The two boys stood there, listening to the sounds that constantly increased in volume, as though approaching rapidly nearer the camp in the timber growing along the little stream.

There could no longer be the slightest doubt as to what made the noise. Before now Adrian had heard enough to fully agree with his chum when the other pronounced it a stampede of cattle. Besides the crash of many hoofs on the earth, they could catch wild snortings, low, frightened lowings, and the rattle of striking horns; all of which were very familiar sounds to both lads, as they had witnessed just such sights on many a previous occasion.

“The queer part of it is,” Adrian had taken pains to say before the noise grew so boisterous as to prevent all ordinary conversation, “that there doesn’t seem to be anything around to start such a wild rush. A storm will do it quicker than most anything else, and there couldn’t be one in the quarter where they’re heading from.”

“Wait and see,” Donald had wisely added; if he suspected anything as to the real facts he did not appear willing to share his thoughts with his chum as yet, waiting doubtless until he could pick up further proof.

“Shall we wake Billie up?” asked Adrian.

“He’d never forgive us if we didn’t,” the other replied. “You’d think the sound would get him to stirring, but Billie could sleep through the biggest earthquake that ever happened; and if you did knock him up he’d want to know who was shaking the floor with dancing. But I’ll get him on his feet, while you fetch our ponies in.”

So Donald stepped over to where the fat chum was cuddled up in his blanket just like an Esquimau. After shaking him several times without any result, save a grunt, Donald shouted in his ear:

“Wake up, Billie! earthquake! cattle stampede, and we’re right in the way!”

“Goodness gracious! is that so?” remarked Billie, as he sat up, and began to dig his knuckles into his eyes; then, hearing the roar of the approaching hoofs he became suddenly greatly excited, as he realized that it was after all no joke his comrades were trying to play upon him.

“Oh! will they grind us to powder, Donald? Can’t we even climb a tree, and get out of reach of their hoofs? Hurry up, and say something before it’s too late! Think what a terrible muss there’ll be if ever they trample on me, and do please tell a fellow what to do!”

“Don’t worry, Billie; they won’t come into the timber at all. Fetch your gun, and come along to join Adrian near by. We want to see what it all stands for as the herd sweeps past. Be quick now, or you’ll lost a sight worth looking at, I tell you!”

Billie hurried at hearing this. Besides, he did not exactly fancy being left behind when his chum departed.

“How about the ponies, Donald; won’t they get in trouble?” he managed to call out, as he trailed along in the wake of the other.

“I reckon Adrian has brought the lot into the timber; he was just starting out to do the same when I came to wake you up. Yes, here he is, and with all our horses safe and sound. Fasten Jupiter to a tree with his rope, and be quick about it, Billie!”

This was speedily done, after which the trio of Broncho Rider Boys crouched there on the edge of the timber, waiting until the herd of stampeding cattle came along.

“If that moon’d only draw out stronger,” said Adrian, as he cast a look upward toward the sky, over the face of which light clouds were drifting lazily; “but it don’t mean to, and we’ll just have to do the best we can. Look sharp, boys!”

“I can see ’em coming right now!” announced Billie.

In fact all of them saw the fast-moving blurr upon the prairie some little distance away, which they knew must be the cattle rushing headlong toward them, spurred on by some unseen power, either fear, or a more tangible force.

Ten seconds later and they were on a line with the hidden boys, who, crouching there, stared as hard as they could, trying to see whether wolves were chasing after the herd, as might happen when the ferocious animals were in great numbers, but not otherwise; or what other cause there could be for such a great commotion among the cattle.

“Oh! did you see that steer go down?” ejaculated Billie suddenly. “He must a put his forelegs in a gopher hole, and before he could get up the rest had trampled him into flinders. Whee! ain’t I glad that wasn’t Jupiter and me!”

“You’ve a right to be thankful, believe me,” said Donald, solemnly; “because it’d be all over with you before you could give more’n a single yelp. That steer was a big and powerful beast, but you saw how even he couldn’t get up again, once those many hoofs began to pound him flat. We’ll find him there afterwards, and only food for the coyotes.”

The stream of cattle had now swept past them, and the thunder of their many hoofs was gradually growing less insistent as they passed on.

“Well, that was a queer sight, sure,” said Billie, rubbing his eyes, as though he hardly knew whether he could believe what they had told him or not.

Adrian was strangely quiet, Donald thought.

“Did you ever see a stampede like it?” asked Donald, determined to find out what the other chum’s opinion might be.

