“The mules came through all right,” observed Dr. Rander. “Cut and bruised, but nothing more.”

“It’s funny,” began Joe, looking up at the sun, which was now in full view. “That was a very queer storm. It came quickly and ended the same way.”

“Hailstorms are rather common in this part,” explained the old man, getting out a box of antiseptics and first-aid remedies.

Their numerous wounds were treated with a soothing salve. Then, after looking over the mules, they moved on around the mountainside.

At a huge notch in the rocky slope they stopped to examine a curious formation that puzzled them. It was a long sloping slide, running gradually down the mountainside. From all appearances it was as smooth as glass.

“I don’t know whether this is natural or man-made,” said Dr. Rander. “I never have been able to find out. But,” he went on, “what concerns us is that we’ll have to slide down to the foot of the mountain.”

“What!” Bob’s surprise was beyond words. “Do you really mean that?”

“Every word of it,” was the old man’s reply. His little eyes twinkled. “Don’t you think much of the idea?”

Bob laughed.

“It was so sudden that I hadn’t given it a thought,” he answered. “But”—gazing far down the smooth slope—“it looks rather inviting. Will you go first?” The youth was not fully convinced that Dr. Rander was in earnest.