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46-573: Hurst Point Lighthouse is located at Hurst Point in the English county of Hampshire , and guides vessels through the western approaches to the Solent . The original lighthouse was the Hurst Tower , sited to the south west of the old Hurst Castle and lit for the first time on 29 September 1786. Richard Jupp was the architect and Joseph Huddart supervised and directed its construction, which

92-472: A chemist who studied rare-earth elements in the 1880s and who had been Robert Bunsen 's student. Ignaz Kreidl worked with him on his early experiments to create the Welsbach mantle. His first process used a mixture of 60% magnesium oxide , 20% lanthanum oxide and 20% yttrium oxide , which he called "Actinophor" and patented in 1887 (March 15, 1887, US patent #359,524). These original mantles gave off

138-457: A complex new array of fixed first-order Fresnel lenses , together with a Douglass-designed six-wick lamp. According to contemporary plans, displayed in the nearby museum in the castle, the 'new' lenses were in fact old lenses reused from elsewhere: one panel 'taken from the first order dioptric apparatus formerly used at St Catherine's ' and one 'taken from the central portion of the old Bishop's Rock apparatus', both of which had been replaced

184-537: A few years earlier. (Three sets of upper prisms were also re-used from St Catherine's.) One panel was positioned on the south-west side of the lamp and aligned with the Low Light to provide the transit guiding passage through the Needles Channel; the other was positioned on the east side of the lamp to guide vessels approaching via The Solent , with a red sector in addition marking a hazard, Solent Banks. In

230-448: A fresh flush of radium-224 into the air. This byproduct can be inhaled if the mantle is used indoors, and is an internal alpha-emitter radio-toxicity concern. Secondary decay products of thorium include radium and actinium . Because of this, there are concerns about the safety of thorium mantles. The Australian Radiation Protection and Nuclear Safety Agency recommends mantles made with yttrium instead. A study in 1981 estimated that

276-616: A green-tinted light and were not very successful. Welsbach's first company established a factory in Atzgersdorf in 1887, but it failed in 1889. In 1889, Welsbach received his first patent mentioning thorium (March 5, 1889, US patent #399,174). In 1891 he perfected a new mixture of 99% thorium dioxide and 1% cerium dioxide that gave off a much whiter light and produced a stronger mantle. After introducing this new mantle commercially in 1892, it quickly spread throughout Europe. The gas mantle remained an important part of street lighting until

322-425: A wire or a ceramic fiber thread. Thorium is radioactive and produces the radioactive gas radon -220 as one of its decay products . Moreover, when heated to incandescence, the thorium volatilizes its in-growth radio-daughters , particularly radium -224. Despite its very short half-life, radium quickly replenishes from its radio-parent (thorium-228), and every new heating of the mantle to incandescence releases

368-418: Is a major concern for people involved with the manufacture of mantles and an issue with contamination of soil around some former factory sites. One potential cause for concern is that particles from thorium gas mantles "fall out" over time and get into the air, where they may be ingested in food or drink. These particles may also be inhaled and remain in the lungs or liver, causing long-term exposure exceeding

414-428: Is a one-mile-long (1.6 km) shingle bank near the village of Keyhaven , at the western end of the Solent , on the south coast of England . The spit shelters an area of saltmarsh and mudflats known as Keyhaven and Pennington marshes . At the end of the spit is Hurst Castle , an artillery fortress originally built on the orders of King Henry VIII , and much enlarged in the 19th century. Hurst Point Lighthouse

460-483: Is attracted there, being on the beach of an open pure sea". The inn building was demolished with expansion of the castle in the mid 19th century, but by the 1870s there was a new inn, called the Castle Inn, which was "kept for the accommodation of the troops and the crews of the numerous stone-dredging vessels, which carry away great quantities of the shingle from the beach to Portsmouth , Southampton etc." The inn

506-422: Is highly flammable and can be explosive. Later, it was discovered that a cotton mantle could be strengthened sufficiently by dipping it in a solution of collodion to coat it with a thin layer that would be burned off when the mantle was first used. Mantles have a binding thread to tie them to the lamp fitting. Until asbestos was banned due to its carcinogenicity , an asbestos thread was used. Modern mantles use

