end of the line. If it is, I'll know there must be a stoppage, or break, somewhere inside the old water tunnel."
"How you going to find that?" inquired Nort.
"Why, we'll get lanterns and ride through," replied Bud. "That's easy!"
"Ride through an underground river!" cried Dick. "You can't!"
"No, we couldn't if the old underground river course was full," agreed Bud, "but it isn't. There's only a comparatively small amount of water flowing through the old course, which is wide enough for two of us to ride or walk abreast, and twice as high as you need. I've ridden through more than once. It's like a long, natural tunnel under the mountain, with water flowing in the center depression, so to speak."
"Must be rather spooky inside there," suggested Nort.
"It is a little; and it's nearly an all-day's ride. But it's the only way to find the trouble. Professor Wright said that some day the water might work through, and go off on a new course, and in that case I'd be dished until I could stop up the break."
"Well, we'll help all we can," offered Nort.
"Sure thing!" echoed his brother.
"We'd better take it a bit easy now," spoke Bud, as the ascent of the mountain became more steep. "We don't want to wind the ponies, and we may have a hard day ahead of us to-morrow."
"It is quite a climb," admitted Nort. "Are we going to ride all night?"
"No, we'll turn in about midnight," said Bud. "But this will give us a start so we can get to the Pocut River end of the flume by morning. We can stop any time you fellows want to."
"Oh, we aren't tired!" Dick hastened to say, a sentiment with which his brother agreed. "This is as much fun as riding herd, and driving off the cattle rustlers."
"Glad you like it," commented Bud. "And the rustlers might as well drive off our stock, if we don't soon get this water to running again. Old Billee said I'd have bad luck when that black rabbit crossed my path, and it sure is coming!"
"What black rabbit was that?" asked Nort, curiously.
"One that gave me a tumble when I was riding to meet you," answered Bud. "I never saw one before, and I don't want to again. Not that I'm superstitious, but there sure is something queer about this! I don't like it for a cent!"
The boy ranchers and the Zuni Indian rode on, mounting higher and higher along the mountain trail, heading for the summit. And when they reached it, and Bud, by a glance at his watch, announced that it was midnight, he followed with the suggestion that they camp there for the remainder of the night.
"We can make the rest of the trip in a couple of hours, for it's down hill," he said.
"Camp suits me," murmured Nort, and soon, after a bite to eat, they rolled themselves in their blankets, having tied the ponies to scrub bushes, and went to sleep. The riding of the boys, coupled with the pure air they had breathed, brought them slumber almost at once, and even Buck Tooth, alert as he usually was, neither saw nor heard anything of the sinister visitor who came softly upon the sleeping ones during the night hours.
For there did come a visitor in the night, as evidenced by a scrawled warning, on a dirty piece of paper, fastened to a stubby tree by a long, sharp thorn.
It was this fluttering bit of paper that caught Dick's eye when he awakened, rather lame and stiff, and stretched himself in his blanket as the sun shone in his eyes next morning.
"Hello!" he cried, taking a hasty look around to see if Bud had, perchance, ridden away without awakening his companions, and had left this note to tell them so. "What's the idea?" and then Dick noticed that all three of his companions were stretched out near him, and the four ponies were standing together not far away.
"What idea?" asked Bud, sitting up and rubbing his eyes.
"That special delivery letter," and Dick pointed to it. "Wasn't here last night," he went on, "for I tied Blackie to that tree before I staked him out. What is it?"
Bud rolled out of his blanket, and took the piece of paper from the tree.
"It's a warning!" he announced.
"A warning?" cried Nort and Dick, while Buck Tooth began making a fire.
"Yes," went on the boy rancher. "Here's what it says:
"'Don't take no more watter frum Pocut River if you want to stay healthy!'"
"Whew!" whistled Dick. "What does that mean?"
"Just what I'd like to know," said Bud, and then all three boys started, and looked toward the upward slope of the mountain, down which they had partly descended. For there came rolling toward them a mass of dirt and stones, indicating the approach of some one.
CHAPTER IV
A STRANGE REAPPEARANCE
Characteristic it was of Bud Merkel, being a son of the west as he was, that his hand instinctively sought the leather holster whence protruded the grim, black handle of his .45. But he did not draw the weapon, nor did Nort or Dick pull theirs, which they had started to get out when they noted Bud's action.
For Bud smiled when he had a glimpse of the newcomer, and Buck Tooth, who had glanced up from where he was making the fire, gave a grunt of welcome.
"Babe!" exclaimed Nort, as he recognized the fat assistant foreman of Diamond X ranch. "Babe!"
"Sure! Who'd you think it was?" came the smiling question. "Looks like you had an idea it might be one of them rustlers that made trouble when you fellers was here before! Eh?
"Glad t' see you two ex-tenderfeet," and Babe Milton grinned broadly as he accented the ex, and held out a welcoming hand to Nort and Dick. "They said you was comin' back to Diamond X, but I sorter missed you – been out tryin' t' locate a bunch of strays," he confided to Bud, "an' I didn't have no luck! Glad to meet yo' all, though, powerful glad! 'Specially on account of that there coffee!" and he sniffed the air as he caught the aroma of the fragrant pot Buck Tooth was putting on to boil.
"But what are you lads doing so far from Diamond X?" Babe went on, when they had moved over to the camp fire, the blaze of which was genially warm this cool morning on the mountain.
"We aren't stopping there this trip," said Nort.
"We're 'on our own,'" proceeded Bud. "I'm raising cattle in the old Buffalo Wallow Valley – Flume I call it now."
"Oh, yes, I did hear you were going to tackle that," spoke Babe. "Didn't know you'd got stocked up, though. Well, I've been over at Square M for so long I don't hear no real news no more. Gosh! But we did have some excitement the time those professor chaps pulled that Trombone out of the ground; didn't we, Bud?" he chuckled.
"Triceratops, Babe! Triceratops!" corrected Bud, laughing at the expression of the fat assistant foreman's face.
"I never could remember the name of them musical pieces, nohow!" sighed Babe. "Fond as I am, too, of singing," and, taking a long breath, he bellowed forth on the unoffensive morning air this portion of a ballad:
"Sing me to sleep with a spur for a rattle,
Fill up the biscuits with lead.
Coil me a rope 'round th' ole weepin' willow,
Curl my feet under my head!"
"Glad you feel that way about it," remarked Bud, rather soberly, as they squatted around the fire for breakfast, which Buck Tooth seemed to have prepared in record time.
"What's bit you?" asked Babe, pausing with a smoking flapjack half way to his mouth, while in his other hand he held a steaming tin cup of coffee. "Git out th' wrong side of th' saddle this mornin'?"
"No, but there's trouble over at the valley," explained Bud. "The water has stopped running and – "
"The water stopped running!" interrupted Babe.
"Yes, and when we start out, intending to see what's the trouble, we get this warning," and Bud extended the dirty piece of paper that had been fastened to the tree with the thorn.
"Whew-ee-ee!"