Lighthouses Completed In 1857
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A lighthouse is a tower, building, or other type of physical structure designed to emit light from a system of lamps and lenses and to serve as a
beacon A beacon is an intentionally conspicuous device designed to attract attention to a specific location. A common example is the lighthouse, which draws attention to a fixed point that can be used to navigate around obstacles or into port. More mode ...
for navigational aid, for maritime pilots at sea or on inland waterways. Lighthouses mark dangerous coastlines, hazardous shoals, reefs, rocks, and safe entries to harbors; they also assist in
aerial navigation The basic principles of air navigation are identical to general navigation, which includes the process of planning, recording, and controlling the movement of a craft from one place to another. Successful air navigation involves piloting an air ...
. Once widely used, the number of operational lighthouses has declined due to the expense of maintenance and has become uneconomical since the advent of much cheaper, more sophisticated and effective electronic navigational systems.


History


Ancient lighthouses

Before the development of clearly defined ports, mariners were guided by fires built on hilltops. Since elevating the fire would improve the visibility, placing the fire on a platform became a practice that led to the development of the lighthouse. In antiquity, the lighthouse functioned more as an entrance marker to ports than as a warning signal for reefs and promontories, unlike many modern lighthouses. The most famous lighthouse structure from antiquity was the Pharos of
Alexandria Alexandria ( or ; ar, ٱلْإِسْكَنْدَرِيَّةُ ; grc-gre, Αλεξάνδρεια, Alexándria) is the second largest city in Egypt, and the largest city on the Mediterranean coast. Founded in by Alexander the Great, Alexandri ...
,
Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Medit ...
, which collapsed following a series of earthquakes between 956 CE and 1323 CE. The intact Tower of Hercules at A Coruña, Spain gives insight into ancient lighthouse construction; other evidence about lighthouses exists in depictions on coins and mosaics, of which many represent the lighthouse at Ostia. Coins from Alexandria, Ostia, and
Laodicea in Syria Laodicea ( grc, Λαοδίκεια) was a port city and an important colonia of the Roman Empire in ancient Syria, located near the modern city of Latakia. It was also called Laodicea in Syria or Laodicea ad mare. For a short period of time un ...
also exist.


Modern construction

The modern era of lighthouses began at the turn of the 18th century, as the number of lighthouses being constructed increased significantly due to much higher levels of transatlantic commerce. Advances in structural engineering and new and efficient lighting equipment allowed for the creation of larger and more powerful lighthouses, including ones exposed to the sea. The function of lighthouses was gradually changed from indicating ports to the providing of a visible warning against shipping hazards, such as rocks or reefs. The Eddystone Rocks were a major shipwreck hazard for mariners sailing through the English Channel. The first lighthouse built there was an octagonal wooden structure, anchored by 12 iron stanchions secured in the rock, and was built by Henry Winstanley from 1696 to 1698. His lighthouse was the first tower in the world to have been fully exposed to the open sea. The civil engineer John Smeaton rebuilt the lighthouse from 1756 to 1759;Majdalany, Fred: ''The Eddystone Light''. 1960 his tower marked a major step forward in the design of lighthouses and remained in use until 1877. He modeled the shape of his lighthouse on that of an oak tree, using granite blocks. He rediscovered and used " hydraulic lime", a form of concrete that will set under water used by the Romans, and developed a technique of securing the granite blocks together using dovetail joints and marble dowels. The dovetailing feature served to improve the structural stability, although Smeaton also had to taper the thickness of the tower towards the top, for which he curved the tower inwards on a gentle gradient. This profile had the added advantage of allowing some of the energy of the waves to dissipate on impact with the walls. His lighthouse was the prototype for the modern lighthouse and influenced all subsequent engineers. One such influence was Robert Stevenson, himself a seminal figure in the development of lighthouse design and construction. His greatest achievement was the construction of the
Bell Rock Lighthouse The Bell Rock Lighthouse, off the coast of Angus, Scotland, is the world's oldest surviving sea-washed lighthouse. It was built between 1807 and 1810 by Robert Stevenson on the Bell Rock (also known as Inchcape) in the North Sea, east of the ...
in 1810, one of the most impressive feats of engineering of the age. This structure was based upon Smeaton's design, but with several improved features, such as the incorporation of rotating lights, alternating between red and white. Stevenson worked for the
Northern Lighthouse Board The Northern Lighthouse Board (NLB) is the general lighthouse authority for Scotland and the Isle of Man. It is a non-departmental public body responsible for marine navigation aids around coastal areas. History The NLB was formed by Act of P ...
for nearly fifty years during which time he designed and oversaw the construction and later improvement of numerous lighthouses. He innovated in the choice of light sources, mountings, reflector design, the use of
Fresnel lens A Fresnel lens ( ; ; or ) is a type of composite compact lens developed by the French physicist Augustin-Jean Fresnel (1788–1827) for use in lighthouses. It has been called "the invention that saved a million ships." The design allows the c ...
es, and in rotation and shuttering systems providing lighthouses with individual signatures allowing them to be identified by seafarers. He also invented the movable jib and the balance-crane as a necessary part for lighthouse construction. Alexander Mitchell designed the first
screw-pile lighthouse A screw-pile lighthouse is a lighthouse which stands on piles that are screwed into sandy or muddy sea or river bottoms. The first screw-pile lighthouse to begin construction was built by the blind Irish engineer Alexander Mitchell. Constructio ...
– his lighthouse was built on piles that were screwed into the sandy or muddy seabed. Construction of his design began in 1838 at the mouth of the Thames and was known as the
Maplin Sands The Maplin Sands are mudflats on the northern bank of the Thames estuary, off Foulness Island, near Southend-on-Sea in Essex, England, though they actually lie within the neighbouring borough of Rochford. They form a part of the Essex Estuarie ...
lighthouse, and first lit in 1841. Although its construction began later, the Wyre Light in Fleetwood, Lancashire, was the first to be lit (in 1840).


