History of Lighthouses in Sweden - 1

Introduction

A lighthouse is a tower, building, or another type of structure designed to emit light from a system of lamps and lenses and to serve as a navigational aid for maritime pilots at sea or on inland waterways. Lighthouses mark dangerous coastlines, hazardous shoals, reefs, rocks, and safe entries to harbors. A maritime pilot, marine pilot, harbor pilot, port pilot, ship pilot, or simply pilot, is a mariner who maneuvers ships through dangerous or congested waters, such as harbors or river mouths. They are navigational experts possessing knowledge of the particular waterway such as its depth, currents, and hazards. The image on the top of the page shows the Pater Noster Lighthouse at Hamneskär, southern Bohuslän, Sweden, built 1868. Wikipedia.

Funding of Lighthouses

The managing of the Swedish lighthouses was funded in several different ways. In 1758, the Crown introduced a lighthouse fee (Swe: fyrpenning) and a beacon fee (Swe: båkavgift) which every ship that called at certain ports had to pay for the funding of lighthouse staffing and the construction of new lighthouses and sea marks/beacons. The fees varied from port to port and the size of the ships. Until the nationalization of the Swedish lighthouses in the 1830s, the managing of lighthouses was undertaken by private contractors that were granted the right to take out the lighthouse fee from all passing ships, Crown-owned ships exempted. The beacon fee was paid in ports. The fees immediately contributed to additional funding of lighthouses and beacons.

Organization

In 1652, the Admiralty Board (Swe: Amiralitetskollegium) was assigned the responsibility for the maintenance and supervision of all lighthouses and pilotages in Sweden. At the time, the system of keeping lighthouses in the Realm of Sweden was not very developed. There were only five lighthouses in the Swedish provinces in the Baltic region (today’s Estonia) and a twin lighthouse at Nidingen, Halland, on the Swedish west coast. Both the system of keeping lighthouses and maritime pilots sorted under the Admiralty Board, i.e., the Navy. From 1803, the two were sorted under the “Förvaltningen för sjöärendena”, a naval authority, which in 1878 was renamed to “Marinförvaltningen” and “Marinstaben” (Naval Staff) in 1908. In the 1690s, the Lotsverket (Pilotage Service) was established, subordinated the Admiralty, now organizing both the lighthouses as well as the pilots. The head of the Lotsverket was Director. In 1726, the managing of beacons was also placed under the Admiralty Board. Until 1872, lighthouse and pilot services, i.e. Lotsverket, was subordinated “Förvaltningen för sjöärendena” under the Admiralty Board (“Amiralitetskollegiet”). In 1872, the Lotsverket was reorganized to Royal Board of Pilot Services (Swe: Kungliga Lotsstyrelsen) and now became an administrative government agency detached from the Navy but under the Minister of the Naval Forces. In 1956, the Kungliga Sjöfartsstyrelsen, (Royal Maritime Board) was established and the “Kungliga Lotsstyrelsen” was transferred to this new agency. In 1969, the Sjöfartsstyrelsen was reorganized to “Sjöfartsverket” (Swedish Maritime Administration). In 1987, this agency became a public enterprise owned by the government.

History of Lighthouses

General information

A lighthouse (Swe: “Fyr”) is constructed to be a daytime navigation mark by its appearance and during the dark hours by emitting light, guiding ships safely past dangerous coastlines. In Sweden, the light navigational systems (lighted beacons) are divided into five major categories: 1. Lighthouses (Swe: Angöringsfyr or kustfyr), are large lighthouse towers guiding ships approaching the coastline or sailing in a major fairway outside the coastline. The range of the light of these lighthouses is exceptionally long and therefore equipped with a very bright lantern to be visible for many kilometers. These lighthouses are generally high towers located on high elevations above sea level, on a rock for example. 2. Beacons (Swe: Ledfyr) guide navigators to their destinations in coastal areas such as archipelagos, harbors, and channels. The navigational bacon’s lanterns aren’t as bright as the lighthouses’. A beacon can be a sector light, leading light, or a combination of these two. 3. Harbor lights (Swe: Hamnfyr) simply sailing in harbors. 4. Warning lights (Swe: Varningsfyr) warn navigators for underwater cables and wires. 5. Fishing lights (Swe: Fiskefyr) are in fishing villages guiding fishing boats returning home. Location, construction/structure, functioning, and characteristics depended on the light’s purpose. Daytime, on clear days they serve as nautical sea marks, each painted in a recognizable way separating it from other lights in the same region.

