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79-488: Souter Lighthouse is a lighthouse located to the North of Whitburn , South Tyneside , England. (It was generally known as Souter Point Lighthouse when in service). Souter Point was the first lighthouse in the world to be actually designed and built specifically to use alternating electric current , the most advanced lighthouse technology of its day. The light was generated by a carbon arc lamp : first lit on 11 January 1871, it

158-402: A rescue service , if necessary. Improvements in maritime navigation and safety, such Global Positioning System (GPS), led to the phasing out of non-automated lighthouses across the world. Although several closed due to safety concerns, Canada still maintains 49 staffed lighthouses, split roughly evenly across east and west coasts. The remaining modern lighthouses are usually illuminated by

237-462: 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. With the development of the steady illumination of the Argand lamp,

316-640: A Diesel generator for backup. Many Fresnel lens installations have been replaced by rotating aerobeacons , which require less maintenance.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 (LED) panels. LED lights, which use less energy and are easier to maintain, had come into widespread use by 2020. In

395-450: A bi-form first-order catadioptric revolving optic (a bi-form lens is double-height, containing two lamps, one above the other). At the same time a new lantern was provided, to accommodate the taller optic. Red shades were placed around the lamps, within the lenses, so that the light now flashed red, once every 5 seconds. The 1914 optic remains in situ in the tower; it weighs 4.5 tonnes and floats on 1.5 tonnes of mercury . A separate lamp

474-451: A complete purpose-built electric installation at Souter. The carbon arc lamp at Souter was placed within a lens array consisting of a third-order fixed catadioptric optic surrounded by a revolving assembly of eight vertical condensing-prisms which produced one bright flash every thirty seconds. Its 800,000 candle power light could be seen for up to 26 miles. The optics were designed and built by James Chance in 1870. In addition to

553-436: A filament source. 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

632-414: A horizontal plane, and horizontally the light is focused into one or a few directions at a time, with the light beam 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

711-522: A lecture by Michael Faraday at the Royal Institution ). An initial installation at Dungeness Lighthouse in 1862 had proved problematic, however, with frequent failures of the lamps and machinery; so Trinity House carried out an extensive testing and selection process over five years (including comparisons with oil lights and examination of equipment in Britain and France) before finalising its plans for

790-461: 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

869-457: A mile to the south. This was the intended site for the lighthouse, but it was felt that Lizard Point offered better visibility, as the cliffs there are higher, so the lighthouse was built there instead. The Souter Lighthouse name was retained in order to avoid confusion with the then recently built Lizard Lighthouse in Cornwall . Souter Lighthouse is approximately three miles south of the mouth of

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948-427: A more powerful hyperradiant Fresnel lens manufactured by the firm of Chance Brothers . 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

1027-533: A navigator with a line of position 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 in the United Kingdom. The closer light

1106-512: 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 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

1185-402: 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. Before modern strobe lights , lenses were used to concentrate the light from a continuous source. Vertical light rays of the lamp are redirected into

1264-406: A series of patents during those years. In normal operation only one generator was used, but in conditions of poor visibility both were connected to the lamp to provide a brighter light. The generators were driven by one of a pair of J. Whitworth & co. 5  nhp ' Allen ' condensing steam engines. (Prior to being installed at Souter, the engines and generators were exhibited by Trinity House at

1343-415: A single stationary flashing light powered by solar-charged batteries and mounted on a steel skeleton tower. Where the power requirement is too great for solar power alone, cycle charging of the battery by a Diesel generator is provided. The generator only comes into use when the battery needs charging, saving fuel and increasing periods between maintenance. John Smeaton is noteworthy for having designed

1422-530: Is a unit of measurement for luminous intensity . It expresses levels of light intensity relative to the light emitted by a candle of specific size and constituents. The historical candlepower is equal to 0.981 candelas . In modern usage, candlepower is sometimes used as a synonym for candla . The term candlepower was originally defined in the United Kingdom , by the Metropolitan Gas Act 1860 , as

