Looking-glass Signaling

A method of signaling invented and extensively used by the North American Indians, both on the Plains and in the regions west of the Rocky Mountains. The reflection of the sun is flashed from a small piece of a mirror held in the hand. Indians have been known to communicate over a distance of several miles by this means. It is also extensively used in their drills,—the chief often directing the movements of his warriors with the greatest ease and certainty from a distant point overlooking the field. This method of signaling, modified by the resources of science, has been lately introduced into the English service, and used both in India and Southern Africa. A concave mirror is used, and an artificial light replaces the sun when he is absent. The method has been called heliography.