Marks for mariners
A light on the shore tells a mariner two things at once: that there is land or a hazard nearby, and, if the light is recognisable, where he is. The oldest aids were simple. Fires lit on hilltops or at harbour mouths guided boats home in the dark, and tall structures served as daymarks even when they showed no light.
The Pharos and Roman towers
The best-known ancient lighthouse stood on the island of Pharos at Alexandria. It was built in the early 3rd century BC under the Ptolemaic rulers and was famous enough that “pharos” became a word for lighthouse in several languages. Accounts describe a very tall stone tower, and it is usually counted among the Seven Wonders of the ancient world. It was damaged by earthquakes over the centuries and eventually fell into ruin; a later fort stands on the site.
The Romans built lights at many harbours and along their coasts. The Tower of Hercules at A Coruña in northwest Spain is traditionally dated to the Roman period, and it is often described as the oldest lighthouse still in use, although it was heavily restored in the 18th century. Remains of a Roman light also survive at Dover. These towers burned wood, oil or similar fuel, and their range was limited by the brightness of an open flame.
Medieval lights and the growth of organisations
After the Roman era, lights were maintained by a patchwork of authorities, including monasteries, port towns and trading associations. In England, Trinity House received a royal charter in 1514 and later became the main body responsible for lighthouses and buoys around England and Wales. The historic harbours of the medieval period often had a tower or a burning cresset at the entrance, and the Hanseatic ports of the Baltic maintained beacons for the merchant traffic that supported them.
The cost of lights was commonly met by charging dues on passing ships, and in some periods private owners built lights under patent and collected the dues themselves.
Building on rocks
The greatest challenge was to build towers on rocks washed by the sea, where the danger was greatest. The Eddystone Rocks off Plymouth show how engineering developed. Henry Winstanley completed a wooden tower there in 1698, and it was lost in a great storm in 1703. A second tower, designed by John Rudyerd, was completed in 1709 and was destroyed by fire in 1755.
The third, built by John Smeaton from 1756 and lit in 1759, is a landmark in engineering. Smeaton shaped the stone blocks so that they interlocked, and he used a hydraulic lime mortar that set in damp conditions. The tower stood for more than a century before the rock beneath it began to show signs of wear, and a replacement was built nearby in the 1880s. Part of Smeaton’s tower was later re-erected on Plymouth Hoe.
Robert Stevenson’s Bell Rock lighthouse off the east coast of Scotland, completed in 1810, followed similar ideas and began a family tradition of lighthouse engineering in Scotland.
From open fire to lens
Early towers burned coal or wood in open braziers, which was costly and smoky. The 1780s brought the Argand lamp, with a hollow circular wick that gave a steadier and brighter flame, and polished metal reflectors were set behind the lamps to throw the light out to sea. Oil lamps steadily replaced coal fires.
The major change came with the French physicist Augustin Fresnel, who in the early 1820s designed a lens built from concentric rings of glass prisms. It captured far more of the light from a lamp and bent it into a strong beam, with much less glass and weight than a conventional lens of the same power. The Cordouan lighthouse at the mouth of the Gironde estuary in France, a tower whose construction ran from the late 16th to the early 17th century, was fitted with a Fresnel lens in 1823.
Fresnel lenses were made in sizes called orders, with the first order being the largest. Towers fitted with them could show distinctive flash patterns, so that each light could be recognised by the pattern of its beam. Many lenses revolved on a bed of rollers or floated in a bath of mercury and were turned by a clockwork mechanism driven by a falling weight. The United States formally adopted the Fresnel system in the 1850s, after the Lighthouse Board was set up in 1852.
Fuels and electricity
The light source itself changed through the 19th century: from colza and other vegetable oils to whale oil, then mineral oil (paraffin or kerosene), and later gas in some places. Electric arc lamps were tried in a few major lighthouses in the second half of the 19th century, and by the 20th century electric bulbs became normal where power could be supplied. In remote places, acetylene gas and later solar power served.
Life as a keeper
Keepers were responsible for keeping the light burning every night, which meant trimming wicks, cleaning glass and brass, winding the clockwork and keeping a written log. On sea towers, keepers worked in shifts and could be stranded for days or weeks by weather. Fog signals, from bells and guns to sirens and horns, were an added responsibility.
Keepers were also a point of rescue. The 1838 rescue of survivors of the steamer Forfarshire by Grace Darling and her father, the keeper of the Longstone lighthouse in the Farne Islands, was widely reported and became one of the best-known lighthouse stories of the century.
Automation and decline
During the 20th century, electrification and remote monitoring made it possible to run lights without resident keepers. Many countries automated their stations in stages, and the last staffed lighthouses were converted in the later 20th century or early 21st century, depending on the country. Many towers remain as working aids to navigation, while others have been preserved as museums or holiday lets.
Modern ships now fix their position by satellite and radar, and the importance of lights has diminished, but they are still used as a visual check and a backup, and lighthouses remain a recognised symbol of maritime history.