1501-413: Is about 0.981 candela. In general modern use, a candlepower now equates directly (1:1) to the number of candelas —an implicit increase from its old value. To measure the candlepower of a lamp, a person judged by eye the relative brightness of adjacent surfaces—one illuminated only by a standard lamp (or candle) and the other only by the lamp under test. They adjusted the distance of one of the lamps until

1580-419: Is one example. Race Rocks Light in western Canada is painted in horizontal black and white bands to stand out against the horizon. 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 trigonometry (see Distance to the horizon ) as D = 1.22 H {\displaystyle D=1.22{\sqrt {H}}} , where H

1659-519: Is owned by the National Trust and open to the public; the engine room, light tower and keeper's living quarters are all on view. There is also an outdoor play area, Trusty Club and indoor activities to accommodate young visitors. Two of the former lighthouse keepers' cottages are used as National Trust holiday cottages. The lamps, lenses and foghorn remain in working order and are still activated from time to time 'on special occasions'. The lighthouse

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1738-517: 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. There are two types of lighthouses: ones that are located on land, and ones that are offshore. Candle power Candlepower (abbreviated as cp or CP )

1817-486: Is said to be haunted, and has even featured on British TV's Most Haunted ghost-hunting programme. Lighthouse Lighthouses mark dangerous coastlines, hazardous shoals , reefs , rocks, and safe entries to harbors; they also assist in aerial navigation . Once widely used, the number of operational lighthouses has declined due to the expense of maintenance and the advent of much cheaper, more sophisticated, and more effective electronic navigational systems. Before

1896-510: Is the height above water in feet, and D is the distance from the lighthouse to the horizon in nautical miles, the lighthouse range . 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

1975-622: The Bureau of Standards (United States), and the Physikalische Technische Reichsanstalt (Germany). The majority redefined the candle in term of an electric lamp with a carbon filament. The Germans, however, dissented and decided to use a definition equal to 9/10 of the output of a Hefner lamp . In 1921, the Commission Internationale de l'Eclairage (International Commission for Illumination, commonly referred to as

2054-601: The Florida Reef along the Florida Keys, beginning with the Carysfort Reef Light 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 . Aligning two fixed points on land provides

2133-476: The Gironde estuary ; its light could be seen from more than 20 miles (32 km) out. Fresnel's invention increased the luminosity of the lighthouse lamp by a factor of four and his system is still in common use. The introduction 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

2212-487: The Paris Exposition of 1867 .) The engines were worked alternately: one week on, one week off. Located in the engine-house, they also drove an air-pump to feed the pressure tank of a foghorn. In December 1891 the lighthouse tower was painted with a broad red band, to make it more conspicuous during the day. Holmes also designed a reed fog signal for the new lighthouse, sounded from a separate foghorn house (east of

2291-549: The River Tyne . Some four miles or so to the north of the mouth of the Tyne is a sister Victorian lighthouse, St Mary's Lighthouse , on St Mary's Island . It has also been decommissioned, and is open to visitors. St Mary's Lighthouse can be seen with the naked eye from the top of Souter Lighthouse. The lighthouse was a much-needed aid to navigation due to the number of wrecks on the dangerous reefs of Whitburn Steel which lay directly under

2370-510: 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 ironwork structures are screwed into

2449-455: The CIE) redefined the international candle again in terms of a carbon filament incandescent lamp . In 1937, the international candle was redefined again—against the luminous intensity of a blackbody at the freezing point of liquid platinum which was to be 58.9 international candles per square centimetre. In 1948, the international unit ( SI ) candela replaced candlepower. One candlepower unit

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2528-452: 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

2607-405: 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

2686-499: 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 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,

2765-439: 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 1777, known as 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

2844-481: The beam was too narrow to be seen easily. 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

2923-525: The collapse of the Soviet government in 1990s, most of the official records on the locations, and condition, of these lighthouses were reportedly lost. Over time, the condition of RTGs in Russia degraded; many of them fell victim to vandalism and scrap metal thieves, who may not have been aware of the dangerous radioactive contents. Energy-efficient LED lights can be powered by solar panels , with batteries instead of

