Lighthouse
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An aid for navigation and pilotage at sea, a lighthouse is a tower building or framework sending out light from a system of lamps and lenses or, in older times, from a fire. Lighthouses also provide coordinate location for small aircraft traveling at night. More primitive navigational aids were once used such as a fire on top of a hill or cliff (see beacon).
Because of modern navigational aids, the number of operational lighthouses has declined to less than 1,500 worldwide. Lighthouses are used to mark dangerous coastlines, hazardous shoals away from the coast, and safe entries to harbors.
Perhaps the most famous lighthouse in history is the Lighthouse of Alexandria, built on the island of Pharos in ancient Egypt. The name of the island is still used as the noun for "lighthouse" in some languages, for example: French (phare), Italian and Spanish (faro), Portuguese (farol), Romanian (far), Bulgarian and Russian (фар), and Greek (φάρος). The word "pharology" (study of the lighthouses), is also derived from the island's name.
Many groups have been formed to restore and save lighthouses around the world. One of the most active and popular is the Amateur Radio Lighthouse Society, or ARLHS. With over 1400 members, this world-wide organization sends ham radio operators to remote lighthouses, sets up radio stations, and communicates via ham radio with hams throughout the world. It offers several prizes and awards for lighthouse operations and activities. Go here ARLHS for web site.
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[edit] History
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Lighthouses originally contained an open fire. Later, they were gas-powered and electric.
The Lighthouse of Alexandria was a tower built in the 3rd century BC (between 285 and 247 BC) on the island of Pharos in Alexandria, Egypt to serve as that port's landmark, and later, its lighthouse. With a height variously estimated at between 115 and 135 metres (383 - 440 ft) it was among the tallest man-made structures on Earth for many centuries, and was identified as one of the Seven Wonders of the World by classical writers. Two lighthouses, each called the Pharos, were built at Dover soon after the Norman conquest of England. They were sited on the two heights (Eastern Heights and Western Heights) and modelled on the one built for Caligula's aborted invasion at Boulogne.
In the Islamic world, lighthouses were also known. The Tang Dynasty Chinese writer Jia Dan once wrote in his book (written between 785 - 805) that in the sea route forming the opening mouth of the Persian Gulf, the medieval Iranians had erected large minaret towers that served as lighthouses. To confirm Chinese reports, a century later, the Arab writers al-Mas'udi and al-Muqaddasi wrote of the same lighthouses.
In China, the medieval mosque at Canton had a minaret that served as a lighthouse. The later Song Dynasty Chinese pagoda tower built in medieval Hangzhou, known as the Liuhe Pagoda (erected in 1165), also served as a lighthouse for sailers along the Qiantang River.
[edit] Design
In order to conserve power, the light is concentrated.
In old lighthouses:
- vertically the light is bundled into horizontal directions
- horizontally the light is bundled into one or a few directions at a time, with the light beam sweeping around; as a result, in addition to seeing the light beam from the side, from every horizontal direction there are instants that one sees the light directly, hence from a larger distance.
This concentration of light is accomplished with a rotating lens assembly. In very old lighthouses, the light source was a kerosene lamp, and the lenses were rotated by a clockwork assembly wound by lighthouse keepers, sometimes as often as every two hours. The lens assembly usually floated in mercury to reduce friction. In more modern lighthouses, electric lights and clock drives were used, generally powered by diesel electric generators. These also supplied electricity for the lighthouse keepers.
Efficiently concentrating the light from an omnidirectional source of the type used in lighthouses requires a lens of very large diameter. This would lead to a very thick and heavy lens if naively implemented. A Fresnel lens is a type of lens developed for lighthouses. Its design enables the construction of lenses of large size and short focal length without the weight and volume of material which would be required in a lens of conventional design. Some lighthouses, such as those at Cape Race, Newfoundland, and Makapu'u Point, Hawaii, used a special hyperradiant lens manufactured by the firm of Chance Bros.
