When he looked in the direction from which the sound had come a blue, sealike expanse seemed to float before him. They had been numerous, those lakelike illusions, and he knew what they were--the deceptive mirage of the dry lands of the high plains. That blue “sea,” and a sort of heatlike shimmer that hovered above it, made it impossible now for him to see a mile in the direction of the shot, whereas before those deceptive things appeared the eye could range to the very limit of vision. While trying to look through that blue illusion he fancied he heard the distant trampling of hoofs. Instantly he dropped from the saddle to the ground and laid an ear against the turf, to aid his hearing. A confused trampling of hoofs reached him now, and he thought he heard a yell, followed by another shot, and then a volley. Lying prone on the ground, the scout looked again across the sealike levels of grass. Then he beheld something that almost frightened him. In the sky over that level grass land the picture of a tragedy was thrown by that strange refractive power of light which produces the mirage. The sky for the moment had been changed to a mirror there, and in that mirror was shown a scene that was being enacted on the ground below. A number of Indians were rushing on a white man. He had evidently fired the cartridges out of his revolver and stood now at bay. The Indians, who were Cheyennes, judging by their general appearance, rushed upon the man with knives and struck him down. Buffalo Bill stared, helpless, fascinated, by that terrible scene. “It is Wild Bill!” he groaned; “and they have killed him!” Buffalo Bill knew that he was looking at a scene in a mirage, yet he knew as well that the mirage pictured something that was happening at the moment. He knew, too, that he was too far from it to be of any immediate help to his old friend. Yet he jumped up from the ground and leaped to the back of his horse. Whether there were ten or a hundred of the red devils, he was going to the aid of Wild Bill. He drove his heels into the flanks of the horse and sent it on with great bounds that bore it over the level land with almost the fleetness of the wind. Where Ben Stevens was at the moment he did not know and had not time to inquire. All he knew was that ahead of him somewhere Wild Bill was in peril of his life, if not dead. The blue heatlike shimmer before him still held up its concealing veil, and the lakelike illusion still continued. It was as if he were galloping toward a wide reach of smoky blue water, yet this “water” fled ever before him as he galloped on. He knew he could never come up with it, for it was of that miragy character which has more than once lured thirsty travelers to death, as they followed the blue vision, in the belief that it was a lake of real water.