3002-457: The development of clearly defined ports , mariners were guided by fires built on hilltops. Since elevating the fire would improve 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

3081-468: The entrance into a harbor, such as New London Harbor Light . 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

3160-538: The illumination that emanates from a lamp burning pure colza oil (obtained from the seed of the plant Brassica campestris ) at a defined rate. Ten standard candles equaled about one Carcel burner. In 1909, several agencies met to establish an international standard. It was attended by representatives of the Laboratoire Central de l’Electricité (France), the National Physical Laboratory (UK),

3239-520: The intensity of the light on a target, rather than the total amount of light it emits. A given lamp has a higher candlepower rating if its light is more tightly focused. Candlepower is still used today in law. For example, it is presently used in the California Vehicle Code to define the legal requirements for headlamps and other lamps, including accessory lamps. Only a few artificial light sources, such as military photoflash bombs , have

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3318-455: 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 and grounding system connected to

3397-531: The light is concentrated, if needed, by the "lens" or "optic". Power sources for lighthouses in the 20th–21st centuries vary. 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 acetylene gas derived on-site from calcium carbide began replacing kerosene around

3476-512: The light produced by a pure spermaceti candle that weighs 1 ⁄ 6 pound (76 grams) and burns at a rate of 120 grains per hour (7.8 grams per hour). Spermaceti is a material from the heads of sperm whales , and was once used to make high-quality candles. At the time the UK established candlepower as a unit, the French standard of light was based on the illumination from a Carcel burner , which defined

3555-434: 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-part Fresnel 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

3634-469: 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 (pronounced / f r eɪ ˈ n ɛ l / ) 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

3713-468: The lighthouse tower a number of other buildings were laid out around a quadrangle, including the engine room and boiler house, and five dwellings; all were built of rubble masonry, rendered with Portland cement . The contract for building the lighthouse and keepers' cottages was reported in March 1869 as being £8,000 and was awarded to the local firm of James Todd, after complaints that local builders had not had

3792-402: The lighthouse was decommissioned. Souter Lighthouse was decommissioned by Trinity House in 1988, but continued to serve as a radio navigation beacon up until 1999 when it was finally closed. As Souter was never automated, it remains much in its original operational state except for updates during its lifespan to its lantern and electrical apparatus. Today the decommissioned Souter lighthouse

3871-534: The main light a red/white sector light shone from a window in the tower below the lantern, to highlight hazards to the south in Sunderland Bay (namely Hendon Rock and the White Stones); it was powered using light diverted (through a set of mirrors and lenses) from the landward side of the main arc lamp. Electricity for the light was provided by two of Holmes' own magneto electric generators for which he took out

3950-457: The main light were the largest in the Trinity House service. Should the electricity supply fail, a diesel generator would be engaged (and in the event that it too were to fail, an additional emergency battery lamp would be engaged). The mechanism which turned the lenses continued to be driven by clockwork at this time, until 1983 when it was replaced by a pair of electric motors. The fog signal

4029-421: 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

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4108-505: The most brilliant light then known. 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),

4187-738: The mouth of the Thames and was known as the Maplin Sands 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). Until 1782 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

4266-682: The opportunity to reply to tender as it had not been advertised locally. The foundation stone was ceremonially laid by Admiral Collinson 's sister on 9 June 1869. Building works were completed in 1870, and the lighthouse entered service in January the following year. After completing this project Douglass and Norris moved on to the building of Hartland Point Lighthouse in Devon. Carbon arc lights for lighthouses were pioneered by Professor Frederick Hale Holmes , with experiments carried out in 1857–60 at Blackwall and at South Foreland Lighthouse (as described in

4345-463: 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

4424-470: The reeds in February 1879; it sounded one blast every minute. It required an additional and more powerful engine, which was installed in the engine room to drive the compressor for the new signal. In 1914 the pioneering electric light at Souter was replaced with the latest type of incandescent oil lamps (i.e. paraffin vapour burners). At the same time Chance Brothers provided a new, much larger lens system:

