The Saddle Boys of the Rockies

CHAPTER I - ACCEPTING A CHALLENGE
"Hello! what brought you here, Frank Haywood, I'd like to know?"

"Well, I reckon my horse, Buckskin, did, Peg."

"And who's this with you—your new chum; the boy from Kentucky?"

"That's who it is, Peg—Bob Archer; and he's come out West to see how life on the plains suits him."

"Oh! a greenhorn, eh?"

"Perhaps some people might call him that, though he knows a heap about horses. But seems to me, Peg, 'twasn't so very long ago that you yourself dropped in on us here. Since when did you climb up out of the tenderfoot class, tell me?"

The boy who answered to the name of Frank Haywood was a rather chunky, well set-up lad of about sixteen. He had blue eyes, that were usually sparkling with mirth; and a mop of yellow hair; while his skin was darkened by long exposure to sun and wind.

Frank was the son of a rancher, who not only owned a large tract of land with many herds, but had interests in paying mines located among the mountains of the Southwest. Of course he knew more or less concerning such things as cowboys practice; though never a day passed on which Frank could not pick up new ideas connected with life in the open.

His companion, Bob Archer, was considerably taller than Frank, straight as an Indian, though rather inclined to be slender; but with a suppleness that indicated such strength and agility as the panther displays.

Coming from Kentucky, Bob could at least boast of long familiarity with horses; and his cleverness in this line promised to make him a crack horseman when he had picked up a few more of the tricks known to range riders.

Both of the boys were especially fond of roaming the country, mounted on their favorite steeds; and indeed, they were becoming known far and near as the "Saddle Boys" because of their being seen so frequently, dashing over the prairies at top-notch speed.

Peg was the nick-name which had followed Percy Egbert Grant all the way from the Chicago suburb, where, for some years, he had played the part of both dude and bully. His father was very wealthy, and Peg always had more money than was good for him.

When he came to the great X-bar-X ranch, not so very far distant from the Haywood home place, Peg had adopted the same tactics that had carried the day for him in the past. The cowboys belonging to his father's estate seemed to knuckle under to him from the first. However much they might ridicule Peg behind his back, they cringed when he gave orders; because he was a liberal paymaster, and no one wished to incur his enmity.

So it came to pass that Peg actually began to believe himself of great importance in the community. He assumed airs that ill became one who was really ignorant of many things connected with ranch life.

He and Frank had never become friends. There was something about the fellow that the saddle boy could not tolerate. More than once they had almost come to blows; and, only for the peace-loving nature of Frank, this must have occurred long ago.

The two chums had taken the long gallop to the town on the railroad on this particular day to do a little important business for Mr. Haywood, who was associated with Bob's uncle in certain large mining enterprises. And it was while entering the town that they met Peg, who, with his customary assurance, had halted them with the question that begins this chapter.

When Frank give him this little cut, the face of Peg Grant showed signs of anger. He knew very well that he was making wretched progress along the line of becoming an accomplished rider and cowboy. And the easy manner in which the other boys sat their saddles irritated him greatly.

"What does it matter to you, Frank Haywood, when I left the greenhorn class and moved up a pace? All the boys of the X-bar-X outfit say I'm full-fledged now, and able to hold my own with nearly any fellow. It'll be some time, I reckon, before your new friend can say the same. But I will own that he's got a horse that takes my eye, for a fact."

"That's where you show good judgment, Peg," said Frank, laughing. "He brought that black horse with him from Kentucky. And he can ride some, you'd better believe me. When he gets on to the ways we have out here, Bob will hold his own against heaps of boys that were born and brought up on the plains."

"Say, I don't suppose, now, you'd care to sell that animal, Archer?" asked Peg, as he eyed the handsome mount of the Kentucky boy enviously. "Because I fancy I'd like to own him more than I ever did that frisky buckskin Frank rides. If you'd put a fairly decent price on him now—"

"I raised Domino from a colt, I broke him to the saddle, and we have been together five years now. Money couldn't buy him from me," replied the tall boy, curtly.

It was not Bob Archer's habit to speak in this strain to anyone; but there seemed to be a something connected with Peg Grant that irritated him. The manner of the other was so overbearing as to appear almost rude. He had had his own way a long time now; and thus far no one connected with the big ranch owned by his father had arisen to take him down.

"Oh! well, there are plenty of horses just as good, I guess," Peg went on; "and some people don't appreciate the value of money, anyway. But see here, Frank, you let your eyebrows travel up when I mentioned the fact that I'd graduated from the tenderfoot class. I could see that you doubted my words. Now, I'm going to tell you something that will surprise you a heap. Are you ready for a shock?"

"Oh; I can brace myself for nearly anything, Peg," replied Frank, easily; "so suppose you tell us your great news. Have you entered for the endurance race at the annual cowboy meet next month; or do you expect to take the medal for riding bucking broncos?"

"Any ordinary range rider might do that, even if he lost out," Peg went on; "but my game is along different lines; see? I'm on my way right now to run down the mystery of Thunder Mountain! I understand that for years it's puzzled the whole country to know what makes that roaring sound every now and then. Many cowboys couldn't be hired to spend a single night on that mountain. As for the Indians, they claim it is the voice of Great Manitou; and steer clear of Thunder Mountain, every time. Get that, Frank?"

"Well, Peg, you have given me a jolt, for a fact," answered the saddle boy, as his face expressed his surprise. "I allow that you show a lot of nerve in laying out such a big plan; and if you only find out what makes that trembling, roaring sound, you'll get the blessing of many a range rider who believes all the stories told about Thunder Mountain."

Peg stiffened up in his saddle, as though he realized that he was engineering a tremendously important thing; and had a right to be looked up to as a hero, even before the accomplishment of the deed.

"Well, that's always the way with you fellows out here, I find," he remarked, loftily; "you leave all the big things to be done by fellows with real backbone. But then, I don't mind; in fact I'm obliged to you for neglecting your opportunities so long. Just you wait, and you'll hear something drop. Couldn't I induce you to name a price on that black beauty, Archer?"

"Domino is not for sale at any price," replied the other, quietly.

"Oh! all right then. So long, Frank. Go back home, and wait till I send you word about what I've found out!" and with a careless wave of his arm Peg whirled his horse around, and galloped off.

"Now, I wonder did he mean that; or was he just bluffing?" said Frank, as he turned to his chum.

"He looked as if he might be in dead earnest," replied Bob; "but you know him better than I do, and ought to be able to say whether he'd have the sand to take up such a job as that."

"Oh! nobody doubts his grit, when it comes to that," Frank went on, as though trying to figure the matter out. "And he seems to want to do something everybody else lets alone. You know what I told you about Thunder Mountain, Bob; and how it has been a mystery ever since the country hereabout was settled by people from the East?"

"Yes," the Kentucky boy replied, "and somehow, what you told me seemed to shake me up as I don't ever remember being stirred before. It was like a direct challenge—just like somebody had dared me to look into this queer old mountain, and find out what it all meant."

"That's just it," said Frank, watching the face of his chum with a show of eagerness. "It struck me the same way long ago, and I can remember often thinking what a great time a few of the right kind of fellows might have if they took a notion to go nosing around that old pile of rock, to see what does make all that row every little while."

"And you tell me nobody knows what it is?" demanded Bob.

"Why, don't you understand, the cowboys all keep away from Thunder Mountain as much as they can. They're worse than the Injuns about it, because while the reds say that is the voice of Manitou talking, these fellows just up and declare the mountain is haunted. Lots of 'em couldn't be hired to spend a night on the side of that big uplift."

"But Frank, we don't believe in any such thing, do we?" pursued Bob, as if he had begun to suspect what all this talk was leading up to, and wished to draw his chum on.

"We sure don't, and that's a fact," declared Frank. "Twice, now, one of our boys has made out that he saw a ghost, but both times I managed to turn the laugh on him. All the same, if you offered a lump sum for any fellow to go and camp out half-way up the side of Thunder Mountain for a week, I don't believe he could be found, not at Circle Ranch, anyhow."

"I've seen the same kind of men myself; and the coons around our old Kentucky home always carried a foot of a graveyard rabbit, shot in the full of the moon, as a sure talisman against ghosts. I've seen many a rabbit's foot. No use talking to any of them; it's in the blood and can't be cured. But about that offering a sum for any fellow to go and camp on the side of that old fraud of a haunted mountain, if you happen to hear about such a snap you might just think of me, Frank."

The other saddle boy smiled broadly. He believed he knew Bob pretty well by this time, and could no longer doubt what the Kentucky lad was hinting at.

"Say, look here, would you take me up if I proposed something right now?" asked Frank, his face filled with sudden animation.

"If you mean that we try and beat Peg Grant at his own game, and learn what the secret of Thunder Mountain is, I say yes!" answered Bob, steadily.

"Shake on that!" he exclaimed. "I'm just primed for something that's out of the common run; and what could be finer than such a game? I saw Billy Dixon in town; and we can send back word to father that we've gone off for a big gallop; so he won't worry if we don't turn up for a few days. Is it a go, Bob?"

"Count on me," replied the other. "I don't know how it is, Frank; but it strikes me that I'd like to cut in on that boaster in this thing. If we managed to find out what makes that fearful booming in the mountain, and told about it before he got a chance to blow his horn, he'd feel cheap, wouldn't he?"

"He sure would, now," Frank said. "And when you look at it, he just the same as gave us the challenge direct, because he hinted that we didn't have the nerve to attempt such a big thing as this. Bob, we'll call it a go! Wonder what Peg will say when he runs across us out there in that lonely place? Wow! I reckon he'll be some mad."

"Let him," remarked Bob, carelessly. "He has no claim on Thunder Mountain; has he? And we want to call his bluff, if it was one. So just make up your mind we're in for a new experience. It may pan out a heap of fun for us. And it will be worth while if we can settle the question that has been giving these superstitious cowmen the creeps all these years."

"Then let's get through with our business, send word by Billy, though not telling what we've got in the wind, and then pick up a few things we might need on a trip like this. After that we can drop out of town, and take our time heading for the mountain; because I think I'd like Peg to get there first, so that he couldn't say we'd stolen his thunder."

Half an hour later the saddle boys, having finished their business, and sent the Circle ranch cowboy galloping homeward bearing the message to Mr. Haywood, were moving slowly through the main street of the town, heading toward a store where they could pick up a couple of blankets, a simple cooking outfit, and some of the substantials in the way of bacon, coffee and the like, when they came upon a scene that instantly attracted their attention.

It was a terrified cry that reached their ears at first, and caused both boys to pull in their horses. Glancing in the direction whence the sound of distress seemed to spring, they saw a small Mexican girl struggling with an over-grown fellow, garbed in the customary range habit, even to the "chaps" of leather covering his trousers.

Both Frank and Bob jumped from their saddles, for the little affair was taking place in the courtyard of an inn that fronted on the street. Whether the brute was simply playing the bully, and trying to kiss the girl; or meant to strike her for getting in his way, Bob Archer did not stop to inquire.

His warm Kentucky blood on fire, he made a swoop for the fellow, and managed to give him a tremendous blow that toppled him over in a heap.

"Lie there, you coward!" he exclaimed.

And then, as the fellow whom he had knocked down struggled to his knees, to stare up at him, Bob discovered, not a little to his surprise, and satisfaction as well, that he was looking into a familiar face.

It was Peg Grant!

CHAPTER II - THE STRANGE ACTIONS OF DOMINO
"Well, I declare!" exclaimed Frank; which remark showed how much surprised he was to recognize the youth whom his chum had sent to the ground.

"What do you mean by hitting me like that?" snarled the rich man's son, as he managed to scramble to his feet again, though he seemed a bit "groggy," and one of his eyes was already turning dark, as if it had come in violent contact with a stone when he struck the ground.

"What do you mean, hurting that poor little Mexican girl?" demanded Bob, who stood on his guard, as though he might not be averse to trying conclusions with the bully, if so be the other felt like seeking satisfaction for his upset.

"She sassed me when I ordered her to get out of my way, that's what she did;" declared Peg, wrathfully, "and I'd look nice now, wouldn't I, letting a little greaser kid talk back to me? So I was just giving her a good shaking when you broke in. Guess you didn't know who you were hitting when you did that, Bob Archer!"

"Perhaps I didn't," replied the Kentucky lad, calmly; "though that wouldn't have made any particular difference. Any cur who would lay his hands on a child like that ought to get knocked down every time. I'd do it again if you gave me the chance!"

Peg stared at him. Perhaps he had never been treated in this manner before. All his life his acquaintances had truckled to him on account of the great wealth of his father, and the liberal way he himself, as a boy, rewarded those who were allowed the privilege of being his cronies or mates.

"You—would, eh?" he gasped, as if hardly daring to believe his ears. "Even if you knew it was Peg Grant you'd treat me that way; would you? I'll remember that! I'm not the one to forget in a hurry. Some day, perhaps, you'll wish you'd never tried to play the hero part, and hit me when my back was turned. I've got a good notion to teach you a lesson right now; that's what!"

"All right," remarked Bob, coolly. "Suppose you begin. I was never in a better humor for trouble. Somehow I seemed to just know we'd hit it up sooner or later if our trails crossed. I give you my word, my friend here won't put a finger on you, if so be you get the better of the row; will you Frank?"

"I should say not," declared the lad, instantly, adding: "and unless I miss my guess there won't be any need of it, either."

"Are you coming on, Peg?" asked the Kentucky lad, temptingly.

From under his drooping eyebrows Peg observed how easily the other had assumed a position of self-defense. Somehow Peg did not fancy the athletic build of his antagonist; for, while Bob was rather slender, he had the marks of one accustomed to exercise; possessing at least ordinary ability to take care of himself.

"It'll keep, and be all the better for the delay," Peg grumbled, as he clenched one fist furiously, and used the other hand to feel of his injured optic. "Besides, I don't feel fit to fight right now, with this bunged-up eye. But just wait till the right time comes, and see what you get then for doing this."

"Oh! well, suit yourself," returned Bob, with a laugh. "If the little brown-faced girl hadn't vamoosed I declare if I wouldn't feel like making you get down on your knees, and asking her to excuse you. Bah! you're not worth bothering about, Peg. Get out!"

The other moved away. He did not like the manner in which Bob said this; and he seemed to be afraid that perhaps the other might yet decide to press some further indignity on him.

When, however, he had reached the door of the inn, so that he could have a way of escape open to him in case of need, he stopped and shook his fist threateningly toward the saddle boys.

"You're both going to pay dear for this little fun, hear that?" he called, his voice trembling with passion. "I'll find a way to get even, see if I don't! And when Peg Grant says that he means it, too! Just you wait till I——"

And then, as Bob started to advance toward the hostelery Peg retreated in a panic, slamming the door after him.

"Well, what d'ye think of that?" asked Frank, who had been an amused observer of this curious scene.

"He's turned out just what I thought he would," remarked Bob, as he once more gained the side of his comrade, a grim smile on his face. "Whenever you run across a fellow who likes to boast of the way he does things, make up your mind he's a rank coward, every time. No matter what he claims he will do, there's a yellow streak in him somewhere, and sooner or later it's bound to show."

"I believe you're just about right, Bob," said Frank; "and it agrees with my own opinion exactly. Still, that fellow can be dangerous if he wants."

"So can a rattlesnake; but at any rate the reptile is honest, for he gives plenty of warning before he tries to strike; and that's more'n Peg would do, if I read him straight."

"You must keep an eye out for him after this, Bob. He'll never forgive you that crack. My! but didn't it drop him, though! Just like a steer would go down when the loop of a lariat closes on his foreleg. That fellow will lie awake nights trying to get even with you."

"Let him," remarked Bob, carelessly; "next time perhaps I'll put a little more steam back of my fist, if he pushes me too hard. That's the way they treat cowards back where I was brought up; and they call anybody by that name who will put his hand in anger on girl or woman. But see here, Frank, is this little affair going to force us to change our plans?"

"Whew! I forgot all about that," said the other, with a whistle, and an uplifting of his eyebrows. "If we go poking around Thunder Mountain, and Peg is there, with a couple of the tough cowboys he has trailing after him most of the time, Spanish Joe and Nick Jennings, perhaps we'll run up against a peck of trouble."

"Well, how about it?" asked Bob, with a shade of annoyance on his face.

"What do you say?" asked Frank, in turn.

"Go, by all means," came the quick response. "You don't think so mean of me as to believe I'd be frightened off by the bare chance of running across that fellow's trail out there; do you, Frank?"

"All right, call it a bargain, then. I'm with you through thick and thin, Bob. Let Peg have a care how he meddles with us. We're going to pay attention to our own business, and he'd better do the same. But what became of the little Mex? I thought I'd seen her face before, somewhere, but she skipped out before I could take a second look. Some cowboy, or cattle rustler's child from beyond the Rio Grande, I reckon. Well, come along, let's get in the saddle again, and finish our shopping. Then we'll go out to the country along the river, and put in a day waiting for Peg to have his chance at finding out what makes Thunder Mountain groan and shake just so often, and scare the Injuns out of their seven senses."

As the two chums swung themselves into their saddles, and cantered away, a head was thrust cautiously out from behind a pile of boxes near by; and then, finding the coast clear, the small girl who had been the cause of all the trouble darted across the courtyard, vanishing beyond the gate.

Frank and Bob went about making their purchases, first fastening their horses to a rail in front of the general store, where everything they needed could be bought.

More than one cattleman in passing would cast an envious eye toward those two splendid mounts, for they could not fail to catch the attention of anyone accustomed to judging horseflesh, as these Western men were. Still, it would be a bold man indeed, white or Indian, who would dare attempt to steal a horse in broad daylight, in a country where such a thief was treated to a rope when caught.

Frank had had considerable experience in roughing it, while his comrade was, in a measure, new to such a life. Consequently it was Frank whose judgment was called into play when making a selection of the things that would be essential to their comfort when on this new campaign.

Many articles they could do without; but a blanket apiece was absolutely necessary, as was a frying pan and coffee pot, two cups, as many platters, as well as common knives, forks and spoons such as prospectors and cattlemen use.

For food they took some bacon, coffee, dried meat, hard-tack in place of bread, a can of condensed milk, and several other things which would carry well.

"We must make them up in two packs," Frank went on; "so that each of us can fasten one to his horse, back of the saddle. And, as I'm an old hand at this business, just watch me get a hustle on. Next time you'll know how to go about it for yourself, Bob."

The Kentucky boy always studied everything his comrade showed him, for it was his ambition to excel in the many little tricks connected with the free life of the plains. Things were done so differently here from what he had been accustomed to in his old Kentucky home, before his father died, that they often puzzled him; but Bob was a persistent boy, and would never rest content until Frank could teach him no more.

Neither of them suspected what was going on outside, while they busied themselves in purchasing the supplies needed for the little campaign in the neighborhood of the mysterious mountain. And yet all was not as quiet as it might be.

The saddle boys had hardly been inside the general store ten minutes before a slinking figure might have been observed drawing nearer and nearer to the horses ranged along the bar. There were several besides the animals of our two young friends; but, somehow, the handsome black seemed to attract the entire attention of this shadowy form.

Twice he stopped, and assumed an attitude that would indicate his utter indifference to such commonplace things as horses. Then, finding that it must have been a false alarm, he would edge closer.

Finally he was beside the black horse, uttering low words such as cowboys make use of to soothe a restive steed when they mean to throw a saddle across his back, and cinch the girth.

Two men came out from the store, and drew near. The slim figure, finding it out of the question to flit hurriedly away, without attracting attention, which was just the thing he wished to avoid, commenced stroking the sleek side of the big black Kentucky thoroughbred, as though he might be a cowboy connected with the far famed Circle ranch of Frank's father.

Casting just one casual glance toward him, the men threw themselves into their saddles with the rapidity and grace of true plainsmen, and went galloping off.

Two minutes later the shadowy figure of the man flitted away from the line of horses that remained. If his purpose had been to steal the black he must have changed his mind, for there was no break in the chain of horses that stood there, impatiently scraping the ground with their forefeet.

A little later out came Frank and Bob, each bearing a compact bundle which they quickly fastened back of their saddles.

Bob was the first to mount, and this action was hurried because he hardly knew what to make of the restless actions of Domino. The animal seemed to be dancing up and down as though he had stirred up a hornet's nest, and the little insects were charging his exposed legs.

No sooner was Bob in the saddle than the horse gave a shrill neigh, and dashed off like a crazy creature. Indeed, a less experienced rider than Bob would have been instantly thrown by the sudden and unexpected move, something that Domino had never been known to attempt before.

Frank looked up in astonishment. His practiced eye told him in an instant that the sudden violent dash had not been engineered in the least by his chum; but was altogether the result of fright on the part of Domino. Why, the big and powerful black acted as though he had gone wild, jumping madly about, now fairly flying off to one side, only to whirl and dance and leap high in the air, until every one within seeing distance was staring at the strange spectacle. And this, too, in a town where bucking broncos were a common sight.

Frank had gained his saddle, and was chasing after his friend, but just then the black had taken a notion to run, and apparently nothing in that country could overtake him while his present savage mood held out.

"What ails the beast?" Frank asked himself, as he drew rein and watched the other passing beyond range of his vision among the stunted mesquites outside of the edge of the town. "He acts like a locoed horse; but there isn't a bit of the poison weed growing within twenty miles of here. And why was Peg Grant standing on the stoop of the tavern grinning as I rode past? Can he have had a hand in this sudden crazy spell of the black? Spanish Joe knows all the tricks of putting a thorn under a saddle, that will stab the horse when the rider mounts. Is that the trouble now? If it is then it's lucky my chum knows as much as he does about managing a horse, or he would never come back alive from that mad ride. And all I can do is to sit here, wait for his return, and watch Peg Grant and his cronies!"

CHAPTER III - OLD HANK COOMBS BEARS A MESSAGE
If there was one thing Bob could do well, it was to ride. Born in Kentucky, where horses take a leading part in the education of most boys, Bob had always spent a good part of his time in the saddle.

Hence, when he came out here to the plains, the cowboys of the ranch found that, in his own way, he was well versed in managing the fine black horse he brought along with him.

Of course there were dozens of tricks which these daring riders of the plains could show the tenderfoot from the South; but when it came down to hard riding Bob was able to hold his own.

When his powerful horse bolted in such a strange fashion Bob simply kept his seat, and tried to soothe Domino by soft words. For once the remedy failed to produce any immediate effect. The animal seemed fairly wild, and tore along over the open country like mad.

"He never acted like this before in all his life," thought Bob, as he found considerable difficulty in keeping his saddle, such were the sudden whirls the black made in his erratic course.

But although he had by no means learned all the things known to old cowmen, Bob had picked up quite a few points since arriving at the ranch. He had even heard of a mean trick practiced by revengeful Mexicans, and others, when they wished to place a rival's life in danger.

"Something has happened to him since we went into that store," Bob said again and again, as he puzzled his wits to hit upon an explanation for the animal's remarkable antics. "Now, what could it have been? Would any fellow be so mean as to fasten some of those prickly sand burrs under his tail? Or perhaps it's a poison thorn under the saddle!"

This last idea seemed to strike him as pretty near the truth. He began to investigate as well as he was able during the rushing of the runaway horse. When, in pursuing his investigations, he ran his hand under the flap of the saddle, he could feel the horse start afresh, and his queer actions seemed worse than ever.

"That's just what it is, as sure as anything!" Bob declared, his whole frame quivering with indignation at the thought of anyone being so cruel and treacherous; "but how in the wide world am I going to get at the thing?"

His first impulse was to ease the strain all he could by removing his weight from the point where he believed the thorn to have been hidden. This he did by leaning forward after the manner of a clever jockey in a race, throwing pretty much all his body upon the shoulders and neck of the horse.

Then he again began to speak soothingly in the ear of Domino. By degrees the horse seemed to slacken his wild pace.

Encouraged by this fact, Bob continued the treatment. It appeared as though the intelligent animal must comprehend what was wanted, for, although evidently still in more or less pain, he gradually ceased his runaway gait, until, finally, at the command of "whoa!" Domino came to a complete stop.

Bob was on the ground immediately. His horse was trembling with excitement and other causes. Bob continued to pat him gently, and speak soothing words. All the time he was working toward the buckle of the band by means of which the saddle was held firmly on the beast's back.

Once he had a grip on this he made a sudden pull. Domino squirmed, and for the moment Bob feared the animal would break away.

"Easy now, old fellow; take it quiet! I'll have that saddle off in a jiffy; and see what is wrong. Softly, Domino! Good old Domino!"

While he was talking in this manner Bob was releasing the band; and, with a sudden jerk, he threw the saddle to the ground.

His quick eye detected signs of blood on the glossy back of the Kentucky horse.

"That's what it was!" he exclaimed, angrily. "A thorn of some kind, put there so that when I jumped into my seat my weight would drive it in. And I reckon, too, it would be just like the cowardly sneak to pick out one that had a poison tip! Oh! what a skunk! and how I'd like to see some of the boys at the ranch round him up! But I wonder, now could I find it? I'd like to get Frank's opinion on it."

