spherical lune

A portion of the surface of a sphere included between two great semicircles, having a common diameter. The angle of the lune is the same as the angle of the planes of the circles. [LUNE.] spherical-polygon, s . A portion of the surface of a sphere bounded by the arcs of three or more great circles. Like plane polygons they are named from the number of sides or angles. [POLYGON.] spherical-projection, s . A representation of the surface of the sphere upon a plane, according to some geometrical law, so that the different points in the representation can be accurately referred to their positions on the surface of the sphere. [PRIM ITIVE-CIRCLE, PRIMITIVE-PLANE.]