They had thought to see mountains. There were none. What they saw was really a break in the level plateau. From where they stood they looked almost straight down into the abyss for something more than a mile.

Gazing straight ahead they saw to the other side of the chasm twelve miles away. To the right and to the left their gaze reached more than twenty miles in each direction.

This great s.p.a.ce was filled with gigantic architectural constructions, with amphitheaters, gorges, precipices, walls of masonry, fortresses, terraced up to the level of the eyes, temples, mountain high, all brilliant with horizontal lines of color---streaks of hues from a few feet to a thousand feet in width, mottled here and there with all the colors of the rainbow.

Such coloring, such harmony of tints the Pony Rider Boys never had gazed on before. It seemed to them as if they themselves were standing in midair looking down upon a new and wonderful world. There was neither laughter nor jest upon the lips of these brown-faced, hardy boys now.

Professor Zepplin slowly took off his hat in homage to what was there at his feet. He wiped the perspiration from his forehead. A glance at Tad Butler showed tear drops glistening on his cheeks. He was trembling. Never before had a more profound emotion taken hold of him.

Ned Rector and Walter Perkins's faces wore expressions of fear. No other moment in the lives of the four boys had been like this.

Dad's face shone as with a reflected light from the Canyon that he loved so well, and that had been his almost constant companion for more than thirty years; whose moods he knew almost as well as his own, and whose every smile or frown had its meaning for him.

The travelers each forgot that there was any other human being than himself present. They were drawn sharply to the fact that there were others present, when one of the little party of sight-seers that had come over from the hotel picked up a rock, the weight of which was almost too much for him.

The lads watched him with fascinated eyes. The man swung the rock back and forth a few times, then hurled it over the edge. The Pony Rider Boys waited, actually holding their breath, to catch the report when the rock should strike the bottom.

No report came. It requires some little time for a rock to fall a mile, and when it does land it is doubtful if those at the other end of the mile would hear the report.

The faces of the Pony Riders actually paled. This was indeed the next thing to a bottomless pit. Walter Perkins recalled afterwards that his head had spun dizzily, Ned that he was too frightened to move a muscle.

Suddenly the silence was broken by a shout that was really an agonized yell. The voice was Stacy Brown's.

"Hold me! Somebody hold me!" he screamed

The others glanced at him with disapproving eyes. Could nothing impress Chunky? The fat boy had begun to move forward toward the edge, both hands extended in front of him as to ward off something.

"Hold me! I'm going to jump! Oh, won't somebody hold me?"

Even then only one in that little party appeared to understand. They were paralyzed with amazement and unable to move a muscle. The one who did see and understand was Tad Butler. Chunky was giving way to an irresistible impulse. He was at that instant being drawn toward the terrible abyss.

CHAPTER VII

ON THE RIM OF ETERNITY

Tad caught his breath sharply. He, too, for the instant seemed unable to move. Then all at once he sprang forward, throwing himself upon the fat boy, both going to earth together, locked in a tight embrace.

"Leggo! Leggo!" shrieked Stacy.

The fat boy fought desperately. He had appealed for help; now he refused to accept it. He was possessed with a maddened desire to throw himself into the mile-deep chasm. It was all Tad Butler could do at the moment to keep from being rolled to the rim himself.

Dad, suddenly discovering the situation, ran at full speed toward the struggling boys.

"Grab his legs. I will look out for his shoulders," gasped Tad, sitting down on Chunky's face for a brief respite.

"I'll handle him," said the guide quietly. "They get taken that way sometimes when they first look into the hole."

By this time the others, having shaken off the spell, started to move toward the scene of the brief conflict. Dad waved them back; then, with Tad holding up the fat boy's shoulders, Dad with Chunky's feet in hand, the two carried him back some distance, where they laid him on the ground. Stacy did not move. His face was ghastly.

"I think he has fainted---fainted away," stammered Tad.

"Let him alone. He'll be all right in a few minutes," directed the guide.

"What made him do that?" wondered Tad, turning large eyes on Nance.

"He jest couldn't help it. I told you you'd see something, but I didn't think Fatty would be taken quite so hard. You go back."

"No, I'll wait. You perhaps had better look after the others, Ned or the Professor might be taken the same way," answered Tad, with a faint smile.

Nance hurried back. After a time Chunky opened his eyes. He sat up, looking dazed then he reached a feeble hand toward Tad.

"I'd 'a' gone sure, Tad," he said weakly.

"Nonsense!"

"I would, sure."

"Come back and look at it."

"Not for a million, I wouldn't."

"Oh, pooh! Don't be a baby. Come back, I tell you. You've got to get over that fright. We shall have to be around this canyon for some time.

If you haven't any nerve, why-----"

"Nerve? Nerve?" queried Stacy, rousing himself suddenly. "Talk about nerve! Don't you think it takes nerve for a fellow to start in to jump off a rock a mile high? Well, I guess it does. Don't you talk to me about nerve."

"There come the others."

The Professor, the guide and the other boys walked slowly up to them at this juncture. Chunky expected that Ned would make fun of him. Ned did nothing of the sort. Both Ned and Walter were solemn and their faces were drawn. They sighed as if they had just awakened from a deep sleep.

"What do you think of it, Professor?" asked Tad, looking up.

"Words fail me."

"I must have another look," announced Butler.

He walked straight to the edge of the rim, then lying flat on his stomach, head out over the chasm, he gazed down into the terrible abyss.

Jim Nance nodded approvingly.

"He's going to love it just the same as I do." The old man's heart warmed toward Tad Butler in that moment, when Tad, all alone, sought a closer acquaintance with the mystery of the great gash. After a time the others walked back, Dad taking Chunky by the nape of the neck.

Perhaps it was the method of approach, or else Chunky, having had his fright, had been cured. At least this time he felt no fear. He was lost in wonder.

"Buck up now!" urged the guide.

"I am bucked. Leggo my neck. I won't make a fool of myself this time, I promise you."