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552-478: Is thought to be a Middle English dialect word meaning "sandbank", which is derived from Old English "hyrst" indicating a hillock or eminence. Little is known about Hurst before the castle was built, although it seems to be mentioned in a document dated 1434 which refers to a wreck off "Hurst". Hurst Castle was built between 1541 and 1544 by Henry VIII as part of his network of coastal defences to protect England against French and Spanish invasion. Hurst Castle

598-407: The visible spectrum . There is also some evidence that the emission is enhanced by candoluminescence , the emission of light from the combustion products before they reach thermal equilibrium. The combination of these properties yields a mantle that, when heated by a kerosene or liquified petroleum gas flame, emits intense radiation that is mostly visible light, with relatively little energy in

644-403: The 1880s a military narrow gauge railway , part of the track of which survives, was built to shift stores and ammunition from the dock to the castle. Mantle lamp Gas mantles are usually sold as a fabric bag which, because of impregnation with metal nitrates, burns away to leave a rigid but fragile mesh of metal oxides when heated during initial use; these metal oxides produce light from

690-480: The 1940s when coast protection works in Christchurch Bay first began to interrupt the flow of the shingle towards the spit. In 1989 the spit was so weakened that it was danger of being permanently breached. A stabilisation scheme took place in 1996-7. This scheme rebuilt the shingle bank using dredged shingle, and saw the building of a new rock revetment utilising larvikite rocks shipped from Norway at

736-565: The Needles Channel; both were equipped with three Argand lamps and reflectors (those in the Low Lighthouse were shown from a lower window in the tower, while a separate lamp in the lantern room above was angled in the opposite direction, to guide vessels navigating along The Solent ). Each tower had been built with a keeper's cottage attached. In light of the expansion of the Castle between 1865 and 1873, it proved necessary to replace

782-441: The corrosive nature of the acidic metal nitrates. The acidic metal corrosion was later addressed by soaking the mantle in an ammonia solution to neutralize the excess acid. Later mantles were made from guncotton ( nitrocellulose ) which can be produced with extremely fine threads when compared with ordinary cotton threads. These had to be converted back to cellulose by immersion in ammonium sulfide before first use as guncotton

828-410: The dose from using a thorium mantle every weekend for a year would be 3–6 microsieverts (0.3–0.6  mrem ), tiny in comparison to the normal annual background radiation dose of around 2.4 mSv (240 mrem), although this assumes the thorium remains intact rather than airborne. A person actually ingesting a mantle would receive a dose of 2 mSv (200 mrem). However, the radioactivity

874-532: The footpath (part of the Solent Way ) along the top of the spit. The sea route past Hurst Spit can be hazardous to boats because the constriction to the tidal flow caused by the spit creates strong tidal streams, as well as spiky waves mixed with circular areas of flat sea caused by the upwelling water. In addition a sand bar , known as The Trap, sticks out 60 m (200 ft) into the Solent just east of

920-532: The gravel, but are now rare. In the 1830s deposits of bitumen were also noted on the spit, and in 1840 there was even an attempt to establish a bitumen factory. The origin of the bitumen is unknown, but it may be that the spit accumulated natural floating deposits of bitumen. Hurst Spit supports an important community of saltmarsh plants especially sea purslane ( Halimione portulacoides ); glasswort ( Salicornia species); annual seablite ( Suaeda maritima ); and golden samphire ( Inula crithmoides ). Behind

966-406: The heat of the flame whenever used. Thorium dioxide was commonly a major component; being radioactive , it has led to concerns about the safety of those involved in manufacturing mantles. Normal use, however, poses minimal health risk. The mantle is a roughly pear -shaped fabric bag, made from silk, ramie -based artificial silk, or rayon . The fibers are impregnated with metallic salts; when

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1012-527: The high cost of these materials and their poor reliability. The first effective mantle was the Clamond basket in 1881, named after its inventor. This device was made from a matrix of magnesium oxide , which did not need to be supported by a platinum wire cage, and was exhibited in the Crystal Palace exhibition of 1883. The modern gas mantle was one of the many inventions of Carl Auer von Welsbach ,

1058-483: The high-intensity sector light, the old dioptric apparatus, with its different focal lengths and red sector, remains in use in the lantern. In November 2020 the main lamp was converted to LED for better reliability, efficiency, lower maintenance and improved visibility. Now known simply as Hurst Point Lighthouse, the tower is open for visitors but cannot be reached by car; access is by foot or boat only. The decommissioned acetylene producers have been preserved in situ and

