It had been decided that Tad Butler should go out on the first guard; Walter Perkins on the second; Ned Rector third and Stacy Brown fourth. Tad was all eagerness to begin. One of the cowmen exchanged ponies with him, riding Tad's horse back to camp. "You see, our ponies understand what is wanted of them," explained Stallings, who had remained out for a while to give Tad some instruction in the work before him. "Give the ordinary cow pony his head and he will almost tend a herd by himself." Three men ordinarily constituted the guard. In this case Tad Butler made a fourth. Taking their stations some four rods from the edge of the herd, they began lazily circling it, part going in one direction and part in another. In this position it would have been well-nigh impossible for any animal to escape without being noticed by the riders. "Now, I guess you will be all right," smiled the foreman. "Make no sudden moves to frighten the cattle." "Do they ever run?" asked Tad. "Run? Well, rather! And I tell you, it takes a long-legged Mexican steer to set the pace. Those fellows can run faster than a horse--at least some of them can. A stampede is a thing most dreaded by the cowmen." "Our ponies stampeded in the Rockies. I know something about that," spoke up Tad. "Well, compare the stampeding of your four or five ponies with two thousand head of wild steers and you'll get something like the idea of what it means. In that case, unless you know your business you had better get out of the way as fast as hoss-flesh will carry you. Now, Master Tad, I'll bid you good night and leave you to your first night on the plains." "How shall I know when to come in?" "When the second guard comes out. You will hear them. If you should not they will let you know as they pass you." With that the foreman walked his pony away from the herd. After some little time Tad heard him galloping toward camp. At first Tad took the keenest enjoyment in his surroundings; then the loneliness of the plains came over him. He began to feel a longing for human companionship. A dense mantle of darkness settled down over the scene. Remembering the advice of the foreman, the lad gave his pony the rein. The hardy little animal, with nose almost touching the ground, began its monotonous crawling pace about the herd. It seemed more asleep than awake. In a short time a sheet of bright light appeared on the eastern horizon. Tad looked at it inquiringly, then smiled. "It's the moon," he decided. The boy felt a great sense of relief in his lonely vigil. Just ahead of him he saw a pony and rider leisurely approaching. It proved to be Red Davis, one of the first guard. Red waved his hand to the boy in passing, but no word was spoken on either side.