Lighting improvements

Until 1782 the source of illumination had generally been wood pyres or burning coal. The
Argand lamp The Argand lamp is a type of oil lamp invented in 1780 by Aimé Argand. Its output is 6 to 10 candelas, brighter than that of earlier lamps. Its more complete combustion of the candle wick and oil than in other lamps required much less frequent ...
, invented in 1782 by the Swiss scientist Aimé Argand revolutionized lighthouse illumination with its steady smokeless flame. Early models used ground glass which was sometimes tinted around the wick. Later models used a mantle of
thorium dioxide Thorium dioxide (ThO2), also called thorium(IV) oxide, is a crystalline solid, often white or yellow in colour. Also known as thoria, it is produced mainly as a by-product of lanthanide and uranium production. Thorianite is the name of the minera ...
suspended over the flame, creating a bright, steady light. The Argand lamp used whale oil, colza, olive oil or other
vegetable oil Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. Like animal fats, vegetable fats are ''mixtures'' of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or f ...
as fuel, supplied by a gravity feed from a reservoir mounted above the burner. The lamp was first produced by Matthew Boulton, in partnership with Argand, in 1784, and became the standard for lighthouses for over a century.
South Foreland Lighthouse South Foreland Lighthouses are a pair of Victorian lighthouses on the South Foreland in St. Margaret's Bay, Dover, Kent, England, used to warn ships approaching the nearby Goodwin Sands. There has been a pair of lighthouses at South Forelan ...
was the first tower to successfully use an electric light in 1875. The lighthouse's carbon arc lamps were powered by a steam-driven
magneto A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current. Unlike a dynamo, a magneto does not contain a commutator to produce direct current. It is categorized as a form of alternator, ...
. John Richardson Wigham was the first to develop a system for
gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...
illumination of lighthouses. His improved gas 'crocus' burner at the Baily Lighthouse near Dublin was 13 times more powerful than the most brilliant light then known. The vaporized
oil burner An oil burner is a heating device which burns #1, #2 and #6 heating oils, diesel fuel or other similar fuels. In the United States ultra low #2 diesel is the common fuel used. It is dyed red to show that it is road-tax exempt. In most markets ...
was invented in 1901 by Arthur Kitson, and improved by David Hood at
Trinity House "Three In One" , formation = , founding_location = Deptford, London, England , status = Royal Charter corporation and registered charity , purpose = Maintenance of lighthouses, buoys and beacons , he ...
. The fuel was vaporized at high pressure and burned to heat the mantle, giving an output of over six times the luminosity of traditional oil lights. The use of gas as illuminant became widely available with the invention of the
Dalén light A Dalén light is a light produced from burning of carbide gas (acetylene), combined with a solar sensor which automatically operates the light only during darkness. Overview The technology was the predominant form of light source in lighthouse ...
by Swedish engineer
Gustaf Dalén Nils Gustaf Dalén (; 30 November 1869 – 9 December 1937) was a Swedish Nobel Laureate and industrialist, engineer, inventor and long-term CEO of the AGA AB, AGA company and inventor of the AGA cooker and the Dalén light. In 1912 he was award ...
. He used
Agamassan Agamassan is a porous substrate used to safely absorb acetylene and thus allow the transport, storage and commercial use of the otherwise unstable gas. It was developed and patented by the Swedish Nobel Laureate and industrialist Gustaf Dalén. ...
(Aga), a substrate, to absorb the gas, allowing the gas to be stored, and hence used, safely. Dalén also invented the ' sun valve', which automatically regulated the light and turned it off during the daytime. The technology was the predominant light source in lighthouses from the 1900s to the 1960s, when electric lighting had become dominant.


