A maar is a broad, low- relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma ). A maar characteristically fills with water to form a relatively shallow crater lake , which may also be called a maar.
154-408: Maars range in size from 20 to 3,000 m (66 to 9,800 ft ) across and from 5 to 200 m (20 to 700 ft) deep. Most maars fill with water to form natural lakes. Most maars have low rims composed of a mixture of loose fragments of volcanic rocks and rocks torn from the walls of the diatreme . The name maar comes from a Moselle Franconian dialect word used for the circular lakes of
308-541: A German colony in 1884 known as Kamerun . After World War I , it was divided between France and the United Kingdom as League of Nations mandates . France took 4/5 and the United Kingdom 1/5 of the territory and both ruled it under mandate until independence in 1960 and 1961 respectively. The Union des Populations du Cameroun (UPC) political party advocated independence but was outlawed by France in
462-460: A magma intrusion to create an explosion crater, the name came to be used for the crater type as well. The present definition of the term relates to both its common and scientific discourse use in language over two centuries. Depending upon context there may be other descriptors available to use in the geological sciences such as the term tuff ring or maar-diatreme volcanoes. These last are volcanoes produced by explosive eruptions that cut deeply into
616-708: A "maar" or "maar lake", although they are not, strictly speaking, maars: In Germany there are also several maars outside of the Eifel. A well-known example is the Messel pit , a former maar lake near Messel in the county of Darmstadt-Dieburg and which is known for its well preserved fossils . In addition in the Swabian Jura and the Albvorland (the Swabian Volcano) there are maar-forming volcanoes. Because
770-624: A Central Office, located at the Prussian Geodetic Institute, whose management was entrusted to Johann Jacob Baeyer. Baeyer's goal was a new determination of anomalies in the shape of the Earth using precise triangulations, combined with gravity measurements. This involved determining the geoid by means of gravimetric and leveling measurements, in order to deduce the exact knowledge of the terrestrial spheroid while taking into account local variations. To resolve this problem, it
924-468: A certain emission line of krypton-86 . The current definition was adopted in 1983 and modified slightly in 2002 to clarify that the metre is a measure of proper length . From 1983 until 2019, the metre was formally defined as the length of the path travelled by light in vacuum in 1 / 299 792 458 of a second . After the 2019 revision of the SI , this definition was rephrased to include
1078-497: A depth up to 300 m (980 ft). These eruptions occurred in a period of about 100,000 years, with the youngest (the Devil Mountain Maar) occurring about 17,500 years ago. Their large size is due to the explosive reaction that occurs when magma comes into contact with permafrost . Hydromagmatic eruptions are increasingly explosive when the ratio of water to magma is low. Since permafrost melts slowly, it provides
1232-473: A determination of the size of the Earth, then considered as a sphere, by Jean Picard through triangulation of Paris meridian . In 1671, Jean Picard also measured the length of a seconds pendulum at Paris Observatory and proposed this unit of measurement to be called the astronomical radius (French: Rayon Astronomique ). In 1675, Tito Livio Burattini suggested the term metro cattolico meaning universal measure for this unit of length, but then it
1386-837: A joint letter to the UNHRC defending China 's treatment of Uyghurs in the Xinjiang region. The Cameroon Armed Forces (French: Forces armées camerounaises , FAC) consists of the country's army ( Armée de Terre ), the country's navy ( Marine Nationale de la République (MNR), including naval infantry), the Cameroonian Air Force ( Armée de l'Air du Cameroun , AAC), and the Gendarmerie . Males and females who are 18 years of age up to 23 years of age and have graduated high school are eligible for military service. Those who join are obliged to complete four years of service. There
1540-654: A maar in the Ardèche department of France, is easily visible from the ground or air. Kilbourne Hole and Hunt's Hole, in southern New Mexico near El Paso, Texas , are maars. The Crocodile Lake in Los Baños in the Philippines, though originally thought to be a volcanic crater, is a maar. The carbon dioxide -saturated Lake Nyos in northwestern Cameroon is another example, as is Zuñi Salt Lake in New Mexico ,