In modern automated lighthouses this system of rotating lenses is often replaced by a very bright light that emits brief omnidirectional flashes (concentrating the light in time rather than space). These lights are similar to the aerodrome beacons used to warn aircraft away from tall structures.
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 characteristic light pattern specific to the particular lighthouse. For example, for the lighthouse of Scheveningen the time intervals between these instants are alternately 2.5 and 7.5 seconds.
Other design techniques are used to aid the navigator. Lights near to each other are painted in a unique style so they can easily be recognized during the daylight (this marking is called a day mark.) Likewise the time interval of the light (see above) or the color pattern of the lens is varied. Sector lights have particular obstructions in one or more sectors, and a portion of the lantern house may have a red or green filter applied so the navigator gets additional input on which side the ship is approaching from. Modern lighthouses have unique metal attachments so the radar signature of the light is also unique.
[edit] Maintenance
In the United States, lighthouses are maintained by the United States Coast Guard. In Britain and Ireland, those in England and Wales are looked after by Trinity House, those in Scotland by the Northern Lighthouse Board, and those in all of Ireland by the Commissioners of Irish Lights. In Canada, they are managed by the Canadian Coast Guard. In Australia, lighthouses are looked after by the Australian Maritime Safety Authority.
[edit] Automation
In the beginning of the 20th century, Swedish inventor Gustav Dahlén invented the AGA Lighthouse which effectively made lighthouse keepers obsolete. However, 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 GPS have led to the phasing out of non-automated lighthouses, with the last keepers removed in the 1990s.
Often in inaccessible locations, modern lighthouses are much more functional and less picturesque buildings; usually they are solar-powered and have a single Flashing light which does not rotate sitting on a steel skeleton tower.
[edit] Notable Lighthouses
In some locations, lighthouses have become popular tourist destinations and the buildings are being maintained as tourist attractions. See, for example, Cape Hatteras lighthouse
Such an example is the Split Point Lighthouse in Aireys Inlet, Victoria, Australia. The popular children's series Round the Twist followed the adventures encountered by a family living in a mysterious lighthouse; and used the area around the Split Point Lighthouse for many exterior scenes. Since summer 2005, half-hour tours are available to those wishing to climb this lighthouse.
Bengtskär lighthouse is the highest (52 meters) in the Nordic countries. It is situated to the south of Hanko, Finland. It was built in 1906 and it is the first lighthouse museum in Finland.
The Soviet Union built a number of automated lighthouses powered by radioisotope thermoelectric generators in remote locations. They operated for very long periods of time without external support with great reliablility [1]. However numerous installations have been found deteriorated, stolen and/or vandalized (Bellona's report). Some of these lighthouses cannot be found due to poor record keeping.
Sambro Island lighthouses, near Halifax, Nova Scotia, is the oldest surviving lighthouses in the Western Hemisphere. Built by the British in 1758, it has survived the many wars that destroyed earlier lighthouses in North and South America.
In Brazil, (South America), "Cabo Branco lighthouse" is strategically located in Joao Pessoa at the easternmost point of the Americas at 34º 47' 38" west longitude and 7º 9' 28" south latitude. Due to its location this lighthouse has become an important touristic attraction.
In December 1900 there was an unexplained disappearance of three keepers from Eilean Mor off the Isle of Lewis in the Flannan Isles.
[edit] Symbolism
Lighthouses are used as symbols by certain organizations. Marriage Encounter uses the lighthouse as their symbol.
Lighthouses are often interpreted in dreams as beacons of truth or as male fertility and influence. One commonly seen has a spiral red stripe said by Milton William Cooper and others to be symbolic of the snake of Lucifer.
[edit] Range Lights
A problem with a single lighthouse is that it is only a point at night. For many navigation problems, this is insufficient.
If the navigator is trying to find the path into a river, he needs a better way, such as the Range light. Two lights are used in this scheme, one is named the front range, the other is called the rear range. The rear range light is always taller than the front range light. When you are on the path into the river, the two lights line up one on top of the other.