Optical systems

With the development of the steady illumination of the Argand lamp, the application of optical lenses to increase and focus the light intensity became a practical possibility. William Hutchinson developed the first practical optical system in 1763, known as a
catoptric Catoptrics (from grc-gre, κατοπτρικός ''katoptrikós'', "specular", from grc-gre, κάτοπτρον ''katoptron'' "mirror") deals with the phenomena of reflected light and image-forming optical systems using mirrors. A catoptric ...
system. This rudimentary system effectively collimated the emitted light into a concentrated beam, thereby greatly increasing the light's visibility. The ability to focus the light led to the first revolving lighthouse beams, where the light would appear to the mariners as a series of intermittent flashes. It also became possible to transmit complex signals using the light flashes. French physicist and engineer
Augustin-Jean Fresnel Augustin-Jean Fresnel (10 May 1788 – 14 July 1827) was a French civil engineer and physicist whose research in optics led to the almost unanimous acceptance of the wave theory of light, excluding any remnant of Newton's corpuscular th ...
developed the multi-part
Fresnel lens A Fresnel lens ( ; ; or ) is a type of composite compact lens developed by the French physicist Augustin-Jean Fresnel (1788–1827) for use in lighthouses. It has been called "the invention that saved a million ships." The design allows the c ...
for use in lighthouses. His design allowed for the construction of lenses of large aperture and short focal length, without the mass and volume of material that would be required by a lens of conventional design. A Fresnel lens can be made much thinner than a comparable conventional lens, in some cases taking the form of a flat sheet. A Fresnel lens can also capture more oblique light from a light source, thus allowing the light from a lighthouse equipped with one to be visible over greater distances. The first Fresnel lens was used in 1823 in the
Cordouan lighthouse Cordouan lighthouse () is an active lighthouse located at sea, near the mouth of the Gironde estuary in France. At a height of , it is the tenth-tallest "traditional lighthouse" in the world. The Tour de Cordouan, the 'Patriarch of Lighthouses ...
at the mouth of the Gironde estuary; its light could be seen from more than out. Fresnel's invention increased the luminosity of the lighthouse lamp by a factor of four and his system is still in common use.


Modern lighthouses

The introduction of electrification and automatic lamp changers began to make
lighthouse keeper A lighthouse keeper or lightkeeper is a person responsible for tending and caring for a lighthouse, particularly the light and lens in the days when oil lamps and clockwork mechanisms were used. Lighthouse keepers were sometimes referred to as ...
s obsolete. For many years, lighthouses still had keepers, partly because lighthouse keepers could serve as a rescue service if necessary. Improvements in maritime navigation and safety such as satellite navigation systems such as
GPS The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
led to the phasing out of non-automated lighthouses across the world. In Canada, this trend has been stopped and there are still 50 staffed light stations, with 27 on the west coast alone. Remaining modern lighthouses are usually illuminated by a single stationary flashing light powered by solar-charged batteries mounted on a steel skeleton tower. Where the power requirement is too great for solar power, ''cycle charging'' by diesel generator is used: to save fuel and to increase periods between maintenance the light is battery powered, with the generator only coming into use when the battery has to be charged.


