Aid to Navigation - Markers, buoys, lights, fog signals, and electronic systems such as G.P.S. & loran. Used to assist mariners in fixing their positions, aid in marking landfalls, mark dangerous shoals and rocks and to enable ships to keep within a channel.

Acetylene Sun-Valve System - An early lamp system used to automate lighthouses. The Sun Valve would automatically turn the gas on as the cold of night arrived and off with the arrival of the warmth of day. A pilot light would remain constantly lit. Equipped with a tank into which acetylene could be pumped from lighthouse tenders, lights could be supplied with sufficient acetylene for an entire season.

Aero-Beacon - A modern type of light presently used in many lighthouses to produce a characteristic. Also used in many airport beacons.

Argand Lamp - A hollow wick oil lamp.

Astragal - Metal bars dividing the lantern room glass into sections.

ATON - Aids to navigation.

Bull's-eye - A convex lens used to concentrate (refract) light.

Characteristic - Individual flashing pattern and/or color of light exhibited.

Clockworks - A series of gears, chains and counter-weights used to rotate the lens. Working similar to that of a grandfather clock the counter-weights were hoisted every day .

Crib - A foundation usually constructed of timber and filled with rock and/or concrete. Sometimes sheathed with steel plate. 

Day-Mark - Unique color and/or pattern that identifies an aid to navigation or vessel during daylight hours.

Ebbing - A tide falling or moving from high to low water.

Fixed Light - A steady, non-flashing beam.

Flooding - A tide rising or moving from low to high water.

Fog Signal - A device used as an aid to navigation in fog or darkness. Some types of devices used are cannons, bells & whistles.

Fresnel Lens - A parabolic type lens invented by French physicist Augustin Fresnel, commonly used in lighthouses throughout the world. Classified by size into six "orders" based on the lens focal length. The First Order is the largest at 12 feet tall with a diameter of 6 feet and a focal length of 36 inches. The Sixth Order is the smallest at 2 feet tall with a diameter of 1 foot and a focal length of 5.9 inches. Click here to see a Second Order lens

Fuel - A material that is burned to produce light (fuels used for lighthouses included wood, lard, whale oil, tallow, kerosene.) Today electricity is common with acetylene gas and solar power also used.

Gallery - On a lighthouse tower, a railed platform, walkway or balcony located outside the watch room and/or lantern room. Also referred to as a Parapet.

G.P.S. - Global Positioning System that operates off of at least (3) satellites to triangulate location and elevation.

Hollow - A concentric cotton wick used in Argon and other type lamps.

Keeper - Individual who takes care of the operation of the light in a lighthouse along with it's maintenance. (The head keeper is responsible for the operation of a light station.)

Lamp - The lighting apparatus inside a lens.

Lamplighters - Civilians who care for minor working lights.

Lantern Room - Area within glass panels surrounding the lamp and lens at the top of a lighthouse tower.

Lens - A curved piece of glass for bringing together or spreading rays of light passing through it.

Lighthouse - A tower used as an aid to navigation marking a hazard or point of entrance. Usually consisting of a very bright light atop a tower and often a foghorn or siren and radio beacon.

Lightship - A vessel used to mark a hazardous area and/or guide shipping traffic, anchored in position with a mast mounted beacon and equipped with a steam whistle for fog warning. 

Log - A book for maintaining complete daily records, 

Loran - Long range aid to navigation. Operates off of (3) land based radio towers to triangulate location. 

Navigation - Directing the course of a vessel. 

Order - Size of the fresnel lens which determined by the brightness and distance the light will travel.

Parabolic - A bowl-like metal, silver or chrome plated, reflector with a small oil lamp in the center.

Parabolic Lens - A lens that has the shape of a parabola rotated about the parabola's axis of symmetry. It reflects rays of light in parallel lines from a light source at the lens' focus.

Parapet - The walkway around the outside of the lantern room. Also referred to as a Gallery.

Port - A Harbor or Port of Call providing protection for vessels. Also the Left side of a vessel, marked by a red light or day-mark.

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

Radio Beacon - A fixed radio beacon that aids navigation by sending a radio signal. Vessels can determine location by taking bearings from several different signals. 

Range Lights - Two lights or Day-Marks, located a distance apart, visible from one direction only. When  one light is visible directly above the other, you are in the marked channel for safe passage.

Reef - A ridge of rocks, sand, or coral at or near the surface of a body of water.

Reflect - Bend or throw back light.

Refract - Bend or slant rays of light.

Revolving Light - A rotating beam of light that produces a flash or characteristic

Rip-rap - A loose foundation or an arrangement of broken stone in water or soft terrain used to help prevent erosion. The material used for this is known as rap or rapping.

Shoal - An area of rocks or sand at or near the surface of a body of water.

SOS - A distress signal.

Spider Lamp - Shallow brass pan containing oil and several solid wicks.

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

Starboard - The right side of a vessel, marked by a green light or day-mark.

"Tall Five" - Five Great Lakes lighthouse towers with supervision of design and construction appointed to U.S. Army Corps of Engineers Major O.M. Poe. They were all constructed from the same plans giving them the classic "Poe" style. The lighthouses are: Michigan's Little Sable, South Manitou Island and New Presque Isle along with Wisconsin's Wind Point and Illinois' Grosse Point.

Tide - The regular rise and fall of the water level along a seacoast or in an ocean port. Gravitational attraction of the moon is the primary cause of tides. With the moon orbiting the earth every 24 hours and 50 minutes, low and high tides are about 12 hours and 25 minutes apart.

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

Vapor Lamp - A device that turns fuel into vapor, after contacting the hot walls of a vaporizing chamber, which then passes into a mantle where it burns with a very bright light.

Ventilator Ball - A ball shaped vent above the lantern room designed to remove excess heat and exhaust fumes, allowing fresh air to enter.

Watch Room - A room immediately below the lantern room used as a service room. Fuel and other supplies were often kept here. The keeper prepared the lanterns for the night and often stood watch of the burning light from this room. The clockworks (for rotating lens) were also located there.

Wick Solid - A solid cord used in spider lamps that draws fuel up to the flame by capillary action.

Weight Well - A cylindrical pit in the center of the tower foundation designed to house the descending clock-work counter-weight as it rotates the lantern.