Beacons and Other Sea Marks

A “båk” is a daymark or day beacon, i.e., an unlighted nautical sea mark, which provides a fixed location that can be used to navigate around obstacles or into port. A “båk” has typically a triangular shape made of wood and 10 - 15 meters high. The image to the right shows a red “båk”. Image: Wikipedia. A “fyrbåk” is a high construction or building designed to guide navigators by emitting light like a lighthouse. In former days, the light was obtained by a fire. A “kummel” is a sea mark, traditionally a mound of stones painted white. By size, it is smaller than a “båk”. The “kummlel” sea mark is among the oldest sea marks in Scandinavia. The image to the right shows a “kummel”. Image: Wikipedia. A “boj” or navigational buoy is an anchored (stationary) floating device intended to guide navigators usually colored in various colors. There are many different navigational buoys such as lateral marker buoys, fairway buoys, wreck buoys, etc. A “prick” or spar buoy is a tall, thin, oblong cylindrical buoy that floats upright in the water, marking shallows and fairways, i.e., a floating sea mark. The most common spar buoys are the so- called black and yellow Cardinal mark (Swe: kardinalprick) and the red or green lateral mark (Swe: lateralprick). A cardinal mark indicates the position of a hazard mark and the direction of safe water and its appearance varies depending on the cardinal direction. A lateral mark indicates the edges of a fairway or channel. The starboard lateral mark is green while the port side lateral mark is green (Region A). The image shows two lateral marks, one green, and one red. Image: Wikipedia. There are also some special spar buoys; the isolated danger mark (Swe: punktmärke) is a sea mark used to indicate a hazard to shipping such as a partially submerged rock. It is recognizable by its black and red bands and top mark of two black balls. Then there is the safe-water mark (Swe: mittledsmärken) which is a sea mark used to indicate safe water lies ahead. It is recognizable by its red and white vertical stripes and commonly bears a top sign in the shape of a red ball. A special mark (Swe: specialmärke) is a sea mark used in maritime pilotage. It is recognizable by its yellow color and X top-mark. It has a distinctive sequence of various flashes that do not match any other navigational mark flashes in its vicinity. A stångmärke, stångtavla or spirbåk (pole mark) is a simpler sea mark consisting of a vertical pole, usually supported by props, equipped with a top mark. It is a daymark and usually smaller than a “båk”. The image to the right shows a “stångmärke” (pole mark). Image: Wikipedia.

Lighthouses in the 1500s

The early lighthouses guiding mariners consisted of open fires on hilltops, rocks, and roofs of towers by the sea or possibly in the harbor of major seaport towns. Since elevating the fire would improve visibility, placing the fire on a platform became a practice that led to the development of the lighthouse. På 1400-talet började man även använda vaxljus och talgljus i enkla handlyktor. The oldest known sea mark in Swedish waters is Falsterbo Sea mark which probably was built in the 1230s (at the time Danish). A fire powered with firewood wasn’t burning for a particularly long time which is why firewood was replaced with black coal and charcoal as the source of light in the 1500s. The coal was burning in open baskets or cauldrons made of iron known as braziers, on top of stone towers. This type of lighthouse is called open coal lights (Swe: öppna kolfyrar) in Swedish. Black coal has a longer burning time than firewood or charcoal. The image to the right shows a model of the open black coal light at Holmögadd, Sweden. Image: Sjöhistoriska museet. In 1560 King Fredrik II of Danmark gave orders that a type of open firewood braziers was to be built at Skagen, Anholt, and Kullen to guide mariners. The lights were ready to be lit in 1561. The Kullen lighthouse came into use on 1 March 1561. In 1563, the light was placed on a brick-built tower and in 1624 the lighthouse was rebuilt to be powered by black coal. Kullen lighthouse is the oldest lighthouse on Swedish territory (Swedish from 1658).

