Lighthouse

History

Before defined ports, mariners used fires built on hilltops for guidance. Elevating the fire on a platform improved visibility and led to the development of the lighthouse. In antiquity, lighthouses primarily served as entrance markers to ports rather than as warnings for reefs, unlike many modern examples. The most famous ancient lighthouse was the Pharos of Alexandria, Egypt, which collapsed after a series of earthquakes between 956 and 1323.

The intact Tower of Hercules at A Coruña, Spain, provides insight into ancient construction, while coins and mosaics depict lighthouses such as the one at Ostia. The modern era began around the turn of the 18th century, with increased transatlantic commerce driving construction. Advances in structural engineering and lighting equipment allowed larger, more powerful lighthouses exposed to the sea. The Eddystone Rocks, a major hazard in the English Channel, saw the first tower fully exposed to the open sea, an octagonal wooden structure built by Henry Winstanley from 1696 to 1698.

Technology

The lamp, whether electric or oil-burning, is the heart of a lighthouse, with its beam focused by a lens or optic. Power sources have shifted dramatically over time. Early lighthouses used open flames and candles, then the Argand hollow wick lamp with a parabolic reflector arrived in the late 1700s. Whale oil and wicks followed, with kerosene gaining popularity in the 1870s.

Around the start of the 1900s, electricity and acetylene gas from calcium carbide began replacing kerosene. The Dalén light could automatically turn the lamp on at dusk and off at dawn. In the later 1900s, many remote Soviet lighthouses used radioisotope thermoelectric generators, which needed no refueling or upkeep. After the Soviet Union fell, records of these locations were reportedly lost, and the generators deteriorated from vandalism and scrap-metal theft, with thieves possibly unaware of the radioactive danger.

Today, energy-efficient LED lights can run on solar panels with battery backup. Many Fresnel lenses have been swapped for rotating aerobeacons, which need less maintenance. Modern automated lighthouses often use high-intensity lights that emit brief flashes in all directions, concentrating light in time rather than direction, similar to aircraft warning lights.

Building

Lighthouse buildings vary by location and purpose but share common components. A light station includes the lighthouse tower and outbuildings such as the keeper's living quarters, fuel house, boathouse, and fog-signaling building. The tower supports the lantern room, a glassed-in housing containing the lamp and lens. Its glass storm panes are held by metal muntins running vertically or diagonally.

Atop the lantern room is a stormproof ventilator to remove smoke and heat, and a lightning rod connected to the metal cupola roof provides a safe conduit for strikes. Beneath the lantern room is a Watch Room or Service Room for storing fuel and supplies, where the keeper prepared the lanterns and stood watch; clockworks for rotating lenses were also located there. An open platform called the gallery is often outside the watch room (Main Gallery) or lantern room (Lantern Gallery), used for cleaning the lantern room windows.

Lighthouses near each other with similar shapes are often painted in unique daymark patterns for daytime recognition, such as the black and white barber pole spiral of Cape Hatteras Lighthouse or the horizontal bands of Race Rocks Light. The lamp must be high enough to be seen before danger is reached; minimum height is calculated by trigonometry. Where dangerous shoals lie far off a flat sandy beach, tall masonry coastal lighthouses are built, often cylindrical to reduce wind effect, like Cape May Light. Smaller versions serve as harbor lights, such as New London Harbor Light.

Maintenance

Lighthouses in Australia are run by the Australian Maritime Safety Authority. India's are looked after by the Directorate General of Lighthouses and Lightships, part of the Ministry of Ports, Shipping and Waterways. In remote northern Russia, the former Soviet Union built automated lighthouses powered by radioisotope thermoelectric generators. These ran reliably for long periods without help, but many later decayed, were stolen, or vandalized, and some are lost because records were poor.

The United Kingdom and Ireland have three separate authorities: Trinity House handles England and Wales, the Northern Lighthouse Board covers Scotland and the Isle of Man, and the Commissioners of Irish Lights manages Ireland. Canada's lighthouses are overseen by the Canadian Coast Guard, while those in the United States are maintained by the United States Coast Guard, which took over the United States Lighthouse Service in 1939.

Did You Know?

• The National Historic Lighthouse Preservation Act of 2000 in the United States allows transfer of lighthouse structures to local governments and non-profits while the Coast Guard maintains lamps and lenses.
• The Amateur Radio Lighthouse Society sends amateur radio operators to publicize preservation of remote lighthouses worldwide.
• The Nova Scotia Lighthouse Preservation Society won heritage status for Sambro Island Lighthouse and sponsored the Heritage Lighthouse Protection Act in Canada.