spherograph (sferograf), (sferograf)

[ IMG:content-1722.png:[ocr errors] IMG:content-1723.png:[ocr errors] tion of the sphere upon a disk of pasteboard, in which the meridians and parall parallels of latitude are laid down to single degrees. By the aid of this projection, and a ruler and index, the angular position of a ship at any place, and the distance sailed, may be readily and accurately determined on the principle of great circle sailing.