Lighthouses in the 1600s

In 1636, a special type navigational beacon was erected near Kolabacken on the Falsterbo isthmus in south Sweden known as Falsterbo vippfyr. This type of lighted beacons (lights) became common in Denmark (“Vippefyr”) and Sweden (“Vippfyr”). A translation of “vippfyr” into English would be “lever light” or “tipping light”. A “vippfyr” consisted of an iron basket with live coal that was hoisted up and down with the help of a lever, at which top end the basket was affixed. At the lower end, a counterbalance was attached making it easy to raise and lower the basket. The “vippfyr” was invented circa 1627 by Dane Jens Pedersen Grove (1584 - 1639). The image to the right shows a “vippfyr” in Kovik harbor, Gotland, Sweden. Image: Wikipedia. On the skerry Nidingen in north Halland’s coastal area, a navigational light was built in 1622 which in 1624 was rebuilt to two firewood-powered lever lights (vippfyr). The reason for the twin lights at Nidingen was to make the lights distinct so they would not be mixed with the nearby lights at Skagen and Anholt. Nidingen was redesigned to a coal lever light in 1635. In the peace treaty of 1645 in Brömsebro Halland became a Swedish province (previously Danish) and the Nidingen Light thereby became the first Swedish Light on Swedish soil. At the southern tip of Öland Island on the Swedish east coast, was a “vippfyr” in use in the 1670s. The first Swedish-built lighthouses were Landsort in 1678, Örskär in 1687, and Korsö circa 1750. At Örskär, the lantern was powered with oil (oil lamp) whose light was intensified with reflectors, made of polished steel plates. The first Landsort Light became operational in 1678 at the island’s southern tip, in the southern parts of the Stockholm archipelago. It replaced an older private light erected in 1651. The light was refined with a brazier and reflectors. This was probably the earliest test with reflectors to intensify navigational lights in Sweden. The lighthouse was a wooden construction and the lighthouse was accidentally set on fire in 1686. In 1687, a new lighthouse was built, this time a cylindrical stone lighthouse with an open brazier powered with coal. The brazier was hanging outside the lighthouse tower to avoid accidental fire. The image to the left is a painting showing the Landsort Light at the end of the 1600s. At the roof of the tower is an open brazier burning, powered with coal. Image: Svenska fyrar, förr och nu. Sjöhistoriska Museet. The first lighthouse on the island Örskär in Östhammar, Uppland, was built in wood in 1687. Before 1687, there had been a day beacon at the spot. The first lighthouse keeper living on the island was Petter Swedman in 1697. In 1738, a stroke of lightning destroyed the lighthouse. A new lighthouse was operational in 1740. Örskär lighthouse is, after Landsort, the oldest Swedish- built lighthouse in the country. Örskär lighthouse was for a very long time, the northernmost lighthouse in Sweden.