The horse had by now ceased his mad prancing. This proved that the cause for his strange actions had been removed when Bob cast the saddle off. And it did not require a hunt of more than two minutes to discover some little object clinging to the cloth under the saddle. It was, just as Bob had suspected, a thorn with several points that were as sharp as needles, and very tough.

Bob put it away in one of his pockets. Then he once more replaced the saddle, carefully adjusting the girth so as to avoid any more pressure on the painful back of Domino than was absolutely necessary.

The horse seemed to understand his master's actions, and, although still restive, allowed Bob to mount.

Cantering along over the back trail, in half an hour Bob came in sight of his chum heading toward him.

"Well," said Frank, as they finally met, "I was beginning to get worried about you, even though I knew you could manage a horse all right. It was a lively run, I should say," as he glanced at the foam-streaked flanks of the gloss black.

"As fierce a dash as I ever want to take," answered Bob, patting his horse gently.

"Did you find out what ailed him?" asked the other.

"After I'd spent some time trying to keep from being thrown, I did."

As he said this Bob drew the thorn from his pocket, and held it before Frank, who took the vicious little thing in his hand.

"I thought so," he muttered. "That's Peg's idea of getting even with us; the coward!"

"But you don't mean to say Peg did that?" exclaimed Bob, astonished.

"Well, not with his own hand. He wouldn't know how, you see; but he had a Mexican cowboy along with him who is up to all these tricks—Spanish Joe. When we were busy in that store, he crept up and fixed this thorn under your saddle. Of course, as soon as you sprang into your seat, your weight just drove one of these tough little points in deeper. And, as the horse jumped, every movement was so much more torture. Get onto it, Bob?"

"Sure I do; and I guessed all that while riding back. But tell me, why did he pick out my horse, instead of your Buckskin?" asked the Kentucky boy.

"Look back a little. Who was it gave Peg his little tumble when he was striking that child? Why, of course it was nobody but Bob Archer. I saw Peg standing on the porch of the tavern as I galloped after you; and give you my word, Bob, he had a grin on his face that looked as if it would never come off. Peg was happy—why? Because he had just seen you being carried like the wind out of town on a bolting nag. And I guess he wouldn't care very much if you got thrown, with some of your ribs broken in the bargain."

Bob proceeded to tell how he had figured on what caused the queer antics of his horse, and then what his method for relieving the pressure had been.

"Just what you should have done!" exclaimed Frank, enthusiastically. "Say, you're getting on to all the little wrinkles pretty fast. And it worked too, did it?"

"Thanks to the smartness of Domino, it did," replied Bob, proudly. "Some other horses might have broken away as soon as their rider dismounted; but he's mighty near human, Frank, I tell you. He just stood there, quivering with excitement, and pain, till I got the thing off. But do you know what kind of thorn this is?"

"I know it as well as you would a persimmon growing on a tree in Old Kentucky; or a pawpaw in the thicket. It's rank poison, too, and will breed trouble if the wound isn't taken care of in time.

"That's bad news, old fellow. I'd sure hate to lose my horse," remarked Bob, dejectedly, as he threw an arm lovingly over the neck of the black.

"Oh! I don't think it'll be as bad as that; especially since I happen to have along with me in my pack some ointment old Hank Coombs gave me at a time I fell down on one of the same kind of stickers, and got it in my arm," and Frank opened the smaller of the two packs he had fastened behind his saddle.

When the ointment was being thoroughly rubbed into the spot where the barb of the thorn had pierced the flesh of the animal, Domino seemed to understand what their object was. He gave several little whinnies, even as he moved uneasily when his master's hand touched the painful spot.

"Now what's the programme?" asked Bob, after he had replaced the saddle.

"Just what we decided on before," replied his chum; "a little rest before we make a start. Twenty-four hours will do Domino considerable good, too. How did you come out about the duffel you were carrying; any of it get lost?"

"None that I've noticed. I'll make a round-up and see, before we go any further," Bob remarked, examining the packages secured behind his saddle.

"How?" queried Frank, in the terse, Indian style, as he saw that the other had gone carefully over the entire outfit.

"Everything here, right side up with care. And now I'll have to mount again, a thing that may not appeal very much to Domino. But it's lucky I long ago learned the jockey way of riding, with most of the weight upon the withers of the horse. In that manner you see, Frank, I can relieve the poor beast more than a little."

Together they rode off slowly. Really, for one day it seemed that the big black must have had all the running his fancy could wish. Besides, neither of the boys knew of any reason for haste. As Frank had suggested, it would perhaps be just as well to allow a certain amount of time to elapse, before pushing their intended investigation of the mysteries supposed to hover around Thunder Mountain.

The afternoon had almost half passed when Frank's sharp eyes discovered a single horseman riding on a course that would likely bring him across their trail soon.

"Seems to me there's something familiar about that fellow's way of sitting in the saddle," he observed; and then, reaching for the field glasses which he carried swung in a case over his shoulder, he quickly adjusted them to his eyes. "Thought so," he muttered, and Bob could see him smile as he said it.

"Recognize the rider, then? Don't tell me now that it's Peg, or one of those slippery cowboy friends he has trailing after him," remarked Bob.

"Here, take the glasses, and see what you think," replied the other, laughingly.

No sooner had the Kentucky lad taken a single good look than he called out:

"Who but old Hank Coombs, the veteran cow puncher of the Southwest! I suppose your father has sent him on an errand, Frank."

"Just as likely as not, because he trusts old Hank more than any man on the entire ranch. You can see he's headed in a line that will fetch up at the Circle Ranch by midnight, if he keeps galloping on. Look there, he sees us, and is waving his arm. Yes, he's changed his course so as to meet us, Bob."

"But if we needed the glass to find out who he was, how does it come that an old man like Hank could tell that we were friends, at such a distance?" asked the young tenderfoot, always eager to learn.

"Because his eyes are as good as ever they were. Some of these fellows who have lived in the open all their lives have eyes like an eagle's, and can tell objects that would look like moving dots to you. Let's swing around a bit, so as to keep old Hank from doing all the going."

As he spoke Frank veered more to the left, and in this fashion they speedily drew near the advancing horseman. He proved to be a cowman in greasy chaps, and with many wrinkles on his weather-beaten face. But Hank Coombs was as spry as most men of half his age. He could still hold his place in a round-up; swing the rope in a dexterous manner; bring down his steer as cleverly as the next man; ride the most dangerous of bucking broncos; and fulfill his duties with exactness. Few men grow old on the plains. Most of them die in the harness; and a cowboy who has outlived his usefulness is difficult to find.

The veteran eyed the additional packs back of the saddles of the two boys with suspicion in his eyes. He knew the venturesome nature of his employer's son; and doubtless immediately suspected that Frank might have some new, daring scheme in view, looking to showing his friend from the East the wonders of this grand country, where the distances were so great, the deserts so furiously hot, the mountains so lofty, and the prairies so picturesque.

"Ain't headin' toward home, are ye, Frank?" was the first question Hank asked, as they all merged together, and rode slowly onward in company.

"Oh! not thinking of such a thing, Hank," replied the boy. "Why, we only left the ranch yesterday, you know, and meant to be away several days, perhaps a week. But I'm glad we ran across your trail right now, Hank, because you can take a message to dad for me."

"Glad to do that same, Frank," the veteran cowman replied, and then added: "but jest why are ye headin' this way, might I ask? It's a wild kentry ahead of ye, and thar be some people as don't think it's jest the safest place goin', what with the pesky cattle-rustler crowd as comes up over the Mexican border to give the ranchers trouble; and sometimes the Injuns off their reservation, with the young bucks primed for a scrap."

"Is that all, Hank?" asked Frank, turning a smiling face upon the old rider. Hank moved uneasily, seeming to squirm in his saddle.

"No, it ain't," he finally admitted, with a half grin; "that's Thunder Mounting about twenty mile ahead o' ye. None o' us fellers keers a heap 'bout headin' that-a-way. Twice I've been 'bliged to explore the canyons thar, arter lost cattle; but I never did hanker 'bout the job. It's a good place to keep away from, Frank."

"You don't say, Hank!" chuckled the boy. "Too bad; but you see that's just the very place we expect to head for to-morrow—Thunder Mountain!"

The old man looked closely at him, and shook his head.

"I don't like to hear ye say that, Frank," he muttered, uneasily; "an' I kinder reckons as how yer father'll feel oneasy when I tell him what yer up to. 'Cause, I opine, ye wants me to carry thet same news back home; don't ye?"

"Sure," answered the other, laughing. "That's what I meant when I said I was glad we'd met up with you, Hank."

"But ye didn't expect to take a turn thar when ye left home, did ye?" the veteran cowman went on.

"Never entered my head, Hank. Fact is, we weren't thinking of Thunder Mountain up to an hour or two ago, when we ran across Peg Grant, who was in town with his two followers, Spanish Joe and Nick Jennings."

"The wust as ever throwed a leg over leather," muttered Hank, between his teeth. "We been talkin' it over, some o' us boys, an' 'bout kim to the conclusion as how them fellers must be in touch with the Mendoza crowd o' rustlers as draps over the Rio Grande every leetle while, to grab a bunch o' long horns."

"My opinion exactly, Hank," went on Frank. "But listen till I tell you what they are thinking of doing about finding out the secret of Thunder Mountain."

Quickly he related the incident of their meeting Peg, and of his boast.

"They'll never do it, mark me," declared Hank, after he had been put in possession of the main facts. "Thet noise ain't human! I been a-hearin' it for the last forty years, an' I give ye my word it's gittin' wuss right along. The reds believe as how it's the voice of the Great Spirit talkin' to 'em. An' honest now, Frank, thems my sentiments to a dot."

"In other words, Hank, you believe the mountain is haunted, and that anyone bold enough to wander into the unknown country that lies back there is going to get into a peck of trouble?" Frank asked, seriously.

"Reckon as how that kivers the ground purty well," replied the cowman, grimly.

"Well," Frank went on, "we happen to believe something different, and we mean to look into the thing a bit. It wouldn't surprise me to find that some sharp crowd has been taking advantage of the bad name Thunder Mountain has always had, to hide among those canyons. And, Hank, I'm going to look for the trail of some cattle while I'm there!"

"Which I take it to mean," Hank continued thoughtfully, "that you kinder think them rustlers might be usin' the ha'nted mounting for a hiding place to keep the cows which they run away with? Um! wa'al now, I never thort o' that afore. But stands to reason no Mexicans'd ever have the nerve to go whar white cowmen kept away from."

"Not unless they had solved the strange mystery of the mountain, and no longer saw any reason to be afraid of the thunder. But listen while I tell you something else that happened to my friend here."

Frank then described the sudden bolt of Domino. At his first words the experienced western man looked wise. He had immediately guessed what caused the unexpected action of the usually tractable black horse.

"As low down a trick as was ever carried out," he remarked, finally, as he looked at the thorn. "And jest sech as thet sneakin' coyote, Spanish Joe, would be guilty of tryin'. I've seen it done more'n a few times; and twict the critter was rounded up, and treated like he'd been a hoss thief; 'case ye see, in each case 'twar a woman as rid the animile as got the thorn. But ye must let me rub somethin' on thet wound right away, Bob."

"Don't bother," sang out Frank, cheerfully; "because we happened to have with us that ointment you gave me, and I used it a while ago. I'll put on more to-night when we get the saddles off, and once again in the morning."

"Then ye mean to go into camp soon?" inquired Hank.

"See that timber over yonder, where a stream runs? We'll settle down for the night there. Better hold over with us, Hank, unless you're in a terrible hurry to get back home," Frank observed.

"I'd like to fust rate, Frank; and p'raps thar aint no sech great need o' gittin' back to the ranch to-night. Yes, I'll hang over. P'raps I kin coax ye to give up that crazy ijee 'bout Thunder Mounting."

And when they had settled down under the trees, with the westering sun sinking toward the horizon where, in the far distance, Frank pointed out to his chum the towering peak toward which they were bound, old Hank did try to influence his employer's son into giving up his intended trip.

It was useless, however. Frank had made up his mind, and obstacles only served to cause him to shut his teeth more firmly together and stick to his resolution. And so they spent the night very comfortably, under the twinkling stars.

"Tell dad not to worry about us at all, Hank," Frank said to the veteran, on the following morning, as they were bidding him good-bye. "We'll turn up all right in the course of a few days. And perhaps, who knows, we might be able to tell you all about the queer noise that shakes the earth every little while around the big uplift. So-long, Hank!"

The old cowman sat in his saddle, and looked after the two boys as their horses went prancing away, each of the riders turning once or twice to wave a jolly farewell, with uplifted hats.

"As fine a pair o' happy-go-lucky boys as ever drawed breath," Hank muttered, as his eyes followed their vanishing forms beyond the mesquite thicket. "But I sure feel bad 'bout them goin' into that 'ere Thunder Mounting territory. I hopes Mr. Haywood'll start out with a bunch o' cowmen to round 'em up. But he thinks that Frank kin hold his own, no matter what comes along. If he don't show signs o' bein' worried, I'm goin' to see if the overseer, Bart Heminway, won't take the chances of sendin' several of us out to hunt for strays; an' it'll be funny now, how them mavericks all run toward Thunder Mounting."

Chuckling, as if the new idea that had appealed to him gave him considerable satisfaction, the old cow-puncher stirred his little bronco into action, and was soon galloping away. But, more than a few times, he might have been observed to turn in his saddle and cast a look of curiosity, bordering on apprehension, toward the dimly-seen mountain that arose far away on the Southwestern horizon.

For to Hank Coombs that peak stood for everything in the line of mystery and unexplained doings.

CHAPTER IV - A NOTE OF WARNING AT THE SPRING HOLE
"Pull up, Bob; I sure glimpsed something moving, out there in the sage brush!"

Both horses came to an immediate stop as the bridles were drawn taut.

"Which way, Frank?" asked the Kentucky lad, eagerly, as he threw back his shock of black hair, and waited to see where the finger of his companion would point.

"Whatever it was disappeared behind that spur of the low foot hills yonder. I just caught a peep of the last of it. Here, Bob, take the glasses, and wait to see if it shows up again on the other side of the rise," and Frank thrust the binoculars into the hand of his chum.

"Think it could have been a prowling coyote; or perhaps a bunch of antelope feeding on the sweet grass around some spring hole, as you were telling me they do?" asked Bob, holding himself in readiness.

"Well," returned Frank, quickly, "the sun was in my eyes some, you see, and so I wouldn't like to be too sure; but somehow, Bob, I just have a notion that it was a horse."

"With a rider on it, of course!" exclaimed the other lad, as he raised the glasses to his eyes, training them on the further end of the squat elevation that stood up in the midst of the sage level like a great hump on a camel.

"There, looks like I was right, Bob!" ejaculated Frank, a minute or so later, as something came out from behind the low hill, moving steadily onward.

"Indians! as sure as anything!" fell from the lips of the one who held the field glasses to his eyes.

"One—two—three—a heap of the reds in that bunch, I reckon," muttered Frank, watching with his naked eye; although the distance, separating them from the spot where the figures were passing steadily into view, was considerable.

"Say, these glasses are jim-dandy ones, all right!" remarked Bob, presently, as he turned to offer them to his chum, who immediately clapped them to his own eyes.

"Huh!" grunted Frank a moment later, "squaws along; each cayuse dragging poles on which they heap their lodges, blankets and such; reckon there's no war party about that, Bob."

"I should think not, if what you've told me about the Indians is a fact, Frank. But look here, what d'ye suppose they're doing so far away from their reservation?" and Bob gripped his quirt, which hung, as usual, from his wrist, in cowboy fashion; and with a nervous slash cut off the tops of the rattlesnake weed within reach.

"That's where you've got me, Bob," replied the one who had been brought up on a ranch, and who was supposed to know considerable about the life of the plains; "unless they've just got desperate for a good old hunt, and broke loose. Pretty soon the pony soldiers will come galloping along, round 'em up, and chase the lot back to their quarters. Uncle Sam is kind, and winks at a heap; but he won't stand for the Injuns skipping out just when the notion takes 'em."

They sat there in their saddles a while longer, watching the long procession pass out beyond the low hill, and track along the plain through the scented purple sage.

"Navajos, ain't they?" asked Bob, who, of course, depended on his comrade for all such information, since one Indian was as much like another as two peas to him.

"Sure thing," replied the other, carelessly. "Tell 'em as far as I can glimpse the beggars. And I just reckon now that's old Wolf Killer himself, ridin' at the head of the line, with his gay blanket wrapped around him. Wonder what he'd say if he knew Frank Haywood was here, so far away from the home ranch?" and Frank chuckled as though amused.

"Do you know the old chief, then?" asked Bob.

"Say, do I?" replied Frank, with a laugh. "Remember me telling you how the boys on our place caught a Navajo trying to run away with one of our saddle herds about three years ago, when I was hardly more'n a kid? Well, I chased him with the rest of the outfit, and saw old Hank throw his rope over his shoulders. He snaked the fellow over the ground and through the short buffalo grass like a coyote, 'till he was punished enough; and then my dad made 'em let him go. But you just ought to have seen the way he folded his arms, stared at each of us, and, never saying a single word, walked away. I've often wondered if he didn't mean to come back some day, and try to get his revenge."

"And that was the chief himself?" asked Bob.

"Just who it was," Frank went on. "He'd left the reservation, and got too much fire-water aboard, they said; so he thought the good old days had come back, when a Navajo always tried to get away with any horses he ran across. They say Wolf Killer used to rustle cattle long ago, till Uncle Sam put his hand down heavy on his tribe, and shut the lot up."

"Then, if he has reason to remember everybody connected with Circle Ranch in that way, I reckon it's just as well we don't try to let him know we're here," remarked Bob, uneasily. "We didn't come out on this little picnic for trouble with the reds. There they go, pushing through the sage brush, Frank. So-long, Navajo, and good luck to you on your hunt," waving a hand after the departing string of distant figures.

"Our way lies yonder, along the foot of the mountains," said Frank, as he turned his head to look toward the grim range that stood out boldly against the skyline.

"Yes," observed his companion, as he allowed his black horse his head, once more advancing in a Southerly direction, "and, unless all signs fail, that's Thunder Mountain towering above the rest of the peaks."

"You're right, Bob, that's what it is; and we're going to camp at its foot unless something goes wrong," and as he spoke Frank urged Buckskin on again.

The yellow bronco was a true range pony. He had been taught many of the clever tricks for which his kind are noted. A stranger would have had a hard time keeping his seat on the back of the animal, such was his dislike for unknown parties. He could dance almost as well as a circus horse; and when Frank had tended the saddle herd at night, as horse-wrangler, he was accustomed to depend on Buckskin to give ample warning of trouble, whether in the shape of a storm, a threatened stampede, or the presence of cattle-rustlers.

Both boys were, of course, dressed pretty much as cowboys are when on the ranch; leather "chaps" covering their corduroy trousers; with boots that mounted spurs; flannel shirts; red handkerchiefs knotted around their necks; and with their heads topped by felt hats, such as the men of the range delight in.

Slung to their saddles were a couple of up-to-date guns of the repeating type, which both lads knew how to use at least fairly well. Of course both carried lariats slung from the pommels of their high Mexican saddles. Frank was accustomed to throwing a rope; while Bob, naturally, had much to learn in this particular.

"Say," remarked the latter, who had fallen a trifle behind his comrade, "to see the way we're just loaded down with stuff makes me think of moving day in the old Kentucky mountains. But no use talking, if a fellow wants to be half way comfortable, he's just got to lug all sorts of traps along."

"That's right, Bob," assented the other, laughing. "And that applies in an extra way when he means to be out in the Rockies for perhaps a week."

"No telling what he may run up against there, eh?" queried Bob.

"Well, if it isn't a grizzly, it may be an avalanche, or a cloud-burst," remarked the boy who had spent his whole life in the open.

"Not to speak of Indians, or Mexican rustlers looking for a chance to drop down on some peaceful ranch, and carry off a bunch of long horns; eh, Frank?"

"Sure; and a lot more besides, Bob," was the reply. "But the sun's getting kind of low, you notice."

"In other words, we'd better be looking around for a place to camp, Frank?"

"You've hit the nail on the head," the other replied. "Suppose we hold up here for a bit, and let me take another squint up yonder through the glass."

"Meaning at old Thunder Mountain?" observed Bob, as his eye traveled upward toward the bare crown of the great uplift, that had so long remained a source of mystery to the entire community.

"Yes. Just look at the pinons growing up the sides like tufts, along with the funny looking clumps of stunted cedars. Then you can see the aspens and silver spruce next. And over the whole outfit is a silence that beats the desert itself. Whew! the closer you examine the place the more it impresses you."

Bob accepted the glasses after Frank had used them and focused them on the slope.

"So that's old Thunder Mountain, is it?" he remarked. "Well, I must say it shows up right well. I've tried to picture the place from all we've heard."

"But you don't feel disappointed, do you?" asked Frank.

"Not a bit, Frank," his companion continued. "I've seen some mountains, even before I came out here to your Rockies; but there's something about this thing that just staggers a fellow. Wow! but we'll sure have our troubles climbing that wild slope."

"Never could make it if it wasn't for the canyons," Frank added. "They all tell me that. Here, let me put the field-glasses away. Half an hour's gallop, and we'll jump off. That ought to bring us to the foot of the slope. Here you go, Buckskin; show us you're not tired after your day's run. Whoop-la!"

Frank brought his hat down on the flank of the horse, accompanying the action with a real cowboy yell. Instantly the spirited steed bounded off, with Bob's Domino close behind, snorting, and giving signs of astonishing animation.

So they sped along, with clanking sounds from the various packages fastened behind the saddles; but after a few minutes both boys gradually drew upon the lines, knowing full well that their mounts had done a fair day's work already; and, besides, there was no possible need of haste.

"How's this for a camping place?" asked Frank, as he suddenly brought Buckskin upon his haunches in a quick stop.

"Suits me first rate," replied his chum, after giving a glance around. "Let's see if I remember all you told me about what a fellow has to look for when he expects to go into camp. Water handy, grass for the horses, wood for a fire, and shelter from a hidden mountain storm. What better could we ask, I'd like to know? Is it a go, Frank?"

For answer the shorter lad jumped from his seat. His first act was to remove the saddle, and then, with a handful of dead grass, rub the sweaty back of the mettlesome animal, as every true son of the plains always does before he thinks of his own comfort.

Next he hobbled the animal, and drove the stake pin, to which the lariat was attached, deeply into the ground. After that the bridle came off; and Buckskin's first natural act was to drop to the ground, and roll over several times.

Bob was following this procedure with Domino. The intelligent animals seemed to understand just what the programme was to be; for after rolling, they walked down to the little watercourse to slake their thirst; and then set about eagerly nibbling the sweet grass that grew all around.

The two chums went about preparing to spend a night under the bright stars, with a readiness that told of long practice. Bob, of course, knew less than his companion about such things, but Frank had often accompanied the cowboys on his father's ranch on their expeditions, and had even spent nights in the company of old Hank, when off on a hunt for fresh meat; so that he knew pretty well what ought to be done to add to their comfort.

It pleased him to show Bob some of the things he had learned. There might be no real reason why he should start a cooking fire in a hole he dug, rather than make a roaring blaze that could be seen a mile away; but Bob was tremendously interested, and would never forget all that he learned.

"Besides," Frank explained, after he had the small fire started, "it is easier for cooking, once you get a bed of red ashes; because in this warm country a fellow doesn't much like to get all heated up, standing over a big blaze."

Bob had, meanwhile, opened some of the bundles. One of these contained a small coffee pot, as well as the frying pan without which camping would be a failure in the minds of most Western boys.

"Look out for rattlers," advised Frank, as his chum went to the spring hole to fill the coffee pot. "They often come to such places in dry season We haven't had rain for so long now, that, when it does come, I expect a regular cloud-burst. That's often the way in this queer country, along the foothills of the Rockies."

Hardly had he spoken than there sounded a sudden and angry whirr, similar to the noise made by a locust, and which Frank knew only too well meant a rattlesnake!

CHAPTER V - THE VOICE OF THE MOUNTAIN
"Hey! take care there, Bob!" shouted Frank, starting up from beside his little cooking fire in something of a panic; for that alarm signal is apt to send the blood bounding through the veins like mad, whenever heard.

"Don't bother!" came the reassuring reply of the unseen Bob, from a point near by; "I think I've got the beggar located, all right. Say, don't he sing though, to beat all creation? He's mad clean through, all right. I'm looking for a stick, so as to knock him on the head."

"Go slow, and keep your eye out for a second one," advised Frank, uneasily; "because they generally hunt in couples. That isn't a measly little prairie rattler either; but a fellow that's come down from Thunder Mountain."

"Nice warm reception for visitors, I should remark," laughed Bob, immediately adding: "there, I've found just the stick I want. Now, old chap, look out for yourself! I'm going to have that rattle of yours to take home, unless you give me the slip."

"No danger of that," remarked Frank; "because a rattler seldom runs away, once he shakes his old box, and gives warning. Hit him just back of the head, and let it be a good smart blow too, so that you break his neck."