1694-930: A member state of the African Union , the United Nations , the Organisation Internationale de la Francophonie (OIF), the Commonwealth of Nations , the Non-Aligned Movement , and the Organisation of Islamic Cooperation . Originally, Cameroon was the exonym given by the Portuguese to the Wouri River , which they called Rio dos Camarões meaning 'river of shrimps ' or 'shrimp river', referring to
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#17327721945421848-916: A metre "too short" compared to a more general definition taken from the average of a large number of arcs. As early as 1861, Johann Jacob Baeyer sent a memorandum to the King of Prussia recommending international collaboration in Central Europe with the aim of determining the shape and dimensions of the Earth. At the time of its creation, the association had sixteen member countries: Austrian Empire , Kingdom of Belgium , Denmark , seven German states ( Grand Duchy of Baden , Kingdom of Bavaria , Kingdom of Hanover , Mecklenburg , Kingdom of Prussia , Kingdom of Saxony , Saxe-Coburg and Gotha ), Kingdom of Italy , Netherlands , Russian Empire (for Poland ), United Kingdoms of Sweden and Norway , as well as Switzerland . The Central European Arc Measurement created
2002-453: A national cash reserve, pay farmers, and finance major development projects; however, many initiatives failed when Ahidjo appointed unqualified allies to direct them. The national flag was changed on 20 May 1975 with the two stars removed and replaced with a large central star as a symbol of national unity. Ahidjo stepped down on 4 November 1982 and left power to his constitutional successor, Paul Biya . However, Ahidjo remained in control of
2156-631: A new value for the flattening of the Earth, which he determinated as 1 / 299.15 . He also devised a new instrument for measuring gravitational acceleration which was first used in Switzerland by Emile Plantamour , Charles Sanders Peirce , and Isaac-Charles Élisée Cellérier (8.01.1818 – 2.10.1889), a Genevan mathematician soon independently discovered a mathematical formula to correct systematic errors of this device which had been noticed by Plantamour and Adolphe Hirsch . This allowed Friedrich Robert Helmert to determine
2310-709: A part of the Survey of the Coast. He compared various units of length used in the United States at that time and measured coefficients of expansion to assess temperature effects on the measurements. In 1832, Carl Friedrich Gauss studied the Earth's magnetic field and proposed adding the second to the basic units of the metre and the kilogram in the form of the CGS system ( centimetre , gram , second). In 1836, he founded
2464-554: A prototype metre bar, distribute national metric prototypes, and maintain comparisons between them and non-metric measurement standards. The organisation distributed such bars in 1889 at the first General Conference on Weights and Measures (CGPM: Conférence Générale des Poids et Mesures ), establishing the International Prototype Metre as the distance between two lines on a standard bar composed of an alloy of 90% platinum and 10% iridium , measured at
2618-502: A regimen of forced labour. This economic policy was much criticised by the other colonial powers. With the defeat of Germany in World War I , Kamerun became a League of Nations mandate territory and was split into French Cameroon ( French : Cameroun ) and British Cameroon in 1919. France integrated the economy of Cameroon with that of France and improved the infrastructure with capital investments and skilled workers, modifying
2772-495: A remarkably accurate value of 1 / 298.3 for the flattening of the Earth when he proposed his ellipsoid of reference in 1901. This was also the result of the Metre Convention of 1875, when the metre was adopted as an international scientific unit of length for the convenience of continental European geodesists following the example of Ferdinand Rudolph Hassler . In 1790, one year before it
2926-668: A series of international conferences was held to devise new metric standards. When a conflict broke out regarding the presence of impurities in the metre-alloy of 1874, a member of the Preparatory Committee since 1870 and Spanish representative at the Paris Conference in 1875, Carlos Ibáñez e Ibáñez de Ibero intervened with the French Academy of Sciences to rally France to the project to create an International Bureau of Weights and Measures equipped with