This provides better aid for the navigator. When the vessel is on the correct course, the two lights line up. But when on the wrong course, the difference in height makes it very obvious whether to travel left or right to correct the problem.
This technology was first developed in Europe in 1837 where they are referred to as Leading Lights. The first usage in the US is not well defined, but there are some listed in the 1854 Light list (Cherry Hill, NJ, North Point, MD, Beacon Island).
This technology works not only for finding the way into a river, it can be used to navigate the entire river. For instance, it is possible to sail on the Elbe river in Germany at night, and each time it is necessary to make a turn, the navigator lines up the next range lights. This takes you all the way from Hamburg out to the sea, using one pair of range lights after another.
[edit] Gallery
 The Long Point Lighthouse in Provincetown, Massachusetts Cape Cod, MA |
 Nauset Light Lighthouse in Eastham, Massachusetts Cape Cod, MA |
 The Peggys Point lighthouse in Nova Scotia, Canada. |
 Fairport Harbor West Breakwater Lighthouse, Fairport Harbor, Ohio viewed from the Headlands Dunes State Nature Preserve |
 Fairport Harbor West Breakwater Lighthouse, Fairport Harbor, Ohio viewed from the Headlands Dunes State Nature Preserve |
 Portland Bill lighthouse, Isle of Portland, Dorset |
 Scarborough Harbour Lighthouse, Scarborough, North Yorkshire, England |
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 A 1999 photo of the Navassa Island lighthouse. The dilapidated lightkeepers quarters appear in the backgound. |
 McClain's State Park Lighthouse, Upper Peninsula, Michigan |
 Point Reyes Lighthouse |
 Nauset Light and lightkeeper's house, Eastham, Massachusetts |
 Spurn Point Lighthouse, East Yorkshire, England. |
 Admiralty Head Lighthouse Inactive, used as interpretive center by a local environmental group |
 Strumble Head Lighthouse, Wales |
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 The Eddystone Lighthouse, situated off the coast of Cornwall, England. |
 Cape Byron Lighthouse, New South Wales, Australia |
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 The tall Bengtskär lighthouse also functions as a museum. |
 Point Arena Light - California |
 Automated lighthouse at the port of Ijmuiden in The Netherlands |
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 Cabo Branco Lighthouse, Joao Pessoa, Brazil |
[edit] See also
- List of lighthouses and lightvessels
- Jean Guichard - Lighthouses photographer
- Lens lantern
- John Richardson Wigham - Innovator in lighthouse engineering
[edit] References
[edit] External links
- Marinas
- Lighthouse Explorer Website The Lighthouse Explorer Database, with over 7500 lighthouses listed in searchable format, with information, photos, maps and other information
- Lighthouse Digest Magazine The online version of Lighthouse Digest, the largest magazine about lighthouses in the world. Over ten years of stories searchable online.
- The WWW Virtual Library: The World's Lighthouses, Lightships & Lifesaving Stations Links to a variety of lighthouse related resources on the web
- LighthouseFans A user-contributed database of lighthouses around the world with community forums and current lighthouse news.
- Maritime Heritage Network, an online directory of maritime history resources in the Pacific Northwest region of the United States, including a list of all lighthouses.
- Lighthouses in the Netherlands Written in Dutch and partly in English, with recent pictures.
- South African Lighthouses English website with photos and detailed info about all the lighthouses in South Africa.
- Top 25 Lighthouse Web Sites List International list of top web sites about lighthouses displaying latest rank, monthly vote count, ratings and more.
- Travel-Island.com - Gallery of Lighthouses
- High resolution low altitude aerial photography of lighthouses across North America, Western Europe, and the Caribbean
- www.us-lighthouses.com - History, photos, driving directions, and GPS coordinates of lighthouses in the U.S., Canada, Australia, Germany
- Lighthouses and Buoys Explanation and Characteristic