Then came a swishing sound, twice repeated. The thrilling rattle immediately subsided.

"Get him?" demanded Frank, ready to take up his task once more, upon receiving a favorable reply from his friend.

"He's squirming some, but helpless," returned Bob, composedly. "I'll cut his head off, so that he can't turn around and jab me while I'm getting that rattle box of his."

Two minutes later he came back into camp, carrying the coffee pot, which he proceeded to place upon the fire Frank had started. The latter noticed that his chum was trembling a little, and could give a shrewd guess that Bob had been more startled than he had thus far admitted.

"Perhaps I'll get used to it in time," Bob remarked, presently; "but it sure does give a fellow a nasty shock to hear that sound burst out close by your feet, knowing as you do what a bite from those fangs means."

"Then it was a narrow squeak, was it?" asked Frank.

"I guess I never want to be closer to a diamond-back than that," Bob admitted, with a shake of his head.

Soon a delightful aroma began to steal through the air in the immediate vicinity of the little camp near the foot of the towering, mysterious mountain; as some bacon sizzled in the pan, and the crushed berry from Java boiled and bubbled most cheerily.

Besides, upon some splinters of wood Frank had thrust small pieces of venison, the last fresh meat they had brought from the ranch. As the heat from the red coals began to turn these to a crisp brown, Bob sniffed the added fragrance in the air after the manner of a hungry range-rider, or a boy with a healthy appetite.

"Seems to be plenty of game around here," he remarked. "I jumped two rabbits near the spring, and they went up the rise, as usual."

"Yes," remarked the cook, "the place looks good for game, and you'd wonder why those Injuns passed it by, only I happen to know. Ten to one there's a deer in that thicket of wild plum over there. And you can just believe an old grizzly wouldn't want a better hang-out than up yonder among the cliffs and crags of the mountain side."

"But to return to our mutton, which after all is antelope meat, when do we start operations? I'm nearly wild, with all these smells, and never a bite. The water just drips from my tongue, I give you my word, Frank."

For answer the other picked up the coffee pot, and set it aside for a minute, to let the contents settle.

"Grub's ready, Bob," he said, laughingly; "and I reckon we'll not bother banging on the frying pan with a big spoon to-night, range fashion. Sit down, and get your pannikin ready for some of this bacon and meat. How does that coffee look?"

"Say, it's got the color, all right, and if it only tastes half as fine as it looks you'll hear no kick coming from me," replied Bob, as he poured his tin cup full of the liquid.

As the boys ate they chatted on various topics, most of which talk had of course some connection with the big cattle ranch they had so recently left.

"I'd give a heap to know if Peg Grant meant business when he said we were riding to a fall if we thought we were the only pebbles on the beach," Bob remarked.

"Oh!" replied Frank, "I reckon he's going to make a try to solve that Thunder Mountain puzzle. But just think of a tenderfoot like Peg let loose on that fierce slope up yonder; will you?"

"Perhaps he's here already," suggested Bob.

"Wouldn't be one bit surprised," Frank continued, readily enough, as though he considered that a foregone conclusion anyway. "He and his cronies had time enough, unless Peg changed his mind. He might be wondering what happened to you, and thinking how the X-bar-X ranch would be safer, in case some of our boys chased after him to give him the tar and feathers he deserves for playing such a mean trick."

"But supposing they did come," said Bob; "Peg and Spanish Joe, and that other treacherous cowboy you told me about; we're pretty apt to meet up with them if we go prowling around here for the next few days."

"Just so, and we'll try to mind our business all the time," remarked Frank; and then his eyes flashed a little as he continued: "but if they try any of their ugly little tricks on us, Bob, they're likely to get hurt."

"I'm with you there, Frank," the other added, shutting his teeth in a determined way. "I can stand a certain amount of fun, and, I hope, take it the right way. Your cow punchers said that when they hazed me, you know. But I certainly do object to any such rough-house business as fastening a poisoned thorn under a fellow's saddle."

"That game has cost more than a few people their lives," Frank declared vehemently. "Cowmen draw the line at it. You noticed how angry old Hank became when he heard about that same thing. But your horse seems to be getting on all right, Bob."

"Sure he does. That ointment made by old Hank's like magic. Domino won't suffer much from that jab. But that was a bully good supper all right, and I don't care how soon we repeat it," he concluded with a laugh.

Finally both lads lay down to secure such rest as they needed after a long and tiresome day.

The drowsy chirp of crickets, and shrill voices of katydids in the lush grass near by, told of the summer night. Many times had Frank listened to this same chorus as he lay in his blanket on the open prairie, playing the part of night-wrangler to the herd of saddle horses belonging to the round-up party of cow-punchers.

He could hear some lurking rabbit slinking through the hazel bushes over at one side. Somewhere off on the level, where the sage grew so heavily, there must have been a prairie dog village; for the sound of the peculiar barking of these queer little animals frequently floated to his ears as the breeze changed.

The two horses were still feeding at the time Frank dropped off into a sound and refreshing sleep, but doubtless they would soon lie down. Bob was already breathing heavily, which would indicate that he had passed beyond the open door to slumber-land.

The minutes passed, and several hours must have gone.

Frank was dreaming of the excitement attending some of the many dashing gallops he had lately enjoyed in company with his chum, looking up stray cattle, helping to brand mavericks, watching the cowmen mill stampeding herds, or chasing fleet-footed antelopes just to give the horses a run.

He was suddenly aroused by a strange sound that seemed to cause the very earth under him to tremble. The trample of a thousand hoofs would make such a noise; if one of those old-time mighty herds of bison could have come back to earth again; or a stampede of an immense herd of long-horns might cause a similar vibration.

But Frank Haywood knew that neither of these explanations could be the true one, even as he thus sat upright on his blanket to listen. The ominous, growling, grumbling noise was more in the nature of approaching thunder, just as though one of those furious summer storms, tropical in their nature, and often encountered in this country where plains and mountains sharply meet, had crept upon them as they calmly slept.

And yet, strange to say, neither of the two boys jumped quickly to their feet in wild dismay, seeking to prepare for the rain that might soon burst upon them. On the contrary they continued to sit there, straining their ears to catch the rumbling reverberations that kept coming, with little respites between.

"Say, now, what d'ye think of that, Bob?" asked Frank, when silence again held sway for a brief period. "Nary a cloud as big as your hand in the sky; and yet all that grumbling oozing out of old Thunder Mountain! Looks like we might have the biggest job of our lives finding out the secret of that pile of rocks. There she starts in again, harder than ever. Listen, Bob, for all you're worth!"

CHAPTER VI - A SECOND ALARM
"It's stopped again!" remarked Bob, after possibly five minutes had passed, during which time the ominous rumbling, accompanied by earth tremors, had kept up, now rising to a furious stage, and then almost dying away.

Frank gave a big sigh.

"It sure has," he admitted; "and I don't wonder now, after I've heard the racket with my own ears, that the reds for a hundred years back have always declared the Great Manitou lived in Thunder Mountain, and every little while let them hear his awful voice."

"Then this thing has been going on forever, has it?" asked Bob.

"The Navajos say so; though even they admit that, of late, it's got a brand new kink to the growl," Frank answered. "They believe it's sure unlucky for any brave to be caught near the mountain after dark, and especially when Manitou scolds. You see, that accounts for the hurry of that hunting party to climb out before sunset."

"Yes," Bob went on. "And now I understand what you said about the Indians never hunting near Thunder Mountain. Perhaps they believe all the game that hides along the slopes, and in the deep gullies, belongs to the Great Spirit, and that he'll punish any warrior bold enough to try and get a line on it. But see here, Frank, do white men—cowboys, prospectors, and the like—believe this mountain is haunted?"

"Heaps of 'em do, and that's a fact," replied the other, chuckling. "I've heard some of our cowpunchers talking about it more'n a few times; and you remember how old Hank took it when we told him what we had in mind?"

"They're a superstitious lot, as a whole, I take it," Bob ventured. "Now, as for me, I never could believe in ghosts and all that sort of thing. If there ever came a time when something faced me that I couldn't understand, I just set my teeth together and vowed I'd never rest easy till I had found out what it meant."

"Same here, Bob; and that's why I just jumped at the chance to beat Peg out in his game. The funny part about it is why I never thought of this racket before. But perhaps that was because I didn't have a chum to stand back of me."

"None of the boys on the ranch would go with you, then?" asked Bob.

"I should say not! Even old Hank would balk at that, and he's never been afraid of thing that flies, runs or crawls. It was old Hank who taught me all I know about range life. He showed me how to shoot, throw a rope, and do heaps of other things a prairie boy ought to know. Hank thinks lots of me, and honest now, Bob, that gruff old fellow would willingly lay down his life for me."

"I reckon he would," assented the other, readily enough.

"But Hank's a rank believer In the Injun story of the mountain, and would never come here of his own accord; but to keep an eye on me, and, stand between me and danger, he'd just crawl down the crater of a live volcano."

"Seems like the show might be over for tonight," Bob suggested.

"The row has stopped, sure enough," Frank remarked, looking up at the dimly-seen outlines of the far-away crest of the rocky elevation, where it stood out against the starry heavens.

"You don't believe, then, that there could have been some kind of storm up there; do you?" questioned Bob.

"Well, it's sure a great puzzle," replied his chum, with a long breath. "My eyes are reckoned prime, but I can't glimpse any sign of a cloud that would bring out all that noise. A mystery it's been these many years; and if so be we can learn the cause for all that queer roaring that shakes the earth, we'll be doing more'n anyone else has ever done in the past."

"That's what we're here for, if Peg gives us half a chance," remarked Bob, with the healthy assurance of youth. "And as neither of us takes any stock in the fairy story about the Manitou's anger, we ought to stand some chance of locating the thing; or 'bust the b'iler trying' as old Hank would say."

Frank had crawled out of his blanket, and stood erect.

"What's on?" asked his camp-mate, presently, noticing that he was holding up his hand, after wetting his finger, a method much in vogue when one wished to learn the direction of the passing air currents.

"Southeast; and blowing strong a bit ago up there on the mountain, I reckon," Frank remarked. "You notice we happen to be sheltered more or less down here, when she comes out of that same quarter?"

"Meaning the wind," Bob remarked. "Yes, you're right, Frank. But what has that got to do with the measly old grumble of the mountain, tell me?"

"Huh! I don't know that it's going to have anything to do with it," came the answer; "but we want to know every little point as we go on. And Bob, just remember that the wind was coming out of the Southeast; and a clear sky overhead!"

"But look here, Frank, you've heard your dad talk about this Thunder Mountain business, I take it?"

"Well, now, I reckon I have, heaps of times; but then you know, he isn't much on bothering about things that don't concern him. Thinks he's got his hands full, looking after the stock, keeping tabs on the doings of those rascally Mexican rustlers, that have been running off batches of cattle every little while; and fighting that big syndicate of Eastern capitalists, headed by the millionaire, Mr. Grant, Peg's father, that wants to throw all the Southwestern ranches into a close trust."

"But what I wanted to remark is this: you must have heard him give an opinion about this thunder sound?" Bob persisted in saying.

"Oh! he thinks the same as several gentlemen did who came out here a few years ago on some business. They declared that once, hundreds of years ago, perhaps, old Thunder Mountain must have been a volcano; and that it still grumbles now and then, as the fires away down in the earth begin to kick up some of their old monkeyshines."

"Yes, I heard one man say that," laughed Bob. "He declared that there's going to be the biggest rumpus some fine day, when the fires inside get to going out of bounds. Then the whole cap of the mountain will go flying into a million pieces; and good-bye to any unlucky cow-puncher caught napping near this place."

"Well," remarked Frank, as he prepared to settle down again into his snug blanket, "I reckon we're not going to be scared away by a little thing like that growl. Unless we hit a snag, or Peg Grant and his guides break up our game, a few days ought to see us heading back to Circle Ranch with a story calculated to make the boys sit up and take notice; or else——"

"Just pull up right there, Frank," interrupted his chum, with a laugh. "There's nothing going to happen to knock us out. If that same Peg comes around, making a nuisance of himself, why, he's due for a nice little surprise, mark me. Besides that; what could there be to make trouble?"

"Oh, I'm not bothering my head over it, Bob," declared the other, as he dropped into the nest he had made in his blanket. "But say, did you take notice of the way our horses acted while that thing was going on?"

"Just what I did," the other replied. "They must have been trembling all over. I could hear your Buckskin snorting to beat the band, and pawing just like he does when he's worried. Reckon they didn't know what to make of it, either, seeing that there's nary a sign of a storm cloud around. But both horses have quieted down again. They think all danger of a howler has passed away."

Frank made no reply. He was already getting ready to resume his interrupted nap; and Bob lost no time in following his example, both confident that in the alert Buckskin they had a sentry capable of giving ample warning should peril threaten.

Once more Frank composed himself for sleep. The many noises of the night, which had seemed to cease while that mysterious rumbling was going on in the heart of the lofty mountain, had again resumed sway. The hum of insects; the melancholy hooting of the lonely owl, in some willow or cottonwood tree near the base of the mountain; the far-off howl of the prairie wolf; or the more discordant voice of the skulking coyote—all these things were as familiar music in the ears of the boy whose cradle had been the rich black earth of the grazing country ever since he was old enough to remember anything.

They all did their share in lulling him to sleep. And, no doubt in dreams, he was once more galloping across the wide prairie on the back of his mount, his nostrils filled with the life-giving Sir of the sage-covered level.

Frank slept, he never knew just how long.

This time it was not the rumbling sound and the fearful vibration of the ground that aroused the two saddle boys; but a far different cause.

When Bob sat up he found his comrade already erect, and apparently listening as though keenly alive to some approaching peril.

"Buckskin's uneasy, you see," remarked Frank in a whisper; "he's pawing the ground and snorting as he always does when he scents danger."

As he said this, Frank dropped back again, and seemed to place his ear to the ground, a trick known and practiced among the Indians from the days of the early pioneers along the Ohio down to the present time; since sound travels much better along the earth than through the air—at least, in so far as the human ear, unaided by wireless telegraph apparatus, is concerned.

"A bunch of horses coming out of the Northwest!" announced the prairie boy, almost immediately; "and we can't get our nags muzzled any too soon, Bob."

Apparently the other lad had been coached as to what this meant. He sprang to his feet, snatching up his blanket as he did so. Together they were off on the jump toward the spot where their animals had been staked out at the end of the lariats.

Arriving at the pins which had been driven into the ground each boy sought to clutch the rope that held his restlessly moving horse; and hand over hand, they moved up on the animals, the blankets thrown over their shoulders meanwhile.

A few low-spoken words served to partly soothe Buckskin and his black mate; then the blankets were arranged about their heads, and secured in such fashion that no unlucky snort or whinny might betray their presence to those who passed by.

CHAPTER VII - THE RUSTLERS
At a word from his master the well trained Buckskin doubled up, and lay down on the ground. Most cowboy ponies are taught to do this trick by their masters, and it is in common use; so that the punchers believe it is a poor animal that has not learned to roll over and play dead on occasion.

Bob, too, managed to induce his mount to do the same thing; but to make it absolutely certain that no unwise flounder on the part of Domino might betray them, he sat upon the horse's head, soothing him by little pats on his glossy hide.

"I hear 'em coming," announced Frank, presently.

The sounds reached him against the wind, so that it was quite natural to believe the approaching horses must by now be very close. There was a confused pounding that could only spring from a large body of animals. The trained ear of Frank caught a significance in the clash of hoofs that told him much more than Bob was able to make out.

"All horses, Bob," he whispered across the little gap that separated him from his chum; "and two thirds of 'em running free, without saddles or riders. Lie low, now, and see if you can glimpse 'em as they go past."

"Won't they be apt to run over us?" asked Bob, a bit nervously.

"Nixy. I looked out to pick a place they'd be apt to avoid. They'll brush past a little further to the south," and Frank ended his words with a hiss of warning.

The pounding of many hoofs continued. Frank, straining his eyes, believed he was now able to make out a confused moving mass at some little distance away, heading directly toward the foot of Thunder Mountain.

As the starlight was so vague he could not make out more than that here and there a figure was mounted on a galloping horse, with several unridden animals trailing along behind, as though led by ropes.

The little caravan passed quickly. Already they were vanishing in the deeper shadows lying closer to the base of the mountain that towered aloft several thousand feet.

Still the two boys continued to sit there, guarding their horses; although all danger of discovery seemed absolutely past.

"Whew!" exclaimed Bob, presently, as the sound of retreating hoofs began to die away; "what d'ye think of that, eh, Frank?"

"Indians?" queried the Kentucky boy, eagerly.

"Well," replied his chum, "not so's you could notice. Say, now, you didn't see any feathers on their heads, did you? And I sure heard the fellow nearest us say something that only a white man would remark, when his horse stepped into a hole, and almost threw him over its head."

"Cow punchers; or perhaps rustlers?" continued Bob, anxious to know.

"What would cowmen be doing away off here, tell me that, Bob? And lugging along a bunch of extra mounts, too, in the bargain? No, I rather think, Bob, that those fellows must have some of Mendoza's cattle rustlers. And they've been making a dandy raid on some ranch's saddle herd; or I miss my guess."

"Perhaps the Circle outfit had gotten careless," suggested Bob.

"I sure hope not, for the boys have had plenty of warning; and I reckon Bart Heminway is some too good an overseer to permit such a raid. I'd rather believe it was the X-bar-X outfit that has gone and got nipped this time. But stop and think Bob; what d'ye expect takes these cattle-rustlers over this way right now, headed straight for the canyons of Thunder Mountain?"

"Oh, I see what you mean!" exclaimed the taller lad, immediately. "Perhaps the secret hiding place of Mendoza and his crowd of cattle thieves may be somewhere around this same old rock pile. It'd be just like the tricky rustler to have a hide-out where nobody else ever came!"

"Now, why didn't somebody ever think of that before?" ejaculated Frank, in a tone of mingled surprise and disgust.

"Looks easy, doesn't it, after we've run across a clue?" admitted Bob, laughing softly. "You remember what they said about discovering America, after Columbus did it. But supposing this thing does turn out to be true; how's it going to affect our little business, Frank? Oh! say, I wonder if that crowd can have anything to do with the rumbling of the mountain?"

Frank laughed heartily at the suggestion.

"Well," he remarked, "they're a pretty tough lot, all right; but even such a bad bunch could hardly get enough hot air together to make a mountain shake and groan like that. Besides, don't you see, Bob, they must have been out yonder, riding this way with their stolen horses, when that little circus came off."

"But one thing is sure," the other went on, sturdily; "they don't seem to take any stock in that notion about a volcano, because, as we saw, they headed straight for Thunder Mountain. That gives it away; they're so used to the row that they don't pay any attention to it any longer."

"Correct!" echoed Frank, as though his mind was made up.

"Do we need to hold the horses down any longer?" asked Bob, who could feel that Domino was becoming very restless under his enforced silence.

"I reckon not," replied the other, at the same time taking the blanket from Buckskin's head; whereupon the animal, recognizing this as a sign to rise, quickly gained his feet and shook himself.

"It's back to the blankets again for another nap," remarked Bob, when he, too, had seen his animal regain an upright position. "Wonder what's next on the programme for us. Twice, now, we've been waked up; and I don't know whether it's really worth while trying to get any more sleep to-night. It isn't a great ways from dawn, is it, Frank?"

The other cast a quick look up at the stars. Accustomed to reading these heavenly sign posts of the night, he was able, from their positions, to give a pretty fair guess as to the hour; just as the sun served him in place of a watch during the day.

"Three hours yet to dawn, Bob; no use staying up all that time," he said, presently. "We expect to be on the move again at peep of day; because, after what's happened, it'll be wise for us to get off the level here before broad daylight comes along. There might be curious eyes on the watch up yonder, on Thunder Mountain; and that, you see, would just spell trouble for our crowd."

"Whew! things are thickening, for a fact!" exclaimed Bob.

"I was only thinking," Frank continued, "whether we ought to try and get word back to the ranch about our discovery. If they knew Mendoza and his rustlers were hiding somewhere about this place they'd comb the whole mountain range so they could run him to earth. He's been the pest of the border too long now, and something's just got to be done to chase him back where he belongs, south of the Rio Grande."

"But you don't want to go back just yet, do you, Frank?" asked Bob, uneasily.

"I'm ready to do what you say, though I'd like to stay," came the prompt answer.

"Then I say, let's stick it out," declared Bob, with animation. "It might turn out to be a false alarm, after all; and we'd feel pretty cheap to bring all the boys along, and then not be able to show 'em any game. No, I say it'll be time enough to go after 'em, when we make dead sure!"

"That settles it, then," remarked Frank, with a little laugh, as though pleased to learn that his saddle chum looked at the matter in such a sensible light.

This time, after they had lain down in their blankets, there was no further alarm. Frank, from long habits of early rising on the range, awakened just as the first faint streaks of dawn began to show in the eastern horizon.

It required but a touch to arouse Bob; and saddling up, with packs in place, the boys soon left the scene of their night bivouac, heading toward the heavy growth of timber directly at the foot of the mountain.

The early morning mists concealed their movements until they had entered among the timber; when they left they were safe from any suspicious eye, should the bold Mexican rustler have posted any watcher upon the side of the mountain.

Again did the saddle boys build a small fire in a hole, over which they proceeded to cook their breakfast; while the horses cropped the grass near by, secured by the ever useful lariats, or riatas.

"There's where this leads into a big gully," remarked Bob, later on, pointing as he spoke to where the ground became broken.

"Yes," Frank went on, thoughtfully, "and the chances are ten to one that it changes into a regular canyon, where the water rushes down whenever they have one of those gushers, or cloud bursts, that come along once in a while around here. Now, I wonder if those riders hit it up this way?"

He jumped to his feet as he said this. Passing back and forth, Frank seemed to be examining the ground, marking the stepping stones of the mountain.

"Signs aplenty around here," he remarked. "Wish old Hank was along to read 'em. I reckon I can tell what they stand for, though."

"Then they went on up that canyon, you believe?" asked Bob.

"Reckon there isn't any doubt about that part of it," chuckled Frank; "though just where that same canyon leads I can't say. P'raps it may be a short-cut across the big range here, leading to the prairie on the other side. P'raps it doesn't go anywhere, but just leads to a blind hole that I've heard prospectors call a cul de sac. Anyhow, we ought to find out, Bob."

"They knew all right," remarked the other, positively. "Wouldn't get any riders going up there in the dark, unless they were mighty familiar with every foot of the way. That's my idea, Frank."

"And I reckon it's the true one," asserted the other. "They know this place as well as I do all around old Circle Ranch."

"There's the sun coming up; and perhaps we'd better be getting a move on about now?" suggested Bob.

"Wait!"

Something in the tone which his saddle chum used caused Bob to turn his head, and look out toward the plain.

"Huh! what does that mean?" he ejaculated. "A single rider heading this way; and he seems to be leading a burro loaded with supplies. Must be a bold prospector, bound to look into the secrets of Thunder Mountain as we're bent on doing; only he hunts for gold, while we're just bent on finding things out."

"But look now," Frank said a little later, as the other came closer. "Don't you see that it's only a little Mexican boy on that bag of bones of a horse? Tell you what, Bob, he must have been sent to town for fresh supplies by some party of gold hunters located right now over the range."

"Yes, and how do we know but what this Mexican boy is hooked up with that Mendoza crowd?" asked the other, seriously. "They might send him off for grub, and such things as they happen to need. And he pays for it with money they get from selling stolen cattle and horses! Nobody would suspect him, Frank, and try to follow. I hope our horses don't give us away now. I'd like to see what that little fellow does."

The boy indeed looked weary as he drew closer, leading his tired burro, upon which a fair-sized load was strapped and roped.

"Get down, Bob," said Frank. "He hasn't glimpsed us, and, luckily enough, our horses are feeding out of sight just now. Doesn't he look sleepy and tuckered out though? See him nodding in his saddle, poor little runt! Oh! what's that moving there among those rocks just ahead?"

"Perhaps it may be one of the rustlers coming down to interview him," said Bob.

"Hist!" Frank uttered almost in his chum's ear as he craned his own neck in order to see better.

The small boy on the tired broncho, and leading the patient burro, kept on steadily advancing, apparently allowing his animal to follow its nose, as though it knew the way fairly well from having passed along it before.

"Look! look!" ejaculated Frank suddenly, jumping to his feet. "Great guns! Bob, would you see what is coming out from among those loose rocks there? A great big grizzly bear; and making straight for the pack mule, sniffing the air as if he smelled grub! There, the horse has scented him. See him rear up, will you? Oh! he's gone and done it, as sure as you live—thrown the boy over his head! And the poor burro is caught fast, with his leading rope held in a crotch of the rocks. The boy will be killed if ever he meets up with that monster! Quick! We must do something to save him, Bob, but whatever shall it be?" and Frank leaped to his feet.

CHAPTER VIII - A STARTLING DISCOVERY
The Mexican boy had apparently escaped serious injury at the time the frightened cayuse made a sudden bolt upon sighting the bear, and threw him over his head onto the rocks.