3080-663: A shallow saline lake that occupies a flat-floored crater about 6,500 ft (2,000 m) across and 400 ft (120 m) deep. Its low rim is composed of loose pieces of basaltic lava and wall rocks ( sandstone , shale , limestone ) of the underlying diatreme , as well as chunks of ancient crystalline rocks blasted upward from great depths. Maars in Canada are found in the Wells Gray-Clearwater volcanic field of east-central British Columbia and in kimberlite fields throughout Canada. Another field of maars
3234-629: A standard metre made in Paris to the United States in October 1805. He designed a baseline apparatus which instead of bringing different bars in actual contact during measurements, used only one bar calibrated on the metre and optical contact. Thus the metre became the unit of length for geodesy in the United States. In 1830, Hassler became head of the Office of Weights and Measures, which became
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#17327721945423388-574: A standard of length. By 1925, interferometry was in regular use at the BIPM. However, the International Prototype Metre remained the standard until 1960, when the eleventh CGPM defined the metre in the new International System of Units (SI) as equal to 1 650 763 .73 wavelengths of the orange - red emission line in the electromagnetic spectrum of the krypton-86 atom in vacuum . To further reduce uncertainty,
3542-423: A standard would be independent of any changes in the dimensions of the earth, and should be adopted by those who expect their writings to be more permanent than that body. Charles Sanders Peirce 's work promoted the advent of American science at the forefront of global metrology. Alongside his intercomparisons of artifacts of the metre and contributions to gravimetry through improvement of reversible pendulum, Peirce
3696-818: A steady source of water to the eruption while keeping the water to magma ratio low. This produces the prolonged, explosive eruptions that created these large maars. Examples of the Seward Peninsula maars include North Killeak Maar, South Killeak Maar, Devil Mountain Maar and Whitefish Maar. Maars occur in western North America, Patagonia in South America, the Eifel region of Germany (where they were originally described), and in other geologically young volcanic regions of Earth. Elsewhere in Europe, La Vestide du Pal,
3850-568: A territorial dispute over the Bakassi peninsula were resolved. The talks involved President Paul Biya of Cameroon, then President Olusegun Obasanjo of Nigeria, and then UN Secretary-General Kofi Annan , and resulted in Cameroonian control of the oil-rich peninsula. The northern portion of the territory was formally handed over to the Cameroonian government in August 2006, and the remainder of
4004-490: A treaty with one of the local kings to annex the region for the German emperor. The German Empire claimed the territory as the colony of Kamerun in 1884 and began a steady push inland; the natives resisted. Under the aegis of Germany, commercial companies were local administrations. These concessions used forced labour to run profitable banana, rubber, palm oil, and cocoa plantations. Even infrastructure projects relied on
4158-616: A withdrawal by both countries and denied the request by Cameroon for compensation due to Nigeria's long-term occupation. By 2004, Nigeria had failed to meet the deadline to hand over the peninsula. A UN-mediated summit in June 2006 facilitated an agreement for Nigeria to withdraw from the region and both leaders signed the Greentree Agreement . The withdrawal and handover of control was completed by August 2006. In July 2019, UN ambassadors of 37 countries, including Cameroon, signed
4312-466: Is Mount Cameroon in the Southwest Region . Cameroon's most populous cities are Douala on the Wouri River , its economic capital and main seaport; Yaoundé , its political capital; and Garoua . Limbé in the southwest has a natural seaport. Cameroon is well known for its native music styles, particularly Makossa , Njang, and Bikutsi , and its successful national football team . It is
4466-945: Is a maar in Bolivia . The maar of Birket Ram lies on the Golan Heights ; further south maars occur in Africa ( Bilate Volcanic Field and Haro Maja in the Butajiri - Silti -Volcanic Field, Ethiopia, the Bayuda Volcanic Field in the Sudan and Lake Nyos in the Oku Volcanic Field in Cameroon). In Saudi Arabia the Al Wahbah crater formed as a result of a maar eruption. In Japan there are maars in
