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Lighthouse

From Wikipedia, the free encyclopedia

The lighthouse of Aveiro, on the west coast of Portugal.

Aerial drone footage of the Roman Rock Lighthouse off the southern coast of South Africa.

A lighthouse is a tower, building, or other type of structure designed to emit light from a system of lamps and 

lenses, and to serve as a

 


Lighthouses mark dangerous coastlines, hazardous
shoals, reefs, and safe entries to harbors, and can assist in aerial navigation. Once widely used, the number of operational lighthouses has declined due to the expense of maintenance and use of electronic navigational systems.navigational aid formaritime pilots at sea or on inland waterways.

History[edit]

Ancient lighthouses[edit]

Graphic reconstruction of thePharos according to a 2006 study

Before the development of clearly defined ports, mariners were guided by fires built on hilltops. Since raising 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 ofAlexandria, Egypt, although it collapsed during an earthquake centuries later.

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 also exist.

Modern construction[edit]

The modern era of lighthouses began at the turn of the 18th century, as lighthouse construction boomed in lockstep with burgeoning 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 shifted toward the provision of a visible warning against shipping hazards, such as rocks or reefs.

Winstanley’s lighthouse at the Eddystone Rocks marked the beginning in a new phase of lighthouse development.

The Eddystone Rocks were a major shipwreck hazard for mariners sailing through theEnglish Channel.[1] The first lighthouse built there was an octagonal wooden structure, anchored by 12 iron stanchions secured in the rock, and was built by Henry Winstanleyfrom 1696 to 1698. His lighthouse was the first tower in the world to have been fully exposed to the open sea.[2]

The civil engineer, John Smeaton, rebuilt the lighthouse from 1756–59;[3] his tower marked a major step forward in the design of lighthouses and remained in use until 1877. He modelled 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 usingdovetail joints and marble dowels.[4] The dovetailing feature served to improve thestructural 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.[5]

John Smeaton‘s rebuilt version of the Eddystone Lighthouse, 1759. This represented a great step forward in lighthouse design.

One such influence was Robert Stevenson, himself a seminal figure in the development of lighthouse design and construction.[6] His greatest achievement was the construction of the Bell Rock Lighthouse 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.[7]Stevenson worked for the Northern Lighthouse Board for nearly fifty years[6] 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 lenses, 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 – 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 Sandslighthouse, and first lit in 1841.[8] Although its construction began later, the Wyre Light in Fleetwood, Lancashire, was the first to be lit (in 1840).[8]

Lighting improvements[edit]

Argand lamp with circular wick and glass chimney. (Illustration fromLes Merveilles de la science [1867–1869] byLouis Figuier.)

The source of illumination had generally been wood pyres or burning coal. The Argand lamp, 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 suspended over the flame, creating a bright, steady light.[9] The Argand lamp used whale oil, colza, olive oil[10] or other vegetable oil as fuel which was 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 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.[11] John Richardson Wigham was the first to develop a system for gas 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.[12]

A 85mm Chance BrothersIncandescent Petroleum Vapour Installation which produced the light for the Sumburgh Head lighthouse until 1976. The lamp (made in approx. 1914) burned vaporized kerosene (paraffin); the vaporizer was heated by adenatured alcohol (methylated spirit) burner to light. When lit some of the vaporised fuel was diverted to aBunsen burner to keep the vaporizer warm and the fuel in vapor form. The fuel was forced up to the lamp by air; the keepers had to pump the air container up every hour or so. This in turn pressurized the paraffin container to force the fuel to the lamp. The “white sock” is in fact an unburnt mantle on which the vapor burned.

The vaporized oil burner was invented in 1901 by Arthur Kitson, and improved by David Hood at Trinity House. 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 by Swedish engineer, Gustaf Dalén. He used Agamassan (Aga), a substrate, to absorb the gas allowing safe storage and hence commercial exploitation. Dalén also invented the ‘sun valve‘, which automatically regulated the light and turned it off during the daytime. The technology was the predominant form of light source in lighthouses from the 1900s through the 1960s, when electric lighting had become dominant.[13]

Optical systems[edit]

Diagram depicting how a sphericalFresnel lens collimates light

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 system. This rudimentary system effectively collimated the emitted light into a concentrated beam, thereby greatly increasing the light’s visibility.[14] 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 developed the multi-partFresnel lens 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 at the mouth of the Gironde estuary; its light could be seen from more than 20 miles (32 km) out.[15] Fresnel’s invention increased the luminosity of the lighthouse lamp by a factor of 4 and his system is still in common use.

Recent[edit]

The advent of electrification, and automatic lamp changers began to make lighthouse keepers 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 the Global Positioning System (GPS) have led to the phasing out of non-automated lighthouses across the world.[16] In Canada, this trend has been stopped and there are still 50 staffed light stations, with 27 on the west coast alone.[17]

Components[edit]

Lighthouse lantern room from mid-1800s

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 metalAstragal 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 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.[27]

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 is one example. Race Rocks Light in western Canada is painted in horizontal black and white bands to stand out against the horizon.

Range lights[edit]

Range Lights in Margaree Harbour, Nova Scotia. When the vessel is on the correct course, the two lights line up above one another.

