Glossary - Part A

•  Aerobeacon: A modern day type of light presently used in many lighthouses to produce a characteristic.

•  Acetylene-powered Navigation Device: A light or sound signal powered by acetylene, a colorless, highly flammable gas, C2H2.

•  Aid to Navigation (ATON): Any device external to a vessel or aircraft specifically intended to assist navigators in determining their position or safe course, or to warn them of dangers or obstructions to navigation.

•  ALC: Atlantic Lighthouse Council. An umbrella group of partners concerned with lighthouse preservation and development in the Maritime region.

•  Alternating Light: A rhythmic light showing light of alternating colors.

•  Alternative Use: The non-navigational use of an authentic Lighthouse to preserve and generate support for the historic structure. This can also take place in a lighthouse that is still used for navigational purposes.

•  Arc of Visibility: The portion of the horizon over which a lighted aid to navigation is visible from seaward.

•  Argand Lamp: A hollow wick oil lamp.

•  Assembly Marks – Numbers or letters stamped on to the frame of the lens assembly to identify the correct position for a lens section or panel within the assembly.

•  Assistant keeper: A position or positions employed to help the lighthouse Keeper perform his duties. Some light stations had as many as four assistant keepers.

•  Astragal: Metal bar (running vertically or diagonally) dividing the lantern room glass into sections.

•  Authentic Lighthouse: A structure genuinely used for a navigational aid, which retains its basic historic properties.

•  Automated: A Lighthouse which has been changed to operate without the aid of a keeper. A keeper may still be retained for maintenance and security.