4620-417: Is a member of both the Commonwealth of Nations and La Francophonie . Its foreign policy closely follows that of its main ally, France (one of its former colonial rulers). Cameroon relies heavily on France for its defence, although military spending is high in comparison to other sectors of government. President Biya has engaged in a decades-long clash with the government of Nigeria over possession of
4774-457: Is a mixture of civil law , common law , and customary law . Although nominally independent, the judiciary falls under the authority of the executive's Ministry of Justice . The president appoints judges at all levels. The judiciary is officially divided into tribunals, the court of appeal , and the supreme court . The National Assembly elects the members of a nine-member High Court of Justice that judges high-ranking members of government in
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4928-565: Is being renaturalised into a maar. In some cases the underlying rock is so porous that maar lakes are unable to form. After winters of heavy snow and rainfall many dry maars fill partially and temporarily with water; others contain small bogs or often artificial ponds that, however, only occupy part of the hollow. The largest known maars are found at Espenberg on the Seward Peninsula in northwest Alaska. These maars range in size from 4 to 8 km (2.5 to 5.0 mi) in diameter and
5082-478: Is currently one limiting factor in laboratory realisations of the metre, and it is several orders of magnitude poorer than that of the second, based upon the caesium fountain atomic clock ( U = 5 × 10 ). Consequently, a realisation of the metre is usually delineated (not defined) today in labs as 1 579 800 .762 042 (33) wavelengths of helium–neon laser light in vacuum, the error stated being only that of frequency determination. This bracket notation expressing
5236-828: Is derived from the Proto-Indo-European root *meh₁- 'to measure'. The motto ΜΕΤΡΩ ΧΡΩ ( metro chro ) in the seal of the International Bureau of Weights and Measures (BIPM), which was a saying of the Greek statesman and philosopher Pittacus of Mytilene and may be translated as "Use measure!", thus calls for both measurement and moderation. The use of the word metre (for the French unit mètre ) in English began at least as early as 1797. Galileo discovered gravitational acceleration to explain
5390-444: Is elected and creates policy, administers government agencies, commands the armed forces , negotiates and ratifies treaties, and declares a state of emergency. The president appoints government officials at all levels, from the prime minister (considered the official head of government), to the provincial governors and divisional officers. The president is selected by popular vote every seven years. There have been 2 presidents since
5544-718: Is found in the Pali-Aike Volcanic Field in Patagonia , South America. and in the Sudanese Bayuda Volcanic Field . The Auckland volcanic field in the urban area of Auckland , New Zealand, has several maars, including the readily accessible Lake Pupuke in the North Shore suburb of Takapuna . Arizona 's Meteor Crater was for many years thought to be a maar of volcanic origin but it is now known to be an impact crater . In
5698-471: Is no conscription in Cameroon, but the government makes periodic calls for volunteers. Human rights organisations accuse police and military forces of mistreating and even torturing criminal suspects, ethnic minorities, homosexuals , and political activists. United Nations figures indicate that more than 21,000 people have fled to neighbouring countries, while 160,000 have been internally displaced by
5852-576: Is on Mount Sempu volcano in Indonesia. The San Pablo Volcanic Field in the Province of Laguna on the island of Luzon in the Philippines contains maars. The Newer Volcanics Province in the States of South Australia and Victoria , Australia, has numerous maars, such as Mount Gambier , Mount Schank and Tower Hill , whose complex system of nested maars is enclosed by one of the largest maars in
6006-406: Is the standard spelling of the metric unit for length in nearly all English-speaking nations, the exceptions being the United States and the Philippines which use meter . Measuring devices (such as ammeter , speedometer ) are spelled "-meter" in all variants of English. The suffix "-meter" has the same Greek origin as the unit of length. The etymological roots of metre can be traced to
