The Gibbs Hill Lighthouse is the taller of two lighthouses on Bermuda, and the first of only a few lighthouses in the world to be made of cast-iron. This is because at that time, steel still was not able to be bent. The optic consists of a Fresnel lens from 1904 revolving on steel bearings. However for most of its history, the lens revolved on a bed of 1,200 pounds of mercury...