beyond the point where the terrific stream issued.

That it was of awful power was evidenced a moment later, for Bud, who had picked up one of the bars of iron, used by the conspirators to set their sinister mine, approached the stream and, raising the bar, brought it down with all his force on the white, spurting jet.

On an instant the heavy rod was torn from his grasp, and whirled forward into the blackness beyond. There was a ringing, metallic sound as it hit some distant rock, and then it came bounding back, sliding across the rocky floor to the very feet of the searchers.

"Look at that!" murmured Bud, as he stooped and picked up the bar. It was bent and twisted into a sort of combined S and U shape, mute evidence of the terrific power of the stream.

"That would bore right through a man!" said d.i.c.k.