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 the second half great circle has moved a full circle, and the lune in between covers the sphere as a spherical monogon — the area formula for the spherical lune gives 4π"R", the surface area of the sphere. A hosohedron is a tessellation of the sphere by lunes. A n-gonal regular hosohedron, {2,n} has "n" equal lunes of π/"n" radians. An "n"-hosohedron has dihedral symmetry D, ["n",2], (*22"n") of order 4"n". Each lune individually has cyclic symmetry "C", [2], (*22) of order 4. Each hosohedra can be divided by an equatorial bisector into two equal spherical triangles. The visibly lighted