Not even in the Rockies had the boys met with such peculiar formations as now appeared on all sides of them.

"I'd hate to travel this trail in the night," growled Stacy.

"You wouldn't have to travel it far," laughed Tad. "You'd be walking on air before you knew it."

Stacy had pressed on ahead while the others were talking. He had observed what they had not. One of the pack mules had lagged behind, and with head lowered almost to the ground appeared to have gone sound asleep. The Shawnee, engaged with his own thoughts, apparently was unaware that he had left a mule behind.

The fat boy, with great glee, was urging his pony quietly along, approaching the pack animal with as much caution as possible. It was Stacy's intention to give the beast the fright of its life, in which ambition he succeeded beyond his fondest antic.i.p.ations.

Getting near enough for his purpose, Stacy slipped from his pony, hunted about until he found a stick long enough for his purpose, and with this crept up on the sleeping mule.

With a shrill shriek the lad brought the stick down on the long-eared animal's rump with a whack that, while it could not have hurt, did all that he had hoped it might.

Both the mule's hind feet shot up into the air, while the beast with a short, sharp bray of fright lunged straight ahead.

The guide uttered a shrill exclamation of warning as he saw the mule tearing through the bushes to the left of the trail. Leaving his two pack animals, Eagle-eye leaped for the fleeing one.

But he was too late.

All at once the frightened beast appeared to stand on his head, his hind feet beating a tattoo in the air; then he disappeared altogether.

The Pony Rider Boys, hearing the disturbance, had hurried up, and just in time to see the final scene in the little tragedy that their companion had caused.

"What's this? What's this?" demanded the Professor. "What's the matter?"

"Pony fall down! Pony fall down!" exclaimed the Indian, with a trace of excitement in his tone.

"He means our long-eared friend has taken a header over that rock there," Ned Rector informed them.

"I am afraid it is more serious than that," added Tad. "It looked to me as if the pack mule went over a cliff."

"Him fall down, fall down, fall down," repeated the guide.

Chunky, frightened at the result of his prank, had quickly scrambled into his own saddle and drawn back from the scene of his late exploit.

Professor Zepplin did not understand how it had happened.

"I'm to blame, sir," announced Chunky, plucking up courage and riding up beside the Professor. "I hit him with a stick and he ran away."

In spite of the disaster that had come upon them, the boys could not but laugh at the boy's rueful countenance. Nor did the Professor find it in his heart to be harsh.

"You deserve to be punished, sir, but somehow when I look at you my anger vanishes instantly. The next question is, how are we going to get the beast up here? What do you say, guide?"

"Him dead."

"What's that?"

"Pack pony, him gone Happy Hunting Ground."

"You don't mean he has been killed?"

The guide nodded with emphasis, at the same time bringing the palms of his hands sharply together to convey the impression that the mule had hit the rocks below so hard that he would never rise of his own accord again.

"Now we are in a fix," said Ned.

"I guess we had better make Chunky walk and use his pony for packing the outfit," suggested Walter.

"Yes, but we have little or no outfit to pack," answered Tad. "Most of it is down there with the dead mule; how far I don't know."

The Pony Rider Boys gasped. This, indeed, was a serious situation.

CHAPTER III

A DARING PROPOSAL

For a full moment the boys looked at each other doubtfully. Professor Zepplin was the first to break the silence.

"Wha--what pack did the mule have?"

"Part of the kitchen outfit and all of the canned goods," answered Tad Butler impressively.

Ned Rector laughed.

"This is where we give our stomachs a rest," he mocked.

"I fail to see anything humorous in our present predicament," chided the Professor. "We are many miles from our base of supplies, with our supplies at the bottom of a gorge, goodness knows how deep down.

Whether we can get down there or not I haven't the slightest idea--"

"Don't we get anything to eat?" wailed Chunky.

"Think you deserve to have anything?" demanded Ned.

"Don't be hard on him," spoke up Tad. "He feels cut up enough about it as it is. We've all done just as foolish things, only they didn't happen to turn out the way this one has."

Chunky turned his pony about and rode a few paces away from them, being more disturbed than he cared to have his companions know.

"Eagle-eye," called the Professor.

The Indian was leaning over the cliff looking down into the deep canyon, trying to find the pack mule. He straightened up and strode over to the Professor upon being called.

"You sure the mule is dead?"

"Mule no pack more."