The lad was already sitting up, and rubbing his knee in a dazed way, as if not fully understanding what had happened. The pony rushed wildly away, heading up the wide gully, as though with a full knowledge of where it was going. And the poor little burro would doubtless have been only too glad of a chance to follow, if only it could break loose from the detaining rope.

Meantime the ugly monster, that had been the cause of all this commotion, was shuffling closer with each passing second, eager to strike down the burro with one savage blow from his mighty paw with its long claws, after which he could proceed to help himself to what those various packages contained.

All this Frank Haywood saw in that one glance he shot toward the scene of action. The boy was apparently directly in the path of the hungry bear. And when his pony had fled in such a panic he must have also carried off the rifle, if the boy possessed so valuable a weapon.

Thus the little fellow was at the mercy of the most feared wild beast to be found in all the territory between the Atlantic and the Pacific.

A wild inclination to hurl himself between that brute and his prospective victim surged over Frank. With but a knife, or even a revolver to back him up, such a rash act would have been little short of madness. Fortunately it was not needed.

"Let me try for him, Frank!" said a trembling voice at his side.

And then, all at once, Frank Haywood discovered his chum was crouching close by, and that he was clutching a rifle in his shaking hands. How he had managed to get hold of the weapon Frank could not even guess, because his own was a dozen feet away just then.

Now Bob Archer had certainly never before set eyes on a ferocious bear outside of the circus or museum. And doubtless that brownish-colored beast looked as big as a house to him, for he was very much excited. But he had true Kentucky pluck, and even that circumstance did not make him quail. If the monster had seemed to equal two houses, still would Bob have tried to do his duty. And just then it was to save that poor little Mexican boy.

The grizzly had advanced so rapidly that he was already almost upon the crouching boy, who stared at him as if in dire dismay, as well he might. It was not too late, even then, for the boy to have escaped, could he have understood the real situation, and that it was the food in the packs the bear craved, rather than his life; but he did not seem to realize the fact.

They had seen him fumbling about his sash, and now he drew something forth that glistened in the early morning sun. Why, the little chap had actually drawn his knife, as though that trifling bit of steel could avail anything more than the prick of a pin against that shaggy monster.

The boy was shivering as with terror, but all the same he showed himself game. Frank was amazed by the sight, and not apt to forget it in a hurry.

But by now Bob had stepped forward, uttering a sharp "hello" as he did so. His object, of course, was to attract the attention of the bear toward himself. This might cause the grizzly to change his course, and allow of a few more seconds' delay. It would also divert the attack from the helpless boy to one who was at least better armed, even though not professing to be a bear-hunter.

Frank aroused himself. He remembered that he, too, had a repeating rifle, leaning against the trunk of a tree not far off. He sprang to secure the firearm, in the belief that possibly his assistance would be needed in order to finish the dreaded animal.

However good Bob's intentions were, when he sought to draw the attention of the grizzly toward himself, they did not succeed as he had hoped. Bruin seemed to know that a feast awaited him as soon as he could clear a way to that frantic little burro with the big load. And he declined to be turned aside on any account.

Seeing this, the Kentucky boy dropped on one knee. He felt that he must find some sort of rest for his gun, since his shaking hands could hardly be expected to hold the weapon steady when it came time to pull the trigger.

Even as Frank swept up his gun he heard the weapon of his chum speak sharply. The report was instantly drowned in a tremendous roar. Looking, even as he drew back the hammer of his rifle, Frank saw that the bear had finally turned away from temptation in the way of meat and supplies. He had started to rush Bob, whom he evidently recognized as the cause of that sudden pain which had shot through his bulky body.

Bob was pumping another cartridge into the firing chamber of his repeater. He seemed cool, although perhaps only he himself knew how his heart was pounding away like mad against his ribs.

Both guns spoke together, it seemed. The grizzly gave another roar, even more furious than before. At the same time, however, he stumbled, and fell over sideways. Then he tried desperately to scramble back to his four feet, still full of fight.

Both the boys again put their guns in a firing condition. Even if tremendously excited at the moment, they seemed to remember what was necessary to do in order to accomplish this result.

But the bear was apparently unable to get up again. One of the bullets must have most luckily reached a vital point in the region of his heart. He was floundering about unevenly, while the little Mexican boy sat and stared, still gripping that ridiculously small blade in his hand.

"We got him that time, Frank!" exclaimed Bob just then, though he could hardly believe his eyes at seeing the monster growing weaker. "He's a goner, as sure as shooting! Look at him wobble! Wow! there he goes over, to make his last kick! Frank, just think of me having a hand in the killing of such royal game! A real grizzly! Oh! I can hardly believe it!"

They now approached the spot where the little Mexican boy was getting on his feet again. He was no longer white. The threatening monster had been placed where he could do no more harm; but the little chap stared uneasily at the two saddle boys. Evidently he was possessed of a new cause for alarm in the mere fact of their unexpected presence.

The burro, meanwhile, had somehow managed to effect his release from the rope that had become fast in the crevice of the rock. Still in a panic because of the wild animal odor so close at hand, the laden animal hurried off after the cayuse that had fled along the gully, heading for where Frank had declared the canyon must undoubtedly lie.

And the boy really looked very much as though he, too, would like to depart with equally scant ceremony.

"Hi! there goes the burro!" called out Bob. "Head him off, Frank; or shall I jump on my horse and try to rope him?"

To the astonishment of both the saddle chums the Mexican boy threw out a detaining hand, crying earnestly:

"Senors, all, there is no need to chase them. They know where to go, believe me, and surely I must soon overtake them. You have saved my life, Senors. Lopez, he thanks you both. Before now have I seen such a bear; but this time I was caught dreaming. He would surely have killed me if it had not been for the brave Americanos."

Frank was struck with the soft tones of the small chap, who did not look as if he could be much more than twelve years of age. His features were regular, if thin, and the big black eyes seemed to be filled with a courage beyond the ordinary. Indeed, they could not doubt this, having seen how he had drawn that small knife on finding himself confronted by the Rocky Mountain terror.

"Well, we were only too glad to have been of help to you, Lopez," Frank remarked, as he advanced with outstretched hand.

The boy looked embarrassed, as though hardly knowing what to do. It seemed to Frank that he had been staring very hard at Bob, and he wondered why. Then again he imagined that the boy must be keeping something back. This would account for the worried look on his small, pinched, but good-looking face.

But undoubtedly Lopez realized that it ill became him to decline to take the hand that had helped save his life.

"You understand that we are your friends, Lopez, don't you?" asked Frank, as he held the small palm of the Mexican in his own strong one for a moment, and looked with a puzzled expression into the big black eyes that quickly fell under his gaze.

"Oh, yes, Senor, surely you have proved it more than enough," the little fellow hastened to say; and Frank was astonished to hear what good language he used.

"You go across mountains, eh?" asked Bob, indifferently; truth to tell he was just then more interested in the size of the great grizzly that had fallen before the guns of himself and his saddle chum, than the mere fact of this stripling being entrusted with such a task as bringing supplies to prospectors, or rustlers, as the case might prove.

A flash crossed the face of the boy, just as though he saw a sudden opening whereby his presence here might be explained without entering into details.

"Oh! yes, across the range. I get supplies for prospectors in camp," he replied, with an intake of his breath, while he watched Bob narrowly, as if, somehow, he believed he had more to fear from that source than from the tawny-haired prairie lad.

"That's kind of queer, seems to me," remarked Bob, slowly, turning to again survey the boy; "for them to send so small a chap on so long a trail. I should think it was more of a man's work, toting supplies across these mountains, through the canyons. And with the chances of running foul of such dangers as bears, not to speak of rustlers."

At that Lopez drew his diminutive figure up, and tried to assume a bold look. The Spanish blood was proud, Bob could see.

"This have I done a long while, Senors, believe me," he said, calmly; "and until to-day never have I met with trouble. Had I not been so tired and sleepy, perhaps even I might have shot the bear, who knows? It would not be the first I have seen, no, nor yet the second; but the horse ran away with my gun. But Senors, I must go on after my animals; they will be waiting for me farther along."

"Then you won't wait for us?" asked Frank. "My friend, he would like to get the claws of this fellow, to remember him by. It will not take very long, Lopez."

"Thank you, Senors, but I must not delay. Perhaps you may overtake me farther along the trail. There is no more danger; and my pack burro might scrape off his load if I am not there to watch. Again I thank you, Senors."

The boy bowed to each of them in turn, just as though he might have been an actor in some old-time play. Frank believed he had never seen such remarkable grace in any half-grown lad. Generally, at that age, boys are apt to be about as clumsy as bear cubs at play. He looked after Lopez with a frown on his face.

"What's the matter, Frank?" demanded Bob, as he noticed this expression. "Are you huffed just because the independent little rascal wouldn't let us mother him? Say, look at his strut, will you? If he was heir to the throne of Alfonso he couldn't walk finer. Give me a whack between the shoulders, won't you, Frank? Perhaps I've been asleep, and dreamed all this."

"Oh, rats! Take a look at the bear, and that'll show you what's what. There, he's disappeared behind that clump of mesquite yonder," and Frank turned to look at his saddle mate with an expression of bewilderment on his face, as though he might be trying to clutch some idea that kept eluding him.

"Suppose you help me cut these awful claws off, Frank. You see I don't know the first thing about how it's done; and I think your idea about keeping 'em for trophies is just immense."

"Well, for that matter," replied Frank, "I don't know as I ever did a job like that, myself; but I've watched old Hank do it, so I reckon we'll get along."

For a few minutes they worked away in silence. Then Bob looked up to remark:

"He said it was prospectors he was taking those supplies to, didn't he; and that he'd been doing the same a long while?"

"That was about the size of it, Bob," returned his chum, thoughtfully.

"Well," Bob went on, "between you and me, Frank, I'd rather believe little Lopez was in touch with the rustlers. I mentioned that word just on purpose to see if he would turn red, or give himself away."

"And did he?" asked the other, quickly.

"Well," replied Bob, "not so you could notice; but then he seemed such a smart chap, like as not he knew how to hide his feelings. He looked frightened when we talked of wanting him to stay with us. Mark me, there's a heap of mystery bound up in that little fellow."

"He sure puzzles me, all right," remarked Frank. "Did you notice how he had a silk handkerchief bound around his head, regular Mex fashion?"

"Sure I did," laughed Bob, without glancing up, as he used his knife industriously after the fashion set by his chum. "And I also took notice that he had a fine, glossy bunch of hair under that same colored silk bandana."

"Great governor!" ejaculated Frank, suddenly.

"What's the matter—you didn't cut yourself, I hope?" demanded his comrade, uneasily, starting up.

"Shucks! no. Something just struck me, that's all," replied Frank, with an air of disgust, and a quick look up the gully where the little Mexican had last been seen.

"Oh! Is that so?" mocked Bob. "Must have hurt right bad then, to make you peep like that. Now, I reckon it might have been something about Lopez?" for he had noted that hasty glance, and the disappointed frown.

"That's just what it was, Bob," Frank continued, in an even tone. "Fact is, I just remembered who Lopez put me in mind of. Only perhaps you'll laugh when I tell you. Remember that poor little girl Peg Grant was cuffing when you knocked him down? Well, if you took that colored handkerchief off Lopez, and let his black hair fall down, I give you my word he'd be a ringer for that Mexican child!"

Bob stared as if dazed, and then the light of a great discovery dawned upon him.

"Say, Frank!" he exclaimed presently. "Honest Indian, now, I believe you've sure struck pay dirt, and that's what!"

CHAPTER IX - WHAT HAPPENED TO PEG
"Then you think the same as I do, eh, Bob?" asked the saddle boy, as if pleased.

"Well, now a heap of things seem to point that way, Frank," replied the other, slowly. "Only for the life of me I can't get it through my poor old head just why a girl like that would want to carry on in such a queer way."

"Nor me, either," laughed his chum. "That's something else for us to lie awake nights puzzling our wits over. Everything around this Thunder Mountain just seems to be plastered with mystery—who little Lopez is; what he, or she may be doing away off here in the canyons of the Rockies; and more particularly the mystery of the mountain that the reds look on as sacred; where Mendoza and his band of rustlers have gone with those stolen horses; and also who the prospectors can be that this pile of grub was meant for—it's all a blank, that's what!"

"Say, I guess that's pretty near the way it sizes up," grumbled Bob. "I don't like to run against a stone wall like this. If I was alone now, d'ye know what I'd likely be doing, Frank?"

"Well, say, perhaps I might hit close to the bull's-eye, since I've come to know you pretty well these days, Bob," replied the other. "I wouldn't be surprised one bit but what you'd go rushing after Lopez, and demand to know all about it. But Bob, I look at it in another light. That's his own private business."

"I suppose so; and I was brought up to mind my own affairs, too," said Bob.

"Wouldn't you put up a great howl now," continued Frank, "if somebody grabbed hold of you, and insisted on your giving him the whole story of your life, where you were born, what your dad did for a living, when you cut your first tooth, how much it cost your father to let you gallop around the country in the saddle with me, and all that? Say, honest now, would you knuckle down like a meek kid; or give the questioner to understand that he was poking his nose into affairs that didn't concern him one whit?"

Thereupon Bob laughed heartily.

"I give up, Frank," he admitted. "You go at a fellow, and put him in a hole as a lawyer might. We'll just let little Lopez alone, no matter whether he's girl or boy; the grub-getter of prospectors; or agent for that sly Mendoza, the cattle-rustler. And, on the whole, I reckon we've got about all the business we can attend to right now on our hands."

"That sure sounds good to me, Bob," said Frank, turning once more to get his horse, the task of securing the grizzly's claws having been completed.

Naturally enough, while the excitement was on, both horses had exhibited the greatest alarm, even though they were out of sight behind some trees. The near presence of that terrible monster had caused them to strain at their ropes, prance wildly, and try in every way possible to break loose; but those lariats had been selected with a view to wonderful strength. After the death of the grizzly the animals had gradually quieted down.

Ten minutes later, and the two saddle boys were slowly picking their way along the gully, heading upward. Frank, as one born to the country, and familiar with many of its peculiarities, amused himself by pointing out to his comrade the various positive signs that as a rule marked these strange water-courses.

"You see, Bob," he remarked, "this is really what might be called a barranca."

"Yes, I've heard you tell about them before," observed the other.

"Most of the year it's only a dry ravine, with high walls; but once in a while there happens to be a tremendous downpour of rain in the mountains, when a heavy cloud breaks against the wall above. When that comes about, this gully is going to be bank-full of roaring, rushing water; and anything caught by the flood is apt to be battered and bruised and drowned before it's swept out below."

"Whew!" observed Bob, with a shrug of the shoulders. "Let's hope then, that the next cloud-burst will have the kindness to hold off till we get out of this hole. If it caught us here, Frank, I reckon we'd just have to let our nags shift for themselves, and take to climbing the sides. And wouldn't I hate to lose Domino the worst way; even if he does give me a raft of trouble at times?"

Frank patted the satiny flank of Buckskin affectionately, as he said:

"And it would just about break me up if anything happened to this fellow, Bob. I've tried heaps of mounts, seeing that we always have hundreds on the ranch; but I never threw a leg over one I fancied like my Buckskin. Why, there are times, Bob, when the game little fellow seems next door to human to me. We understand each other right well. He knows what I'm saying now; listen to him whinny, soft-like, at me."

Possibly Bob, knowing considerable about horses himself, may have had a strong suspicion that the animal understood the touch of his young master's hand much more readily than he did spoken words; but this was a subject which he never debated with Frank. The latter had a habit of talking confidentially with his horse, and seemed satisfied to believe the animal understood.

Slowly they made their way along. Now and then Frank would dismount to examine the rocks and scanty earth that formed the trail over which they were passing.

"Always plenty of signs to tell that horses have been going along here off'n on, both ways—stacks of 'em," he announced, when perhaps an hour had elapsed since they left the scene of the encounter with the grizzly.

The ravine, or gully, which he called a barranca, had gradually changed its character. It was now more in the nature of a canyon; though there were still places where the walls, instead of towering high above their heads, sloped gradually upwards.

"Smart horses could easy climb out of here up that rise," remarked Frank, thoughtfully eyeing one of these places.

"Are you thinking that perhaps we'd better get out with our nags, while we have the chance, and leave them, while we keep up the game on foot?" asked Bob, suspecting that his chum might be considering such a move.

"Well," remarked the other, "it stands to reason that our horses aren't going to be of much use in the mountains. If we shook 'em now, we'd be able to climb almost anywhere, and peek into places we'd never be able to find as long as we stuck to our mounts. So, if you're of the same mind, Bob, we'll try and find a place where we might rope 'em out, an' take the chances of finding 'em again when we're done poking around."

"I hope then, none of the rustlers will run across them while we're away," said Bob, as he looked across a deep little pool that lay just at the foot of a very high slope; and then fastened his gaze on a peculiarly twisted cedar that seemed to cling to the bank, half way up.

"Leave that to me, my boy," returned his chum, confidently. "I'll make sure they leave no trail behind to catch the eye of a horseman riding past. Besides, we're not dead sure, you know, that the rustlers have really got a camp around these diggings. P'raps now, they just push through the canyon to get to some other point across the divide. Or it may be a favorite trail for them to carry off the cattle they rustle. In some hidden valley, you see, they can change the brands; and then openly drive the steers to a shipping station on the railroad."

"All right, then," agreed his companion, who was ready to put the utmost faith in any plan proposed by his saddle chum. "We'll keep our eyes peeled for a chance to get the horses out of this place. Here's a slope they might climb, as you say; but it looks as if they'd have to swim that pool first."

"No use trying it," remarked Frank, casting a rapid glance upward to where, at a distance of possibly a hundred feet, he could see little bushes growing on the edge of the top of the rise, which slope formed an angle of something like forty-five degrees; "sure to be better places further on, where the holding is firmer."

"And yet," remarked Bob, suddenly, "horses have made this climb only a short time ago, Frank!"

"What makes you say that?" asked the other, interested at once.

"Why, there are tracks going up slantingly, you see; and even if I am next door to a greenhorn I can tell that the marks look fresh," Bob declared, pointing.

"Say, I take a back seat, Bob," Frank remarked, laughingly. "That's the time you saw my lead, and went me one better. Sure there have been horses climbing that slope—one, two, three of 'em. And Lopez, he had only two; so it can hardly be him. I wonder now if that measly tenderfoot, Peg——"

"Look up yonder!" interrupted Bob, suddenly pointing again. "I saw the bushes moving along the edge of the top there. Somebody's got an eye on us right now, Frank. D'ye reckon it could be one of those rustlers; and would they try to hold us up so as to get our mounts?"

Bob instinctively snatched his rifle, and began to make a demonstration, as though half tempted to shoot. His action looked so decidedly hostile that it naturally created something of a panic in the breast of the unknown who was lying concealed behind the fringe of bushes.

They saw a sudden hasty movement, as though, in alarm, the hidden one had started to change his position. Then something not down on the bills occurred.

The loose earth at the edge of the top of the long slope seemed to give way in a treacherous manner. Immediately a human figure came into view, struggling, clawing desperately, and trying in every way possible to clutch at something firm in order to halt his downward progress.

But it was all of no avail. A second figure attempted to grasp the imperiled one in time, but evidently failed to secure a firm hold. And so the fellow started to roll down the slope. He came much after the manner in which a bag of corn might turn over and over. Sometimes he was head-first; and then again resuming the side motion, he whirled around in a way that was enough to make anyone dizzy.

All the while he kept letting out shrill squeals of real alarm; as though the prospect of a final plunge into that deep dark pool at the base filled him with dread.

By some rare chance the rolling man struck the twisted little cedar that tried to keep its dying hold on the scanty soil half way up the rise. Caught by the seat of his stout trousers on one of the scrubby tree's broken branches, the unfortunate one was suspended in midair, kicking, floundering and yelling at a tremendous rate.

"Say!" exclaimed Frank, when he was able to catch his breath again, "What d'ye think of that, now? Our friend Peg is so glad to see us he couldn't wait to walk down, but tried to skate. And see what's happened to him! Next thing he wants is a bath; and I sure reckon he's due for one when that cedar pulls out its last root. Wow!"

CHAPTER X - THREATS OF TROUBLE
"Splash!"

Hardly had Frank ventured upon his prediction before it came true. The stout cloth of which Peg's garments were composed might have sustained his weight indefinitely, and had it depended on his trousers giving way, his friends above must have been compelled to use their ropes in order to release him from so unfortunate a predicament.

But the roots of the little stunted cedar were soon torn from their hold. And when this came about, of course the unfortunate Peg continued his roll down the balance of that steep slope, clawing at every object which he thought might stay his progress.

He certainly did drop into the pool with a tremendous splash that sent the water flying in every direction.

At first he vanished entirely from view. Then his head emerged, and it could be seen that he was swimming furiously to keep afloat. Somehow his awkward movements made Bob Archer think of a hippopotamus he had once seen in a tank.

Peg must have had his mouth open when he struck. Perhaps he was trying to shout for somebody to stop him, and in this manner he swallowed a quantity of water. At any rate he spouted forth quite a little fluid as he floundered about, kicking and beating with feet and hands, as though he were being run by an engine that had gone wild.

Both of the saddle boys grinned. They could not help it, the thing looked so laughable. Had it been a dear friend, instead of an enemy, they must have enjoyed the sight just the same.

Twice Peg bobbed under, to come up again, paddling for all the world like a puppy that was having its first swim. His face had taken on a look of terror.

"Help! Can't keep up much longer! Something pulling me down!" he spluttered.

Frank and Bob exchanged a quick glance. Of course this put quite another face on the matter. If Peg was really in danger they had no business to stand there, laughing. It might seem funny to them, but to Peg the matter was not at all comical.

"I don't believe the critter knows how to swim, Bob!" exclaimed Frank.

"That's what," answered the other, seriously. "He's just keeping up because he's crazy with fright. We've got to get him out of there, Frank."

"We sure have; come along," echoed the western boy.

Fortunately Frank was possessed of a quick mind. He never wasted any time in wondering what methods he should use in order to accomplish things.

The pool was of considerable width, and even though he bent over its border he would not be able to come within five feet of the struggling Peg.

Without hesitation he stepped into the water, holding his gun. Two feet from the bank and it was to his knees. But he believed he had now reached a point where he could hold out his rifle and touch Peg.

"Take hold, and I'll pull you out!" he called, as he extended the gun.

It was laughable to see how eagerly the other seized upon the chance. And, when Peg had fastened himself to the other end of the rifle Frank easily drew him shoreward.

The bully came out, dripping wet, and in anything but an angelic temper. It was bad enough, in his eyes, to have fallen into the pool; but to be rescued by a fellow he hated, as he did Frank Haywood, added to the aggravation.

After spluttering for a minute or two, so that he could get rid of the balance of the water he had swallowed, Peg faced the two chums.

Strange to say he did not seem to consider that Frank had placed him under any obligations in the least when he dragged him out of the water.

"See what you did," Peg exclaimed, now spluttering with burning anger. "What d'ye mean pointing your old gun up at me, and making as if you meant to shoot?"

"Oh!" remarked Bob, elevating his eyebrows; "was that what forced you to take that header down the slope? Well, now, we had an idea you were so glad to see us that you just couldn't wait to walk down, but wanted to fly! But, if I was to blame at all for your trouble, I'm sure I'm sorry. But you see, we didn't know whether we were going to be held up by rustlers or Indians. That's what comes from hiding, Peg."

"Bah! guess I'll do just whatever I want," spluttered the other, wiping his dripping face on his sleeve without doing either much good, however. "And do you know what I think?"

"Well, no, I must say I don't happen to be a mind reader, Peg. Suppose you tell me," replied the unruffled Bob, who had taken the measure of the other, and knew he might be set down as a great boaster, but one not particularly dangerous when it came to a show-down.

"I believe you just did that on purpose, that's what," Peg went on, hotly. "You've got it in for me ever since that time we had our little affair, when I laid a hand on the Mexican girl who sassed me. You just knew I'd jump up in a hurry if you made out you was going to shoot; and I bet you even remembered this lake at the bottom of the slope. Oh! it worked all right; but don't you forget; my time will come. I'm going to pay you back in full! I've got friends who'll stick by me, all right. Bah! what're you two fellers doing here on Thunder Mountain, anyhow?"

A new suspicion had apparently seized upon Peg. He viewed their presence as a personal insult; just as though they might have plotted to forestall him in the glorious adventure he had planned to carry out.

"Well, if the old mountain belongs to you," spoke up Frank, thinking it time he took a hand in the talk, "we'll ask you to excuse us, and back out. But I don't think you have any claim on it; so we'll hang around as long as we see fit. And remember this, Peg, we're going to mind our own business; but we don't stand for any bother from you, or those with you. Understand that?"

Peg looked at him long and steadily. The eyes of Frank never wavered in the slightest degree.