Famous lighthouse builders

John Smeaton is noteworthy for having designed the third and most famous Eddystone Lighthouse, but some builders are well known for their work in building multiple lighthouses. The Stevenson family ( Robert, Alan, David, Thomas, David Alan, and Charles) made lighthouse building a three-generation profession in Scotland. Richard Henry Brunton designed and built 26 Japanese lighthouses in Meiji Era Japan, which became known as Brunton's "children". Blind Irishman Alexander Mitchell invented and built a number of screw-pile lighthouses. Englishman James Douglass was knighted for his work on the fourth Eddystone Lighthouse. United States Army Corps of Engineers Lieutenant
George Meade George Gordon Meade (December 31, 1815 – November 6, 1872) was a United States Army officer and civil engineer best known for decisively defeating Confederate General Robert E. Lee at the Battle of Gettysburg in the American Civil War. H ...
built numerous lighthouses along the Atlantic and Gulf coasts before gaining wider fame as the winning general at the Battle of Gettysburg. Colonel Orlando M. Poe, engineer to General William Tecumseh Sherman in the siege of Atlanta, designed and built some of the most exotic lighthouses in the most difficult locations on the U.S. Great Lakes. French merchant navy officer Marius Michel Pasha built almost a hundred lighthouses along the coasts of the Ottoman Empire in a period of twenty years after the Crimean War (1853–1856).


Technology

In a lighthouse, the source of light is called the "lamp" (whether electric or fuelled by oil) and the light is concentrated, if needed, by the "lens" or "optic". Power sources for lighthouses in the 20th–21st centuries vary.


Power

Originally lit by open fires and later candles, the Argand hollow wick lamp and parabolic reflector were introduced in the late 18th century. Whale oil was also used with wicks as the source of light. Kerosene became popular in the 1870s and electricity and carbide (
acetylene gas Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure f ...
) began replacing kerosene around the turn of the 20th century. Carbide was promoted by the
Dalén light A Dalén light is a light produced from burning of carbide gas (acetylene), combined with a solar sensor which automatically operates the light only during darkness. Overview The technology was the predominant form of light source in lighthouse ...
which automatically lit the lamp at nightfall and extinguished it at dawn. During the Cold War, many remote Soviet lighthouses were powered by radioisotope thermoelectric generators (RTGs). These had the advantage of providing power day or night and did not need refuelling or maintenance. However, after the breakdown of the Soviet Union, there are no official records of the locations or condition of all of these lighthouses. As time passes, their condition is degrading; many have fallen victim to vandalism and scrap metal thieves, who may not be aware of the dangerous radioactive contents. Energy-efficient LED lights can be powered by solar panels, with batteries instead of a diesel generator for backup.


Light source

Many Fresnel lens installations have been replaced by rotating
aerobeacon An aerobeacon is a light assembly used to create a fixed or flashing signal visible over long distances. It consists of a high intensity electric lamp mounted with a focusing device in a cylindrical housing, which usually is rotated on a vertical ...
s which require less maintenance. In modern automated lighthouses, the system of rotating lenses is often replaced by a high intensity light that emits brief omnidirectional flashes, concentrating the light in time rather than direction. These lights are similar to obstruction lights used to warn aircraft of tall structures. Later innovations were "Vega Lights", and experiments with
light-emitting diode A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (co ...
(LED) panels. LED lights, which use less energy and are easier to maintain, had come into widespread use by 2020. In the United Kingdom and Ireland about a third of lighthouses had been converted from filament light sources to use LEDs, and conversion continued with about three per year. The light sources are designed to replicate the colour and character of the traditional light as closely as possible. The change is often not noticed by people in the region, but sometimes a proposed change leads to calls to preserve the traditional light, including in some cases a rotating beam. A typical LED system designed to fit into the traditional 19th century Fresnel lens enclosure was developed by Trinity House and two other lighthouse authorities and costs about 20,000, depending on configuration, according to a supplier; it has large fins to dissipate heat. Lifetime of the LED light source is 50,000 to 100,000 hours, compared to about 1,000 hours for a filament source.


Laser light

Experimental installations of laser lights, either at high power to provide a "line of light" in the sky or, utilising low power, aimed towards mariners have identified problems of increased complexity in installation and maintenance, and high power requirements. The first practical installation, in 1971 at Point Danger lighthouse, Queensland, was replaced by a conventional light after four years because the beam was too narrow to be seen easily.


