A
Apron Paving – the concrete paving surround the base of the lighthouse tower.
Astragal – the bars which support the glazing of a lantern. They may also support the roof. Simply a framing member between the glazing bars in the lantern glazing. In its true meaning an astragal is a moulding that has a rounded profile. In lanterns this is almost never the case.
B
Balcony – a walk way around the outside of the lantern, used for maintenance and (formerly, when lighthouses were manned) for observing ships. Principal parts are the balcony floor and the balcony balustrade. (Synonym: gallery deck).
Balcony Floor – floor of the balcony. Gabo Island’s balcony floor is of 1862 stone slab.
Balcony Balustrade – a handrail together with its supports. The supports are called balusters. Simply a railing or wall on the outer perimeter of the balcony, to prevent people from falling off the balcony. Generally made of metal stanchions and rails – Gabo Island’s balcony balustrade is 1962 welded mild steel.
Balcony door – door in the lantern base to give access to the balcony. In AMSA lanterns two doors are sometimes fitted but only one is operational. (Synonym: parapet hatch, service room door). Gabo Island has two balcony doors, one is operation and the other is sealed shut.
C
Cast iron – a mixture of iron and carbon with a relatively high carbon content and a low melting point, produced directly from a blast furnace.
Chance Bros – English manufacturer of optical apparatus, lanterns, cast iron stairs, cast iron towers, and other lighthouse components. The Chance family established a glass-making business in Smethwick, England in 1824 and is often described as ‘near Birmingham’. The business was absorbed into the Pilkington group of companies in 1951 and now ceases to exist.
Character – pattern of flashes of light emitted by a lighthouse, designed to identify that particular lighthouse.
Copper – a red malleable metal of low resistivity.
E
External catwalk – a landing around the external face of the tower, usually complete with handrail. Gabo Island’s external catwalk is comprised of 1888 Chance Bros. cast iron lattice floor panels with no handrail.
I
Intermediate Floors – levels found mid-way up a building. Gabo Island has 6 intermediate half-floors of original iron plate. Some portions made of recent steel chequer plate.
Internal – an open landing inside the tower complete with handrail. Gabo Island internal catwalk is comprised of 1888 Chance Bros. cast iron lattice floor panels.
Iron – there were two common types of iron used in lighthouse construction; wrought and cast. Older lights will almost certainly contain these iron types. Wrought iron has been worked by hand and is an iron alloy with a very low carbon content in contrast to steel, it also has fibrous inclusions. Cast iron is iron which has been heated until it liquefies, and is then poured into a mould to solidify.
L
Lantern – the glazed enclosure, usually of cylindrical or polygonal shape, at the top of a lighthouse, which surrounds and protects the optical apparatus. It contains the optical apparatus, made up of the lantern roof, lantern glazing and lantern base sections.
Lantern Floor – the level in a lighthouse at which the lantern is installed, and by which access may be gained to the optical system and to the inside and outside of the lantern glazing. The lantern floor is generally at or near the same level as the catwalk and cane be made from steel, concrete, or timber. Gabo Island’s lantern floor is of iron plate.
Lantern Glazing – the middle section of the lantern, circular or polygonal in plan, between the lantern roof above and the lantern base below, made up of glass panes held in a framework of glazing bars. On the landward side there may be blank panels in place of glass, or other opaque construction. Types of lantern glazing include: flat & curved trapezoidal panes and curved diamond/triangular panes. Gabo Island’s lantern glazing is of flat trapezoidal glass.
Lantern Roof – the roof of the lantern. Usually made of copper sheeting over a framework of rafters.
Lens Assembly – a transparent optically refracting element of glass. The surface is usually spherical in form.
Light Source – electric bulbs now illuminate most lighthouses.
Lighthouse – the principal structure of a lightstation, generally made up of a lantern, balcony and tower.
Lightstation – a precinct containing a lighthouse structure and other related buildings, for example. Keepers’ cottages, store room, signal house.
O
Oil store – building originally used to store fuel of the lighthouse, typically found on lightstations.
Order – a shorthand expression of the size of an optical apparatus or lantern. At the time the system of orders was established, when kerosene burners were used, longer range lights needed larger burners, and larger burners needed lens assemblies of longer focal length to ensure a sharply defined beam. Thus in turn the lantern rooms were required to be larger to house these lens assemblies. AMSA historic lantern rooms range from 1st to 4th order.
P
Pedestal – part of the optical apparatus, consisting of a metal column or base standing on the balcony floor inside the lantern and supporting the lens assembly and light source. Some later Chance documentation (such as their tariffs 1908) also refer to the lantern base as a pedestal.
T
Tower – structure to support the lantern at a sufficient height above the ground. The most common types are the masonry tower, timber-framed tower, cast iron tower, and lattice tower. Gabo Island’s tower is comprised of local granite.
W
Windbreak Wall – a structure, generally a wall or fence, used to prevent or reduce forceful wind.