Lighthouses in the 1700s

Still, at the end of the 1700s, the lighthouses were rather primitive; usually, an open coal fire in an iron basket or a brazier on the roof of a tower, powered by coal. Keeping coals of fire in an open brazier required a great deal of work and the great amount of coal needed was making them costly. Further, open braziers were submitted to the elements of weather. The possibility to improve the light intensity on lights powered with firewood or coal was limited. The image to the right is a painting showing the open coal-powered brazier at Djursten Lighthouse in 1765. Image: Svenska fyrar, förr och nu. Sjöhistoriska Museet. During the second half of the 1700s, covered braziers came into use which made them less exposed to bad weather and easier to keep alive (Swe: täckta kolfyrar). Until the end of the 1700s, there were only four lighthouses on the west coast of Sweden – Falsterbo, Kullen, Nidingen, and Carlsten (Marstrand). During the 1700s, the following lighthouses were built in Sweden; Holmögadd in 1760, Djursten 1767, Grönskär 1770, Carlsten 1782, and southern Öland in 1785 (1674). However, there was a light in use at the southern tip of Öland between 1674–1675. The image to the right shows a model of the covered coal brazier at the Holmögadd Lighthouse (Umeå) in 1838 when it was equipped with a covered coal brazier. At the top is the funnel visible. Image: Sjöhistoriska museet. In 1765, French Lavoisier theoretically proved that a parabolic reflector intensified the light. Swedish engineer Jonas Norberg (1711 – 1783) designed a system of rotating reflectors powered with a clockwork with a plumb weight. The first rotating reflector was installed in 1781 at Marstrand Lighthouse, powered by clockwork. This was the first device of its kind in the world. In 1795, Swede Anders Polheimer (1746 – 1811) designed a new type of covered coal braziers with a powerful air supply from underneath through the tower up to the brazier. The brazier was placed in a protected lantern which diminished the amount of coal needed. Danish Poul de Löwenörns (1751 – 1826) developed the design of the covered coal brazier further. In Löwenörn’s design, the brazier was placed in a roomy iron lantern covered with panes of glass. Further, the lantern was covered with a roof of iron equipped with a smoke hood which like a weather- vane, always in a position to exhaust as much smoke as possible from the lantern. Several lighthouses were built in Sweden based on the Löwenörn design of covered lighthouses, in which Polheimer’s ”braziers” came into use. In Sweden, the following lighthouses were rebuilt to lighthouses with covered coal braziers: • 1812 Östergarnsholm • 1817 Svartklubben • 1822 Ölands Södra Udde • 1834 Nidingen’s both lighthouses (twin lighthouses) • 1837 Holmögadd • 1839 Storjungfrun With covered braziers, it was possible to achieve a brighter light than with open braziers. Reflecting steel plates behind the flame made it possible to emit the light at a longer distance. However, the light was usually not bright enough. A great problem was the quickly sooty and blackened glass panes around the braziers caused by the burning coal, which needed cleaning regularly. The period of covered coal braziers was therefore comparatively short. The Argand oil lamp: A great improvement was the introduction of oil lamps (usually vegetable oil) in lighthouses. A decisive invention was the Argand lamp. In 1784, Swiss Argand came up with an invention that improved the source of light in lighthouses. He managed to design an oil lamp with much brighter light without smoke and did not cause sooty panes. The Argand oil lamp was equipped with a sleeve- shaped wick mounted so that air can pass both through the center of the wick and also around the outside of the wick before being drawn into a cylindrical chimney of glass which steadies the flame and improves the flow of air. Its output is 6 to 10 candelas, brighter than that of earlier lamps and it didn’t need continuously tending. Lighthouses with oil lamps now drove the older coal- powered lighthouses out of the market and the parabolic metal reflectors intensified the light further (Stevenson reflectors). In Sweden, it was foremost colza oil used as fuel in the Argand oil lamps in lighthouses. Colza oil is a vegetable oil similar to rapeseed oil. A disadvantage of the original Argand arrangement was that the oil reservoir needed to be above the level of the burner because the heavy, sticky vegetable oil would not rise far up the wick. This made the lamps top-heavy and cast a shadow in one direction away from the lamp's flame. The Carcel lamp of 1800, which used a clockwork pump to allow the reservoir to sit beneath the burner, and Franchot's spring-driven Moderator lamp of 1836 avoided these problems. There were still many lighthouses in Sweden at the beginning of the 1900s which used the Argand oil lamp.

