"I only hope those two fly-by-night birds don't take a notion to double on their trail, and come back to pay us a visit," Frank remarked; and of course Bob understood that he meant the bad men who were being rounded up by Sheriff Stanwix, aided by the official of Coconino County.

"Perhaps we'd better douse the glim, then?" Bob suggested.

"Let it burn out," Frank remarked; "I don't believe there's much chance of anybody else seeing it now; because it's pretty low. Our tent shows up about as plain, come to think of it; but I don't mean to do without shelter."

They sat there, chatting on various subjects, for some time. Of course their mission to the region of the greatest natural wonder in the world took a leading part in this conversation. But then they also spoke of their recent visitors; and as Bob showed signs of considerable interest, Frank told all he had ever heard about the valor of the Prescott sheriff.

"I don't know how you feel about it, Bob," he said, at length, with a yawn, "but I'm getting mighty sleepy."

"Same here; and I move we turn in," Bob immediately replied.

Accordingly, as the idea had received unanimous approval, they took a look at the horses, now staked out with the ropes, and, finding them comfortable, both boys crawled under the canvas.

Some hours later they were aroused suddenly by a shrill yell. As they sat up, and groped for their rifles, not realizing what manner of peril could be hanging over them, the loud snorting of the horses came to their ears.

"Come on!" exclaimed Frank, in considerable excitement. "Sounds like somebody might be bothering our mounts!"

Bob had not been so very long in the Western country; but he knew what that meant all right. Horses were supposed to be the most valuable possessions among men who spent their lives on the great plains and deserts of this region. In the old days it was deemed a capital crime to steal horses.