It had struck Victor more than once that whoever acted as sentinel was—for most of the time—wasting the hours that might as well have been spent in rest. Not once had anyone been in danger of attack from wild animals, nor since crossing the Mississippi had any Indians molested them. Moreover, he was sure that in the event of anything of the kind the horses would give timely warning. But Deerfoot had made the order, before leaving the young State of Ohio, that never was the camp to be left unguarded, and while he was with them the rule had not been disobeyed. It was useless to protest to the Shawanoe, who had a way of enforcing his views which no one dared oppose. No argument, therefore, had been offered, and that sense of honor which was ingrained with the twins made each more careful of carrying out the views of the “guide, counsellor and friend” during his absence than when he was with them. Consequently, Victor Shelton, resting his gun over his shoulder, began slowly pacing to and fro, after the manner of a veteran sentinel. His beat was twenty steps or so, and one termination brought him near where the horses had already lain down for the night. Rather it should be said that only three of them had done so, for Zigzag, acting out his queer disposition, was seen moving slowly here and there as he munched the lush grass. He was likely to keep it up for an hour or two, and the boy gave no heed to him. A monotonous hour had worn away when Victor’s attention was drawn to the wakeful horse. He was standing with head raised, bits of grass dripping from his jaws, ears pricked, and staring toward the other side of the valley, as if he had discovered something in that direction. “I guess Mul-tal-la is coming back,” was the thought of the lad, “and Zigzag hasn’t noticed that he is absent.” But no Blackfoot came into view in the dim light, and the animal’s restlessness, instead of passing, became more marked. He threw his head still higher, looked more keenly and emitted a faint neigh. “I wonder what’s the matter with him,” said Victor, turning aside from his beat and walking out to the animal, whom he patted and tried to soothe. To his astonishment he found the horse was in a tremor, as if scared by something he either saw or heard. Victor turned his gaze in the same direction, but could discover nothing to explain the alarm of the brute. Then he listened. From the direction of the mountains he heard a peculiar sound. It was a dull but steadily increasing roar, such as you have noticed at night when a railway train was first detected miles distant. The boy supposed it was a gale of wind, similar to what he had felt more than once since crossing the Mississippi, and, indeed, while still on the other side of that river. But no sooner had he formed this conclusion than he was sensible of a difference in the sound from that which had come to mind. It was more intense and its volume was growing faster than he had ever observed before.