Lighthouses in the 1800s

Attendance by the government, state-owned lighthouses: During the 1800s, the Swedish government passed several acts in the Parliament regarding the expansion of the lighthouse services. After 1845, and especially after 1880, the number of lighthouses substantially increased. One reason was the introduction of new, cheaper technical solutions but also new cheaper constructions. About 400 new lights and lighthouses were established during the 1800s. Until the nationalization of the Swedish lighthouses in the 1830s, the managing of lighthouses was undertaken by private contractors. The chart shows the number of lights and lighthouses in Sweden between 1645 and 1910. Chart: “Lista öfver svenska fyrar utgifven i april 1912 af Kungl. Lotsstyrelsen”. Until the middle of the 1800s, the number of lighthouses in Sweden was modest. However, a great expansion of lighthouses commenced at that time. The Fresnel Lens: Lighthouse services took a great leap forward when the Fresnel lens was invented. In 1822, the French lighthouse Cordounan was equipped with the first Fresnel lenses, designed by physicist Augustin-Jean Fresnel. The light was visible to the horizon, more than 30 km (20 mi) out. A Fresnel lens is a type of composite compact lens for use in lighthouses. The design allows 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. So, a Fresnel lens can be made much thinner than a comparable conventional lens. The catadioptric form of the lens, entirely invented by Fresnel, has outer elements that use total internal reflection as well as refraction; it can capture more oblique light from a light source and add it to the beam of a lighthouse, making the light visible from greater distances. The Fresnel lens reduces the amount of material required compared to a conventional lens by dividing the lens into a set of concentric annular sections. In each section, the overall thickness is decreased compared to an equivalent simple lens. The lens apparatus looked like a cylindrical drum encircling the flame. Fresnel designed six sizes of lighthouse lenses, divided into four orders based on their size and focal length. Fresnel's next lens was a rotating apparatus with eight "bull's-eye" panels, made in annular arcs giving eight rotating beams—to be seen by mariners as a periodic flash. The image to the right shows an example of how the Fresnel lenses disperse the light as parallel beams. Wikipedia. The first two Swedish lighthouses equipped with the Fresnel lens apparatus were Vinga in 184,1 and Falsterbo in 1843. Kullen Lighthouse is Sweden’s and Scandinavia’s brightest lighthouse. It is equipped with three rotating Fresnel lenses of the first order, each with a diameter of 2.55 meters (8.4 ft). The Klipp Apparatus: With a “klipp” apparatus the intervals between light and darkness are achieved with vertical blinds or slats, which are either rotating around its center line like in Baron C. G. von Otter’s system or around the source of light like in engineer Lindberg’s Rotator. Swedish naval officer Carl Gustaf von Otter (1827 – 1900) designed a “klipp” apparatus (slat apparatus) which released, respectively blocked the light with slats of metal which was turned back and forth by a strong clockwork. However, this solution demanded continuous tending. It was installed on a lighthouse in Sweden for the first time in 1877 and was later installed on several lighthouses in Sweden and abroad. The image to the left shows von Otter’s “klipp” apparatus with 20 slats. Image: Sjöhistoriska museet, ID: 259.58. With this invention it was possible to have the light from a lighthouse emitted in an exact controlled manner with regard of time, direction (sectors), and characteristics. Thereby it was possible for mariners to navigate with great precision through dangerous waters by knowing exactly where they were in relation to the lighthouse. The image to the right shows the lens apparatus at Kullen Lighthouse in 1900. Image: Sjöhistoriska museet, ID: Fo21818A. A klipp valve for acetylene lights releases flammable gas intermittently. A klipp apparatus for electric light, switches on and off the electric current to a lamp. At the end of the1890s, the kerosene incandescent lamp (Swe: fotogenglödljus) was developed in France. It burned vaporized kerosene.