“I surely never did, if it was a real stampede,” returned Adrian, slowly, as if he might still be struggling to see light.

“Oh! it was that, all right, but not one brought about by a storm, nor yet by fear of wild animals,” Donald continued.

“Then you heard them too, did you?” demanded the other.

“What was that?” asked Billie, arousing to the fact that he was somewhat behind, and never liking to be left out of a race through any handicap.

“Cowboys yelling like mad!” Donald went on to say, seriously.

“Oh! you mean that they were trying the best they knew how to head off the herd and start them to milling; was that it?” Billie went on; for he had managed to pick up considerable information connected with a cattle ranch during the time he had spent on the border with his cousin, down in Arizona.

“On the other hand,” Donald remarked, still more solemnly, “it struck me they were yelling like that to make the long-horns more frightened than ever; because they whooped like wild Injuns off their reservation, and in for a gay old time.”

Billie gave it up. His wits were inclined to be a little dense at best; and on being so suddenly aroused from a sound sleep, to witness this strange passing of a stampeded herd of cattle, he was hardly in a fair condition to do himself justice when it came to figuring what a mystery meant.

“I throw up the sponge!” he hastened to say; “somebody’ll just have to take hold and whisper what it all means; because for the life of me I ain’t able to get a grip on the thing. What’s the answer, fellows? Cowboys awhooping things up, and making more work for themselves by scaring the life half out of their cattle. Say, that’s a silly thing to do, strikes me, now, boys. Tell me what possesses the chump to act that way? And be quick about it, because when I’m that curious it’s dangerous to leave me groping in the dark. Don’t you know fellows have been known to pine away to nothing just because they kept aworrying about something. Donald, what’s it mean?”

“Adrian you tell him, while I get that little electric torch we used to find so valuable; I’d like to step out and take a look at that dead steer, now that the danger’s gone past.”

The roar of many hoofs was dying away by degrees in the near distance, showing that the herd must still be on the full run, and as filled with fright as when the boys saw them sweep past.

“Why,” began Adrian, as the other hurried back to where the red embers of the little camp-fire glowed like a wakeful eye among the trees, “all I can say, Billie, is that the herd was in a panic, and had been frightened. If there were punchers galloping along, as both Donald and I think we made out, they didn’t seem to be trying to head the cattle off, or turn them, but kept in the rear, or the flank, and yelled just to keep them hustling. Now do you catch on, Billie?”

“Rustlers, you mean, Adrian; cattle thieves carrying off a bunch of the long-horns!” ejaculated the astonished Billie. “Just to think of running on a game as old as that the very first thing we come up here? Why, I thought that was only a practice along the border, where the rustlers could drive the stolen cattle over into Mexico, and be safe from pursuit.”

“Oh! that’s all a mistake, Billie!” declared Adrian; “wherever cattle are raised on any large scale you’ll find men trying to steal them, and change the marks; because once this is done it’s hard to pick out your own property. And unless both of us are mighty much mistaken, that’s what was being done with that herd we saw pass by on the gallop. But here comes Donald with the little torch; and as the dust has partly settled by now, we can go out and take a look around.”

“And,” said Billie, as if to show that he was not so dull as he had been once upon a time, “if them rustlers were chasing along behind the herd we’ll find the plain hoofprints of their ponies there; because they’ll show up different from the split hoofs of the steers, eh, Adrian?”

“Good for you, Billie; you’re on to the racket nowadays!” declared the other; and then Donald coming up, the three stepped out toward the spot where they had seen the unlucky steer fall never to rise again.

There was little trouble about finding the remains, for these prairie boys had a fashion of locating things at the time they happened, so that they could head straight to them again when they wished.

And just as Donald had said, the wretched animal had been pounded almost flat by the many hoofs that passed over him. They might find some decent pieces of beef to make use of, and that was all, for even the hide had been ruined.

Adrian took the torch from his chum’s hand. They saw him bend down closer as if to examine the flank of the dead steer. Hardly had he done so than he gave utterance to a loud cry.

“What have you found now?” demanded Billie, scenting new developments in the remarkable mystery which had greeted their advent into the Wyoming cattle country.

“Look at this mark here!” was what the other said, as he drew in a long breath; and of course both Donald and the fat chum dropped on their knees, the better to see what was meant.

And there, plainly branded on the flank of the dead animal was the sign manual which Adrian recognized as his own property, a bar, and the letter S!