Light characteristics

In any of these designs an observer, rather than seeing a continuous weak light, sees a brighter light during short time intervals. These instants of bright light are arranged to create a light characteristic or pattern specific to a lighthouse. For example, the Scheveningen Lighthouse flashes are alternately 2.5 and 7.5 seconds. Some lights have sectors of a particular color (usually formed by colored panes in the lantern) to distinguish safe water areas from dangerous shoals. Modern lighthouses often have unique reflectors or Racon transponders so the radar signature of the light is also unique.


Lens

Before modern
strobe light A strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope. The word originated from the Ancient Greek ('), meaning ...
s, lenses were used to concentrate the light from a continuous source. Vertical light rays of the lamp are redirected into a horizontal plane, and horizontally the light is focused into one or a few directions at a time, with the
light beam A light beam or beam of light is a directional projection of light energy radiating from a light source. Sunlight forms a light beam (a sunbeam) when filtered through media such as clouds, foliage, or windows. To artificially produce a light ...
swept around. As a result, in addition to seeing the side of the light beam, the light is directly visible from greater distances, and with an identifying light characteristic. This concentration of light is accomplished with a rotating lens assembly. In early lighthouses, the light source was a kerosene lamp or, earlier, an animal or vegetable oil Argand lamp, and the lenses rotated by a weight driven clockwork assembly wound by lighthouse keepers, sometimes as often as every two hours. The lens assembly sometimes floated in liquid mercury to reduce friction. In more modern lighthouses, electric lights and motor drives were used, generally powered by diesel electric generators. These also supplied electricity for the lighthouse keepers. Efficiently concentrating the light from a large omnidirectional light source requires a very large diameter lens. This would require a very thick and heavy lens if a conventional lens were used. The
Fresnel lens A Fresnel lens ( ; ; or ) is a type of composite compact lens developed by the French physicist Augustin-Jean Fresnel (1788–1827) for use in lighthouses. It has been called "the invention that saved a million ships." The design allows the c ...
(pronounced ) focused 85% of a lamp's light versus the 20% focused with the parabolic reflectors of the time. Its design enabled construction of lenses of large size and short focal length without the weight and volume of material in conventional lens designs. Fresnel lighthouse lenses are ranked by ''order'', a measure of refracting power, with a first order lens being the largest, most powerful and expensive; and a sixth order lens being the smallest. The order is based on the focal length of the lens. A first order lens has the longest focal length, with the sixth being the shortest. Coastal lighthouses generally use first, second, or third order lenses, while harbor lights and beacons use fourth, fifth, or sixth order lenses. Some lighthouses, such as those at
Cape Race Cape Race is a point of land located at the southeastern tip of the Avalon Peninsula on the island of Newfoundland, in Newfoundland and Labrador, Canada. Its name is thought to come from the original Portuguese name for this cape, "Raso", mean ...
, Newfoundland, and Makapuu Point, Hawaii, used a more powerful hyperradiant Fresnel lens manufactured by the firm of
Chance Brothers Chance Brothers and Company was a glassworks originally based in Spon Lane, Smethwick, West Midlands (formerly in Staffordshire), in England. It was a leading glass manufacturer and a pioneer of British glassmaking technology. The Chance fam ...
.


Building


Components

While lighthouse buildings differ depending on the location and purpose, they tend to have common components. A light station comprises the lighthouse tower and all outbuildings, such as the keeper's living quarters, fuel house, boathouse, and fog-signaling building. The Lighthouse itself consists of a tower structure supporting the lantern room where the light operates. The lantern room is the glassed-in housing at the top of a lighthouse tower containing the lamp and lens. Its glass storm panes are supported by metal muntins (glazing bars) running vertically or diagonally. At the top of the lantern room is a stormproof ventilator designed to remove the smoke of the lamps and the heat that builds in the glass enclosure. A
lightning rod A lightning rod or lightning conductor (British English) is a metal rod mounted on a structure and intended to protect the structure from a lightning strike. If lightning hits the structure, it will preferentially strike the rod and be conducte ...
and grounding system connected to the metal cupola roof provides a safe conduit for any lightning strikes. Immediately beneath the lantern room is usually a Watch Room or Service Room where fuel and other supplies were kept and where the keeper prepared the lanterns for the night and often stood watch. The clockworks (for rotating the lenses) were also located there. On a lighthouse tower, an open platform called the gallery is often located outside the watch room (called the Main Gallery) or Lantern Room (Lantern Gallery). This was mainly used for cleaning the outside of the windows of the Lantern Room. Lighthouses near to each other that are similar in shape are often painted in a unique pattern so they can easily be recognized during daylight, a marking known as a daymark. The black and white barber pole spiral pattern of
Cape Hatteras Lighthouse Cape Hatteras Light is a lighthouse located on Hatteras Island in the Outer Banks in the town of Buxton, North Carolina and is part of the Cape Hatteras National Seashore. The lighthouse’s semi-unique pattern makes it easy to recognize and famou ...
is one example. Race Rocks Light in western Canada is painted in horizontal black and white bands to stand out against the horizon.


