Technics of the Lights

Glossery of Lighthouse and Marine terms

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Words used by lightkeepers and sailors, and their meaning. As is the case in most specialized professions, many of the terms related to lighthouses are unique.
This enumeration of lighthouse terminology, while not considered exhaustive, may be helpful in exploring how lighthouses work.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A	Acetylene	A gas that was used after 1910 as fuel for lamps. So also for lighthouse lamps. The first fuel for which the lighthouse keepers no longer had to carry liquid (oil) up the tower. It could be kept on the ground and transported through pipes to the light chamber (lamp).
	Argand lamp	Used in lighthouses, a hollow-wick oil burner with a glass 'chimney', with a silver-plated parabolic reflector behind it to amplify the light. The Argand lamp is named after Aimé 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.
B	Breakwater	A fixed or floating structure that protects a shore area, harbour, anchorage, or basin by intercepting waves.
	Bulls eye	A convex lens used to concentrate (refract) light.
C	Candela	The Candela (symbol cd) is the SI base unit of light intensity.
	Catoptric	It's from the Greek word (Catoptron) for mirror, or reflection, and the lighthouse illumination system based on the principle of reflection was given the name Catoptric System in English.
	Catwalk	A narrow elevated walkway, allowing the keeper access to light towers built out in the water.
	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.
D	Daymark	Unique color, pattern or architecture of towers and other markers used by navigators to mark their location during the day.
	Directional lights	Lights illuminating a sector of very narrow angle and intended to mark a direction to be followed. Vertical lights—Two or more lights disposed vertically or geometrically to form a triangle, square, or other figure. If the individual lights serve different purposes, those of lesser importance are called Auxiliary lights.
F	Focal Height	The height between the lamp focus point (lightroom) to the mean sea level.
	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.
	Fresnel lenses	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.
G	Gallery	Outdoor railed walkway encircling the watch room where the keeper sat and monitored the lantern and weather conditions.
	GLA	General Lighthouse Authority of Great Britain
	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.
I	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.
	Inner (or rear) Range Light	The light in a pair of range lights that is situated behind the other as viewed from the water.
L	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.
	Light Characters	Individual flashing pattern of each light. The principal Characteristics are generally the sequence of intervals of light and darkness, and, in some cases, the sequence of colours of light exhibited.
	Lighthouse Height	The height of the lighthouse tower, from ground to the lighting rod.
	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-signalling 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
N	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.
	Nominal range of the light	The luminous range of a light in a homogeneous atmosphere in which the meteorological visibility is 10 nautical miles.
	Northern Lighthouse Board	The General Lighthouse Authority for Scotland and the Isle of Man. (in short NLB)
O	Occasional lights	Lights exhibited only when specially needed:  ⛆ - Tidal light—shown at the entrance of a harbour, to indicate tide and tidal current conditions within the harbour.  ⛆ - Fishing light—for the use of fishermen and shown when required.  ⛆ - Private light—maintained by a private authority for its own purposes.      The mariner should exercise special caution when using a private light for general navigation.
	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.
P	Parapet	A walkway with railings which encircled the lamp room
	Period of a light	The time occupied by an entire cycle of intervals of light(s) and eclipse(s).
	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 harbour.
R	Refracting (Fresnel lens)	Is the redirection of a wave as it moves from one medium to another. Refraction of light is the most commonly observed phenomenon.
	Range: Geographical range of a light	The greatest distance at which a light can be seen as a function of the curvature of the earth, the height of the light source and the height of the observer. The visibility of a light is usually the distance that it can be seen in clear weather and is expressed in nautical miles. Visibilities listed are values received from foreign sources.
	Range: Meteorological visibility	The greatest distance at which a black object of suitable dimensions can be seen and recognized against the horizon sky or, in the case of night observations, could be seen and recognized if the general illumination were raised to the normal daylight level. Luminous range of a light—the greatest distance at which a light can be seen merely as a function of its luminous intensity, the meteorological visibility, and the sensitivity of the observer’s eyes.
	Range Lights	Two or more lights at different elevations, so situated to form a range (leading line) when brought into transit. The light nearest the observer is the front light and the one farthest from the observer is the rear light. The front light is normally at a lower elevation than the rear light.
	Reflecting (Fresnel lens)	Reflection (Latin reflexio, bending back) of electromagnetic radiation (such as light) is the reflection of radiation at the transition to a substance with a different impedance for this radiation. The directional reflection of light is called a reflection.
	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.
S	Seasonal lights	Usually shown only during the navigation season or for a lesser time period within that season.
	Sector limits and arcs of visibility	These are arranged clockwise and are given from seaward toward the light. Thus, in the diagram, the sectors of the light are defined as: obscured from shore to 302°, red to 358°, green to 052°, white to shore. These are bearings of the light as seen from a vessel crossing the sector lines. Under some conditions of the atmosphere, white lights may have a reddish hue. The mariner should not judge solely by colour where there are sectors but should verify this position by taking a bearing of the light. On either side of the line of demarcation between white and red there is always a small sector of uncertain colour, as the edges of a sector of visibility cannot be clearly defined. When a light is obscured by adjoining land and the arc of visibility is given, the bearing on which the light disappears may vary with the distance from which it is observed. When the light is cut off by a sloping point of land or hill, the light may be seen over a wider arc by a ship farther off than by one closer.
	Shoal	A shallow area, such as a sandbar or rock formation.
	Shore station	A lighthouse on the mainland of Scotland.
	Stag Light	A lighthouse with no family living in it, i.e. inhabited by men only.
T	Tender	A vessel used in the servicing of lighthouses and buoys.
V	Ventilator	Round 'ball' at the top of most lighthouse towers to provide exhaust for heat of the lamp and air circulation within the tower.
W	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.