Within the lantern are a certain number of lights and reflectors, each suspended on gimbals, so that they always maintain their perpendicular position, notwithstanding the rolling of the vessel.  Each of these lights consists of a copper lamp, placed in front of a saucer-shaped reflector.  The lamp is fed by a cistern of oil at the back of the reflector.  This being a revolving light, a number of reflectors were fixed to the iron sides of a quadrangular frame, and the whole caused to revolve once every minute by means of clockwork.  The reflectors on each side of the revolving frame--eight in number--are thus successively directed to every point in the horizon; and the combined result of their rays form a flash of greater or less duration, according to the rapidity of their revolution.  In the fixed lights eight lamps and reflectors are used, and are arranged in an octagonal lantern; they do not differ much in appearance from the others.