Aid to Navigation: A buoy, beacon, lighthouse, lightship or any other structure or device installed, built or maintained for the purpose of assisting the navigation of vessels.
Alternating (abbreviation “Al”): A light which shows alternating colors. For example, "Al.W.G." shows white and green lights alternately. Arc of Visibility: The portion of the horizon over which a lighted aid to navigation is visible from seaward. |
Chariot: The wheeled carriage at the bottom of a Fresnel lens assembly, which allows the lens to rotate around a circular iron track atop the lens pedestal.
Clamshell Lens: Rather than being round as most lenses are the Clamshell, or Bivalve, lenses has a flattened shape reminiscent of a clamshell. They usually have two bull's-eyes, one on each side of the lens. Clockwork Mechanism: The mechanism that turned the light in early lighthouses. It was made up of a series of gears, pulleys and weights, which had to be wound periodically by the keepers. |
Directional Light: A light illuminating a sector or very narrow angle and intended to mark a direction to be followed.
Eclipse (abbreviation “ec”): An interval of darkness between appearances of a light. Emergency Light: A light of reduced intensity displayed by certain aids to navigation when the main light is extinguished. |
Fresnel Lens: An optic array manufactured using the design principles of Augustin Fresnel, the French physicist who first established the design, and after whom the Fresnel Lens was named. A type of optic consisting of a convex lens and many prisms of glass, which focus and intensify the light through reflection and refraction.
Fuel: A material that is burned to produce light (fuels used for lighthouses included wood, lard, whale oil, tallow, kerosene). Today, besides electricity and acetylene gas, solar power is also used. |
Incandescent Oil Vapor Lamp: A type of lamp in which oil is forced into a vaporizing chamber, and then into a mantle. Similar to the Coleman lamps, used in camping today.
Inner (or rear) Range Light: The light in a pair of range lights that is situated behind the other as viewed from the water. Interrupted Quick Light (abbreviation “I.Q.”): A quick flashing light in which the rapid alternations are interrupted at regular intervals by eclipses of long duration. |
Light Sector: The arc over which a light is visible, described in degrees true, as observed from seaward towards the light. May be used to define distinctive color difference of two adjoining sectors, or an obscured sector.
Light Station: A complex containing the lighthouse tower and all of the outbuildings, i.e. the keeper’s living quarters, fuel storage building, boathouse, fog-signaling building, etc. Light Tower: A tall structure used to elevate a light beacon so that mariners can see it at a distance. |
Navigation: Determining a path for travel over water.
NGA: An acronym for National Geospatial-Intelligence Agency Nominal Range: The maximum distance a light can be seen in clear weather (meteorological visibility of 10 nautical miles.) Listed for all lighted aids to navigation except range lights, directional lights, and private aids to navigation. |
Pharologist (or Pharophile): One who studies or is interested in lighthouses.
Pharology: The scientific study of lighthouses and signal lights, as well as their construction and illumination. Pier: A structure extending into navigable waters for use as a landing place, or to protect or form a harbour. Primary Aid To Navigation: An aid to navigation established for the purpose of making landfalls and coastwise passages from headland to headland. |
Revetment: A facing placed on a bank or bluff of stone to protect a slope, embankment, or shore structure against erosion by wave action or currents.
Revolving Light: One that produces a flash or characteristic due to the rotation of the Fresnel lens. Rhythmic Light: A light showing intermittently with a regular periodicity. |
Tower: Structure supporting the lantern room of the lighthouse.
Ventilator: Round “ball” at the top of most lighthouse towers to provide exhaust for the heat of the lamp and air circulation within the tower. Watch Room: A room, usually located immediately beneath the lantern room, outfitted with windows through which a lighthouse keeper can observe water conditions during storm periods. |