“Don’t forget that we need about twenty-five mules—for both parties of the expedition,” Professor Allan reminded him.

“I haven’t,” the naturalist returned. “We can get as many as we need. Suppose we do it now.”

Mr. Wallace, Dr. Rust, and Professor Kelley set out at once to get the pack animals.

Meanwhile, Bob and Joe took movie cameras and walked leisurely up the hillside, intending to photograph anything that would come before them.

The boys had not gone far when they came upon a large group of Indian men, dressed in short, coarse trousers, hand-woven shirts, and brightly colored blankets. On their heads were the flat “pancake” hats which are common in this region.

“Here’s a good chance to take movies,” said Joe happily. He had brought the camera to his shoulder and pointed it toward the Indians, turning the crank steadily.

Suddenly the natives rushed angrily at the youths and made a grab at the motion-picture cameras.