Lighthouse Terminology Part 2


The lighting apparatus inside the lens. Originally the lamps were oil lamps burning whale oil and later kerosene. Oil-burning lamps were replaced by electric lamps with high-powered light bulbs. In 1924, the lamp within the Fresnel lens at Sea Girt Lighthouse was changed from an oil-vapor lamp to a 300 Ps35 lamp with 100,000 candlepower.

Land-based Lighthouse

A lighthouse built on land, e.g. Sea Girt, as opposed to an off-shore light, such as Brandywine Shoal and Ship John Shoal, in Delaware Bay, and Great Beds in Raritan River, South Amboy.

Lantern Room

The round or multi-sided room at the top of the lighthouse tower in which the lens stands on a pedestal and projects its beacon through the room’s surrounding windows.


The optic placed around the light source to capture, bend and intensify the light rays to project a beam great distances.

Lens Access Panel

The hinged door(s) or panel(s) typically located between the bull’s-eye prisms that opened to give the keeper access to the interior of the lens and the lamp inside lens. In large lenses, including clamshell lenses, access was usually not through doors but through the pedestal into the base.

Lens Bag

A linen cover placed over a lighthouse lens after dawn, when the lantern was turned off and no beacon projected during daylight hours. The bag protected the lens from being discolored by the sun as well inadvertently scratched while the keeper was working in the lantern room. The lens bag also blocked the rays of the sun from heating up the lamp and reigniting the flame. The lighthouse beacon was turned off during daytime, when mariners navigated by landmarks, to save on fuel, the biggest expense in operating a lighthouse. The lens bag would be removed before dusk, and the lamp turned back on, the lens set in motion, and the beacon projected throughout the night, until dawn.

Lens Curtain

Canvas or linen curtains hung on the inside of the lantern room and were drawn across the windows during daytime when the lamp was extinguished and no beacon projected. The curtains and the lens bag (see previous entry) blocked the sun’s rays from discoloring the lens prisms and heating up the lamp and reigniting the flame. The beacon was turned off during daytime, when mariners navigated by landmarks, to save on fuel, the biggest expense in operating a lighthouse. The curtains were opened before dusk, the lamp turned back on, the lens set in motion, and the beacon projected throughout the night. At Sea Girt, in response to neighbors who complained about the beacon keeping them awake at night, the curtains on the west side of the lantern room remained drawn to prevent the light from projecting inland.


A vessel, anchored offshore at a strategic point, which is equipped with a lens atop a metal tower located on the ship’s superstructure or deck.

Examples: Ambrose Lightship (served at various locations in New York Harbor, now decommissioned and docked at South Street Seaport Museum) and Barnegat Lightship (served at various locations off southern New Jersey, now decommissioned and privately owned. Ambrose Lightship is docked in Camden awaiting restoration).

PHAROS_thumb_thumbLight Source

The source of the illumination used to aid navigation. The earliest navigational lights were produced by burning wood and other combustibles on beaches, hilltops, cliffs and later on the tops of manmade towers. The first lighthouse was 400-foot-tall Pharos, built in the 3rd century B.C. in Alexandria, Egypt as a daymark.

Eventually, wood was carried up to the columned, open-air room at the top of Pharos where bonfires were set at night. At Pharos and the other lighthouses that followed, other fuels were also used to keep the fire burning, including coal, hay, hemp, peat and tar. With the development of oil lamps in the 1600s, lamps became popular in lighthouses. Fuels used in lamps included whale oil, lard and later kerosene. In 1696 England’s Eddystone Lighthouse was the first to enclose the lantern room with glass windows, enabling the use of candles set in chandeliers. In 1862, the Dungeness Lighthouse in England became the first lighthouse using electricity to power carbon arc lamps. In 1886, the Statue of Liberty was the first U.S. lighthouse to be illuminated with electric lights.

Live-in Lighthouse

Lighthouse in which the tower is attached to the living quarters, e.g. Sea Girt Lighthouse. In the more typical design, found at Sandy Hook and Barnegat, the tower is separate from the keeper’s quarters.


Acronym for long-range radio navigation, the name given to a terrestrial system of navigation in which a ship’s crew can calculate speed and fix their position by tracking the radio beacons transmitted from three or more stations. LORAN was developed by the British and Americans and used by the Allies during W.W. II as an alternative to navigation by lighthouses, whose beacons were turned off so as not to give direction to enemy ships.

Offshore Lighthouse

A lighthouse located offshore, built on a foundation of pilings, rocks or caissons.

Examples of offshore lights include: Ambrose Light Station (steel pilings) in the approach to New York Harbor 7 miles east of Sandy Hook, Robbins Reef (cast-iron sparkplug tower on a granite pier foundation) at the entrance of Kill van Kull between Upper New York Bay and Newark Bay, Ship John Shoal (caisson) in Delaware Bay, off Fortesque, New Jersey.


