Where a tower will not stand
Lighthouses need solid ground. Many of the worst hazards for shipping, however, are sandbanks, shifting shoals and reefs in deep or soft-bottomed water, where building a permanent tower was impractical or impossible, at least until later engineering methods arrived. Two kinds of floating mark filled the gap: the lightship, a crewed vessel anchored on station, and the buoy, a smaller, usually unmanned float held by a chain and anchor.
The first lightships
The first lightvessel in England is generally dated to 1731, when a ship was moored at the Nore, in the Thames estuary, to mark the approach to the river. It was established by two private individuals, Robert Hamblin and David Avery, who obtained a patent to do so and charged dues on passing shipping. The early lightvessels were ordinary hulls, with lanterns hoisted on the masts, so that the lights could be raised and lowered easily.
The idea spread along the busy coasts of Britain, where sandbanks in the southern North Sea and the Thames approaches claimed ships regularly, and on to other countries. In the United States, a lightship was stationed in Chesapeake Bay in 1820, and others were placed along the east coast as the century progressed. A well-known station was at Nantucket Shoals.
Life on a lightship
Lightship stations were not comfortable postings. The vessel rolled and pitched at anchor in all weathers, the crew lived in small quarters and relief was by boat, which could be delayed by heavy seas. Many lightships had no engines of their own and relied on the anchors, so that the crew’s job was to hold position, keep the light and fog signal working, and watch for ships in trouble. In fog, bells, horns and later sirens sounded continuously.
Lightships were also vulnerable. Stations on busy lanes had a record of being struck by vessels that missed the warning, and some were driven from their moorings by storms. In 1934 the liner Olympic collided with the Nantucket lightship in fog, an event that is often cited in discussions of the danger of the stations. More generally, the sinking of a lightship in a gale could cost the crew their lives.
Lights, signals and refinements
As technology advanced, lightships were fitted with the same kinds of lamps and lenses as lighthouses, including optics based on the Fresnel principle, which are covered in the article on lighthouse development. Some had radio beacons so that ships could take bearings by direction finding, and others carried underwater bell signals, which could be heard through a ship’s hull by a receiver on board, in the days before radar.
Distinctive painting helped as well. Lightships were often painted in strong colours, with the station name in large letters on the hull, so that they could be identified by daylight.
The buoy
Buoys are older and simpler. A float of wood, later of iron or steel, anchored over a danger or along a channel edge, has been used since medieval times. Port authorities and bodies such as Trinity House were commonly responsible for buoyage in their waters, and the Hanseatic ports are traditionally credited with early systems of marking approaches to their harbours. Because buoys drag in tide and storm, mariners treated their positions as approximate until the chart was checked against other marks.
In the 19th century, buoys gained signals. Bell buoys rang with the motion of the waves, and whistle buoys used the same motion to force air through a whistle. Gas-lit buoys, in which compressed gas fed a lamp that could burn for weeks, appeared in the later 19th century, and their light made channels usable at night. Later buoys used batteries, solar panels and electric lamps.
Colours, shapes and the search for a system
Buoys carry information in their colour, shape and light characteristics, so that a navigator can tell which side of a channel to take and which marks indicate danger. For much of the age of sail and steam, systems varied from one country to another. In the 20th century, international bodies worked to standardise this. An agreement reached in 1980 under the International Association of Marine Aids to Navigation and Lighthouse Authorities, known as IALA, created a combined system with two regional variants, which differ in the colours used for the port and starboard sides of a channel. The details are of interest mostly to mariners, but the effort reflects how important a shared language became as ships of many nations used the same waters.
Replacement and survival
From the middle of the 20th century, many lightships were withdrawn. Large automatic buoys, sometimes called large automatic navigational buoys, could carry powerful lights, radio beacons and fog signals without a crew, and fixed offshore structures were built in places where engineering allowed. Several countries ended their lightship services in the later decades of the century. A number of old lightships have been preserved as museums or as floating exhibits in harbours, and they give a good impression of how a crew lived on a lonely station.
Lightships and buoys remain a quiet part of navigation. They do not attract the attention of a famous tower, but for centuries they marked the edge of safe water in places where a vessel could run aground in the dark.