1104-466: The installation of an acetylene lamp controlled by a sun valve , fuelled from an adjacent producer plant. (The producer plant, which generated the gas using rainwater and calcium carbide , was decommissioned in 1968; stores of bottled gas were subsequently provided by Trinity House vessels.) Electric power was provided at the lighthouse in 1997. Due to increased use of the shipping lanes, a high-intensity sector light (designed to be seen day and night)

1150-404: The intervening arc (i.e. between the outer Needles Rock and Sconce Point ) the faint light of the naked flame of the lamp was left visible (at a later date a much smaller optic was incorporated to cover this arc). Together with the dioptric array, a complex occulting mechanism was installed, which eclipsed the light for two seconds every ten seconds whilst maintaining a fixed light over the arc of

1196-474: The mantle is first heated in a flame, the fibers burn away in seconds and the metallic salts convert to solid oxides, forming a brittle ceramic oxide shell in the shape of the original fabric. A mantle glows brightly in the visible spectrum while emitting little infrared radiation. The rare-earth ( cerium ) and actinide ( thorium ) oxides in the mantle have a low emissivity in the infrared (in comparison with an ideal black body ) but have high emissivity in

1242-421: The nitrites finally decompose into a fragile mesh of solid oxides with very high melting points. Early mantles were sold in the unheated cotton mesh condition, since the post heating oxide structure was too fragile to transport easily. The mantle converts to its working form when the cotton burns away on first use. Originally, unused mantles could not be stored for very long because the cotton quickly rotted due to

1288-493: The old acetylene burner array is displayed at the base of the tower. A small lighthouse-related museum is maintained by the Association of Lighthouse Keepers in the casemates of the castle. Both the 1866 and the 1911 Low Lights, though decommissioned, remain in place: (painted grey to camouflage them and prevent confusion for mariners). The 1911 lantern still contains its old lamp and lens. Hurst Spit Hurst Spit

1334-544: The risk of background radiation. Also of concern is the release of thorium-bearing dust if the mantle shatters due to mechanical impact. All of these issues have led to the use of alternatives in some countries, usually yttrium or sometimes zirconium , although these are usually either more expensive or less efficient. Safety concerns were the subject of a federal suit against the Coleman Company ( Wagner v. Coleman ), which initially agreed to place warning labels on

1380-411: The round tower of Hurst Castle. Storms regularly uncover unexploded ordnance on the spit, some dating back more than a century. Soldiers stationed at the castle used to practice the firing of shells . The spit formed from loose flint pebbles which had been eroded from the cliffs further west. Although originally formed by natural processes, Hurst Spit has been declining in volume, probably since

1426-467: The spit is an area of saltmarsh and mud flats known as Keyhaven and Pennington marshes . The marshes contain a variety of wildlife especially birds, invertebrates, and plant life. There are colonies of black-headed gulls and dunlins , and many wading birds including oystercatchers , ringed and grey plovers , and redshanks . Glanville fritillary butterflies have been reported on the spit probably only as wind blown individuals. The name "hurst"

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1472-562: The top of the Low Light was visible, but a red screen was positioned outside the walls of the fort as a day-mark, so as to make the tower look 'apparently complete' when the lighthouses were in line. The lights displayed were similar to those of the old towers, but the light directed up the Solent now shone from the High rather than the Low lighthouse. In the 1890s the High Light was provided with

1518-432: The transit with the Low Light. By 1911, shifting sandbanks had left the Low Light out of line with the channel. It was therefore replaced with a red square metal tower, mounted on steel joists alongside the castle wall to enable it to be moved laterally so as to adjust to future changes. It too was fitted with a first-order lens. By now the towers were lit by incandescent oil burners. In 1923 both lights were automated with

1564-404: The two lighthouses. In 1865, a new Low Light was built: a white circular granite tower with a red lantern, which was attached to the new curtain wall of the castle; then, in 1867, a new High Light was built to designs by James Douglass : a freestanding 26 metre tower (which, in order to maintain the transit in relation to the channel, was positioned 15 metres to the east of the old High Light). Only