Design

For effectiveness, the lamp must be high enough to be seen before the danger is reached by a mariner. The minimum height is calculated by trigonometric formula d = 1.17 \sqrt where ''H'' is the height above water in feet, and ''d'' is the distance to the horizon in nautical miles. Where dangerous shoals are located far off a flat sandy beach, the prototypical tall masonry coastal lighthouse is constructed to assist the navigator making a landfall after an ocean crossing. Often these are cylindrical to reduce the effect of wind on a tall structure, such as Cape May Light. Smaller versions of this design are often used as harbor lights to mark the entrance into a harbor, such as
New London Harbor Light New London Harbor Light is a lighthouse in Connecticut on the west side of the New London harbor entrance. It is the nation's fifth oldest light station and the seventh oldest U.S. lighthouse. It is both the oldest and the tallest lighthouse in Co ...
. Where a tall cliff exists, a smaller structure may be placed on top such as at Horton Point Light. Sometimes, such a location can be too high, for example along the west coast of the United States, where frequent low clouds can obscure the light. In these cases, lighthouses are placed below the clifftop to ensure that they can still be seen at the surface during periods of fog or low clouds, as at
Point Reyes Lighthouse The Point Reyes Lighthouse, also known as Point Reyes Light or the Point Reyes Light Station, is a lighthouse in the Gulf of the Farallones on Point Reyes in Point Reyes National Seashore, located in Marin County, California, United States. The ...
. Another example is in San Diego, California: the Old Point Loma lighthouse was too high up and often obscured by fog, so it was replaced in 1891 with a lower lighthouse, New Point Loma lighthouse. As technology advanced, prefabricated skeletal iron or steel structures tended to be used for lighthouses constructed in the 20th century. These often have a narrow cylindrical core surrounded by an open lattice work bracing, such as Finns Point Range Light. Sometimes a lighthouse needs to be constructed in the water itself. Wave-washed lighthouses are masonry structures constructed to withstand water impact, such as Eddystone Lighthouse in Britain and the St. George Reef Light of California. In shallower bays,
Screw-pile lighthouse A screw-pile lighthouse is a lighthouse which stands on piles that are screwed into sandy or muddy sea or river bottoms. The first screw-pile lighthouse to begin construction was built by the blind Irish engineer Alexander Mitchell. Constructio ...
ironwork structures are screwed into the seabed and a low wooden structure is placed above the open framework, such as Thomas Point Shoal Lighthouse. As screw piles can be disrupted by ice, steel caisson lighthouses such as Orient Point Light are used in cold climates. Orient Long Beach Bar Light (Bug Light) is a blend of a screw pile light that was converted to a caisson light because of the threat of ice damage. Skeletal iron towers with screw-pile foundations were built on the Florida Reef along the Florida Keys, beginning with the
Carysfort Reef Light Carysfort Reef Light is located approximately six nautical miles east of Key Largo, Florida. The lighthouse has an iron screw-pile foundation with a platform, and a skeletal, octagonal, pyramidal tower, which is painted red. The light is above ...
in 1852. In waters too deep for a conventional structure, a lightship might be used instead of a lighthouse, such as the former lightship ''Columbia''. Most of these have now been replaced by fixed light platforms (such as Ambrose Light) similar to those used for offshore oil exploration.