Lighthouses in the 1900s

The Lux Light: In 1901 - 1902, the Swedish company Lux developed a light for lighthouses which was powered with a kerosene gas burner equipped with one or several incandescent mantles. The light is known as the Lux light. The first lighthouse in Sweden equipped with the Lux light was the southern Sandhammaren Lighthouse in 1902. The Lux light produced a brighter and whiter light than a regular kerosene lamp with a wick could give. The Lux light was 3 - 4 times more luminous. The Lux light demanded continuous tending and the light was therefore only used in lighthouses which was permanently manned. In 1912, there were about 50 major lighthouses equipped with the Lux light and some lighthouses used the light until the 1960s. The AGA Light: A new invention for producing flashing lights was introduced at the beginning of the 1900s by the Swedish engineer Gustaf Dalén (1869 – 1937). His invention is known as the AGA Light or Dahlén Light. A Dalén light is a light produced from the burning of carbide gas (acetylene), combined with a solar sensor which automatically operates the light only during darkness. This technology was the predominant form of the light source in lighthouses from the 1900s through the 1960s, when electric lighting had become dominant. The system was marketed by his company AGA, hence the name, AGA light. The Dalén light is notable because of its sun valve (solar valve). This device allowed the light to operate only at night, conserving fuel, and extending their service life to over a year. The 'Dalen Flasher' was a device that, except for a small pilot light, only consumed gas during the flash stage. This reduced gas consumption by more than 90%. The AGA lighthouse equipment worked without any type of electric supply and was thus extremely reliable. Dahlén’s mass-produced, robust, minimal maintenance buoys were a significant boon to safety and livelihood. In 1900, the AGA light was installed at the Marstrand Lighthouse on the Swedish west coast. In 1912 Dahlén was awarded the Nobel Prize in Physics for his "invention of automatic regulators for use in conjunction with gas accumulators for illuminating lighthouses and buoys". Dalén later invented the AGA cooker in 1922. With a “klipp” valve for acetylene gas, which distributed the gas jerkily, the light produced with the AGA system could be made brighter and much more varied compared to the kerosene incandescent lamp. The AGA flame wasn’t ignited continuously, only at short intervals, for example for 0.3 seconds every third second. This made the AGA light very economical to run. With a short flash every third second, it only consumed about 10% of a fixed light. The image to the left shows an AGA klipp valve/klipp appartus. Image: Sjöhistoriska museet, ID: SM 22805.B. DigitaltMuseum. In 1912, Blockhusudden Light in the Stockholm harbor entrance became the first light in the world equipped with the AGA solar valve. The breakthrough of the AGA light took place in the 1920s. The image to the right shows Gustaf Dahlén’s award-winning solar valve. Image: Sjöhistoriska museet, ID:SM 24911. In 1990, the last Dahlén light was phased out in Sweden. Electrification of Lights: During the first half of the 1900s, the predominant form of the light source in lighthouses was lights powered by acetylene. However, in the 1960s, electric lighting became dominant. Gradually the electric network was expanding also to the remote areas where many lighthouses were located and the electrification and automation of lighthouses were expanding, which was a rapid process in Sweden that also made many lighthouse keepers obsolete. In 1908, two harbor lights in Oxelösund, Sweden, were equipped with fixed light, powered with electricity. These two lights were the first in Sweden powered with electricity (bulbs). In 1923, the harbor lights in Trelleborg and Helsingborg were electrified. The Helsingborg lighthouse was the first major lighthouse electrified in Sweden. However, it took many decades before the majority of all Swedish lights were electrified. Today, all Swedish lights and lighthouses are automated, but in the 1990s about 90 lighthouses were still tended by lighthouse keepers.

Related Links

• Pilotage services - History • History of the Swedish Customs Service

Source References

• Uppbyggnaden av det svenska fyrväsendet 1645–1890: privata och statliga intressen, Erik Lindberg, Historiska institutionen, Uppsala universitet • Sjösäkerhet på entreprenad, Ett kontraktsteoretiskt perspektiv på privata och statliga fyrar i Sverige före 1840, Erik Lindberg, Uppsala universitet 2012 • Svenska lots- och fyrväsendets utveckling, fyrarnas historia och framtid, Esbjörn Hillberg. Särtryck ur Tidskrift i Sjöväsendet N:r 3 2007, Sid 209-226. • Utbyggnaden av fyrsystemet i Sverige 1800 - 1950, Staffan Rydergård 1997, Tekniska Högskolan. • Mardrömskust blev populär badstrand, artikel av Curt Nordh i Kvällsstunden, vecka 34 2020. • Wikipedia • Svenska Fyrsällskapet • DigitaltMuseum • Nordisk familjebok / Uggleupplagan. 6. / 1157- 1158 Top of page

Characteristics of Lighthouses

The Lights’ Operational Hours

The lights must be lit during the dark hours during the part of the year when shipping was excepted. During winter, when the sea was frozen over in Swedish waters, the lights were unlighted. However, in 1838, the duration of the operational period was extended to all year round, starting 30 minutes after sunset to 30 minutes before sunrise. The image to the right shows a sign with information (in Swedish) about the lights’ operational hours in 1907. Image: Kungörelse om fyrbelysning från Sjöfartsverket 1907. Sjöhistoriska museets arkiv ID: SM 20605.