1610-525: The unwanted infrared, increasing the luminous efficiency. The mantle aids the combustion process by keeping the flame small and contained at higher fuel flow rates than in a simple lamp. Concentrating combustion inside the mantle improves the transfer of heat from the flame to the mantle. The mantle shrinks after all the fabric material has burned away during installation leaving a very fragile ceramic oxide shell after its first use. For centuries, artificial light has been generated using open flames. Limelight

1656-564: The west. The Hurst Tower light was found to be obscured behind the Needles from certain directions; consequently, in 1812, this tower was supplemented by the High Lighthouse , a new tower at a higher level. The High Lighthouse, which was designed by Daniel Alexander , was a red, brick-built elliptical tower of an unusual and striking conical design. The two towers together functioned as leading lights for vessels approaching through

1702-479: The western end of the spit and near the castle. The spit has to be replenished from time to time, most notably in the aftermath of the 2013-14 UK winter storms when New Forest District Council had to rebuild and reinforce parts of the spit. The spit no longer has its original natural appearance and looks "more like a railway embankment." Fossils from the Barton Beds were at one time a common sight amongst

1748-415: The widespread introduction of electric lighting in the early 1900s. To produce a mantle, cotton is woven or knit into a net bag, impregnated with soluble nitrates of the chosen metals, and then transported to its destination. The user installs the mantle and then burns it to remove the cotton bag and convert the metal nitrates to nitrites which fuse together to form a solid mesh. As the heating continues,

1794-547: Was built on the end of Hurst Spit in the 1860s. Hurst Spit is a hook-shaped shingle spit which extends for 1.4 miles (2.25 km) from the Hampshire shore into the Solent towards the Isle of Wight . The spit forms a barrier which shelters a Site of Special Scientific Interest known as Hurst Castle And Lymington River Estuary . To reach the end of the spit one can either catch the seasonal ferry from Keyhaven , or follow

1840-483: Was established to defend the western entrance of the Solent. During the English Civil War the castle was occupied by parliamentary forces and at the end of 1648 Charles I was held prisoner in the castle. The castle was enlarged in the 1860s, and two large wing batteries were built to house heavy guns. Soldiers were stationed at Hurst Castle as recently as World War II . The first lighthouse at Hurst

1886-615: Was installed in one of the lower seaward-facing windows of the High Lighthouse, adjustable in case of further shifts in the sandbanks and using white, red and green light to mark with precision the narrow passage between the Needles and the Shingles Bank. This removed the need for a leading light, and the Low Light was therefore decommissioned that same year. The High Lighthouse is still working today, having been converted from acetylene to electric power in 1997. In addition to

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1932-502: Was invented in the 1820s, but the temperature required to produce visible light through black-body radiation alone was too high to be practical for small lights. In the late 19th century, several inventors tried to develop an effective alternative based on heating a material to a lower temperature but using the emission of discrete spectral lines to simulate white light. Many early attempts used platinum - iridium gauze soaked in metal nitrates , but these were not successful because of

1978-424: Was still operating at the beginning of the 20th century. There was also a coastguard station "near the castle" in 1878 "with four men and a chief boatman", and there was a depot for " smacks employed in collecting from the adjacent coasts the septaria nodules, used in the manufacture of Roman cement ." A small dock , originally stone built, was constructed in the early 1850s, to aid the new building work. In

2024-426: Was the "High Light" – the free standing Hurst Point Lighthouse built on the end of Hurst Spit between 1865 and 1867. In the 18th century a small community of houses, including an inn, grew up just outside the castle, serving the needs of the soldiers, some of whom lodged in the houses with their families. The inn was called The Shipwright's Arms, and in 1808 it was said that "in the summer season, much company

2070-518: Was the Hurst Tower, sited to the south west of Hurst Castle, and lit for the first time on 29 September 1786. An additional and higher light - the High Lighthouse - was constructed in 1812. These lighthouses were dismantled and replaced by two new lighthouses built in the 1860s. The first was the "Low Light" built into the rear wall of the west wing of the castle, which was superseded by the adjacent iron lighthouse in 1911. The second lighthouse

2116-408: Was undertaken at the same time as the erection of two other lights nearby: one on St Catherine's Down and the other on the clifftop above The Needles (it being envisaged that the three would be used in conjunction). The red, brick-built Hurst Tower displayed a fixed white light, but the north-west part of the lantern was 'darkened' to prevent it confusing vessels navigating further along the coast to

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