"To give you another ill.u.s.tration, were you to combine England, Ireland, Scotland, France and Italy, you still would lack considerable of having enough to make an Alaska. Then, added to this, are the great mountains, thousands of feet high, and one great river--not to speak of the smaller ones--that flows through more than two thousand miles of wonderful country. I have given you a bird's-eye-view of the country, a small part of which you have started to explore."

"Yes, a fellow needs a bird's-eye up here. He has to have or he's a goner," declared Chunky.

"And by the way, Professor," said Tad. "Your pony is yawning with his left hind leg."

"Haw, haw, haw! That's a good one," laughed the fat boy.

"What do you mean?" wondered the Professor.

"He is stretching himself. His left hind foot at this moment is suspended over several hundred feet of s.p.a.ce. But don't startle him for goodness' sake," laughed Tad.

The Professor glanced back. Afterwards the boys declared he had gone pale at the sight of that foot held so carelessly over the yawning chasm, but the Professor denied the accusation. He clucked very gently to the pony. The little animal lazily drew the foot in, and, after trying several places, at last found a spot that appeared to suit it and on which it placed the small foot. The boys drew a sigh of relief.

"My, but that was a narrow escape," derided Ned. "Just think of it, Professor."

"Gid ap," commanded Professor Zepplin. "Look sharp that none of you does worse."

Now and then reaching a spot where they could get an un.o.bstructed view of the distance the boys were fairly thrilled by the sight of the jagged peaks, sparkling in the sunlight, many hidden in the clouds and too high to be seen. It was an awesome sight and at such times stilled the merry voices of the Pony Rider Boys as they gazed off over the array of wonderful heights.

"What are they?" asked Ned when he first caught sight of this vista of mountain peaks.

"The first one should be Mt. Lituya and the next Mt. Fairweather," Tad replied.

"That is correct, according to the map," spoke up the Professor. "The former is ten thousand feet high, the latter five thousand, five hundred."

A series of low wondering whistles were heard from the lips of the boys.

It did not seem possible that the distance to the tops of those mountains could be so great.

"I should like to climb one of the highest," declared Butler.

"You can't," answered the Professor sharply.

"Why not, Professor?"

"Because I shall not allow it."

"And there's another reason," announced Stacy. "You can't because you can't. But if you did succeed in getting to the top think what sport you could have!"

"How so?" asked Butler.

"You could do a toboggan slide two miles long. I reckon it would land you somewhere over in Asia. Wouldn't that be funny?"

"I don't know about that," reflected Butler.

"You wouldn't know about it if you were to take the slide, either. But how it would surprise some of those Asiatics to see a Pony Rider Boy suddenly landing in their midst, coming from the nowhere," chuckled Stacy.

"I rather think it would surprise almost anyone to have a Pony Rider Boy land in his midst," answered Tad with a smiling nod.

"Is that some kind of joke?" demanded the fat boy.

"No, that's an axiom," spoke up Rector.

"An axiom?" reflected Chunky. "Oh, I know what that is. It is something that something else revolves around, isn't it? That's the sort of thing the world is supposed to revolve about. I know, for I read it in my geography."

The boys groaned. The suspicion of a smile played about the corners of Professor Zepplin's mouth.

"You had better go back to school rather than be traveling with real men," advised Ned.

"Isn't that an axiom, Professor?" called Stacy indignantly.

"It is not."

"Then what is one?"

"You are a living example of one yourself," was the whimsical reply.

Stacy pondered over the Professor's retort all the rest of that day. But when noon came and pa.s.sed and no stop was made for a noonday meal, the fat boy began to grow restive.

"Don't we stop for something to eat?" he demanded.

"I should like to know where?" answered Tad.

"Isn't there a place wide enough for us, Tad?"

"There is not."

"But when are we going to find one?"

"You know as much about that as I do. Remember none of us ever has been over this trail. For aught I know we may have to sleep standing up to-night."

"Well, I reckon I'd just as soon fall off before dark as after. Anyhow, I don't propose to sleep on this trail as it looks to me now--"

"Hark!"

Tad's voice was sharp and incisive. He was holding up one hand to impose silence on his companions. Walter Perkins' face grew pale, the fat boy's eyes were large and frightened. Professor Zepplin halted his pony sharply and turning in his saddle glanced anxiously back toward his charges.

"What is it?" stammered Rector.

"I don't know," answered Tad Butler. "It's something awful, whatever it is."

"Have no fear, young men. I know what that sound is. There is no danger here where we are, for--"

The Professor did not complete his sentence. The distant rumbling that had at first attracted their attention suddenly merged into a deafening roar, and the trail quivered under their feet. The ponies snorted and threw up their heads, chafing at the bits.

"Hold fast to your horses!" shouted Tad. His voice was lost in the great roar that now overwhelmed them, sending terror to the hearts of every Pony Rider Boy on that narrow ledge of rock known as the Yakutat trail.

CHAPTER VI