“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.”

“You can’t blame him,” said Tad, rising from his perilous position and walking calmly back to them.  “I nearly got them myself.”

“Got what?” demanded Stacy.

“The jiggers.”

“That’s it.  That describes it.”

Professor Zepplin, who had informed himself before starting out, now turned suddenly upon them.

“He’s going to give us a lecture.  Listen,” whispered Tad.

“Young gentlemen, you have, perhaps, little idea of the vastness of that upon which you are now gazing.”

“We know it is the biggest thing in the world, Professor,” said Ned.

“Imagine, if you can,” continued the Professor, without heeding the interruption, “that this amphitheatre is a real theatre.  Allowing twice as much room as is given for the seat of each person in the most comfortable theatre in the world, and you could seat here an audience of two hundred and fifty millions of people.  These would all be in the boxes on this side.”

The boys opened their eyes at the magnitude of the figures.

“An orchestra of one hundred million pieces and a chorus of a hundred and fifty million voices could be placed comfortably on the opposite side.  Can you conceive of such a scene?  What do you think of it?”

“I—–­I think,” stammered Chunky, “that I’d like to be in the box office of that show—–­holding on to the ticket money.”

Without appearing to have heard Stacy Brown’s flippant reply, Professor Zepplin began again.

“Now that you are about to explore this fairy land it is well that you be informed in advance as to what it is.  The river which you see down there is the Colorado.  As perhaps some of you, who have studied your geography seriously, may know, the river is formed in southern Utah by the confluence of the Green and Grand, intersecting the north-western corner of Arizona it becomes the eastern boundary of Nevada and California, flowing southward until it reaches the Gulf of California.”

“Yes, sir,” said the boys politely, filling in a brief pause.