A glossary of lighthouse terms Seeing The Light

Words used by light keepers & mariners, and their meanings



As is the case in most specialized occupations, many of the terms related to lighthouses are unique. This listing of lighthouse terminology, while no means expected to be exhaustive, may serve useful when researching lighthouse operation.
Aerobeacon - A searchlight-type light originally designed for use at airports and adapted for use in a number of lighthouses throughout the Great Lakes.

Acetylene -
A fuel used which began to be used in lighthouses after 1910. It was the first fuel to eliminate the need for a keeper to carry oil up the tower, since it could be stored on the ground and an automatic sun valve used to turn the light off at daybreak and on again at dusk.

Argand lamp - A variety of light used in lighthouses that featured a hollow wick in a glass chimney, with a silvered parabolic reflector behind to intensify the light. The Argand lamp was named after Aimee Argand, the Swiss inventor who developed the design.

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

ATON - An acronym for Aid TO Navigation

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

Bulls eye - A convex lens used to concentrate (refract) light.

Catwalk - A narrow elevated walkway, allowing the keeper access to light towers built out in the water.

Characteristic - Individual flashing pattern of each light.

Chariot - The wheeled carriage at the bottom of a Fresnel lens assembly which allowed the lens to rotate around a circular iron track atop the lens pedestal.

Crib - A structure, usually of timbers, that was sunk in water through filling with stone, and served as the foundation for a concrete pier built atop it.

Daymark - Unique color, pattern or architecture of towers and other markers used by navigators to mark their location during the day.

Focal Plane -
The height above the water level at which the center of the beam of light emanates.

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.

Fog Signal -
Any type of audible device that could warn mariners from obstacles during period of heavy fog when the light could not be seen. Bells, whistles and horns, either manually or power operated were all used with varying degrees of success.

Gallery - Outdoor railed walkway encircling the watch room where the keeper sat and monitored the lantern and weather conditions.

GPS - An electronic system for identifying position, GPS is an acronym for Global Positioning System. A GPS receiver triangulates satellite transmissions to calculate position on the Earth.

Inner (or rear) Range Light - The light in a pair of range lights that is situated behind the other as viewed from the water.

Lantern - A room surrounded by windows which housed the lighthouse lens.

lens - Glass optical system used to concentrate the light in a desired direction.

Lewis Lamp - A variety of light that used a silvered copper reflector behind a glass lens. The design of the Lewis Lamp was heavily "borrowed" from that of the Argand Reflector, and was named for Winslow Lewis who imported the design from Europe.

Lighthouse Board - A nine member board appointed by the US Congress in 1852, established to manage the lighthouses throughout the United States.

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.

LORAN - An electronic system for identifying position, LORAN is an acronym for Long-Range Radio Navigation. A LORAN receiver measures the differences in the arrival of signals from three or more transmitters to calculate its position

Nautical Mile - A unit of distance used primarily at sea. The nautical mile is defined to be the average distance on the Earth's surface represented by one minute of latitude. This may seem odd to landlubbers, but it makes good sense at sea, where there are no mile markers but latitude can be measured. A nautical mile equals about 1.1508 statute miles.

Incandescent Oil Vapor (IOV) Lamp - A type of lamp in which oil was forced into a vaporizing chamber, and then into a mantle. Similar to the Coleman lamps in camping use today. 

Outer (or front) Range Light
The light in a pair of range lights that is situated in front of the other as viewed from the water. This light was situated at a lower level that the inner range, to allow both lights to be seen, one above the other.

Parapet - A walkway with railings which encircled the lamp room

Pharologist - One who studies or is interested in lighthouses.

Pier - a structure extending into navigable waters for use as a landing place, or to protect or form a harbor.

Range Lights - A pair of lights placed in such a manner that when they are visually lined up one behind the other, they lead a vessel into harbor.

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.

Rip-rap - A loose arrangement of broken rocks or stone placed to help stem erosion.

Shoal - A shallow area, such as a sandbar or rock formation.

Stag Light - A lighthouse with no family living in it, i.e. inhabited by men only.

Tender - A vessel used in the servicing of lighthouses and buoys.

Ventilator - Round 'ball' at the top of most lighthouse towers to provide exhaust for 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 could observe water conditions during storm periods.

Wickies - A nickname give to early lighthouse keepers who spent a great deal of their time trimming the wick on the lamp in order to keep it burning brightly, and to minimize sooting.

This page last updated 12/07/2003

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