"All right," said Peg, finally, as his own eyes dropped. "You wait and see; that's what! This thing's been hanging fire a long time now; and some day we're bound to have it out, Frank Haywood. My dad's after yours with a sharp stick; and perhaps the trouble is going to come down to the next generation. You'll get yours good and plenty when the right time comes!"

He turned away, and, limping to where the slope could be reached by skirting the edge of the pool, laboriously commenced to climb, following the tracks of the three horses.

"There's one of his guides up yonder, Frank," remarked Bob; "sitting on the top of the bank. Looks to me like he was grinning to beat the band."

"Yes, that's Nick Jennings," replied Frank. "Used to work on the Circle Ranch, but he got his walking papers because he was caught stealing from the other men. He's got a grudge against me because I'm a Haywood. But Nick likes a joke as well as any cowboy; and who could keep a straight face after seeing what happened here? Look a little farther on, and you'll just glimpse the colored handkerchief Spanish Joe wears on his head."

"I see him peeping at us from behind the bushes," returned Bob. "And say, he's handling that gun of his just like he'd be glad to use it if anybody gave him the dare. I reckon Spanish Joe is some ugly customer, Frank."

"That's just what he is; but let's be moving on. If Peg takes another flop and splashes in this puddle again, he'll have to swim for it, or else depend on his own guides to yank him out. No more for me. I'm wet to the knees; and did you hear him thank me for it? He's sure the limit."

So the two boys went on.

They were not interfered with, which pleased Frank not a little. Knowing the nature of Spanish Joe, and the revengeful character of Nick Jennings, he would not have been much surprised had they attacked him and Bob, and carried things with a high hand.

Presently a turn in the canyon shut out the scene of their late adventure. The last glimpse they had of Peg Grant, he had nearly arrived at the top of the slope, and it seemed possible that he would not make a slip that might cause him to repeat his recent circus act.

"Why do you think they left the trail, and made their horses climb up?" asked Bob, presently.

"Well, they might have talked it over just as we did, and chosen to leave the horses so they could look around on foot," Frank replied.

"But you suspect they might have another reason, too?" Bob insisted.

"That's a fact," replied his chum, seriously. "For all we know they may have run across some sign of the rustlers, and thought it best to get out of the beaten rut here before they got caught."

"Then you don't believe that little Lopez had anything to do with it, Frank?"

"What, that Mex boy? Oh! he's out of the business long ago," replied the other.

"In what way? Didn't he come along this trail ahead of us?" asked Bob.

"Sure thing," Frank went on. "But you see I've missed the marks of that burro's little hoofs for nearly twenty minutes. I made up my mind Lopez had some slick way of climbing out of the barrancaa ways back, without leaving much of any trail. I told you he was a sly one, and I say the same now, no matter whether he's a brother to the girl you defended against Peg, or the girl herself."

"All right, Frank. Get us out of this as soon as you can," Bob remarked, looking ahead, as though he did not much fancy the appearance of things there.

Ten minutes later Frank drew rein sharply.

"What's doing?" asked Bob, nervously, as he half raised his rifle, which he had insisted on holding in his hand all the time since that meeting with Peg. "Think you see signs of trouble from Peg and his bunch; or is it something else?"

"Something else this time," remarked Frank. "Fact is, our chance has come to get up out of here with the nags!"

CHAPTER XI - THE BLACK NIGHT
"How does this suit you, Bob?"

Frank asked this question as he and his comrade sat there in their saddles, and glanced around at the peaceful scene. They had climbed the bank of the barranca, and reached a spot where the grass was growing under a cluster of mesquite trees.

"It looks good enough for me," replied the young Kentuckian.

"Plenty of forage for the horses," Frank went on, nodding his head as he looked; "and do you see that little trickling stream of water that crawls along? All we have to do is to hide the horses here. When we want 'em, the chances are we'll find 'em safe."

"I hope so," remarked Bob, as he alighted.

In a short time they had removed saddles and bridles, hiding these among the neighboring rocks, together with their supplies, and had picketed the horses by means of the lariats.

"Now what?" asked Bob.

"You sit down here, and wait till I come back," Frank remarked.

"What are you going to do?" the Kentucky lad inquired; "something that I might lend a hand at?"

"No, I reckon you're a little shy on knowing how to hide a trail, Bob. Old Hank showed me, and I've practiced it often. This promises to be a chance to see whether I learned my lesson half-way decent."

"Oh! all right, Frank. But some day I expect you to show me all about that sort of thing. You know I want to be in the swim, and learn how to do everything there is. I'll wait here by the water," and Bob dropped down to rest.

"I won't be gone long," Frank observed. "Pretty much all the slope was made up of stone; and what a great time the horses did have, trying to hang on. Once I thought your nag was going to take a nasty plunge, because he isn't as used to the work as a Western pony would be. But he recovered, thanks to the help you gave him, and made the top all right. So-long, Bob."

"I notice you're taking your gun along," remarked the one who was to stay.

"Well, when you're in the mountains it's just as well to be prepared all the time. You never can tell when you'll run slap into something. It might be a big grizzly like the one we met; then perhaps a hungry panther might take a notion to tackle you. I knew a cowman who had that happen to him. Yes, and perhaps you heard him tell the story."

"You must mean Ike Lasker," Bob replied, quickly. "Yes, I remember how he said he was lying down, waiting for some feeding deer off to windward to work closer, when, all of a sudden, something struck him on the back, and nearly knocked the wind out of him for keeps. He managed to get his knife out, and they had it there, good and hard."

"Ike said he nearly cashed in his checks that time," Frank added. "Some of his mates found him, after they discovered his horse feeding near by. The panther was dead as a stone, and Ike was clawed and bit till he looked like a map of the delta of the Mississippi—anyhow, that's the way he told it. Keep your shooter handy, too, Bob."

"I will that," returned the Kentucky boy, impressed by his chum's earnestness.

After a little while Frank came back again. His manner told that he was quite satisfied with what he had done.

"A sharp-eyed trailer might find where we left the canyon," he admitted; "but I don't believe any ordinary fellow would notice the marks. So I think our horses stand a first class chance of being here when we come back for 'em."

Bob got on his feet.

"I've fixed up some grub, just as you told me," he remarked. "It isn't much, but ought to serve in a pinch."

"And as it's nearly noon now," observed Frank. "Why not take a snack before we leave our base of supplies? Let's get the stuff out of the cache again, and have a round of bites."

"I don't see the use of hurrying away from here right now, anyhow," Bob remarked, while they were eating.

"You mean," said Frank, "that we only came here to see what we could find out about the secret of old Thunder Mountain, and why it kicks up such a rumpus every little while?"

"Yes, and seems to me that since we're right on the ground now, we might just as well start business, here," Bob asserted.

"That is, hang around until night, and wait to see if the grinding begins again, as it did when we were in camp below?"

"We'd be in a position to guess what it was, better than before," Bob went on.

"That's a fact," laughed Frank. "And if, as lots of people think, this old mountain is a played-out volcano, perhaps we might even smell the sulphur cooking, by sticking our noses down into some of these crevices in the rocks."

"Now you're joshing me, Frank!" declared the Kentucky lad, reprovingly.

"I am not," replied the other, immediately. "Suppose there was any truth in that fairy story about the fires away down in the earth here; don't you think a fellow might get a whiff of the brimstone if he was Johnny on the spot? Why, honest now, Bob, it was on my mind to find some sort of cave up here, and go in just as far as we could. Don't you see the point?"

"Oh! I reckon I do, Frank. You take little stock in that yarn; but, all the same, you think we ought to look into it, now we're on the ground?"

"That's it, Bob. Why, even my dad kind of favors that idea, and I want to either prove it a fake, or learn that there's something to it."

So they lay there, lazily enough, instead of climbing farther up the side of the mountain. It was very pleasant to keep in the cool shade of the trees, with that trickling little stream so near, for, as the afternoon advanced, it seemed as though the air became very oppressive.

Frank was looking up at the sky many times, and finally his companion asked him what was on his mind.

"I don't pretend to be a weather sharp," Frank replied; "but, all the same, there are signs up there that've got me guessing."

"Well, it is clouding up some," replied Bob, as he swept a look around at what they could see of the arch overhead. "Perhaps the long drought is going to be broken at last, Frank. Your father will be tickled, if it turns out that way. He's been complaining of late about the stock having to hunt twice as far away from the ranch for forage. A rain would make things green again."

"Sure it would," replied Frank; "but, as I said to you before, a rain storm up in the Rockies is sometimes no joke. We may have to do some tall climbing if it gets a whack at us when we're in the canyon."

The day was passing. They had seen nothing more of Peg Grant and his two guides, but could easily believe the others were not a great way off. Perhaps they, too, were only waiting for night to come in order to start their investigation.

"I don't think either Spanish Joe, or Nick, could be depended on, if the thing began to look too spooky," Frank had said more than once, showing that his thoughts must be running in the direction of the rival party.

"Oh! this is easy," chuckled Bob. "If all we've got to do is to squat here and take notes when the menagerie begins to wake up, it's going to be a snap."

Frank did not want to make his chum nervous by confessing that he had another reason for agreeing to remain there idle the balance of the day, besides the fact of there being no hurry, and that they could take notes just as easy there as farther up the mountain.

The fact was, he had concluded, it would be safer for them to remain in hiding while daylight lasted, and do what searching they expected to accomplish in the darkness of night.

It was too easy, for anyone who had no scruples, and wished to do them injury, to drop a rock down from the wall of the canyon. Against this sort of attack their rifles would be useless; and terrible damage might result.

As to who would be guilty of such an outrage, Frank only remembered that Peg was in a white heat of indignation, and fully capable of doing some madcap prank in order to frighten off the two saddle boys. He was also not a little worried about the rustlers, supposed to be lurking somewhere not far distant.

Last, but not least, there were the prospectors to whom little Lopez had admitted he was carrying the supplies that were secured on the pack burro. Frank had not heard of any treasure-hunters having invaded the slopes and valleys around Thunder Mountain; but this did not mean it could not be true.

If these men were secretly taking out possibly large quantities of precious ore, and did not wish to be discovered, or disturbed in their operations, even they might try to alarm the invaders by hostile demonstrations.

"It's as pretty a mixup as ever I heard tell of," Frank had said several times that afternoon, while they were exchanging confidences in connection with the remarkable possibilities around them. "What with the rustlers, Peg and his crowd of thunder investigators, the little Mex. boy and his unknown prospector bunch; and last but not least, Bob, ourselves, it sure has me going some."

"Yes," the other had returned, "but I hope we'll keep clear of the whole lot, and be able to find out something worth while. I wish the next night was over, and we were galloping along over the plains headed for good old Circle Ranch."

"Me too, Bob, always provided we carried with us an explanation for those deep grumblings that shake the earth, and seem to come out of the heart of Thunder Mountain. I'm a stubborn fellow, as I reckon you know; and when I throw my hat into the ring I like to stick it through till they carry me out."

"The same here," Bob had declared, after which the chums had to shake hands on it again, thus sealing the compact to stick.

And so the day went, and night came on apace.

The air did not seem to cool off to any extent as darkness approached. Frank took pains to call the attention of his comrade to this fact.

"You can guess what that means, Bob," he remarked. "It's sure going to bring on a whopper before a great while. All the signs point that way right now. So we can expect to get ready for a ducking."

"Oh! that doesn't bother me," declared Bob. "I've been through many a one. All I hope is that we don't happen to be in the old canyon when that cloudburst you mentioned comes along. I'm not hankering after a ride on a forty foot wave, and down that crooked old canyon, too. Excuse me, if you please!"

"Of course if we only stick it out here, there's going to be no danger," Frank remarked, indifferently.

"I see that you're just itching to be on the move, old fellow," ventured Bob, who knew the restless nature of his chum.

"Do you? Well, Bob, to tell the truth, if I was alone now, I suppose I'd be making for the top of the old hill, bent on finding out whether there was any sign of smoke oozing from the cracks and crevices at just the time the rumblings came on."

"Then what's to hinder both of us going at it?" demanded the proud Kentucky lad, fearful that Frank might think him timid because he had suggested their remaining out of the danger zone.

"We may, later on. Just now it's our business to get some supper; and hot or not, I'm going to make a cooking fire back of this big boulder, where nobody could ever glimpse the blaze."

"Did you say coffee?" remarked Bob. "All right, I'll go you, old fellow. I feel a little that way myself, and that's no yarn."

So Frank got things started, and it was not a great while before the coffee pot was bubbling as merrily as ever, with that appetizing odor wafting from it.

The darkness kept on increasing while they ate. An hour later it was very black all around them, and Bob viewed the possibility of their venturing into the unknown perils around them with anything but a comfortable feeling.

It was just when he was wondering whether Frank would not conclude to remain in the safe position they occupied that he heard his comrade give a sharp cry.

"What have you discovered, Frank?" asked Bob, starting to get up.

"A light up the side of the mountain yonder," replied the other, "and, Bob, perhaps if we could only manage to climb up there, we'd learn something worth while. The question is, have we the nerve to try it?"

CHAPTER XII - LOSING THEIR BEARINGS
Bob chose to consider this a direct challenge.

"I expect that it would be queer if we didn't make some sort of effort to find out what the light means. Where is it, Frank?" he remarked, with perfect coolness.

"Well, it must have gone out while you were speaking, Bob, as sure as anything," the other replied. "But I saw it, I give you my word I did. Huh! there she comes again, just like it was before. Step over here; the spur of the rock is in your way there. Now look straight up. Get it?"

"Easy, Frank. A fellow might think it was a star, if he didn't know the mountain was there. Now it's getting bigger right along."

"That's so, Bob. And yet it doesn't seem to be a fire, does it?"

"More like a lantern to me," declared the Kentucky boy. "Say, what d'ye reckon anybody could want a lantern up there for? Can you see any swinging motion to the light Frank?"

"It does seem to move, now and then, for a fact," admitted the other, after watching the gleam for a short time.

"About like a brakeman might swing his lantern if he was on a freight train in a black night, eh?" continued Bob.

"Hello! I see now what you're aiming at, Bob; you've just got a notion in your head that the lantern is being used for signaling purposes."

"Well, does that strike you as silly?" demanded Bob Archer.

"Silly? Hum! well, perhaps not, because it may be the right explanation of the thing. But whatever would anybody up there be signaling for, and who to, Bob?"

"There you've got me," laughed the other. "I'm not so far along as that yet. P'raps it might be one of the rustlers, telling something to another of the same stripe, who is located in camp out yonder on the plain. Then, again, how do we know but what it might be that Peg Grant lot? And Lopez. Don't forget little Lopez, Frank. Prospectors could have a lantern; in fact, I understand they often do carry such a thing along with 'em when they go into the mountains to pan for dust in the creek beds."

"So," said Frank, who evidently was doing considerable thinking.

They stood there for some little time, looking up at the light. Bob was merely indulging in various speculations regarding its source. On the other hand Frank busied himself in locating the strange glow, so that he might be able to know when he reached the spot, in case it was invisible at the time they arrived.

"Do we go?" asked Bob, when he, too, found his impatience getting the better of him; whereupon Frank, who had evidently been waiting for some sign, immediately took him up on it.

"If you're ready, we'll start right away," he said, quietly. "Luckily I've been studying the face of Thunder Mountain at times during the afternoon, and I reckon I can pilot the expedition all right."

But when Frank said this so confidently he failed to consider the intense darkness that might baffle all his plans of campaign. Still, Bob had the utmost confidence in his chum's ability to pull out of any ordinary difficulty. And, since his Kentucky spirit had been fully aroused, he was ready to accompany Frank anywhere, at any time.

Before they had been ten minutes on the way each of the boys sincerely wished that the idea to investigate had never appealed to them, for they began to have a rough time of it. But both were too proud to admit the fact, and so they kept crawling along over the rocks with their rifles slung on their backs, at times finding it necessary to clutch hold of bushes or saplings in order to save themselves from some tumble into holes, the actual depth of which they had no means of even guessing in the darkness.

The light was gone. Of course that might not mean it had vanished entirely; but at least it could no longer be seen by the boys who were climbing upward.

Bob was hoping his comrade would propose that they call it off, and proceed to spend the balance of the night in the first comfortable nook they ran across. But Frank himself was loath to give the first sign of a back-down. Consequently they continued the laborious task which was likely to bring no reward in its train, only the satisfaction of knowing they had accomplished the duty which they had in mind at the time of the start.

An hour must surely have gone since they first left the little green glade where the horses were staked out, and their supplies cached.

Bob found himself blown, and trembling all over with fatigue, because of the unusual exertion. The heat, too, was troublesome. But not for worlds would he be the first to complain. Frank was setting the pace, and he must be the one to call a halt.

"Phew! this is rough sledding," remarked Frank, finally, as he stopped to wipe his streaming face.

Of course Bob also came to a halt.

"Well, it is for a fact," he admitted with a little dry chuckle; for he felt really pleased to think that he had held out so long, and forced Frank to "show his hand."

"Seems to me we ought to have struck something," suggested Frank.

"Do you really mean you think we've come far enough for that?" questioned Bob.

"I reckon we have, though it's so dark I can't be dead sure. You don't happen to glimpse anything queer around here, do you, Bob?" and while speaking Frank, perhaps unconsciously, lowered his voice more or less.

"Nary a thing," replied the other, breathing fast, as if to make up for lost time.

"And I don't get any whiff of smoke, do you?" continued Frank.

"Oh! you're thinking about that volcano business again, eh?" chuckled Bob. "Nothing doing, Frank. Gee! we must be up pretty high here!"

"Feels like it," returned the prairie boy, accustomed to the heavier air of the lower levels at all times. "Makes me breathe faster, you know. But that was a hot old climb, Bob."

"All black up yonder in the sky, with never a star showing," observed the boy from Kentucky.

"Oh! we're going to get it, sooner or later," declared Frank, cheerfully. "Can't escape a ducking, I take it. But here we are, half way up old Thunder Mountain, and not a thing to show for our work. That's what I call tough!"

"Got enough?" asked his chum, invitingly.

"You mean of course for to-night only, because you'd never think of such a thing as giving up the game so early, Bob?"

"Well, I was only going to make a little suggestion," returned the other.

"Hit her up, then; though perhaps I could guess what it's like, Bob."

"All right then. You know what I mean—and that since we're away up here, we might as well make up our minds to hunt an overhanging ledge, and take a nap. But say, what're you sniffing that way for, Frank?"

"Just imagined that I got a faint whiff of smoke; but of course it was all in my eye," replied the other.

"Was it? I tell you I had a scent of it myself right then," declared the taller lad, showing signs of considerable excitement.

"Seems to come and go, then, for I don't get it any more. What was it like, Bob? Did you ever smell sulphur burning?"

"Lots of times, and helped to use it too, disinfecting," replied Bob, readily. "Spent months with my uncle, who is a doctor in Cincinnati, during an epidemic, and he often had to clean out rookeries just to stamp out the disease. But this wasn't any sulphur odor I caught, Frank."

"Then you could recognize it; eh?" asked his chum.

"It was burning wood, I give you my word for that," replied Bob, firmly.

"Hum. That sounds more like it. We'll let the volcano matter sizzle for a little while, and look around for something smaller. Burning wood must mean a fire, Bob!"

"That's what they say, always; where there's smoke there must be fire. But it seems to me we ought to see such a thing on this black night, Frank."

"Unless it's hidden, as we make our cooking fire; or else the blaze is at the last gasp. Then, after all, we may have been a little off about that light we saw," Frank continued.

"The one we said was a lantern? Then you think, now, it might have been a fire?" questioned the Kentucky lad.

"Well, I just don't know what to think. But let's look around a bit, and see if we can locate this fire," Frank suggested.

After moving around for a short time as well as the darkness allowed the two boys came together again.

"No luck, eh?" questioned Frank.

"Didn't find a thing; but I stumbled over a creek and came near taking a header down-grade that would have made that plunge of Peg's take a back seat. Just in the nick of time I managed to grab a little tree. Phew! it shook me up, though," and Bob rubbed one of his shins as though he might have "barked" it at the time of the encounter.

"Same here; only I didn't happen to fall," replied Frank.

"So it seems as if we were no better off than before," remarked Bob, dejectedly.

"We've learned where the fire isn't, if that's any satisfaction to us," chuckled his chum, trying to make the best of a bad bargain.

"And that smoke smells so meaning-like, it's sure a shame we can't just get a line on where it comes from," Bob went on to say.

Frank seemed to catch a significance in his words, for he turned sharply on his companion, saying:

"Look here, have you been getting a whiff of it again, Bob?"

"Why, yes, several of 'em in fact, Frank," replied the other, in what seemed to be a surprised tone. "But what does that matter, when neither of us can find any fire around? I sniffed and sniffed, but although I just turned my eyes in every direction not even a tiny spark could I see. And that happened just three times, Frank."

"What! do you mean you smelled smoke three separate times since you left me?" demanded the saddle boy.

"I'm sure it must have been three, because it was between the first and second times that I tripped. Yes, and always in just the same place too, which was queer enough."

"That sounds kind of encouraging, Bob," declared Frank.

"Do you think so?" asked the other, puzzled to account for Frank's newly awakened interest. "Tell me why, won't you, please, Frank?"

"Sure, after you have answered me a question," Frank promptly remarked.

"All right, let's have it, then," his chum returned.

"Do you think you could find that exact spot again?" asked Frank.

"Meaning where I sniffed that smoke each time? Why, I guess I can, because I went back there twice, all right. Couldn't be quite satisfied that there wasn't something around there I ought to discover. But it turned out a fizzle, Frank."

"Perhaps it wouldn't be so unkind to me, though," the Western boy declared. "Take me to that place, Bob, and right away. It strikes me I'd just like to get another little whiff of that same wood smell, myself. It wouldn't be the first time I'd followed up a smoke trail."

"Gracious! that sounds interesting, and I hope you can do it, Frank!" breathed Bob, his admiration for his chum awakening once more.

"First of all, get me to that place. Lead off, and I'll be close at your heels. And, Bob, don't forget that spot where you came near having your tumble. Keep your level head about you."

"I'll sure try to, Frank. Come on then."

Bob led the way through the darkness. Although he had been out West for so short a time Bob Archer was rapidly learning the ways practiced by those who live close to Nature. He began to observe always all that he saw, and in such a way that he could describe it again, in every detail.

And so it chanced that, having marked his course when coming back after his unsuccessful search for the fire, he was able, not only to lead his comrade thither, but to warn him every time they approached a dangerous slide, where a trip might hurl one some hundreds of feet down the face of Thunder Mountain.

"Here is the place, Frank," Bob suddenly said, in a cautious whisper.

CHAPTER XIII - THE SMOKE TRAIL
"Are you sure of it?" asked Frank, in the same low voice.

"Why, try for yourself, and see if you can't get a whiff of smoke right now," Bob replied.

"You're right, because I caught it just then; but I reckon the wind must be changing some, for it's gone again," Frank remarked.

"You never spoke truer words, Frank, because I can hear the breeze beginning to shake the leaves in the trees up yonder, and it wasn't doing that before."

Bob pointed upwards as he said this cautiously. And Frank, always watchful, noticed a certain fact. The trees were so situated that they could be said to lie almost in a direct Southeast line from where he and Bob stood! This might appear to be a very small matter, and hardly worthy of notice; but according to Frank's view it was apt to prove of considerable moment, in view of what was likely to follow.

"Well, as the smoke's gone again, let's see if we can locate it by moving a little this way," and Frank led off as he spoke, with Bob following.

Both lads were very cautious now. Even Bob, greenhorn as he was, so far as Western ways were concerned, understood the need of care when approaching a camp that might be occupied by enemies. And as for Frank, he had not been in the company of an old ranger like Hank Coombs many times without learning considerable.

They had not been moving in the new direction more than five minutes when Bob reached out his hand and clutched the sleeve of his chum's jacket.

"What is it?" asked the leader, stopping short, and crouching there.

"I got it again, Frank," whispered the Kentucky boy, eagerly.

"Sure," replied his comrade, immediately. "Why, I've been smelling smoke for more'n a whole minute now. And I'm following it up, foot by foot."

"Oh!" murmured Bob, taken aback by this intelligence.

"Don't say a word above your breath, Bob. Whoever it is can't be far away now. We may run in on 'em any minute, you know," and as if to emphasize the need of caution Frank drew his chum close while he whispered these words directly in his ear.

Bob did not make any verbal reply; but he gave the others sleeve a jerk that was intended to tell Frank he understood, and would be careful. Then they moved along again.

It was no easy task making progress through the darkness, and over such rough grounds, without causing any sound. Bob found that he had almost to get down on his hands and knees and creep, in order to accomplish it. But his chum had not forgotten that he was new to this sort of business, and hence he gave Bob plenty of time.

Then Bob in turn began sniffing, and Frank knew that now he, too, had caught the trail-odor, which was constantly becoming stronger. Thus they were positive that while they moved forward they must be gradually drawing nearer the source of the smoke.

Another tug came at Frank's sleeve, at which signal he bent his head low so that his chum might say what he wanted in his ear.

"Sounds like voices!" whispered the excited Kentucky lad.

Frank gave a little affirmative grunt.

"Rustlers, maybe?" Bob went on.

