“That river drains a territory of some three hundred thousand square miles, and from its source is two thousand miles long.  This gorge is slightly more than two hundred miles long.  Am I correct in my figures, Mr. Nance?” demanded the Professor, turning to Dad, a “contradict-me-at-your-peril” expression on his face.

“I reckon you are, sir.”

“The river has a winding way-----”

“That’s the way with rivers,” muttered Chunky to himself.

“Millions of years have been consumed in the building of this great Canyon.  In that time ten thousand feet of non-conformable strata have been deposited, elevated, tilted, and washed away; the depression of the Canyon Surface serving for the depositing of Devonian, Lower Carboniferous, Upper Carboniferous, Permian, Triassic, Jurassic, Cretaceous; the formation of the vast eocene lake and its total disappearance; the opening of the earth’s crust and the venting from its angry stomach the foul lavas—–­the mind reels and whirls and grows dizzy-----”

“So do I,” almost shouted Chunky, toppling over in a heap.   “Quit it! 
You make me sea sick-----”

“I am amazed,” bristled the Professor.  “I am positively amazed that a young gentleman—–­”

“It was the whirling, reeling suggestion that made his head swim, I think, Professor,” explained Tad, by way of helping out the fat boy.

The lecture was not continued from that point just then.  The Professor postponed the rest of his recital until a more opportune time.

“Will you go down to-day, or will you wait?” asked the guide.

“I think we shall find quite enough here on the edge of the rim to occupy our minds for the rest of the day, Nance,” returned the Professor.

The boys agreed to this.  They did not feel as if they ever would want to leave the view that fascinated and held them so enthralled.  That day they journeyed over to the hotel for dinner.  The guests at the quaint hotel were much interested in the Pony Rider Boys, and late in the afternoon quite a crowd came over to visit Camp Grand, as the lads had named their camp after the pack train had arrived and the tents were pitched.

There were four tents all pitched in a row facing the Canyon, the tents in a straight line.  In front the American flag was planted, the camp fire burning about midway of the line and in front, so that at night it would light up the entire company street.

They cooked their own supper, Tad attending to this.  But the boys were too full of the wonderful things they had seen that day to feel their usual keen-edged appetite.

The dishes put away, the Professor having become deeply absorbed in an argument with some gentlemen from the hotel regarding the “processes of deposition and subsidence of the uplift,” Tad slipped away, leaving his chums listening to the conversation.  Dad was also listening in open-mouthed wonder that any human being could use such long words as were being passed back and forth without choking to death.  He was, however, so absorbed in the conversation that he did not at the moment note Butler’s departure.  Tad passed out of sight in the direction of the Canyon.