You'll never see the beat of that." With long manes and tails flying, the mustangs came on apace and passed us in a trampling roar, the white stallion in the front.

Suddenly a shrill, whistling blast, unlike any sound I had ever heard, made the canyon fairly ring.

The white stallion plunged back, and his band closed in behind him.

He had seen our saddle horses.

Then trembling, whinnying, and with arched neck and high-poised head, bespeaking his mettle, he advanced a few paces, and again whistled his shrill note of defiance.