an orthographic projection of the sphere on the plane of the meridian, the eye being supposed at an infinite distance, and in the east or west point of the horizon.-an instrument of wood or brass, on which this projection of the sphere is made, having a movable horizon or cursor; -- formerly much used in solving some common astronomical problems.-a scale of the sun's declination for each day of the year, drawn across the torrid zone on an artificial terrestrial globe.