Every part of life contains new vocabulary that does not
always have meaning outside its discipline.
Lighthouses are no exception. The following terms are
just a few that will aid in understanding
lighthouses and their functioning.

Adrift --- Afloat or unattached in any way to shore or seabed.

Aerobeacon --- A modern-day type of light currently used in many lighthouses.

Aid to Navigation --- United States Coast Guard term used to describe any device used as an aid in travel over water.

Alternating light --- A rhythmic light showing light of alternating colors.

Arc of visibility --- The portion of the horizon over which a lighted aid to navigation is visible from seaward.

Articulated beacon --- A beacon-like buoyant structure, tethered directly to the seabed and having no watch circle.

Assigned position --- The latitude and longitude position for an aid to navigation.

Astragal --- Metal bar that runs vertically or diagonally and divides the lantern room glass into sections.

Attached tower --- Means that the tower is connected to or built against the dwelling structure, but is not part of it like the integral tower.

Beacon --- A lighted or unlighted fixed aid to navigation attached directly to the earth's surface.

Bearing --- The horizontal direction of a line of sight between two objects on the surface of the earth.

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

Bifurcation --- The point where a channel divides when proceeding from seaward; also, the place where two tributaries meet.

Bulls eye --- A convex lens used to refract light.

Buoy --- A floating device of defined shape and color, which is anchored at a given position and serves as an aid to navigation.

Characteristic --- The audible, visual, or electronic signal displayed by an aid to navigation to assist in its identification.

Commissioned --- The action of placing a previously discontinued aid to navigation back in operation.

Conical Tower --- Lighthouse tower that is shaped like a cone  (i.e. tower tapers in from bottom to top).

Cylindrical Tower --- Lighthouse tower that is shaped like a cylinder (i.e. top is as wide as bottom).

Daybeacon --- An unlighted fixed structure which is equipped with a dayboard for daytime identification.

Dayboard --- The daytime identifier of an aid to navigation.  Its shape is either a square, rectangle, or triangle, and its color is red, green, white, orange, yellow, or black.

Daymark --- Unique pattern and/or color scheme that identifies a specific lighthouse during daylight hours.

Diaphone --- A sound signal which produces sound by means of a slotted piston moved back and forth by compressed air.
Discontinued --- To remove from operation (permanently or temporarily) a previously established aid to navigation.

Eclipse --- The dark period in a lighthouse flash characteristic.

Emplaced --- Means "to put in place or position" and therefore indicated the foundation is whatever was at the spot the light tower was positioned.

Established --- To place an authorized aid to navigation in operation for the first time.

Fixed Light --- A light showing continuously and steadily.

Flashing Light --- A light in which the total duration of light in each period is shorter than the total duration of darkness and the appearances of light (flashes) are usually of equal duration.

Fog Signal --- A device such as a cannon, bell, whistle, siren, reed trumpet, diaphone (BEEEEooooh) horn or diaphragm (brrrrrrrrr) horn that provides a specific noise to aid navigation in dense fog.

Fresnel Lens --- A type of optic invented in 1821 by Augustine Fresnel 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.  In the past these included wood, lard, whale oil, tallow or kerosene.  Today, acetylene gas, electricity and solar power are used to illuminate lighthouses.

Gallery --- A platform, balcony, or walkway located outside the lantern room  or watch room on a lighthouse tower.

Horn --- A sound signal which uses electricity or compressed air to vibrate a disc diaphragm.

Integral Tower --- Means the light tower is integrated into or is a part of the dwelling structure.

Junction --- The point where a channel divides when proceeding seaward; also, the place where a distributary departs from the main stream.

Keeper --- The person who takes care of keeping the light burning at a lighthouse.

Lamp --- The lighting apparatus inside a lens.

Lantern Room --- Glassed-in area at the top of a lighthouse tower which contains the lamp and lens.

Lens --- A curved piece of glass used to gather or spread rays of light that are passing through it.

Light --- The signal emitted by a lighted aid to navigation;  also, the illuminating apparatus used to emit the light signal.

Light Station --- Complex necessary to support the lighthouse including the keeper's quarters, oil house, fog signal building, cisterns, boathouse, etc....

Lighthouse --- A building or structure that includes or supports the lantern room & lens and provides a fixed aid to navigation.

Lightship--- Vessel moored at an area such as a shoal or harbor entrance where it was too dangerous or expensive to build a lighthouse.  Lightships were in reality floating lighthouses.  This duty was always considered the most dangerous because lightships were not allowed to leave their position under any circumstances and no matter how severe the weather was.  Lightships were replaced by buoys.

Lighthouse Depot --- Place where supplies needed to service lighthouses were shipped.  Some also had manufacturing plants, and experiments were performed on new types of lighting apparatus and building materials for towers.

Lighthouse Tender --- Ship used to supply the light and fog signal stations, maintain buoys, and service lightships.  Similar vessels today are called buoy tenders.

Local Notice to Mariners --- A written document issued by each USCG district to disseminate important information affecting aids to navigation, dredging, marine construction, special marine activities, and bridge construction on the waterways within that district.

Log --- A book used to maintain a daily record at a lighthouse.

LORAN (LOng RAnge Navigation) --- An electronic aid to navigation consisting of shore-based radio transmitters.  The LORAN system enables users equipped with a LORAN receiver to determine their position quickly and accurately, day or night, in practically any weather.

Octagonal Tower --- Lighthouse tower that has 8 sides.

Oil House --- A small concrete or stone building which stored oil for a lighthouse.  Oil houses were built after kerosene, a highly flammable fuel, began to be used.

Occulting Light --- A light in which the total duration of light in a period is longer than the total duration of darkness and the intervals of darkness (eclipses) are usually of equal duration.

Offshore tower --- A monitored light station built on an exposed marine site to replace a lightship.

Order --- Size of the Fresnel lens which determines the distance the light will travel (i.e. how far away the light can be seen).

Period --- The interval of time between the commencement of two identical successive cycles of the characteristic of the light or sound signal.

Pharologist --- One who studies or is interested in lighthouses.  This name is derived from Pharos, the first known lighthouse of the world.

Prism --- A transparent piece of glass that disperses light.

RACON --- A radar beacon which produces a coded response, or radar paint, when triggered by a radar signal.
Radiobeacon --- Electronic apparatus which transmits a radio signal for use in providing a mariner a line of position.
Range --- A line formed by the extension of a line connecting two charted points.

Range Lights --- A pair of fixed aids that allow a mariner to know his position in a channel or river by "lining up" the two aids to form a single line of light.

Reflect --- Bend or throw back light.

Refract --- Bend or slant rays of light.

Revolving Light --- One that produces a flash or characteristic.

Shoal --- A place where a body of water suddenly shallows, usually exposing a sand bar or rock formation at low tide.

Siren --- A sound signal which uses electricity or compressed air to actuate either a disc or cup-shaped rotor.
Sound signal --- A device which transmits sound, intended to provide information to mariners during periods of restricted visibility and foul weather.

Square Tower --- Lighthouse tower that has 4 sides.

Tower --- Structure supporting the lantern room of the lighthouse.

Watch Room --- A room immediately below the lantern room where fuel and other supplies were stored and where the keeper often kept watch.

Wickie --- Nickname given to lighthouse keepers because of the task they performed of trimming the wick of the lamps.

Whistle --- A wave actuated sound signal on buoys which produces sound by emitting compressed air through a circumferential slot into a cylindrical bell chamber.
Withdrawn --- The discontinuance of a floating aid to navigation during severe ice conditions or for the winter season.