Range lights

Aligning two fixed points on land provides a navigator with a
line of position A position line or line of position (LOP) is a line (or, on the surface of the earth, a curve) that can be both identified on a chart (nautical chart or aeronautical chart) and translated to the surface of the earth. The intersection of a minimum o ...
called a range in North America and a transit in Britain. Ranges can be used to precisely align a vessel within a narrow channel such as a river. With landmarks of a range illuminated with a set of fixed lighthouses, nighttime navigation is possible. Such paired lighthouses are called range lights in North America and
leading lights Leading lights (also known as range lights in the United States) are a pair of light beacons used in navigation to indicate a safe passage for vessels entering a shallow or dangerous channel; they may also be used for position fixing. At nigh ...
in the United Kingdom. The closer light is referred to as the beacon or front range; the further light is called the rear range. The rear range light is almost always taller than the front. When a vessel is on the correct course, the two lights align vertically, but when the observer is out of position, the difference in alignment indicates the direction of travel to correct the course.


Location

There are two types of lighthouses: ones that are located on land, and ones that are offshore. ''Offshore Lighthouses'' are lighthouses that are not close to land. There can be a number of reasons for these lighthouses to be built. There can be a shoal, reef or submerged island several miles from land. The current
Cordouan Lighthouse Cordouan lighthouse () is an active lighthouse located at sea, near the mouth of the Gironde estuary in France. At a height of , it is the tenth-tallest "traditional lighthouse" in the world. The Tour de Cordouan, the 'Patriarch of Lighthouses ...
was completed in 1611, from the shore on a small islet, but was built on a previous lighthouse that can be traced back to the 880's and is the oldest surviving lighthouse in France. It is connected to the mainland by a causeway. The oldest surviving oceanic offshore lighthouse is
Bell Rock Lighthouse The Bell Rock Lighthouse, off the coast of Angus, Scotland, is the world's oldest surviving sea-washed lighthouse. It was built between 1807 and 1810 by Robert Stevenson on the Bell Rock (also known as Inchcape) in the North Sea, east of the ...
in the North Sea, off the coast of
Scotland Scotland (, ) is a Countries of the United Kingdom, country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a Anglo-Scottish border, border with England to the southeast ...
.


Maintenance


Asia and Oceania

In Australia, lighthouses are conducted by the
Australian Maritime Safety Authority Australian Maritime Safety Authority (AMSA) is an Australian statutory authority responsible for the regulation and safety oversight of Australia's shipping fleet and management of Australia's international maritime obligations. The authority ...
. In
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
, lighthouses are maintained by the Directorate General of Lighthouses and Lightships, an office of the
Ministry of Ports, Shipping and Waterways The Ministry of Ports, Shipping and Waterways is the Indian ministry responsible for formulation and administration of the rules, regulations and laws relating to ports, shipping and waterways. The minister is Sarbananda Sonowal. Ministers ...
.


Europe

The
Soviet Union The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
built a number of automated lighthouses powered by radioisotope thermoelectric generators in remote locations. They operated for long periods without external support with great reliability. However numerous installations deteriorated, were stolen, or vandalized. Some cannot be found due to poor record-keeping. Both the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...
and the
Republic of Ireland Ireland ( ga, Éire ), also known as the Republic of Ireland (), is a country in north-western Europe consisting of 26 of the 32 Counties of Ireland, counties of the island of Ireland. The capital and largest city is Dublin, on the eastern ...
together have three bodies: lighthouses around the coasts of England and Wales are looked after by
Trinity House "Three In One" , formation = , founding_location = Deptford, London, England , status = Royal Charter corporation and registered charity , purpose = Maintenance of lighthouses, buoys and beacons , he ...
, those around Scotland and the Isle of Man by the
Northern Lighthouse Board The Northern Lighthouse Board (NLB) is the general lighthouse authority for Scotland and the Isle of Man. It is a non-departmental public body responsible for marine navigation aids around coastal areas. History The NLB was formed by Act of P ...
and those around Ireland by the
Commissioners of Irish Lights The Commissioners of Irish Lights ( ga, Coimisinéirí Soilse na hÉireann), often shortened to Irish Lights or CIL, is the body that serves as the general lighthouse authority for Northern Ireland and the Republic of Ireland and their adjacen ...
.


North America

In Canada, lighthouses are managed by the
Canadian Coast Guard The Canadian Coast Guard (CCG; french: links=no, Garde côtière canadienne, GCC) is the coast guard of Canada. Formed in 1962, the coast guard is tasked with marine search and rescue (SAR), communication, navigation, and transportation issues ...
. In the United States, lighthouses are maintained by the United States Coast Guard.


