Glossary - Part B

•  Ball Bearing: The method of supporting a rotating Fresnel lens (optic) on steel ball bearings enclosed in a race or cage.

•  Barometer: An instrument for measuring atmospheric pressure.

•  Beacon: A lighted or unlighted fixed aid to navigation.

•  Beam: The shaft of light emitted from each flash panel of a revolving navigation light apparatus (optic) of a lighthouse or light vessel.

•  Beehive Lens: A Fresnel lens with a magnifying central lens belt or belt of multiple bull’s-eye lenses surrounded above and below by sets of concentric annular prisms receding in diameter, presenting the general outline of a traditional type of beehive.

•  Bell: A sound signal producing bell tones by means of a hammer actuated by electricity of fixed aids and by sea motion on buoys.

•  Bi-form Lens: Two sets of Fresnel lenses, one on top of the other.

•  Bi-Valve Lens: A style of lens having two faces where the central dioptric element, on each face, is a bull’s-eye lens panel, which is surrounded by circular rows of catadioptric prisms arranged around the central, horizontal, axis of the bull’s-eye.

•  Bowsprit: A spar extending forward from the stem of a sailing ship.

•  Breakwater: A fixed or floating structure that protects a shore area, harbor, anchorage, or basin by intercepting waves.

•  Bubbles: Small cavities of gas trapped in lens glass during the manufacturing process.

•  Bug Light: Usually a very small tower.

•  Bulb Changer: An electro-mechanical or clockwork device used to automatically detect and replace defective electric light bulbs in a lighthouse optic.

•  Bull’s-eye Lens: A convex lens used to concentrate (refract) light.

•  Bull’s-eye Lens Panel: A plano/convex lens with the plano, or flat, side closest to the illuminant. Flashing (rotating) Fresnel lenses usually have one or more bull’s-eye lens panels.

•  Buoy: A floating aid to navigation used to mark channels, obstructions, and serve as information guides. Buoys, usually metal, are moored with a chain and a sinker. Unlighted buoys are nuns and cans. Lighted buoys have cages and are lighted and with or without sound signals.

•  Buoy Tender: A Lighthouse Service or Coast Guard vessel used to tend buoys, work shore aids, and occasionally perform other duties like delivering keepers, families and supplies in time past and today performing search and rescue and other duties as directed.