By this time Nance and the Professor had walked along, climbing over boulders, great blocks of stone that had tumbled from the walls above, making their way to the edge of the river.
The others followed, talking together at the tops of their voices, laughing and joking. They felt relieved that the terrible climb had come to an end. As they approached the river, their voices died away. It was a sublime but terrifying spectacle that the Pony Rider Boys gazed upon.
"This is more wonderful than Niagara," finally announced the Professor.
"The rapids of the Niagara River would be lost in this turbid stream."
Great knife-like rocks projected from the flood. When the water struck these sharp edges it was cleanly cut, spurting up into the air like geysers, sending a rainbow spray for many yards on either side.
What puzzled the lads more than all else were the great leaping waves that rose without apparent cause from spaces of comparatively calm water. These upturning waves, the guide explained, were the terror of explorers who sought to get through the Canyon in boats.
"Has any one ever accomplished it?" asked Tad.
"Yes; that intrepid explorer, Major J.W. Powell, made the trip in the year 1869, one of the most thrilling voyages that man ever took. Several of his men were lost; two who managed to escape below here were killed by the Indians."
"I think I should like to try it," said Tad thoughtfully.
"You won't, if I have anything to say about the matter," replied Dad shortly.
"No one would imagine, to gaze down on this stream from the rim, that it was such a lively stretch of water," remarked the boy. "It doesn't seem possible."