Spiral Staircases and Lighthouse Interiors
The World Inside the Tower
From the outside, a lighthouse is a simple shape: a cylinder, a cone, an octagon. The exterior communicates function, not interior complexity. But inside even a modest tower the visitor finds a world of considerable intricacy — cast-iron staircases that spiral with geometric precision through a shaft barely two metres across, plastered rooms that served for a century as kitchen, bedroom, watch room and store, and at the summit a lantern room of fine Victorian metalwork enclosing an optical apparatus of demanding technical refinement. The interior of a lighthouse is a machine for keeping a light, and every element of it was designed with that purpose in mind.
The Staircase as the Spine of the Tower
The spiral staircase is the dominant interior feature of any masonry lighthouse. In towers from the eighteenth and early nineteenth centuries, the stair was usually cut stone: individual treads cantilevered from the inner face of the wall or supported on a central stone newel. The stair at Bell Rock lighthouse, built by Robert Stevenson and completed in 1811 on a submerged rock eleven miles off the Angus coast, is a stone spiral that winds from base to summit within a granite tower 35 metres tall. Each step is a single dressed block, fitted with precision into the curve of the wall. The Bell Rock stair has been climbed more than two hundred years without significant deterioration.
From the mid-nineteenth century, cast iron replaced stone as the standard material for lighthouse stairs. The reason was partly cost — a cast-iron stair could be manufactured to a standard pattern and assembled on site, whereas stone stairs required skilled masons working in difficult conditions — and partly the adaptability of iron to the circular geometry of a cylindrical tower. A cast-iron stair is fabricated from a series of identical wedge-shaped treads, each with a raised non-slip surface, bolted together into a helical unit and fixed to a central iron column. The individual components are light enough to be carried by one or two men, which made them practical for rock tower construction where all materials had to be lifted from a boat or a temporary derrick.
The Cape Hatteras Interior
Cape Hatteras lighthouse in North Carolina, the tallest brick lighthouse in the United States at 59 metres, contains one of the finest cast-iron staircases in any lighthouse tower. Completed in 1870, the stair spirals through the tower in 268 steps arranged in a double helix — two independent flights sharing the same central column and rising in parallel, allowing keepers and their families to ascend and descend without meeting on the narrow treads. The handrail is a continuous curve of cast iron, decorated with simple mouldings characteristic of the period, and the lantern at each step is visible through a narrow slot in the stair column, giving a vertiginous view of the full height of the interior.
The iron stair was designed by the United States Lighthouse Board's engineering staff and was typical of the federal construction standard of the period. Similar staircases, cast by the same contractors and installed to the same specification, can be found in lighthouses from Cape Lookout in North Carolina to Ponce Inlet in Florida.
The Watch Room
Between the last domestic floor and the lantern itself, most towers contain a watch room — the station from which the keeper monitored the light and made observations of the weather. The watch room is typically a circular chamber with windows on all sides, below the level of the lantern gallery. In the watch room stood a table for the log book, a chair, sometimes a small stove, and the controls for the light's mechanism.
At the Eddystone lighthouse off Plymouth, rebuilt by Sir James Douglass and completed in 1882, the watch room is finished in painted cast iron with a polished brass binnacle and hooks for weather instruments. It has the quality of a well-fitted ship's cabin: everything secured, everything close to hand, nothing superfluous. The observation windows are set at eye level for a seated keeper, and the ventilation system — a network of bronze grilles in the walls — was designed to carry the smell of the lamp oil out of the room and up to the lantern rather than down into the living quarters below.
Living Floors and Domestic Quarters
In towers designed to be occupied rather than merely maintained by periodic visits, the lower floors served as domestic quarters. The floors were typically stacked vertically: the oil store at the base, then the principal keeper's quarters, then the assistant keeper's room, then a store room, and finally the watch room below the lantern. Each floor was a single circular room, barely four metres in diameter in a medium-sized tower, with a fireplace or a stove pipe for heating and a cistern or piping for water.
