As he had expected, he found the herd, nearly five hundred in number, but he kept out of sight of them, as it was so near dark, and camped until morning, when he found they had gone up the valley for some miles. Cautiously he followed them, and getting near unobserved at last made a dash upon them. Into their midst he went and a good horse was picked out and lariated in the twinkling of an eye and quickly hoppled and turned loose. Then another and another, until Billy felt that he had done a pretty good day's work. He had discovered two things, however, and that was that Little Grey seemed more than a match for any of the herd with one exception, and that one was a large, gaunt-bodied black stallion, that appeared to drop him behind without much effort. "I've got to have him," said Billy, as he returned to his hoppled prizes and began to drive them toward the fort. It was a long and tedious work, but the boy was not impatient and reached the fort at last and received his reward, which he at once carried to his mother and received her warm congratulations upon his first success. Back to the herd's haunts went Billy, and again he camped for the night, but was aroused at dawn by a sound that he at first thought was distant thunder. But his ears soon were undeceived as he sprung to his feet, well knowing that it was the herd of wild horses. Instantly Billy formed his plan of action and mounting Little Grey rode into a thicket near by, which wholly concealed him from view. Here he waited, for he knew that the herd was coming to the river to drink, and a cry of delight burst from his lips as he beheld the black stallion in the lead. "It is the horse the settlers call Sable Satan and that belonged to a horse thief, father told me, who was shot from his back one night. "Well, if I can catch him I'll be in luck, and I'll try it, though they say he is awful vicious. Be quiet, Gray, or you'll spoil all." On came the large drove at a trot directly for the river, and a beautiful sight it was as they moved forward in solid mass, with flowing mane and tail and the rising sun glancing upon every variety of color. The leader was a perfect beauty, black as ink, with glossy hide and long mane and tail--the equine king of the herd. With his reins well in hand, his lariat ready, and full of excitement, Billy waited for the horses to reach the stream, which they entered to quench their thirst. As every head was lowered and the nostrils driven deep into the cool waters, out of the thicket dashed the Boy Horse-Hunter, and the clattering hoofs startled the drove, and in confusion and fright they turned to fly. Straight as an arrow went the boy toward the black stallion, which attempted to dash by with the mass. But with an unerring hand the lariat was thrown, the coil settled down over the haughty head, a tremendous jerk followed, and Sable Satan was thrown to the ground.