Aligning two fixed points on land provides a navigator with a line of position called a range in the U.S. and a transit in Britain. Ranges can be used to precisely align a vessel within a narrow channel such as in 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 the U.S. and leading lights in the United Kingdom. The closer light is referred to as the beacon or front range; the furthest away is called the rear range. The rear range light is almost always taller than the front.

When the vessel is on the correct course, the two lights line up vertically. But when the observer is out of position, the difference in alignment indicates the proper direction of travel to correct the course.

Maintenance[edit]

In the United States, lighthouses are maintained by the United States Coast Guard (USCG).[28] Those in England and Wales are looked after by Trinity House; in Scotland, by the Northern Lighthouse Board; and in Ireland by theCommissioners of Irish Lights. In Canada, they are managed by the Canadian Coast Guard. In Australia, lighthouses are conducted by the Australian Maritime Safety Authority.

The Soviet Union 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.[29] However numerous installations deteriorated, were stolen, or vandalized. Some cannot be found due to poor record keeping.[30]

Preservation[edit]

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.[31]

Many groups formed to restore and save lighthouses around the world. They include the World Lighthouse Society and the United States Lighthouse Society.[32] A further international group is the Amateur Radio Lighthouse Society, which sends amateur radio operators to publicize the preservation of remote lighthouses throughout the world.[33]

Public good[edit]

Lighthouses were once regarded as an archetypal public good, because ships could benefit from the light without being forced to pay. The Confederate States Constitution explicitly allowed public funds to be spent on navigation, including lighthouses.[34]

Popular culture and symbolism[edit]

Their isolated and mysterious nature makes lighthouses a frequent setting of works in the genres of horror, suspense, and adventure.

Branding[edit]

Due to their function as beacons of safety, some organizations choose lighthouses as a symbol. For example, the lighthouse is the symbol of Lighthouse International, a U.S. organization for the blind.[35] That is also true for theLighthouse: Center for Human Trafficking Victims and the Lighthouse Foundation for Sri Lanka.

Collecting, events, photography, and tourism[edit]

Visiting and photographing lighthouses are popular hobbies, as is collecting ceramic replicas. Some lighthouses are popular travel destinations in their own right, and the buildings are maintained as tourist attractions. In the U.S., National Lighthouse and Lightship Weekend is celebrated on the first weekend of August, and International Lighthouse and Lightship Weekend on the third weekend. Many lighthouses are open to the public and amateur radio operators communicate between them on these days.[citation needed]

Films[edit]

The Disney film Pete’s Dragon (1977) featured a lighthouse and the song “Candle on the Water“, written for the film and sung by Helen Reddy, who plays Nora, alludes to it. The song was nominated for the Academy Award for Best Song in 1977 (though it lost to “You Light Up My Life“).

A lighthouse played a pivotal role in Martin Scorsese‘s neo-noir mystery psychological thriller film Shutter Island (2010) and was featured in the film’s final shot.

The movie The Light Between Oceans features the Cape Campbell Lighthouse.[36]

License plates[edit]

Lighthouses are popular icons on vehicle license plates. Barnegat Lighthouse, Biloxi Light, Saybrook Breakwater Light,Thomas Point Shoal Light, Tuckerton Island Lighthouse, and White Shoal Light (in Michigan), and are so depicted.[37]

Literature[edit]

Music[edit]

  • Erika Eigen‘s 1969 song “Lighthouse Keeper” expresses a wish to “marry a lighthouse keeper and keep him company.”[39]
  • The country of Croatia entered a song named “Lighthouse” in the 2016 Eurovision Contest.[40]

Namesakes[edit]

To recognize the role of lighthouse keepers in maritime safety, the U.S. Coast Guard named a class of 175-foot (53 m)coastal buoy tenders after famous U.S. lighthouse keepers. Fourteen ships in the class were built between 1996 and 2000.[41] The USCGC Abbie Burgess, based in Rockland, Maine, is one such ship.[42]

Television[edit]

St. Anthony’s Lighthouse, at St. Anthony’s Head near Falmouth, Cornwall, was featured in the title sequence of the children’s live action puppet television program series Fraggle Rock created by Jim Henson.

The long-running American soap opera Guiding Light has featured a lighthouse in many of its opening title segments, and the fictional Springfield, Illinois has a lighthouse situated near the town.[43]

The Australian television series Round the Twist involved a family living in the Split Point Lighthouse at Aireys Inlet,Victoria.

The Adventures of Portland Bill was a British stop motion animated children’s television series made in 1983. Set in a fictional lighthouse, the name of its main character was a reference to the Portland Bill Lighthouse in Dorset. Many of the other characters were plays on the names of coastal regions, made familiar to the wider public by the BBC Radio 4Shipping Forecast.

Urban legend[edit]

A widely disseminated urban legend tells of a radio conversation between a U.S. or British naval vessel, and what is believed to be another ship on a collision course. The naval vessel insists the other ship change course, but the other ship continues to insist the naval vessel do so. After the captain of the naval vessel identifies himself and demands a course change, the other party responds: “I’m a lighthouse. It’s your call”.

Heraldry[edit]

Lighthouses are used as charges in heraldry, especially for towns along the seaside.[citation needed]