Light Characteristics

The lighthouses’ would be less important to mariners if the light emitted from all lighthouses along a specific coastal area would be identical. If they were, ships would have great difficulties in identifying the lighthouse they have in the sight of the ship, which would complicate their navigation. Therefore, lighthouses in the same coastal area have different light characteristics, easily identifiable. Different lights use different colors, frequencies, and light patterns. Light patterns: • Fixed light (Swe: fast fyr), a continuous, steady, light. • Flashing (Swe: blänkfyr), the total duration of light in each period is less than the total duration of the dark and light appearances (flashes) usually have the same duration. • Fixed and flashing (Swe: fast fyr med blänk), a light that combines a fixed light with a light flashing with a stronger intensity. • Occulting light (Swe: intermittent fyr), the total duration of light in each period is greater than the total duration of darkness and the dark intervals (occultations) usually have the same duration. • Alternating light (Swe: växelfyr), light that alternately displays different colors. • Continuous quick (Swe: blixtfyr or klippfyr), quick flashes are repeated regularly.

The Light’s Range

The range in which light is visible in darkness is called the luminous range. This range corresponds to the maximum range in which the light can be watched, with visibility equivalent to an optical daylight sight of 10 nautical miles. Many things affect a light’s luminous range such as the light source’s brightness, elevation above sea level, the observer’s elevation above sea level, the curvature of the Earth, etc. Three major factors: • Weather conditions. The weather condition can have a great effect on visibility, both positive and negative. Rain, snowfall, mist, low height of clouds will all harm the visibility. Visibility at sea is given in nautical miles. • The luminous intensity of the light source. The luminous intensity is given in candela. The luminous range corresponds to the maximum range in which the light can be watched, with visibility equivalent to an optical daylight sight of 10 nautical miles. Light with very high brightness is visible at a greater distance than light with low brightness. • Geometrical range. The geometrical range is usually the most restricting factor for lighthouses due to the curvature of the Earth. Two factors are important for the geometrical range; the elevation of the light source above sea level and the observer’s height above sea level. If the observer is at sea level and the elevation of the light source is 100 meters (328 ft), the geometrical range is 35.7 km (22 mi) while a light source with an elevation of 200 meters (656 ft) has a geometrical range of 50.5 km (31 mi). The range is also called the geometrical horizon.

Fog Signal

A foghorn or fog signal is a device that uses sound to warn vessels of navigational hazards such as rocky coastlines in foggy conditions. When visual navigation aids such as lighthouses are obscured, foghorns (Swe: mistlur) provide an audible warning of rock outcrops, shoals, headlands, or other dangers to shipping. Audible fog signals have been used in one form or another for hundreds of years, initially, simply bells or gongs struck manually. At some lighthouses, a small cannon was let off periodically to warn away ships. Throughout the 1800s efforts were made to automate the signaling process. However, most lighthouses were still using bells and cannons at the end of the 1800s. A major problem with audible fog signals is that foggy weather conditions usually make it impossible to determine the direction and range to the source of the signal. Besides, the sound of the signals was next to torture to the lighthouse tenders who had to stand the signals for several consecutive days and nights. In 1766, Nidingen Lighthouse, Halland, was provided with a fog bell (Swe: mistsignalklocka) which was struck 4 beats every 30 minutes in foggy conditions. The bell was mounted in a 12 meters (39 ft) high wooden bell tower which also served as a nautical sea mark. In 1869, Vinga Lighthouse became the first lighthouse in Sweden equipped with fog signal cannons (Swe: mistsignalkanon), two cannons. In 1875 Nidingen was provided with three cannons. Later, several different types of steam-powered foghorns were introduced. The Tyfonen and Nautofonen were both developed in the 1920s in Sweden. The Tyfon (meaning typhoon) was invented by Swede Helge Rydberg in 1920 and the “tyfon” generated an audible tone by compressed air forcing diaphragms to vibrate. In 1923, the first Tyfon foghorn was implemented at Hakens Lighthouse on Ven Island. The Nautofon is an electrically powered diaphragm that is set to vibrate through electromagnets. In 1928, the first Nautofon foghorn was implemented at Hållö Lighthouse, Bohuslän. Since the automation of lighthouses became common in the 1960s and 1970s, most older foghorn installations have been removed to avoid the need to run the complex machinery associated with them, and have been replaced with electrically powered diaphragm or compressed air horns.

Lighthouse Structures

Stone

Most Swedish lighthouses are stone structures, usually circular towers. The lighthouse to the left is a circular stone structure and is the Landsort Lighthouse, as seen from an easterly direction, 2013. Image: Wikipedia.

