The caravans of the Santa Fé Trail, also, moved with considerable regularity and order, but their make-up was more heterogeneous and there was no dominating control. Where there were many waggons, they marched in three or four parallel columns, "but in broken lines, often at intervals of many rods between." At night they were arranged in a quadrangle with a gap left at the rear corner as an entrance for the animals, which after grazing for a few hours were shut up in this corral of waggons. One of the difficulties was the stampede. This frequently started from some slight cause. The oxen, even if yoked, dashed at headlong speed across the plain, with the mules and horses intermingled. Oxen when frightened were the most difficult to control and did not recover their calm as speedily as horses and mules. Mules were the most advantageous, but were also the most expensive. They possessed one characteristic which was useful as well as peculiar. They could detect the presence or the approach of an Amerind long before it could be learned in any other way, but I have seldom seen this peculiarity noted. It was indicated by a restlessness, a pricking up of the ears, and a general alertness as of a dog approaching game. When I have been riding a mule in the mountains, I have often been apprised of the approach of natives in this way, before I noticed any other sign. I am satisfied that no Amerind could ever approach on the windward a mule not accustomed to them, without being discovered. It used to afford us amusement when an Amerind guide tried to mount a mule, and we sometimes were forced to hold the animal securely till he could get on. With usual mule perversity, once the native was in the saddle the scene calmed, only to be repeated when he tried mounting again. A cry of "Indians!" set the caravan in commotion, and amidst great excitement all prepared for defence. If the party were a large one it was seldom troubled, hence all who wished to cross combined, forming an annual caravan for mutual protection which went out and back at fixed periods, but sometimes small parties ran the risk of crossing alone. [Illustration: An Old Beaver Haunt. Photograph by F. S. Dellenbaugh.]