The other made a low sound that somehow Bob seemed to interpret as meaning a negative to his question.

"Then prospectors—Lopez and his bunch?"

"Uh!" Frank replied; and then himself lowering his lips to the ear of Bob he went on: "What's the matter with Peg and his crowd? They might have got up here ahead of us. Quiet now!"

Bob did not attempt to say another word. He had new food for thought. Yes, to be sure, Peg and his two cowboy guides had had plenty of time to climb that far up the side of Thunder Mountain. If they had taken daylight for the task of course they avoided the danger of getting lost, such as had overtaken the saddle boys. And if the nerve of Spanish Joe and Nick Jennings continued to hold out, when strange things began to happen, the boastful tenderfoot from the East stood a chance of making a discovery.

As the two crept closer, on hands and knees, they could hear the murmur of voices grow louder, even though the speakers were evidently talking in low tones. While the experience was altogether new to Bob, he enjoyed it immensely. Why, after all, it was not so very hard to place his hands and knees in such fashion that he felt able to move along almost as silently as a snake might have done.

Now he was even able to locate the spot from which the murmur of voices came. Yes, and when he looked closer he saw a tiny spark that glowed regularly, just as a firefly might sparkle every ten seconds or so.

Bob solved that little mystery easily. Of course it was Spanish Joe, smoking one of the little cigarettes which he was so frequently rolling between his fingers.

To be sure, the odor of tobacco smoke mingled with that of burning wood. And if Spanish Joe, why not the other cowboy who was in bad repute among the ranches; yes, and Peg himself?

Bob began to wonder what the programme of his chum might be. Surely they would not take the chances of crawling up much closer now. If discovered they would run the risk of being fired upon; and besides, there was no necessity for such rashness.

Then Bob discovered that when the wind veered a little, as it seemed to be doing right along, he could actually catch what was being said.

Peg was talking at the time, and grumbling after his usual manner about something or other.

"Ten to one the fellow's gone and deserted us, Nick!" he remarked, suspicion in every word.

Apparently the lounging cowboy did not share in his opinion, for he laughed in a careless way as he drawled out:

"Oh! I reckon not, Peg. Me and Joe has hit up the pace fur some years in company, and I knows him too well to b'lieve he'd break loose from a soft snap like this here one. Jest lie low, an' he'll be back. Let's hope Joe's found out somethin' wuth knowin'."

"But he's been gone nearly an hour now," complained Peg.

"What of that? It ain't the easiest thing gettin' around on this rocky ole mounting in the pitch dark, let me tell ye, Peg," Nick remarked; and by the way he seemed to puff between each few words, Bob understood that it must be Nick who was using the cigarette, and not Spanish Joe.

"Say, that's so," admitted Peg, as if a new idea had come to him. "Perhaps he's slipped, and fallen down into one of those holes you showed me when we were coming up!"

This also amused the cowboy, for he chuckled again.

"Too easy an end for Spanish Joe," he said, carelessly. "Born fur the rope, and he can't cheat his fate. Same thing's been said 'bout me. Don't bother me none, though, and sometimes it's a real comfort; 'specially when a landslide carries ye down the side of a mounting like a railroad train, like I had happen to me. Nawthin' ain't agoin' to hurt ye if so be yer end's got to come by the rope."

"A landslide! Do they often have that sort of thing out here?" asked Peg, showing some anxiety, as though he had read about such terrible happenings, and did not care to make a close acquaintance with one.

"Sure we does, every little while," remarked Nick, cheerfully. "Why, jest last year the hull side of a peak 'bout forty mile north of here broke away, and a Injun village was wiped out. Never did hear anything from a single critter after that slip bore down on 'em."

"It might happen here on Thunder Mountain, too, couldn't it, Nick?" pursued Peg, as if the subject, with all it pictured to his active mind, held his interest gripped in such a fashion that he could not shake himself free.

"Easiest thing goin', Peg. And let me tell ye, if it ever do happen here, thar's agoin' to be a slide to beat the band!" Nick asserted, positively.

"But what makes you say that, Nick?" demanded the boy.

"Oh! lots of people says the same thing," replied the other, as if carelessly.

"That a landslide is going to start things going on Thunder Mountain any time—is that what you mean?" Peg insisted on repeating.

"Any day, er night. Things have been lookin' that way for some time now. I reckon she's due with the next big cloud-burst that sails this way."

It was evident that, for some reason, Nick was trying to frighten his young employer. Perhaps he himself really wished to get away from the mountain with the bad name; and took this means of accomplishing his end without showing his hand. If that were true, then he was gaining his end, for Peg certainly gave evidence of increasing uneasiness.

"But why didn't you tell me all this before?" he demanded, indignantly.

"What was the use, boss? Ye was sot on comin' here, and ye made Joe and me a rattlin' good offer. 'Sides, it didn't matter much to me. I had my life insured. A rope might have skeered me; but say, I don't keer that for landslips," and Nick snapped his fingers contemptuously.

But Frank, who knew the sly cow puncher so well, believed that more or less of his indifference was assumed.

"Well, I do!" declared Peg, with emphasis; "and if I'd only known about that sort of thing before, blessed if I'd a come. I've heard what happens when the side of a mountain tears away, and how everything in the path goes along. They showed me the bare wall where one broke loose up in Colorado. Say, it was the worst sight ever. You'll have to excuse me from nosing around here another day, if that sort of thing is hanging over this place. Me for the ranch on the jump. Get that, Nick?"

"Oh! now, what's the use botherin'? Chances are three to one they ain't agoin' to be any sech upsets as that yet awhile," the cowboy said.

"Only three to one!" burst out Peg. "All right, you can stick it out if you want, and I'll pay you all I agreed; but just you understand, Nick Jennings, when to-morrow comes, I want you to get me down on the prairie, where I can make a blue streak for the X-bar-X ranch house."

"But ye sed as how ye was detarmined to find out what made them roarin' n'ises, up here on old Thunder Mountain!" protested the guide, although he evidently expressed himself in this way only to further arouse the obstinate boy.

"I've changed my plans, that's all," Peg announced. "Any fellow can do that. It's always the privilege of a gentleman to alter his mind. I'd like to crow over Frank Haywood and that greenhorn chum of his mighty well; but I ain't going to run the chance of being carried down in a landslip just for that. Huh! I guess not! What I said, stands, Nick. And I hope the old slide comes while those two chaps are on the mountain; yes, and gives them a dandy free ride, to boot!"

"Oh! jest as ye say, Peg! I'm willin' to do anythin' to please ye. But p'raps we ain't goin' to git off so easy arter all," remarked Nick, suggestively.

"Now, what do you mean by hinting in that way? And I've noticed you twisting your neck to look up at the sky more'n a few times. Think it's going to rain, do you?" demanded Peg.

"Don't think nawthin' 'bout it; I know it be." And, Nick added, with emphasis, "I reckons as how it'll be jest a screamer when she comes."

"A storm, you mean?"

"A howler. Allers does when the wind backs up that way into the sou'east. 'Sides, if so be ye air still sot on findin' out what makes that thunder up this ways, p'raps ye'll have the chanct to look into the same afore long, Peg."

"Oh! was that what I felt just now?" cried the boy, scrambling to his knees. "It seemed to me the old mountain was trembling just like I did once, when I had the ague. And Nick, I believe you're more'n half right, because I sure heard a low grumble just then, like far-away thunder. I wish I hadn't been such a fool as to come up here. Never get me doing such a silly thing again as long as I live. Listen! It's coming again, Nick, and louder than before. Don't you feel how the ground shivers? Perhaps there's going to be a terrible landslip right now! Do you think so, Nick?"

Frank and Bob, crouching close by, had also felt that quiver under them. It gave the saddle boys a queer feeling. When the solid earth moves it always affects human kind and animals in a way to induce fear; because of the confidence they put in the stability of the ground.

And then there arose gradually but with increasing force a deep terrible rumble.

Thunder Mountain was speaking!

CHAPTER XIV - A CALL FOR HELP
"Oh! what shall we do, Nick?" cried Peg.

His voice was now quivering with fear. Evidently whatever little courage the fellow possessed, or the grit which had caused him to start upon this mission of attempting to discover the cause of the mystery connected with Thunder Mountain, had suddenly disappeared.

"Nawthin' 'cept stick it out, I reckons," replied Nick Jennings.

The superstitious cowboy was more or less anxious, himself. Frank, eagerly listening, could tell this from the way in which the fellow spoke. But Nick did not mean to fall into a panic. To try and rush down the precipitous side of that mountain in the dark would be madness. And with all his faults Nick was at least smart enough to understand what it meant by "jumping from the frying pan into the fire."

Another roar, louder than any that had yet broken forth, interrupted the excited conversation between the son of the mining millionaire and his guide. The whole mountain quivered. Bob himself was much impressed, and began to wonder more than ever what it could mean.

The noise died away, just as thunder generally does, growing fainter, until silence once more brooded over that wonderful mountain. Then again the two crouching lads caught the complaining voice of Peg. Bully that he was under ordinary conditions, he now showed his true colors. That awful sound, coming from the heart of the rocky mountain, as it seemed, had terrified Peg.

But Frank was not surprised, for he had all along believed that a fellow who could lift his hand to strike a small girl must be a coward at heart, no matter how much he might bluster and brag.

"This is terrible, Nick!" exclaimed Peg. "Can't you think of some way we might get out of this? Oh! I'd give a thousand dollars right now if only I was safe down on the plains again! What a fool I was to come here!"

"Well," drawled Nick, possibly with a touch of real envy in his voice, "I'd like right smart to 'arn that thousand, sure I would, Peg. But hang me if I kin see how it's agoin' to be done. We can't slide down; walkin's a risky business, and likely to take hours; an' right now I don't feel any wings asproutin' out of my shoulders, even if you do."

"Oh stop joking, Nick, and talk sense," complained Peg. "We've just got to do something. Why, the old mountain might take a notion to slide, and carry us along with it."

"I sure hopes not, at least right now," replied Nick, uneasily. "But I do reckons as how we're agoin' to git that storm afore mornin'."

"But see here, Nick," Peg went on, anxiously; "didn't you notice anything when you were leading me up here like a lamb to the slaughter? I mean, you ought to have seen whether this side of the old mountain was more likely to drop off than any other."

"Ye never kin tell nawthin' about such things," returned the cowboy. "Reckons all we kin do is to root around, an' see if we might find some sorter cave, where we'd be safe from the rain, if so be she comes arter a while."

"A cave!" echoed the other, as though startled. "What under the sun do we want to get inside the mountain for? Don't you understand that all that noise is coming out of this old thing? I tell you, I believe it is a volcano, just as they told me, and perhaps she's going to break loose this very night!"

"Hey! what ye a sayin' that for?" demanded Nick. "Supposin' she is what ye tell, that ain't any reason the explosion's got to come this particular night, is it? She's kept on a growling for a hundred year now, an' nawthin's happened. Reckons it ain't agoin' to come off jest acause we pilgrims happens to be up here."

"But you said we ought to find a cave, and go in, Nick," continued the youth. "Suppose we do, and the sulphur fumes suffocate us? They must be just awful inside the mountain. This is a nice pickle for me to get into! If I stay out here I'm in danger of being drowned, or swept away by a landslide; if I go inside there's all the chance in the world that I'll be soaking in poisonous sulphur gas till I keel over. I'm up against it good and hard."

"We're all in the same boat, remember, Peg," declared the cowboy.

"But you knew more about this thing than I did, Nick. Why'd you let me come? It was all a fool business, and you're most to blame," protested Peg.

"Aw! let up on that kind of talk, will ye?" growled the cowboy, who was himself losing his respect for his employer, owing to the presence of those things which he did not understand, and the nearness of which aroused his own fears.

"I will, Nick; only get me out of this hole safe and sound, and I give you my word I'll pay you that thousand dollars. But where do you suppose Joe can be all this time? Has he run away, or dropped over into one of those pits we saw on the way up here? I wish he'd show up. Three would be better than two; and perhaps Joe might have a plan for us to get out of this."

Again did the low grumbling sound begin again, and silenced the conversation between Peg Grant and his cowboy guide, every word of which had come distinctly to the ears of the crouching saddle boys near by.

The rumble grew rapidly in volume, until once more the whole great mountain seemed to tremble. Bob was shivering partly from the excitement, and because he felt a touch of alarm.

But he could not help noticing the actions of his chum. When the thunderous roar was about at its height Frank had thrown himself flat on the ground. Bob could not see what he was doing, but his groping hand came in contact with the head of his comrade; and he discovered that it rested on the ground, with one ear pressed to the rock.

Frank was listening!

He knew how the ground carried sounds more distinctly than the air, and evidently he hoped to discover something concerning the thunder by this method of wireless telegraphy.

Then, as the volume of sound gradually decreased, just as a lion's roar dies away, Bob discovered that Peg and Nick were undoubtedly moving off. He supposed that Nick had made up his mind to hunt for an outcropping ledge, or some friendly opening, where he could be sheltered from the storm; and as Peg dared not stay alone, he was compelled to accompany his guide. The complaining voice of the rich man's son could be heard for a minute or so. Then even that ceased.

"They're gone, Frank!" exclaimed Bob.

"Yes, I know it," replied the other, as he arose from his position flat on the rocks. "And Peg is badly rattled, too. Say, I always told you he lacked real grit, and this proves it. He's scared at that noise. Think of him wanting to fly down to the plain! I reckon he's had about all of the exploring he wants. It's 'take me back to my daddy!' now with Peg."

"Well," remarked Bob, with a sigh, "I don't blame him so very much, Frank. I tell you what, that noise is enough to give anybody fits. I'm all of a tremble myself, and I'm honest enough to admit it."

"That's all right, Bob," replied his chum, quickly; "but are you ready to give the game up here and now?"

"Who, me?" answered the Kentucky boy, instantly; "well, I should say not—not by a long sight! No matter what comes, I'm ready to stick it out on this line if it takes all summer!"

"Just what I thought," chuckled Frank. "That's what makes all the difference between a brave fellow and a coward. Why, to tell you the truth, Bob, I'm shaking all over right now myself; but it isn't with fear. I'm excited, curious, and worked up; so are you. When you say you don't want to back out it tells the story that you're not afraid."

"But it wouldn't make any difference, Frank, seeing that we couldn't get away from here, even if we wanted to just now," remarked Bob.

"That's so," returned his chum; "just as Nick said; we're here, and we've just got to stick it out, no matter what comes."

"But do you take any stock in what Peg said about an avalanche?" asked Bob.

"Mighty little," Frank replied. "This mountain is made up mostly of solid rock. That's what makes lots of people believe in the volcano idea. A slide would be hard to start here, and it just couldn't carry much along with It. Where mountains have sides made up of earth and loose rocks, that happens sometimes."

"I'm glad to hear that," remarked the other. "But there comes another shake. Whew! feel how she trembles, Frank! Whatever sort of power can it be that makes this noise and shivering sensation?"

Frank waited until the convulsion had passed before replying.

"I've got a strong suspicion, Bob," He said, finally; "and it's something that came into my mind since feeling the sound, for that's the only way I can express it. Now, what does it make you think of, most of all?"

"I did think it was thunder," declared Bob; "but now it seems to me the only thing I can compare it to is the beating of the terrible billows against the coast away up in Maine, when a fierce northeast storm is blowing. They seemed to make the rocks quiver just as this does now."

If Frank had intended to reply to this remark he was prevented by something unexpected that happened just then. This time it was not the furious roar of the unknown force within the mountain that disturbed him; but a cry that rang out shrilly.

"Help! Help!"

Bob clutched his companion's arm.

"Something has happened to Peg!" he exclaimed. "Perhaps the guide has thrown him over, and he's lost, and scared nearly to death!"

But Frank was more accustomed to reading voices in the open than was his chum.

"No, you're wrong there!" he cried, "that's Spanish Joe yelping; and he must be in a bad hole to call for his companions. Come on, Bob, we've just got to see what we can do to help him. Rascal that he is, he's human. Follow me!"

CHAPTER XV - SPANISH JOE DROPS A CLUE
"Where can he be, Frank?" cried Bob, after they had been climbing for several minutes up the side of the rough mountain, almost groping their way, such was the darkness around them.

"Listen!"

"Help! Nick, this way, quick, or I'll go under!" came a shrill shout, only a little way above them.

They started for the spot; but before they had taken half a dozen steps once more the thunderous sound was heard; and under them the mountain quivered. As the boys were not more than human, it was only natural that they should halt until the convulsion had passed. Bob could not help clutching a spur of rock as though he feared that something dreadful was about to happen.

As the roaring noise began to die out the boys caught the cries of Spanish Joe once again. He seemed to be nearly frantic with fear, and was calling upon his cowboy crony not to forsake him in his extremity.

"It's going to tumble on me the next shake! Hurry, Nick, or I'm a goner!" they heard him pleading.

"Whatever can have happened to him?" asked Bob, awed by the exciting incidents by which they seemed to be surrounded.

"I reckon he's caught in some sort of trap, judging from his talk," Frank sent back over his shoulder; for both of them were climbing upward as rapidly as the conditions allowed.

It was no wonderful feat for Frank to make straight for the spot where the loud voice came from. He had located it; and even when Joe ceased calling for a minute or two, Frank was able to continue right on.

Apparently the cowman had heard some sound that told him of their coming. That accounted for his silence, since he was listening eagerly. And of course he fully expected that it must be Nick Jennings hastening to his assistance, perhaps with Peg at his heels. At least his words would indicate as much, when he cried again.

"Hurry, boys! There ain't any too much time. This way, right straight ahead! Oh! I'm in a hole, I tell ye. Ye ain't stopping, are ye? Come on! come on!"

They were now close to where the speaker must be located. Frank was already straining his eyes to make out his figure, so as to get some idea as to the nature of the new task that confronted them.

He presently could make out some object that squirmed and tugged between groans.

Then he knew that his first guess was probably correct. Spanish Joe, in making his way along over the rocks, had in some way managed to catch his foot in a crack, and was unable to get it out again. Perhaps the more he struggled the firmer it became fastened. And, considering the surroundings, his fright could hardly be wondered at.

So Frank crept up alongside the prisoner of the rock.

"It's my leg, Nick," cried the man, eagerly. "I can't get it loose and I've twisted and pulled till it's near jerked out of the socket. See if ye can't do somethin'. Every time she shakes, that rock up there just starts to drop down on me! If it comes I'll be smashed."

Frank knew Spanish Joe. The man from across the Rio Grande had worked on the Circle Ranch for many months, until he was discharged after being caught in the suspicious business of conveying information to the cattle rustlers.

"Wait 'till I strike a match, so I can see what things look like," Frank said.

And as the match suddenly flared up the dark-faced Spanish-American stared with astonishment into the countenance of the one who had come in answer to his frantic calls for assistance.

"You, Senor Frank?" he exclaimed.

"Sure," replied the rancher's son, as he bent over to examine the way in which the prisoner's foot had become caught.

Although the match only shone for a few seconds, Frank's quick eyes had sized up the situation.

"How is it, Senor Frank; can you get me out, camerado?" asked Joe, with a quiver in his voice.

Something of a desperado the man might be under ordinary conditions; but just then, when facing death, he proved very tame indeed.

"I reckon I can, Joe, if that tottering rock up there only holds off long enough. Let's hope it will. Now, do just what I tell you; and when I say pull, again, get busy for all you're worth!"

While Frank was talking he had been manipulating the foot of the Mexican, who had worked so long on American ranches that he had lost much of his national ways, though retaining a few of the characteristics of dress that always distinguish his kind.

Frank himself was not wasting time. He did not like the looks of that over-hanging rock any too well. It seemed to be about ready to crash down, and when it did come the result would be disastrous to anything human caught underneath; for it surely weighed many tons.

"Now, draw easily at first, and then increase gradually," Frank said. "I'll hold onto the foot, and keep it in this position. I think that's the way it first slipped into the crack!"

Spanish Joe eagerly obeyed. He groaned several times as he felt his leg hurt, but desperation lent him new determination; for if this attempt failed, as others had done, he believed that he was doomed.

Suddenly the foot came free. Joe fell over on the ground, but his last groan turned into a cry of delight. It was almost comical to see how quickly he rolled over several times, so as to get away from the danger zone.

Frank, turning, clutched his companion, and also drew him back. It was none too soon, it seemed. As if the release of Spanish Joe might have been the signal for the groaning mountain to once again take up its strange action, they felt the quiver with which all the performances. seemed to begin. Then the grumble commenced, rapidly advancing into a fearful stage, until Bob could feel himself trembling violently because the rocks under him were moving.

"There she comes!" cried Frank.

His words were drowned in a deafening crash close by. Had Peg Grant been there he must have believed that the top of the mountain had blown off, and that fire and boiling lava would immediately begin to pour down the sides. But Bob had not forgotten about that swaying rock. And he understood that it had fallen with a crash just at the spot where the three of them stood a minute before.

"What a narrow escape!" exclaimed Frank, after the clamor had in some measure died away again.

"Oh! I should say it was," echoed Bob, feeling quite weak as he realized what must have happened to them had they not gotten away in time.

"How about your leg, Joe; can you walk?" asked Frank, turning to the cowman, who was scrambling to his feet close by.

"Seems like I can, Senor Frank. But it was a close call for Spanish Joe. Only for you coming, where would I be right now? Let us get away from here!" exclaimed the man, limping around as he tried his crippled limb.

"You are free to go, if you want, Joe," remarked Frank; "but Bob and myself mean to stick it out. We came here to learn the cause of all this racket, and we'll do it, or know the reason why."

"Excuse me, companero, I know when I have had enough. This mountain is surely bewitched. There must be an evil spirit living inside. Do I not know it? And even the door is guarded by demons that spring at a man and tear him. My clothes, once so handsome, Senors, are torn into tatters, just because Joe, he was fool enough to step into that black opening above!"

Frank started as he heard the Mexican say this. It seemed to him that possibly here was a clue worth following up.

"Tell us what you mean, Joe," he asked, quickly. "What black opening did you try to enter; and what happened to you, amigo? We have done you a service, saved your life, perhaps. In return, tell us this."

"It is little enough, Senor Frank. Up above, not more than seventy feet from here, lies a hole in the ground. I was looking for shelter from the storm, because Senor Peg wished it. I entered. Hardly had I taken ten steps than something flew at me. I think it was a demon, for it had sharp claws, and I thought I could smell brimstone and sulphur. Just then the mountain yawned, and what with the terrible noise, and having to fight off that unseen enemy, I climbed out of there fast, but with all my fine clothes ruined. That was why I came down the side of the mountain in such haste that I caught my foot. I thought that fury was chasing me. Nothing in this wide world could tempt Spanish Joe to go back there. The storm, it is a joke besides that terror of the darkness!"

If he expected to alarm Frank, the Mexican cowman mistook the character of the boy. Frank believed that the fellow's fears had made him imagine more than half of what he declared had happened to him.

"Well, we leave you here, then, Joe," the boy remarked, sturdily; "because we're going to find that cave, and see what lies inside it. If you want to come along, all right; if not adios!"

He turned and started to climb, Bob tagging at his heels. But Spanish Joe could not bring himself to accept the invitation. He looked after the disappearing figures of the two saddle boys, and shook his head.

"No, not for Joe," he muttered. "He knows when he has had enough. Money could not drive him to enter there again, and meet that unseen thing. Out here the danger can be understood, but Joe he takes off his hat to the young Senors; for grit they surely possess. Adios, Senor Frank; but I doubt much whether we ever meet again."

But staunch of heart, Frank was leading the way upward, determined to accept of the challenge which the cowboy's due seemed to throw at his feet.

CHAPTER XVI - THE VENT HOLE IN THE WALL
The way grew rougher with every yard they traversed. How Spanish Joe had come dashing down over this ground at headlong speed without breaking his neck was a puzzle.

Frank was feeling his way along carefully when he heard Bob call his name. The rattle of falling shale at the same time gave him a pretty strong suspicion as to what had happened.

"Hello! what's the matter Bob?" he cried.

"I slipped, and fell over the edge of some sort of place here," came back the answer. "Luckily I've managed to get hold of a rock and stopped my tumble. But don't waste any time lending me a hand, Frank, because it seems to me I feel the thing move. If another quake comes it'll let me drop; and perhaps the ground may be a full dozen feet below."

By this time Frank had reached the edge of the drop. He remembered skirting it in climbing upward just a minute before; but had been more successful about doing so than Bob, who was less accustomed to this kind of work.

Frank again had recourse to his handy match-safe. Leaning over he struck a match on the face of the rock. Immediately he drew a quick breath. It was not because he could see the face of his chum only a couple of feet away, as the latter clung to a spur of rocks; it was something else that thrilled him.

As far down as his eyes could see there was only a black void! Instead of the simple dozen feet mentioned by Bob, the yawning precipice extended perhaps a full hundred feet downward!

But there was no need of telling Bob that it might alarm the boy and cause him to weaken, so that his grip would give way.