Size of the Fresnel lens. There are seven basic orders: 1st, 2nd, 3rd, 3rd-½, 4th, 5th and 6th. First order, the largest lens with an optical area measuring 8½ feet high, projects a beacon 22 miles. A 6th order lens, the smallest lens measuring 1½ feet in height, projects a beacon five miles. Sea Girt was equipped with a 4th order lens, 2½ feet tall, that produced a beacon that could be seen for 15 miles.

Parabolic Reflector

The light system widely used at lighthouses in the decades before the development of the far-superior Fresnel lens. The light source – candles or oil-burning lamp – was placed on the bottom of a large, stationary bowl, the inside of which was lined with a concave mirror known as a parabolic reflector.


The metal platform and railing that wrap around the outside of the lantern room at the top of the tower. Also known as the gallery.

The keeper would go onto the parapet for an unobstructed view of the water and ship traffic and to clean the exterior of the windows and access the vent.


The length of time of one full revolution of the lens during which the beacon would have completed one cycle, projecting its characteristic pattern of blinks on and off.


A lighthouse enthusiast, student or scholar. The name derives from the first known lighthouse, Pharos, which was built in the 3rd century B.C. in Alexandria, Egypt.

Pier Lighthouse

A lighthouse built on a sandbar or natural rock foundation. Large boulders – known as rip-rap – would be dropped around the perimeter of the pier to protect the foundation from ice, floating debris and ships off course. ROBBINS_REEF_njlhs_thumb_thumb

An example of a pier lighthouse is Robbins Reef, built on a granite pier on a sandbar off the tip of Staten Island at the entrance of Kill van Kull, the channel linking Newark Bay and Upper New York Bay.

Range Lights

Range lights work in pairs – a front-range light and a taller rear-range light – to guide mariners safely through narrow channels. To keep on course in a narrow body of water, mariners steer their craft so that beams from the front-range light and the rear-range light align to produce one beam. If a mariner sees two beams of light, the ship is sailing outside the channel’s safe area.


The capture of light from the light source and throwing the light back.


The bending of the light. Light disperses in all directions. The angled prisms in a Fresnel lens refract the light so that it projected outward horizontally in a compressed, intense beam.

Revolving Light

A lens that revolves, creating the illusion of a pulsing or blinking light. (See definition for flashing light).


Large boulders placed around an offshore lighthouse built on a pier or sandbar, such as Robbins Reef Lighthouse off Staten Island, to protect the pier foundation from ice, floating debris and ships off course.

SCREW_PILE_LIGHT_uscg_thumb_thumbScrew-Pile Lighthouse

A design first developed in 1838 that was used for off-shore lighthouses built close to shore in soft-bottomed waters, such as Chesapeake Bay.

The lighthouses stand on platforms that were held above the water line by metal piles – or poles – that at the other end were screwed deep into the sand or mud floor.


See definition for chimney.


The unique appearance of a lighthouse’s beacon to enable mariners to distinguish it from the beacons of other lighthouses in the area. There are several variables that determine a beacon’s signature: one or more lights, color of a beacon (white, red, green, etc.), one color or changing colors, a steady light or a blinking light, if a blinking light the length and number of flashes and dark periods per minute. Also known as character(istic).

Skeleton Tower

A skeleton tower consists of a platform that stands on metal legs that are reinforced by metal cross bars. Range lights are often installed on skeleton towers.

The skeleton tower may have a center cylinder inside of which is a spiral staircase to allow access to the platform and light, as in the case of Tinicum Rear Range Light near the Delaware River in Billingsport, New Jersey. The shorter Tinicum Front Range Light in nearby Paulsboro does not have the center cylinder but does have a ladder attached to the skeleton.


Supply ships of the U.S. Lighthouse Service that brought supplies to lighthouses and lightships. Supplies would be off-loaded from the tender to a rowboat that crewmen rowed to the lightship, offshore light, or to the beach by a land-based lighthouse. Each tender carried the designation USLHT (U.S. Lighthouse Service Tender) preceding the ship’s name. Sea Girt Lighthouse was serviced by USLHT Tulip.


A vent at the apex of the lantern room to allow fumes from the burning fuel to escape and fresh air to enter the lantern room. The exterior of the vent is protected by a round metal cap.

Watch Room

The storage room immediately below the lantern room where wicks, fuel and other lantern supplies and tools are kept. The room also serves as a lookout point.


Nickname for a lighthouse keeper whose duties include trimming the wick in the lamp inside the lens to insure the lamp burned bright and didn’t dirty the lens and lantern room windows with soot.

Contributing to this list: Kraig Anderson,; Bob Gleason, Chair of Educational Outreach and the Speakers Bureau of the New Jersey Lighthouse Society; Thomas Tag, Technical Advisor, U.S. Lighthouse Society; and Historian’s Office, the United States Coast Guard.