River Lune to the Irish Sea at Glasson Dock. In 1847 the Commissioners built a pair of lighthouses near Cockersand Abbey to help guide ships into the port. The lower lighthouse, known as the Plover Scar Lighthouse, (sometimes called Abbey lighthouse) still stands on Plover Scar, and it remains operational. The old high light, a square wooden tower, was demolished in 1954; but the former keepers' cottage, built alongside the high light, can still be seen. Lancaster (and hence also Lancashire) is named after the Lune. The name of the ancient hundred of Lonsdale is also derived from the river. The river
Spherical lune two polar opposite points. Common examples of great circles are lines of longitude ("meridians") on a sphere, which meet at the north and south poles. A spherical lune has two planes of symmetry. It can be bisected into two lunes of half the angle, or it can be bisected by an equatorial line into two right spherical triangles. The surface area of a spherical lune is 2θ "R", where "R" is the radius of the sphere and θ is the dihedral angle in radians between the two half great circles. When this angle equals 2π radians (360°) — i.e., when