Heidenstam type of lighthouses

During the 1860s and 1870s, many lighthouses in Sweden were constructed as towers made of iron. These iron lighthouses were designed by Swede Gustav von Heidenstam (1822 – 1887) and are known as the Heidenstam lighthouses. From 1849, Gustav von Heidenstam was a lighthouse engineer with the Swedish Royal Board of Pilot Services (Swe: Lotsverket) where he was involved with the work to cover Sweden's coastal areas with lighthouses. In 1858, he was appointed senior lighthouse engineer. Heidenstam designed a new lighthouse structure built of iron consisting of iron pipes, oblique-angled stays, around a central circular iron tower with a spiral staircase up to the top of the construction where the light is. The lantern was powered with clockwork with weights. The great advantage of the Heidenstam lighthouse was that the building parts could be prefabricated and erected very fast at the spot of the lighthouse. The image to the right shows the type of lighthouse known as Heidenstam lighthouses. The lighthouse on the image is the Svenska Högarna Lighthouse, built in 1874, height 18 meters (59 ft). Image: Wikipedia. Gustav von Heidenstam was the father of Verner von Heidenstam (1859–1940), poet, novelist, and laureate of the Nobel Prize in Literature in 1916.

Caisson lighthouses

A caisson lighthouse is a type of lighthouse whose superstructure rests on a concrete caisson developed in the late nineteenth century. Caisson lighthouses usually have living quarters made of cast iron. The caisson lighthouses are built to stand on open waters, on shoals, or close by. The caisson rests on a foundation at the bottom of the sea or lake. The upper part of the caisson is above the surface and the superstructure rests on the caisson. In Sweden, the caisson is usually made on land and transported to the spot where it is immersed. It was foremost caisson lighthouses that replaced the lightvessels in Swedish waters mainly because they were more economical to run than the lightvessels. The image to the right shows a caisson lighthouse, Trubaduren, located south of Vinga in the Gothenburg archipelago. Height: 25.5 m (84 ft). The top part of the caisson is visible, on which the light is built. Image: Wikipedia.

Lightvessels

A lightvessel, or lightship, is a ship that acts as a lighthouse. They were (are) used in waters that are too deep or otherwise unsuitable for lighthouse construction. The type has become largely obsolete nowadays. The 19th century was the main century for the lightvessels. The lightvessel was anchored beside a shoal acting as a lighthouse. A crucial element of lightvessel design is the mounting of a light on a sufficiently tall mast. Initially, this consisted of oil lamps that could be run up the mast and lowered for servicing. Later vessels carried fixed lamps, which were serviced in place. . Fresnel lenses were used as they became available, and many vessels housed these in small versions of the lanterns used on lighthouses. Initially, the hulls were constructed of wood, with lines like those of any other small merchant ship. This proved to be unsatisfactory for a ship that was permanently anchored, the shape of the hull evolved to reduce rolling and pounding. In Sweden, there have been 37 lightvessels but these have gradually been replaced by caisson lighthouses. The lightvessels’ bright red hull is something that unites most lightvessels around the world, for purposes of visibility, and the displaying of the respective station’s name in white upper-case letters on both sides of the hull. The first Swedish lightvessel was the Cyklop which was anchored by the Falsterbo reef in southern Sweden from 1844. The lightvessel Finngrundet was launched in 1903 and during the ice-free part of the winters, she was anchored by the Finngrund banks in the southern part of the Gulf of Bothnia. Initially, her light was powered with kerosene but in 1927, the light was replaced with an AGA beacon. Foghorns were installed at the same time, a “tyfon” (typhoon) as well as a “nautofon” (nautophone). Further modifications in 1940, included the addition of wireless communication along with equipment for her to function as a weather station, and the electrification of her light. Finngrundet was in service until 1969 when she was replaced by an unmanned caisson lighthouse and became a museum ship attached to the Vasa Museum in Stockholm. The vessel’s length is 31 m and she had a crew of 8. The image to the right shows the lightvessel Finngrundet in 1958. Photo Lennart Bergqvist, Image: Marinmuseums arkiv - V17200. In Sweden, the era of lightvessels lasted between 1831 and 1972.