Frank was quick to understand what must be done. He could just touch the hand of his chum by bending far down; but that was not enough. Instantly he wrapped one leg about a sturdy, if dwarfed, little cedar that chanced to grow at that very spot, as if designed for the very purpose to which he was putting it. Then he was able to thrust himself still further down the face of the wall.

"Take hold, and grip like iron, Bob," he managed to say.

He felt the other obeying him, and thus they caught hold of hands.

"Now, try and dig your toes into the face of the wall if you can," Frank went on, calmly, so far as Bob could know. "It'll help me get you up. Climb over me. I've got a leg around a cedar, and nothing can break away. Now!"

"Say, perhaps you'd better let me drop down." said Bob, thinking his comrade was going to unnecessary trouble in order to save him from a little jolt.

"Climb, I tell you!" snapped Frank.

"Oh! all right, Frank, if you say so," and Bob started to obey.

Fortunately he was an agile lad, and a very fair climber, for the task which he had set himself was no ordinary one. But, by wriggling more or less, Bob managed to finally get a grip on the cedar. After that it was easy work; and having succeeded in reaching solid ground himself, he aided the almost exhausted Frank to draw back.

"Whew! that was some work, now, and all because I was so silly as to slip over the edge of that little hole!" remarked Bob, as though disgusted with himself.

"Look here," said his chum; "lean over carefully, while I drop this match down."

As he struck the match, and then cast it from him it went downward twenty, thirty, forty feet before it was extinguished.

"Ugh!" shuddered Bob, "why, it must be all of a thousand feet down to the bottom, Frank! It scares me just to think of the narrow escape I had."

"Well, I reckon it's all of one hundred feet," replied Frank; "and that's enough to settle a fellow. But let's lie back here, and get our breath a bit before going on up. The cave can't be far off now, if what Joe said is so."

Both of the boys were panting after their unusual exertion, and Bob was glad of a chance to rest for even a brief time. Besides, another burst of thunder was starting in, and he fancied that it was louder than any that had gone before; just as if they might be drawing closer to the place from whence all this clamor came.

The cave that Spanish Joe had found and entered—could it have anything to do with the mystery of the mountain? Frank seemed to think so, and was bent upon ascertaining the facts.

"Listen to that, Frank?" shouted the Kentucky lad in the ear of his mate, while the racket was at its height. "I can hear rocks dropping all around, just like the one did where Joe was grabbed by the leg. Do you think this always happens when the old mountain breaks loose; or is this an extra big celebration?"

"I was trying to get that myself, Bob," admitted Frank; "but we can only guess at it, because you see, nobody's ever been up here when the thunder was rocking the whole range, and so we don't know. But, honest, now, I'm of the opinion this happens only once in a great while; else the mountain would have been racked to pieces long ago."

"And just to think, we had the nerve to come here at a time when it was bound to do its worst," said Bob.

"Glad of it," Frank immediately returned. "It gives us a better chance to learn a few things worth while. I always did like to be in where the roping was fastest. Are you feeling better, Bob?"

"Oh! yes, I reckon I'm all right now," returned the other, rising.

"Ready to go on, then?" continued Frank.

"Try me, that's all. If I turn tail and run, don't ever speak to me again," came the steady, but not boastful, answer.

"Good boy! All right, let's be off again; and be mighty careful how you move. There may be more of those drops lying around loose. And next time you mightn't be so lucky about grabbing a spur of rock."

"That's so, Frank. Wow! but it makes me shiver to even think of it. Talk about Joe's narrow squeak, it wasn't any worse than mine," and Bob started to crawl after his better-trained chum.

Two more evidences came to them of the violence of the unseen force that was making Thunder Mountain shake, before Frank stopped to let his chum reach his side, so that he might exchange a few sentences.

"Looks like that might be the hole ahead," he ventured.

"I can see something that seems blacker than the night itself; is that what you mean, Frank?" asked Bob.

"Yes," his chum continued. "When Joe pointed up this way I took note of just the line, and followed it closely. That was why we came so near the precipice. And if that is the opening to the cave, we want to lie here and listen."

"Why, do you really believe the racket comes out of that hole?" demanded Bob, astonished at the very idea of such a thing.

"Wait and see," replied the other, confidently. "In the meantime, here's our opportunity to pick up a few candles that will come in handy."

They had come to a halt directly under a tree; and Bob had already discovered that the ground was thickly strewn with broken branches. Some of these were apt to be fat with the inflammable gum that exudes from certain species of cedar, and would, as Frank said, make splendid torches.

Frank was already on his hands and knees searching for suitable ones; and as Bob grasped the idea he, too, set to work.

"I have four already; how do you stand?" asked Frank, presently.

"Just as many—no, here's the fifth one, and the best of the lot," came the reply from the Kentucky lad, who went into everything with ardor and enthusiasm.

"That ought to do for us," Frank went on. "And now, listen for all you're worth, because the war is on again!"

Lying there, Bob heard what seemed to be the first signal. It was as though some giant hand had tapped the solid rock with his club. Then faster came the blows, and more and more did the din increase, until it was fairly deafening. Only for his intense eagerness to hear every sound Bob might have been tempted to thrust his fingers into his ears in order to shut out the awful clamor.

To him it seemed as though a thousand anvils were being beaten in chorus, with a few other minor chords thrown in for good measure.

And what interested Bob most of all, as he crouched there listening, was the fact that all this dreadful noise seemed to be coming directly from the spot where his comrade had pointed out as the opening of a cave.

There was not the faintest trace of lightning accompanying the manifestation; and this proved, beyond all question of dispute, that the mystery connected with Thunder Mountain had nothing to do with an electrical storm. Possibly the observing Indians had many years ago discovered this same thing; and it had strengthened their belief that the great Manitou spoke to his red children through the voice of the wonderful mountain.

It took longer, this time, for the noise to die away; just as though, whatever its cause, there was increasing reluctance to subside again.

"That was a screamer, sure enough!" said Frank, when he could make himself heard above the declining roar.

"And Bob, you noticed, didn't you, that it seemed to come right out of that hole? All right, it begins to look now as if we were Johnny on the spot, if we've got the nerve to push things. Somewhere in there, Bob, lies the explanation of the mystery. Do we take the dare; or stay out here and wait till the fuss is over before entering?"

Bob possibly swallowed hard before replying. It was no easy thing for him to say the words that would thrust them up against so terrible a thing as this unknown peril awaiting them in the gloom of that crack of the great mountain. But his hesitation was brief. In fact, he only wanted to catch his breath, shut his teeth hard together, and summon his Kentucky blood.

"It's a go, Frank!" he said, with determination in his voice; "the chance may never come to us again. Let's go in, and discover for ourselves the secrets of the Indian god they say is guarding Thunder Mountain. I'm ready, so lead on!"

CHAPTER XVII - FRANK HOLDS THE HOT STICK
"No hurry," said Frank, who realized that his comrade was worked up to a high pitch of excitement, and thought it the part of wisdom to do something in order to quiet Bob's nerves.

"But if we've got to try it, Frank, what's the use of waiting?" demanded the impetuous one.

"Well, for one thing, we don't want to be carrying these candles without making use of one, you see," replied Frank, who was again getting out his handy matchsafe.

"What a silly I am, to be sure," laughed Bob; "why of course we want a light, if we're going to invade that den of the demon Joe told us about. What do you think about that yarn, Frank; did he meet up with anything; or was he just scared out of his seven senses? Perhaps there's a strong current of air in that place, along with the noise, and that took hold of Joe."

"Well, I wouldn't like to say," replied the other, cautiously. "This I do know, and I saw it with my own eyes. Joe's fancy Mexican jacket was torn nearly into ribbons; and I could see marks of blood, too."

"Whew! you don't say?" ejaculated Bob. "Then something did get hold of him; didn't it, Frank?"

"Looked like it," admitted the other.

"His jacket was torn into ribbons, you said—then I reckon whatever tackled Joe had pretty sharp claws, Frank!" Bob continued.

"I thought as much myself. In other words, Bob, the man was attacked by some wild beast that has its den in yonder. In the dark, with all that terrible noise going on, Joe thought it was a monster from the underworld. If he keeps on telling that story, ten to one, after a while, he'll vow it had eyes of fire, and a tongue of blue flame. Joe was frightened half to death, and a man in that condition gets to seeing things that never did exist. Now, how's that?"

While speaking Frank had managed to light one of the cedar torches he carried. The wood burned readily, and with persistence. It would make a good substitute for a lantern. Indeed, Bob was enthusiastic over the success attending his chum's effort.

"Couldn't be beat, that's what!" he cried.

"Well, there's nothing to keep us now," declared Frank.

"But what can I do?" asked the other. "Want me to light a torch too, Frank?"

"No, one ought to be enough. You fall in just behind me, and Bob, perhaps you'd better keep your gun handy."

"Oh! you're thinking now of that demon Joe told about, eh, Frank?"

"Perhaps. If it jumps out at us give a center shot, if you can," the saddle boy advised, as he led the way forward toward the black spot which they had guessed must be the cave entrance spoken of by Spanish Joe.

They were quickly at the wall, and had no difficulty in learning that, just as they had guessed, the yawning hole was there. Frank, without the slightest hesitation, stepped through the opening. Bob did likewise, holding his gun in readiness for immediate use.

The light of the blazing torch lighted up the interior. They could see that, so far, there was nothing remarkable about the cave, save that it seemed to stretch away into dim distance, with various twists and curves.

"What are you sniffing about, Frank?" demanded Bob, who, in the silence, heard what his comrade was doing.

"I think I scent something, that's all," replied the other.

"Not brimstone and sulphur, I hope?" cried Bob.

"Well, hardly," chuckled the other. "In fact, it seemed to me that it was only such an odor as you can always detect around the den of a wild beast!"

"Glory! then Joe didn't dream it, after all; and there may be an old grizzly in this cave!" ejaculated Bob.

"Not a grizzly," declared Frank, quickly. "If anything, I think it must be a panther. But he may have left after attacking Joe, so that we'll have no trouble with the beast."

"I hope so," Bob remarked, as he strove to look seven ways at once, keeping his finger on the trigger of his repeating rifle all the while.

They were now advancing into the cave.

"Do you think Joe had a torch?" asked Bob, as a new idea came to him.

"Well, he isn't the man to take chances, and he couldn't help but see the good torch material at the door yonder. But the beast may have jumped on his back, so he lost his torch before he could see. And then he fought in the dark. Joe has always been known as a hard fighter, and with his knife I reckon he could give a good account of himself. Hello! see here!"

Bob started when his chum gave this sudden exclamation.

"Oh! I thought you had sighted the panther!" he gasped as he lowered the gun, which had, perhaps through mere instinct, gone up to his shoulder.

Frank was bending down. He held his torch in such a fashion that he could see better; and he appeared to be examining something on the rock.

"What is it?" asked Bob, eagerly; "footprints?"

"No, just a little spot of blood," came the reply.

"Fresh, too, I can see," declared the tenderfoot, as he looked. "Does that mean this is the exact place where Joe had his little circus, Frank?"

"I reckon it is," replied the other.

"Then if that beast hasn't cleared out we might run across him before long!" remarked Bob.

"Oh!"

Frank gave utterance to this cry. He had seen some object flash through the air, and knew it could be nothing else than the lithe body of a panther making a leap.

The animal must have had a place of hiding close by, from which it had probably jumped upon the shoulders of Spanish Joe, and now sought to repeat that act.

Bob was struck by the descending body of the animal; and while he did not suffer serious injury from the blow, it jarred his arm, and caused him to drop his rifle. He instantly leaped forward to recover the weapon, but through chance picked it up by the end of the barrel.

The panther had recovered, and was crouching as though to repeat its jump. Only a yard lay between the fierce beast and the boy who held the gun. Perhaps a veteran hunter would have proceeded to reverse the weapon, and discharge it without taking the trouble to throw the stock to his shoulder. But Bob did not dream that he would be given enough time for all this.

He saw the beast there close to him, and his first thought was to poke the butt of the rifle directly at its head, striking with all his force. The blow landed heavily, but as the beast gave way, Bob lost his balance, and fell directly toward the panther.

It looked as though the boy might be in for a terrible clawing, and so it must have turned out had he been alone. But he had a comrade close at hand who did not hesitate an instant about taking part in the affair.

Frank could not get at his gun, which was slung across his back; but he knew he had a better weapon than that in hand. Wild animals dread fire above all things; and every lad brought up on the prairie knows this fact.

Suddenly Frank brought down his torch upon the beast with all the force he was capable of using. There was a snarl and the animal jumped aside, evidently not fancying the closeness of the stick that burned. The lad again raised his torch, but evidently the panther had already endured quite enough of the conflict. It was bad enough fighting two human beings at a time; but when one of them persisted in belaboring him with such a hot weapon he drew the line.

And so with a parting snarl, that was full of defiance and venom, the panther sprang back out of sight, departing just as silently as he had come.

"That's just like the luck," grumbled Bob.

"What's the matter now?" asked Frank, looking sharply to make sure that the treacherous beast did not sneak back in order to attack them from another quarter.

"Why, I'd just got my gun slewed around, and was ready to fire when he skipped out. I'd liked to have bagged him, I reckon. A grizzly and a panther, all on one trip, would be worth talking about."

"Oh! I don't know that you'd have been so very proud over it," observed Frank.

Bob looked at him as he said this.

"Now, you've got some reason for making such a remark as that," he observed.

"Perhaps I have," answered his chum, nodding wisely.

"Then out with it, Frank, and don't keep me wondering. Besides, I reckon that we'll have another bellow from the old mountain at any time now."

"I guess you didn't notice something queer about that animal, then, Bob?"

"About the panther, you mean?" came the reply. "Well, to tell the honest truth I was knocked all in a heap when I missed hitting him, and didn't have time to bother looking at him close enough to see anything. But what was so funny about him, Frank? Did he have only one eye; or was he three-legged?"

"Oh! nothing of that sort," declared the other; "so far as I know he is in possession of all his members. It was about his neck."

"What about it? Did he have a rubber neck, you mean?" demanded Bob, trying to be a little humorous so as to conceal the fact of his excitement.

"The beast had a collar on!" Frank remarked, positively; "and that means he must be the pet of somebody who has a hiding place in this cave!"

CHAPTER XVIII - A GUESS THAT HIT THE BULLSEYE
As Frank made this astonishing declaration his chum looked blankly at him, the information having evidently surprised him not a little.

"A tame panther, you mean, Frank?" he exclaimed, weakly.

"That's just what I'm hinting at," replied the other, positively.

"With a collar around his neck, too?" murmured Bob.

"Yes. I saw it as plain as I see you now," Frank went on. "It was when I jumped forward, and gave him the first crack that made him fall away in a hurry. A collar that was broad and stout. Why, Bob, when he threw back his head to avoid punishment I could even see where a chain could be fastened, and the animal kept in confinement."

"Whew! but he acted like a wild one, all right," protested Bob.

"He sure did, Bob; but that was because he had already been stirred up by the fight with Spanish Joe. I reckon the cowboy must have give him a few jabs with that handy knife he owns. Anyhow, the panther was spoiling for a scrap, and didn't care a cent how many there were."

"That was before you gave him his finish with that fire-stick, Frank. Didn't that knock the old chap silly, though? Why, it took all the fight out of him, for a fact. He was the tame panther all right when he ran away, with his tail between his legs. Think he'll tackle us again?"

"No telling; but I don't believe the beast cares much for running against my torch again. It might pay for both of us, though, to keep on the watch," Frank replied, always on the side of caution.

"But I say, Frank, is the fact that he's private property going to make any difference; that is, do I shoot straight if I get the chance again?"

"Well, I say yes," answered the other. "Given half a chance and he'd maul us the worst way. No matter who's property he may be, I'd advise him to keep clear of Haywood and Archer. They're marked, dangerous—hands and claws off, but come along, Bob; let's be moving."

"Wait, there it comes again, Frank. Don't you think we'd better lie down till the worst is over?" ventured Bob, as he caught the opening notes of the mighty anvil chorus that would soon be in full blast.

"Well, now, perhaps that wouldn't be a bad idea, Bob. Suppose we do stretch out here, you facing one way and I another."

The two crouched there. Frank had thrust the torch into a crevice, for he wanted the use of both hands in gripping his rifle. If the wild beast guardian of the cave tried to attack them again, he felt that he would like to be in a position to shoot.

"Feel the wind, will you?" called Bob, as the sounds mounted higher and higher.

"I'm afraid our torch is going to be blown out," Frank replied, pointing to the flaring light, which was being hard pressed by the suction that seemed to rush through the cave, heading always toward the mouth.

"Say, Frank, the air feels wet!" shouted Bob, while the racket was at its height.

Of course this was no special news to Frank. He, too, had noticed the same thing, and mentally commented on it. And as it was in line with certain suspicions which he already entertained, he had felt amply repaid for taking such hazards in plunging into that black cave.

Then suddenly an extra strong blast put the torch out.

"Wow! there she goes, Frank! What will we do now?" yelled Bob, of course feeling a new uneasiness because of the intense darkness, the presence of an angry animal near by, and the general air of mystery that hung over the scene.

"Nothing. Just wait till the storm blows by; and then we'll light up again," was what Frank shouted back at him.

Already it was diminishing. Like the receding waves of the great ocean the uproar died down, growing fainter with each pulsation.

And finally there came again the silence that in one way was almost as dreadful as the clamor; during which Frank proceeded to light the torch again, though not without some difficulty.

"Frank, you felt that wet sensation, like fine spray, didn't you?" demanded Bob, as soon as he could speak with comfort. "Why, touch your face right now; and you'll find it moist. Whatever can it mean?"

"I think I know," Frank said, slowly. "I suspected it before, and this seems to make it look more than ever that way."

"Do you mean that you've guessed what makes all that frightful noise?" asked Bob, astonished.

"I believe I have," came the reply.

"And it has to do with this misty feeling in the air; has it?" continued the Kentucky boy.

"If my idea proves the right one, and I'm bound to find out before I go away from this place, it's got everything to do with it, Bob."

"Where there's smoke you'll find fire; and where there's mist I reckon water can be looked for," remarked Bob, quickly.

"Just so. Now Bob, have you ever been up in the Yellowstone Park region?"

"I can't say that I have, Frank."

"Then you see I've got the advantage over you; and that's what gave me a point in the game. Because I've stood and watched Old Faithful and the other great geysers play every half hour or so," Frank went on, as they slowly advanced into the passage which seemed possibly to act as one of many funnels through which the tremendous roaring sound was carried to the outside world.

"Geysers!" cried Bob. "Oh! now I get onto what you mean. You think, then, that in the heart of Thunder Mountain a giant geyser spouts every once in a while; and that as the water is dashed against the rocky walls it makes the ground shake. Is that it, Frank?"

"Yes," replied the other, "and the noise is so like thunder that when it is forced out through several queer, funnel-shaped openings like this one, it has puzzled the Indians for hundreds of years. Bob, more than that, I believe that every once in so many years, when an extra convulsion shakes things up here, the water bursts out through some passage, and rushes down that barranca in a wave perhaps twenty feet high."

"But they call it a cloud burst, Frank," suggested Bob.

"I know they do, but still I stick to my idea," Frank went on.

"And this promises to be an extra strong outburst. Nick said so anyhow; didn't he, Frank?" Bob queried, a new anxiety in his tone.

"Just what he did. You're wondering now, that if what I said is true, whether this passage right here is one of those through which all that water dashes, on its way to the rocky barranca?"

"Yes, that's the truth. How about it? Could you see any signs here to tell about that?"

"I suppose I could if they were here, but I don't discover any. Besides, I thought of that before we entered, and I give you my word that I don't believe any big volume of water ever went out through here. It couldn't do it and not leave some sign behind."

Bob heaved a big sigh.

"Well, I'm right glad to hear you say that, Frank, seeing that we're so far in now, we wouldn't have any chance to escape if it came along. Whew! I wouldn't like being carried through here, and shot out of the muzzle like a bullet. But seems to me the place is getting bigger right along, Frank."

"Just what it is. Now you can see how like the neck of a bottle the cave is; and I think that has had a heap to do with the way that thunder noise gets loose. Why, they say that some days, or nights, it can be heard more than twelve miles away. I've seen Navajo Injuns drop flat on their faces, and lie there all the time we could hear the distant thunder in a clear sky over our way."

"But is it possible that some hermit is living in this cave?" asked Bob, thinking that it must be a queer sort of person who would remain where he must listen to such fearful sounds every once in a while.

"I told you to notice when we heard the noise the first time," Frank went on; "while we were in camp on the plain, that the night was clear, and the wind almost in the Southeast. Well, I made sure that it was in exactly the same quarter tonight when we were climbing the mountain. That means something, Bob."

"To you; but to me it's only a blank," admitted the tenderfoot, regretfully.

"I fancy that the direction of the wind has something to do with the working of this queer old geyser in the heart of Thunder Mountain. It only rears up when the wind is in the Southeast, as it is now. But say, you said something about a hermit just now?"

"I only said I thought it strange a fellow could live here through all the racket, year in and year out, just to get away from his kind," Bob remarked.

At that Frank laughed.

"But what if he had a big object in it, Bob? What if some daring prospector, taking his life in his hands, had plunged into one of these caves of the winds, this one right here, for instance, and struck it rich. Gold will make men do nearly anything. I've seen 'em go crazy over finding a nugget, or yellow sand in their pan. Don't you see what I mean, Bob? Have you forgotten little Lopez, and how frightened he looked when we spoke about keeping him company?"

Bob uttered a cry that might stand for either astonishment or delight, perhaps both.

"Frank, it just takes you to see through the mill stone, even if it hasn't got any hole in it," he declared. "I understand what you mean now. Little Lopez has been coming here for a year or more, always bringing supplies. Perhaps he carries away the gold dust the miner has gathered in that time, and no one the wiser. It has all been a dead secret. And the terror of the Indians for this haunted mountain, as well as the way the cowboys leave it alone, has helped this bold miner. Frank, your shot hit the bull's eye, and who knows but what we may be on the way to find out the truth right now?"

CHAPTER XIX - THE WORKING OF THE GOLD LODE
"Now you know what I think, Bob; but after all I may be on the wrong track," said Frank, after his companion had expressed himself so freely.

"Of course," Bob went on saying; "but all the same I don't think you are. After you've shown me, it's just like that egg Columbus stood up on end, after cracking the shell a bit—as easy as jumping off a log, once you know how. But now we're in here, I hope we find out the truth soon, don't you, Frank?"

"Honest now, Bob, I don't care how quick it comes," replied his chum, frankly.

"This is a terrible place, with panthers hanging around, and that thunder banging to beat the band every minute or so. I'm only wondering, Frank, what would become of us if that old geyser should take a notion to explode suddenly, and flush every avenue out of the heart of the mountain."

"Don't mention it, please," Frank answered, with a shrug of his shoulders. "If such a thing happened we wouldn't know what hurt us, I'm afraid."

"Huh! some consolation in that, anyhow," grunted Bob. "If a fellow has to go up against the buzz-saw, the sooner it's over the better."

"But nothing of the kind is going to happen," Frank insisted; "and you want to get the idea clean out of your head. We're making fine progress, and any minute, now, I expect we'll run across the party who occupies this cave."

"But every time the blowout comes, away goes our light; and another spouting is about due now, I reckon," ventured Bob.

"I've got an idea I may be able to save the torch," Frank remarked. "I don't know just how it's going to work; but anyhow the thing's worth trying."

"Then here comes your chance," his chum called.

As before, the grumbling began with an earth tremor. It was as though some giant, whose mighty limbs were shackled, was trying to break loose; and in so doing made things near him tremble.

Rapidly the noise increased, until it became terrifying. Bob had dropped flat, and cowered there, almost holding his breath with awe. Not so Frank, in whose care was the burning torch.

He had whipped off his coat at the first sign of the disturbance. This he hastily arranged so as to partially protect the burning brand. Of course in such a violent draught the suction was enough to make the flame flare and flicker until at one time Frank feared it could not stand the struggle. But just as he was ready to give up the attempt, the furious wind seemed to slacken.

Bob raised his head to see the torch still burning, and it soon recovered its full capacity for illumination.

"Bully!" he exclaimed, beginning to rise from his position of hugging the rocky floor of the cave; "you did it that time, Frank. But hurry up, and get your coat on. Gee! but this air feels chilly in here, and damp too!"

Frank had found that out for himself. He was even shivering; and made haste to don his jacket.

"Now let's be moving while we have the chance," he said. "I hope that before the next rush comes we'll sight what we're looking for."

Perhaps his sharp eyes had discovered certain signs that told him they were near the working part of the cave. Men cannot mine a lode of precious ore without leaving many traces behind to tell of their presence. And the stream of clear water that passed across the place seemed to offer a splendid chance for panning any golden treasure that might be found in the shape of soft quartz.

Now and again Frank would place the torch behind him. Bob wondered what he did this for until he saw his chum bending his head forward as though endeavoring to discover what lay ahead. Then he realized that the light blinded him while it was before his eyes, and he sought to avoid the trouble in this way.

"There's another bend ahead, Bob," Frank remarked, presently.

