Shagbark kept continually scanning the horizon in all directions. It lacked an hour of sunset when the flickering forms to the northwest passed over the rim of vision. But the guide was not misled by the fact. He thought it likely that some of the red men, whose tribe he did not know, had galloped farther away, fearing they had been observed by the emigrants. Even in those days, the dusky rangers of the plains knew of the artificial eyes used by the whites, which enabled them to see far beyond the unaided vision.