The Fastnet lighthouse off the southwest tip of Ireland, rebuilt by William Douglas and completed in 1904, had four living floors in its granite tower, each accessed from the central stair. The rooms are surprisingly habitable — the plaster is painted in light colours, the windows are double-glazed to exclude the Atlantic wind, and the fireplace surrounds are neatly tiled. The keepers who occupied these rooms lived in genuine confinement: the Fastnet Rock is barely 0.1 hectares in area at low water, the seas around it frequently too rough for a boat to land, and the only communication with the mainland was by radio after its installation in the twentieth century.
The Lantern Room
The lantern room is the most precisely engineered space in the lighthouse. Its purpose is to protect the optical apparatus from wind and weather while admitting the maximum possible light through its glazing. The structural framework of the lantern — the cast-iron or mild-steel members that divide the glazed panels — must be strong enough to withstand gale-force wind and wave impact in the most exposed positions, yet as slender as possible to minimise the shadow sectors where the lantern frames obstruct the outgoing beam.
The glazed panels of a Victorian lantern were typically 6-millimetre plate glass, set in putty within the iron framework and sealed against water ingress. In the largest lanterns — first-order stations such as Bishop Rock or Ile Vierge in Brittany — the glazing could stand nearly two metres tall and be divided by the vertical astragal bars into panels 30 or 40 centimetres wide. The astragal bars cast a rotating shadow as the lens revolved, and their width was the subject of considerable engineering attention: every millimetre of additional width meant a fraction more light lost to the beam.
Modern lanterns are often glazed with borosilicate glass or polycarbonate, which withstands the thermal shock of LED optics cycling from cold to hot and back more reliably than plate glass. In the most exposed positions, laminated glass bonded with an interlayer is used to prevent the lantern from breaching entirely if a single pane is struck by wind-driven debris or a wave.
The Lens Pedestal and Rotation System
At the centre of the lantern room, the optical apparatus sits on a pedestal that varies in design from a simple iron plinth, in stations with a fixed light, to an elaborate mercury-bath rotation system in the great revolving lights. The mercury-bath, in which the lens floats on a shallow trough of liquid mercury so that it can be rotated with minimal friction by the clockwork drive, was the standard arrangement for major lighthouses from the mid-nineteenth century until electric motor drives became standard in the middle of the twentieth.
The pedestal for a first-order Fresnel lens in a mercury bath was itself a work of precision engineering. At Cape Bonavista in Newfoundland, where a first-order dioptric lens dating from 1874 is preserved intact, the mercury trough is visible in cross-section in the museum display. The lens, weighing several tonnes, was designed to rotate once every three minutes driven by a falling weight equivalent to a large grandfather clock — an elegant solution that, once wound, required no external power and worked regardless of wind or weather.
Maintenance and Cleaning
The keeper's primary technical duty was the care of the optical apparatus. The Fresnel lens gathered dust, salt and the residue of lamp oil. A daily programme of cleaning was mandatory: the prisms wiped with lens cloths dampened in spirit; the brass fittings polished; the lamp wick trimmed to the precise height specified by the authority's instructions; the mercury trough inspected for contamination. The watch room log at many preserved stations contains entries noting the exact character of the cleaning done on each watch.
The physical condition of these preserved interiors reflects this discipline. At the Pointe-au-Pere lighthouse in Quebec, opened as a museum in 1979, the Fresnel lens is in working condition after more than a century of use. At the Makapuu Point lighthouse on the island of Oahu in Hawaii, an unusual hyper-radiant lens — the largest Fresnel lens type, 2.5 metres in diameter — remains in the lantern room and can be viewed from the public path below.
Open the map to find lighthouses open for interior visits, where you can climb the spiral stairs and stand in the lantern room.
Preservation and Access
The interiors of historic lighthouses are among the most evocative spaces in industrial archaeology. They record, in their fittings, their inscriptions and their physical wear, the lives of the men and women who kept the light through war, storm and isolation. The spiral stair worn smooth on the outer edge by generations of feet; the log book entry for the night a great ship went ashore nearby; the painted name of a keeper above the door of a room he occupied for twenty years — these details survive in lighthouses that have been carefully preserved and opened to the public, and they are absent from the smooth modern towers that have replaced them.