Preservation

As lighthouses became less essential to navigation, many of their historic structures faced demolition or neglect. In the United States, the National Historic Lighthouse Preservation Act of 2000 provides for the transfer of lighthouse structures to local governments and private non-profit groups, while the USCG continues to maintain the lamps and lenses. In Canada, the Nova Scotia Lighthouse Preservation Society won heritage status for Sambro Island Lighthouse, and sponsored the Heritage Lighthouse Protection Act to change Canadian federal laws to protect lighthouses. Many groups formed to restore and save lighthouses around the world, including the World Lighthouse Society and the
United States Lighthouse Society The United States Lighthouse Society is a non-profit organization dedicated to aiding in the restoration of American lighthouses and educating the public about their history. With four chapters, and more than a dozen affiliates, it is one of the ...
, as well as the Amateur Radio Lighthouse Society, which sends amateur radio operators to publicize the preservation of remote lighthouses throughout the world.


See also

* Crib lighthouse *
Day beacon A day beacon (sometimes "daybeacon") is an unlighted nautical sea mark. A signboard identifying it is called a day mark. Day beacons typically mark channels whose key points are marked by lighted buoys. They may also mark smaller navigable rout ...
* Foghorn * Fresnel lens sizes (orders) * Lens lantern *
Lighthouse keeper A lighthouse keeper or lightkeeper is a person responsible for tending and caring for a lighthouse, particularly the light and lens in the days when oil lamps and clockwork mechanisms were used. Lighthouse keepers were sometimes referred to as ...
*
Lists of lighthouses This article contains links to lists of lighthouses around the world. According to ''Lighthouse Directory'', there are more than 18,600 lighthouses worldwide. Africa *''Note: Click on the country or place name of your choice in the table belo ...
*
Lists of lightvessels This article lists lightvessels around the world. Most surviving light vessels reside in the United Kingdom and the United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is ...
*
Pharology Pharology is the scientific study of lighthouses and signal lights, their construction and illumination. The variation ''pharonology'' is occasionally attested. Those who study or are enthused by lighthouses are known as pharologists. Origin of t ...
*
Pintsch gas Carl Friedrich Julius Pintsch (6 January 1815 – 20 January 1884) was a German tinsmith, manufacturer and inventor who is primarily known for the invention of Pintsch gas. The gas, distilled from naphtha or other petroleum products, was wi ...
*
Sea mark A sea mark, also seamark and navigation mark, is a form of aid to navigation and pilotage that identifies the approximate position of a maritime channel, hazard, or administrative area to allow boats, ships, and seaplanes to navigate safely. Th ...


References

;Notes ;Bibliography * Bathurst, Bella. ''The lighthouse Stevensons''. New York: Perennial, 2000. * Beaver, Patrick. ''A History of Lighthouses''. London: Peter Davies Ltd, 1971. . * Crompton, Samuel, W; Rhein, Michael, J. ''The Ultimate Book of Lighthouses''. San Diego, CA: Thunder Bay Press, 2002. . * Jones, Ray; Roberts, Bruce. ''American Lighthouses''. Globe Pequot, 1998. 1st ed. . * Stevenson, D. Alan. ''The world's lighthouses before 1820''. London:
Oxford University Press Oxford University Press (OUP) is the university press of the University of Oxford. It is the largest university press in the world, and its printing history dates back to the 1480s. Having been officially granted the legal right to print books ...
, 1959. ;Further reading * Noble, Dennis. ''Lighthouses & Keepers: U. S. Lighthouse Service and Its Legacy''. Annapolis: U.S. Naval Institute Press, 1997. . * Putnam, George R. ''Lighthouses and Lightships of the United States''. Boston: Houghton Mifflin Co., 1933. * Rawlings, William. 2021. ''Lighthouses of the Georgia Coast.'' Macon, GA: Mercer University Press. * Weiss, George. ''The Lighthouse Service, Its History, Activities and Organization''. Baltimore: Johns Hopkins Press, 1926.


External links


United States Lighthouses"Lighthouses Of Strange Designs, December 1930, Popular Science
* Research tool with details of over 14,700 lighthouses and navigation lights around the world with photos and links. *Pharology Website: http://www.pharology.eu . Reference source for the history and development of lighthouses of the world. * Includes 54 diagrams and photographs. {{Authority control Heraldic charges Articles containing video clips Ancient Greek technology Egyptian inventions Greek inventions