"Put him out! Put 'em both out!" cried Ned and Tad, while Tom Parry's stolid face relaxed into a broad smile.
"It appears to me that you young gentlemen are very humorous to-day," laughed the Professor.
"It's dry humor, Professor," retorted Ned.
Tad unslung his lariat.
"I'll rope the next boy who dares say anything like that again," he threatened. "See, even the burros are ashamed. They're hanging their heads, they're so humiliated."
"I don't blame them. Mine's swimming from the heat," rejoined the guide.
"Say, what's that?" demanded Chunky, pointing ahead of him, with a half-scared expression on his face.
"I don't see anything," answered the other lads.
"Chunky's 'seeing things,'" suggested Ned.
The fat boy was pointing to a bright circle of light that hung over the desert some five feet from the ground, directly ahead of him. The peculiar thing about it appeared to be that the circle of light kept continually moving ahead of him, and at times he caught the colors of the rainbow in it.