4503-451: 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

4582-541: 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). In a lighthouse, the source of light is called the "lamp" (whether electric or fuelled by oil) and

4661-484: 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 . 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

4740-516: The surface during periods of fog or low clouds, as at Point Reyes Lighthouse . 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

4819-587: 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

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4898-399: The tower) through a pair of vertical trumpets (angled north-east and south-east, facing out to sea). It sounded one blast every 45 seconds. Compressed air for the foghorn was piped underground from the engine room, on the other side of the lighthouse, where the air compressor was driven by a common drive shaft from the engines powering the magnetos. A more powerful siren fog signal replaced

4977-483: 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

5056-407: 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

5135-476: The turn of the 20th century. Carbide was promoted by the Dalén light , which automatically lit the lamp at nightfall and extinguished it at dawn. In the second half of the 20th century, many remote lighthouses in Russia (then Soviet Union ) 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

5214-438: The two surfaces appeared to be of equal brightness. Then they calculated the candlepower of the lamp under test from the two distances and the inverse square law . "Candlepower" is largely an obsolete term. However, people still sometimes use it to describe the luminous intensity of high powered flashlights and spotlights. Narrow-beamed lights of all sorts can have very high candlepower specifications, because candlepower measures

5293-463: 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

5372-523: 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

5451-430: The water in the surrounding area. In one year alone – 1860 – there were 20 shipwrecks. This contributed to making this coastline the most dangerous in the country, with an average of around 44 shipwrecks per every mile of coastline. The lighthouse and associated buildings were designed for Trinity House by their Chief Engineer, James Douglass ; its construction was supervised by on-site engineer Henry Norris . Alongside

5530-476: 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 in 1810, one of the most impressive feats of engineering of

5609-643: 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 , Newfoundland, and Makapuu Point , Hawaii, used

5688-425: The world to have been fully exposed to the open sea. The civil engineer John Smeaton rebuilt the lighthouse from 1756 to 1759; 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

5767-437: 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

5846-403: Was described at the time as 'without doubt one of the most powerful lights in the world'. After being decommissioned by Trinity House (the national lighthouse authority) in 1988, Souter Lighthouse was acquired by the National Trust , who now manage it as a visitor attraction with holiday lets . The lighthouse is located on Lizard Point, but takes its name from Souter Point, which is located

5925-543: Was installed, sounded through a pair of Rayleigh trumpets. (These replaced the twin Holmes trumpets formerly employed; the foghorn house was remodelled at the seaward corners to accommodate them). The siren gave a 4-second blast every minute. Hornsby oil engines were installed to drive the compressors for the new siren. In 1952 the lighthouse was again converted to run on electric power (this time using incandescent lamps , powered by mains electricity ). The 4,500W bulbs used for

6004-407: Was sometimes tinted around the wick. Later models used a mantle of thorium dioxide suspended over the flame, creating a bright, steady light. The Argand lamp used whale oil , colza , olive oil or other vegetable oil 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

6083-550: Was the Pharos of Alexandria , Egypt , which collapsed following a series of earthquakes between 956 and 1323. 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. The modern era of lighthouses began at

6162-488: Was upgraded in 1953: a Stone Chance diaphone signal was installed and a pair of exponential horns replaced the Rayleigh Trumpets on top of the foghorn building. At the same time the engine room was provided with two new Reavell compressor sets, one driven by an electric motor, the other by a diesel engine. The diaphone produced a five-second blast every 30 seconds in poor weather, and remained in use up until 1988, when

6241-576: Was used for the fixed red/white sector light, which continued to shine from its window lower down in the tower. Having removed the two Holmes magneto-electric machines from the engine room, the Corporation of Trinity House presented one to the Institution of Electrical Engineers in 1915; it is now on display at the Science Museum, London . The fog signal was improved in 1919 when a more powerful siren

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