"Yes?" said the Kentucky lad, eagerly, suspecting what was coming.

"And I can see signs of light at the curve," Frank went on.

"Hurrah! Everything seems to be coming out just as you figured, Frank. When I get back to the ranch I'm going to write to the president, proposing that he put you in charge of the weather bureau. Every old farmer will know then when to look out for storms."

"Well, we may be in for one now," observed Frank, dryly.

"Look here, you mean something by that remark," Bob cried. "Do you expect we're going to have a peck of trouble with these miners?"

"I don't know. It all depends on what sort of men they are," Frank replied.

"But we wont let 'em drive us out of here until we know all about that geyser, if there is such a thing; will we, Frank?"

"Well, I reckon it won't take a great deal of driving to get both of us out; but of course I do hope we'll learn something about the real cause of all this awful racket. Are you ready to turn the bend, Bob?"

"Sure," and the Kentucky boy ranged alongside his chum, by this movement plainly indicating that he did not mean to let Frank take any more risk than he himself was ready and willing to assume.

No sooner had the two saddle boys turned the bend in the passage than they saw a singular spectacle.

A couple of lanterns were hung from wooden pins driven in the wall. These lights, being protected by glass, could safely resist the tremendous suction that accompanied each successive convulsion, as the rocks trembled, and the air swept through toward the outer exit.

Only two figures were in sight—a man and a boy. In the latter they recognized little Lopez, the hero of the adventure with the grizzly; and if their suspicions proved true also, the little girl whom Bob had rescued from the anger of the bully, Peg Grant.

The man was a rugged specimen, with long, iron-gray hair. Frank recognized him as Lemuel Smith, whom he remembered to have met several years ago when in a border town with his father.

Smith had always been a rolling stone, a prospector who spent his time in hunting new strikes, and who lived year in and year out in the wild hope of sometime or other hitting it rich. Frank suddenly remembered that Smith had had one daughter, who, he believed, had married a Mexican. And that would make the little girl his grand-daughter.

"They're packing up," remarked Frank, whose quick eye had noticed the fact.

"Perhaps he's done his work here, and means to vamoose the ranch," Bob suggested. "Then again," he added, as another thought raced through his brain, "maybe he doesn't altogether like the looks of things, and wants to get out of this rat-hole before it all goes to smash. He must have been here a long time, and ought to know something about that geyser, Frank."

"There, they have discovered us!" the other exclaimed, as he waved his torch in what he meant to be a friendly way, and kept on advancing.

"Whew! I just hope he doesn't try to fire on us," muttered Bob, who was nervously fingering his rifle, and wondering how dreadful it would feel to be compelled, even in self-defense, to shoot at a fellow human being.

But the old miner held up both hands. It was the Indian peace sign, understood by every savage tribe on the face of the globe.

Quickly the two boys hurried forward, for the first symptoms of another burst of thunder and furious wind began to make themselves felt.

This time Frank did not take off any of his outer clothing in order to protect the torch. He had noted that the old miner had two lanterns, and he expected to borrow one, if necessary.

Of course his torch was snuffed out while the furious blast swept by. Bob noted that each successive outbreak tried to beat the record, and he was wondering just when the limit of endurance might be reached.

The old miner, after the roar had subsided, offered the two boys his hand.

"How are ye, young Haywood?" he asked, recognizing Frank. "I heard about what you done for my little gal here, Inez Lopez, whose father was once a cowboy on the Circle ranch, and lost his life in a fight with some of his countrymen when they quarreled. I'm glad to see you. Found a nice little pocket here a year or so back. Kept it on the quiet; and the gal, playing the part of a boy, has been fetchin' me supplies once in two months, an' takin' away the dust I winnowed. Pocket's played out now, but I reckons as how I've got plenty. 'Sides, I just don't like the way things is agoin' here. That spoutin' geyser that rises up inside the old mountain every once in a while acts like it meant to break loose. Never saw it carry on that bad before; and we're just ready to cut and run, leavin' most of the truck behind. What brings ye here, Frank?"

So Frank had to explain in a few words, while the old miner looked admiringly at the boys, and grinned.

"I admire your nerve, young fellers," he declared, at the conclusion of the explanation. "And, Frank, ye guessed the true facts, blessed if ye didn't! I got onto the same by accident. Fell in through a hole, and just had to creep along this passage to the end. Then havin' guessed what made the roar, I wondered if so be I could find any stuff in here. So I took a lot of wood along, and made my discovery."

"And you say you're bound out now?" asked Frank.

"That's what we are, little Lopez and me; and we can't get to the open any too soon, either, to please both of us," Smith replied, shouldering his pack.

"Oh! say, Mr. Smith," cried Bob, "have you lost a pet that wears a collar?"

"Meanin' my pet painter, Nero, I take it," replied the miner. "I raised him up from a cub, and he's as fond of me as my dog. But he's gone somewhar. We ain't seen him for hours, and like as not the critter knowed it was gettin' dangerous in here. Trust animal sense for that. But wait till this next whoop gets by, and then we'll make for the door. Here's hopin' we'll all be smart enough to get to the open. Bend your backs to the wind, boys; ye wont feel it so much then," and all of them carried out his instructions as, with a rapidly rising roar, the spouting geyser that played in the heart of Thunder Mountain again started to break loose.

CHAPTER XX - TRAPPED IN A CANYON
Once the little party started toward the opening, they made rapid progress. The turmoil was at their backs, for one thing. Then, again, each time the noise broke forth it seemed so much worse than before, that every one felt anxious to get beyond the portal of the cave before the climax came.

And when finally this opened before them, Bob drew a long sigh of relief.

"Glory!" he burst out. "Maybe I'm not glad we've arrived! But I reckon your pet, Nero, has skipped, Mr. Smith, or he would have come out when you and the little Lopez passed. Sorry for you; but perhaps it's just as well for the rest of us; because you see the fellow might have had it in for us."

So they passed into the outer air.

"Seems pretty much the same as when we left," remarked Bob, as he stared up at the dark sky against which they could see the rocky crown of Thunder Mountain dimly outlined.

"Why, what did you expect?" asked Frank.

"I didn't know but what some of that thunder might be the genuine article, and we'd find the rain coming down to beat the band. Glad it isn't, because we want to get down from this to where our horses are."

"Little Lopez has our burro and bronco quartered in a small ravine where they can't escape," remarked the old miner, as he handed Frank the lantern he had been carrying, the girl taking the other.

"But would they be in danger in case of a storm-burst?" asked Bob.

"We counted on that when we arranged the exit by piling up stones," came the ready reply. "There is little danger, for the ravine has high banks, where they are able to go in case of hard luck. But now we have a tough job ahead, boys. Mind your steps all the time. A slip might cost you dear."

"Reckon I know that, Mr. Smith," remarked Bob. "I've had experience, you see. And only for the helping hand of my trusty chum here, I'm afraid I wouldn't be alive right now. Oh! I'll be careful, I give you my word."

And he was, seldom putting a foot forward without first making certain how the land lay below, and that the stone he expected to step upon was firmly planted.

They were making fair progress when the old miner called out:

"We've reached the parting of the ways, boys. Little Lopez and me have to turn to the left here, so as to hit the place whar our animals are cached. You keep right on. Wish you the best of luck, Frank. Hope to see you some time at my shack. And I tell ye, son, thar's agoin' to be a ranch soon, with hosses for the gal, an' an ottermobile for the old couple. I struck it rich in this here lode and pocket. So-long, boys!"

He shook hands with each of them, as did also the girl, whose astonishing nerve, when facing that terrible grizzly, Bob would never forget. Then they separated. And a minute afterward there came another of those fearful shocks that seemed to make the very rocks of the mountain quiver, as the pent-up force of that great geyser beat against its prison walls.

"We must be getting down somewhere near the canyon, aren't we, Frank?" asked Bob, after they had been a long while descending the side of the rough mountain.

"That's right, we are," replied his chum. "And I've been wondering whether we ought to take the chances of going along that barranca just now."

"It's the shortest way to where we left our horses, I reckon," remarked Bob.

"And the only way we happen to know of," Frank went on; "but if that flood just happened to break loose while we were between those high walls we'd have an experience that would be fierce, let me tell you!"

"But then, it may not come for hours yet?" remonstrated the Kentucky boy, who was anxious to be once again in the saddle, and leaving the haunted mountain well in the rear.

"Oh! for that matter, it may not come at all," Frank went on. "Although Smith did say he really believed that this was going to finish the old geyser, which he believed empties into one of those queer underground rivers we know are to be found all through the Southwest. And Smith ought to know something about it, for he's been watching this business a whole year now, from close quarters."

"I'm willing to take the chances, if you are," declared Bob.

Frank was not at all surprised when he heard his chum say this. He knew that the Kentucky boy was apt to be rash; and that meant more caution on his part, in order to counteract this spirit, that might border on recklessness.

A quick decision had to be made, for delay could do them no good. He cast one last look up at the dark heavens, as though questioning how long they might remain mute.

"All right, we'll risk it, Bob," he declared, suddenly; for even if the worst came Frank believed he knew how to avoid a calamity.

"Good for you, Frank!" exclaimed the other; but Bob understood the nature of the risk they were taking, and he was not quite so buoyant as usual.

The canyon was just below them now, and fortunately there seemed a narrow bit of slope down which they might make their way. This they did with considerable difficulty. Indeed, Bob was secretly sorry, after they had started, that he had urged his companion to take this step; but there could be no going back now.

Finally, after several slips, and more or less excitement, they managed to gain the bottom of the canyon.

"Say, I don't remember this place any, Frank!" declared Bob, as he stared about him as well as he could by the flickering light of the lantern which his companion still carried, and which had served them well through all their descent.

"For a mighty good reason," replied Frank. "We were never here before."

"But this is the same old turtle crawl, isn't it; the barranca we followed up to the time we climbed the slope with our horses?" Bob asked.

"It sure is, only a lot farther along, Bob. Notice how the walls tower upon each side. I knew something about this, and that was why I held back when you wanted to come down here. But let's hurry. We've got to make that slope as soon as we can."

"Supposing the thing broke loose before we could find any place to climb out?" suggested Bob, looking up again with awe, as he stumbled along after his chum, who was already hurrying down the canyon.

"We might try to outrun it first," Frank replied, over his shoulder.

"And if that didn't work, what then?" the other continued.

"Nothing left but to climb the walls, Bob."

"Whew! then perhaps I'd better be keeping an eye out as we go along, and see how the land lies?" suggested the boy from Kentucky.

"A good idea, Bob. Just notice where the chances look half-way decent for a climb. And remember, at the same time, that the wave may be all of thirty feet deep when it sweeps through here."

"You don't say? That would mean some hustling then to get up out of reach, Frank."

"I reckon it would. Look out for that nasty rock; it nearly tripped me, Bob."

"What was that flash, Frank? Don't tell me it was lightning, real lightning, and that the long delayed storm is going to break right now, when it's got us cooped up in this hole?"

"It was lightning, all right. There, that proves it!"

Frank's words were drowned in a crash of genuine thunder that made the foundations of the mountain shake just as much as the mad efforts of the imprisoned geyser had ever done.

"No mistake about that sort of thing," cried Bob, as he stumbled along after his chum. "There it comes again, Frank. I guess I'd better be picking out a good way up the wall somewhere, for it looks like we'd have to climb!"

Frank was doubtless sizing up the situation in his mind. He was also listening for some sound which he expected to hear, but which was going to prove a very unwelcome one.

"No use going any further, Bob, if so be you've seen anything that looks promising here," he declared, when the reverberations of the thunder had ceased to echo through the canyon.

"Then you think we're going to get caught here, Frank?" questioned the other.

"I'm afraid to take the chances of keeping on any further. It may be a long run to the next broken wall, that offers us a chance to climb. Some places the sides go up as smooth as glass. Have you see an opening here, Bob?"

"Yes, yes, right on the left, Frank!" exclaimed Bob, eagerly. "I couldn't see so very far up, but it looks good to me."

Frank turned his gaze up to where his comrade pointed.

"I think it's rough as far as that ledge," he said; "and let us hope that will be out of the reach of the water. Come on, Bob; let's see how you can climb; but be careful, boy, be mighty careful!"

"Frank, that roaring sound didn't seem like the others we've been hearing; d'ye think it means anything has happened?" Bob called, as he started to clamber up the rough face of the wall, taking advantage of every jutting rock, and showing a nimbleness a mountain goat might almost have envied.

"I reckon it does, Bob," replied the other. "Get along as fast as you can with all caution."

"Has the cloudburst arrived?" demanded Bob, who was already ten feet from the floor of the canyon.

"Either that, or else with that last shock the geyser burst its bonds, and the flood Smith expected is rushing out from all the passages into this same channel! Perhaps both things have happened at the same time," Frank replied.

"Wow! then we'd better be climbing some, I reckon, if that's the case!" cried the Kentucky boy, as he increased his efforts to ascend to the ledge.

CHAPTER XXI - A CLOSE CALL
"It's sure coming down on us, Frank!" cried Bob, shortly, as he caught a strange mixture of terrifying sounds.

"Climb!" shouted back the other; for he knew they would have about all they could do to reach the shelf of rock before the mighty wave swept through that narrow channel between the high walls of the canyon, with a force utterly irresistible.

Bob was doing his best. He realized that the ledge was just above his head now, and also how necessary it was that they reach it before the rushing flood arrived to fill the gap.

Now his eager fingers clutched the edge, and he strove to pull himself up higher. But his breath was exhausted from his violent efforts, and the excitement attending the occasion.

Bob realized that the torrent was very close at hand. Its roar dinned in his ears so that he could hear nothing else. The rocks seemed to be quivering under the impact of the released forces. He felt a cold shiver pass over him as he was seized with a dreadful fear that the rock to which he clung was giving way.

Then something seized him by the back of the neck, and Bob found himself being helped up to a firm foundation. Frank had succeeded in gaining the ledge ahead of his chum; and naturally enough his first thought was to assist Bob.

Panting, and completely exhausted, Bob lay there on the shelf of rock. He could look down, and when the lightning played, see the oncoming of that foam-crested bank of mad waters that rushed pell mell down the canyon.

Now it was speeding past them, rising higher and higher with each second, until a new fear began to grip at Bob's anxious heart. He dreaded lest the wave might attain such a height that he and his chum would be swept from their perch, to be carried away, helpless victims on the crest of the flood.

It was raining now, in sheets. The boys were quickly soaked to the skin; but neither of them paid the least attention to this fact, which, after all, was of minor Importance.

"Frank, do you think it's going to reach up here?" called Bob, as he watched the rising line of water come within three feet of the ledge.

"I hope not," came the reply, and then Bob saw that his chum was moving along the ledge looking carefully above as though in hopes of finding it possible to climb higher, in case of necessity.

"Any chance of getting up the rocks, Frank?" he asked again, a minute later.

"Mighty little, Bob," replied the other, dropping beside him; "how's the water coming along?"

"Less'n two feet from us now, and still rising," reported Bob, disconsolately.

"But it comes slowly, you notice," Frank declared, with hope in his voice.

"I could just touch it the last time the lightning played; now I can put my hand clear in it!" Bob called, uneasily.

Another minute passed. The lightning was of considerable assistance to the trapped saddle boys, for it enabled them to see. Frank had lost his lantern during the climb, as it was torn from his belt by a rock he struck; so that only for this heavenly illumination they must have been in utter darkness. And when peril threatens it is some satisfaction at least to see the worst.

"Now it's only one foot down, Frank!" cried Bob.

"That's so," replied the other, instantly; "but I reckon it's about reached its limit. You see, the higher it rises the broader the channel becomes, and that takes a heap of the water. Bob, cheer up, I'm nearly sure it won't reach the ledge!"

"Oh! don't I hope it won't!" cried the Kentucky boy, a little hysterically; for his nerves had indeed been sorely tried during this night.

Five minutes more passed, during which the torrent continued to rush downward through the gorge with all the attendant clamor.

"It's at a stand!" shouted Frank, who had himself been making soundings with his hand.

"And only six inches from the shelf!" echoed Bob. "That's what you could call a close call; eh, Frank?"

"It sure is, old fellow," replied the prairie boy, himself more relieved than his words would indicate; for he had discovered, during his brief search, that there was absolutely no hope of ascending any farther up that blank wall.

"Shake hands, Frank! We're as lucky as ever, I tell you!" said Bob; and when their hands clasped neither of them thought it strange that he could feel the other trembling.

"Well, what are we going to do about it?" asked Bob, when some time had passed, and the flood still rushed through the canyon, although in diminished fury.

"I don't know that we can do anything except camp out right here on this rock-shelf, and wait for the storm to pass by," replied Frank.

"Even if it takes till morning?" Bob went on.

"Nothing else left to us; and morning won't be so very long coming, perhaps, Bob. You notice, don't you, that the thunder now is about all natural?"

"Well, that's a fact," declared Bob. "The geyser has stopped beating against the inside of the mountain, hasn't it? Got tired of the job, and quit for another rest, perhaps."

"I've got my idea about that," Frank said "You can see how the water is still rushing along down there. It must be nearly ten feet deep, and for some time, now, I don't believe it's varied. Don't you understand what that means, Bob?"

"Good gracious! do you mean that the old geyser has turned into a river, and will keep on running like this right along?" cried the other.

"Looks that way to me," Frank replied. "It is a great big syphon, and once started, the water that has for centuries been wasting in some underground stream is now flowing down this canyon. Perhaps long ago it did this same thing, till some upheaval—an earthquake it might have been—turned things around."

"But I say, Frank!" Bob exclaimed; "If what you tell me turns out to be true, it looks as if we were bottled up in a nice hole, doesn't it? We can't get up any farther; and if we go down we'll just have to swim in a torrent that'll knock us silly. This is what I call tough!"

"Oh! don't look a gift horse in the mouth, Bob. This is a pretty good sort of a shelf after all; and we'll be glad to stick to it till morning comes. Time enough then to plan what we're going to do to get away."

"That's right, and I'm ashamed of complaining," the taller lad burst out.

"It is a grand old shelf; and if I wasn't afraid of rolling off I believe I could even snatch a few winks of sleep, wet clothes or not."

"Oh! I'll prop you up with some loose rocks If you want to try it," declared Frank; "but the chances are you'll get to shivering. Better sit up, and whack your arms around as I'm doing every little while. It makes the blood circulate, you see, and keeps you from going to pieces."

Bob saw the wisdom of this advice. He was beginning to shudder every minute or so. They were up the side of the mountain a considerable distance; and after the electrical storm the air had changed from hot to cold.

Time passed very slowly. Every now and then the boys would go through that motion of slapping their arms across their chests; and it never failed to start the chilled blood into new life.

"Was there ever such a long night?" groaned Bob, as he stretched his neck for the thirtieth time to look up at the narrow strip of sky that could be seen between the overhanging walls of the canyon, in hopes of discovering signs of the coming dawn.

"It won't be long now," said Frank, who carried a little watch along with him, and had several times struck a match to consult its face. "One good thing, Bob; it has cleared up. You can see the stars overhead."

"Yes, and how bright they look from here in this black hole. How long did you say now, Frank?" asked the anxious and weary Bob, yawning.

"Half an hour ought to see us through, and bring daylight."

"But Frank, that river is still running below us. However in the wide world will we get out of this?" asked Bob.

"No use crossing till you get to the bridge," laughed Frank. "Just you make up your mind there's going to be some way open for us to get out of this. And if the worst comes, I'm a boss swimmer, remember, Bob."

After another spell of waiting the Kentucky lad cried out:

"I believe it's getting light! Yes, you can see things now that were hid before!"

The morning came. Overhead the sun shone, for they could see that the sky was clear. And looking down they saw the rushing torrent that had not filled the bed of the canyon for perhaps centuries back.

When another hour had elapsed Bob began to grow impatient, and suggested various wild schemes for getting out of the difficulty. To all of these Frank shook his head. He himself was considering something, when he suddenly lifted his head as though listening.

"Some one shouting up yonder!" exclaimed Bob, pointing upward to the top of the canyon wall; whereupon Frank seized upon his gun, and fired several shots in rapid succession.

Then came answering shouts, upon which Frank repeated his signal for help.

"They hear you; they're coming closer! Oh! Frank, I believe that's Old Hank Coombs hollering!" exclaimed the excited Bob.

"Hello! down there, air ye all safe?" came a hail; and looking up the two boys on the shelf saw the grizzled head of the old cowman thrust into view.

CHAPTER XXII - ONCE MORE AT CIRCLE RANCH—CONCLUSION
After all, it was not a very great task, getting the two saddle boys up from the friendly shelf. Old Hank lowered his lariat; and after Bob had slipped the loop under his arms, he was pulled to safety. Then Frank followed.

They found that Hank had half a dozen cowboys with him, some of the most daring connected with Circle Ranch. Overtaken by the storm while at the base of the mountain, they had waited for daylight, and then started afoot to make the ascent. The presence of the new river in the bed of the long empty barranca astonished these cowmen exceedingly. And when they heard all that the boys had to tell they were almost of the opinion that they must have been dreaming.

But there was the evidence before their very eyes, and nobody could deny that the old-time river, that had been bottled up underground for so long, had finally found a way to break forth once more, aided by the geyser that for a century had beaten that tremendous tattoo every little while against the inner walls of the rocky mountain.

"Then there won't be no more racket, will there?" old Hank asked, as he lay there, looking down at the rushing current of the new stream that would no doubt readily follow its long abandoned course, until it reached the distant Colorado, somewhere along the Grand Canyon.

"The chances are against it," replied Frank.

"But let's try and find our horses," Bob suggested, after he had finished eating what food the newcomers had taken the pains to prepare for the lost ones.

"Yes, I'm anxious myself to find out how Buckskin's weathered the gale," Frank put in.

The two horses were found in good shape, but glad to once more see their masters, if the whinnies that greeted the coming of Frank and Bob might be looked upon as evidence of this.

And then another difficult task awaited them. To get the animals down to the level plain, now that the canyon was out of commission, taxed the ingenuity of even so expert a plainsman as Hank Coombs; but it was finally accomplished.

Then the horses of the cowboys were found, and the entire party started for the distant ranch, expecting to complete their jaunt before sundown.

Old Hank was deeply interested in what the boys had to tell about the band of rustlers passing, with all the led horses.

"Didn't git 'em from our ranch," he declared; "an' I reckons the X-bar-X must 'a suffered; or it might be the Arrowhead, over on the creek, was the one. But if so be Pedro Mendoza has been usin' that canyon to cross over the range with his stolen cattle an' horses, he'll hev to go further away now to do the same, 'cause his road's a rushin' river."

"We sure have had a great time of it," declared Bob, as they came in sight of the buildings of the ranch, and heard the loud calls of the cowboys who were driving some of the stock in from the range, to get it ready for shipment later.

"Yes, and think what we found out," Frank pursued. "First of all the mystery of Thunder Mountain is known, and from this time on those roaring sounds will never again be heard."

"And the Indians will be wondering why the Great Spirit is angry with his red children, so that he refuses to speak to them," Bob continued.

"And then there is that little affair about Lopez," Frank remarked, smiling at the recollection. "We have learned who Lopez is, and what his grandfather, Lemuel Smith, was doing in that cave. Think of Peg and his two guides getting out of the region without finding out a thing!"

"Say won't they be just as mad as hops, though, when they learn about what we saw and heard," chuckled Bob. "It's been a great time, all right. And Frank, we'll never again have anything like the fun we had in that old barranca. It makes my blood just jump through my veins to think of it."

"You're right," said Frank, "I don't believe we ever will!"

But like many other persons who cannot look ahead even one hour, and know what the future holds for them, both the saddle boys were very much mistaken. There were plenty of stirring adventures awaiting them ere many weeks had passed, some of which will be related in the next volume of this series, called "The Saddle Boys in the Grand Canyon; Or, The Hermit of the Cave." And those of our boy friends who have found more or less interest in the present story of life in the far Southwest, will doubtless be glad to read more of the doings of Frank Haywood and his brave Kentucky chum, Bob Archer.

That Peg and his guides reached home safely Frank knew shortly, when he happened to meet the bully on the trail. Peg was eager to hear at first hand all that had happened, and made friendly overtures with that design in view; but this did not deceive Frank in the least. He realized that Peg was more bitter than ever, and believed that if the opportunity ever came the bully would not hesitate to do anything that he thought would annoy the chums.

Frank had also found that the prospector, Smith, and his little Mexican granddaughter, had reached home in safety. The successful lode hunter purchased a ranch; and when Frank met him some time later he was riding around the country in a fine automobile, buying stock. Inez was with him, and never again would the brave little girl have to dress as a boy in order to carry supplies up into the canyons of the mountains.

Thunder Mountain never again uttered a sound of warning. The Indians marveled much, and consulted their greatest medicine men as to why the voice of Manitou called no more. But the whites knew; and a load was thereby taken from the mind of many a superstitious cowboy, who, when watching his charges through the vigils of the night, could look toward the rocky height without that feeling of uneasiness that had always been present when he believed the mountain to be haunted. THE END