6160-699: The Alban Mountains is a complex maar, and there is also a submarine maar ( Kolumbo ) near Santorini in Greece. The Campo de Calatrava Volcanic Field in Spain contains numerous maars; a typical example being the maar of Hoya del Mortero at Poblete in the Province of Ciudad Real . Active maars were commonplace in Fife and Lothian , Scotland during the Carboniferous period. The location of one such maar
6314-524: The Baka hunter-gatherers in the southeastern rainforest. Portuguese explorers reached the coast in the 15th century and named the area Rio dos Camarões ( Shrimp River ), which became Cameroon in English. Fulani soldiers founded the Adamawa Emirate in the north in the 19th century, and various ethnic groups of the west and northwest established powerful chiefdoms and fondoms . Cameroon became
Maar - Misplaced Pages Continue
6468-612: The Bay of Plenty Region . Metre The metre (or meter in US spelling ; symbol: m ) is the base unit of length in the International System of Units (SI). Since 2019, the metre has been defined as the length of the path travelled by light in vacuum during a time interval of 1 / 299 792 458 of a second , where the second is defined by a hyperfine transition frequency of caesium . The metre
6622-642: The British Crown . Instead of the seconds pendulum method, the commission of the French Academy of Sciences – whose members included Borda , Lagrange , Laplace , Monge , and Condorcet – decided that the new measure should be equal to one ten-millionth of the distance from the North Pole to the Equator , determined through measurements along the meridian passing through Paris. Apart from
6776-693: The Cameroon range extends from Mount Cameroon on the coast—Cameroon's highest point at 4,095 metres (13,435 ft) —almost to Lake Chad at Cameroon's northern border at 13°05'N. This region has a mild climate, particularly on the Western High Plateau , although rainfall is high. Its soils are among Cameroon's most fertile, especially around volcanic Mount Cameroon. Volcanism here has created crater lakes . On 21 August 1986, one of these, Lake Nyos , belched carbon dioxide and killed between 1,700 and 2,000 people. This area has been delineated by
6930-406: The Committee Meter in the United States and served as standard of length in the United States Coast Survey until 1890. According to geodesists, these standards were secondary standards deduced from the Toise of Peru. In Europe, except Spain, surveyors continued to use measuring instruments calibrated on the Toise of Peru. Among these, the toise of Bessel and the apparatus of Borda were respectively
7084-475: The Daun area of Germany. The word evolved from its first use in German in the modern geological sense in 1819 and is now used in English and in the geological sciences as the term for the explosion crater, even if water from rainfall might always have drained from the crater after the formation event. This extension in meaning was due to recognising that the lake may no longer exist. Since maar lakes are formed after initially ground or subsurface water interacts with
7238-421: The Gulf of Guinea , and the Atlantic Ocean . Due to its strategic position at the crossroads between West Africa and Central Africa, it has been categorized as being in both camps. Cameroon's population of nearly 31 million people speak 250 native languages, in addition to the national tongues of English and French, or both. Early inhabitants of the territory included the Sao civilisation around Lake Chad and
7392-440: The Kirishima - Yaku volcanic field in the Kirishima-Yaku National Park on Kyushu . These include the several maars of the Ibusuki volcanic field such as Lake Unagi . On Honshu in Myōkō-Togakushi Renzan National Park there is Kagamiike Pond as well as many on the volcanic island of Miyake-jima , Izu Islands (Furumio, Mi'ike, Mizutamari, Shinmio). Koranga Maar and Numundo Maar are in Papua New Guinea . Kawah Masemo maar
7546-410: The North Sea and the Baltic Sea in the north. In his mind, the cooperation of all the States of Central Europe could open the field to scientific research of the highest interest, research that each State, taken in isolation, was not able to undertake. Spain and Portugal joined the European Arc Measurement in 1866. French Empire hesitated for a long time before giving in to the demands of
7700-401: The Southern Cameroons National Council advocated complete secession as the Republic of Ambazonia . The 1992 Labour Code of Cameroon gives workers the freedom to belong to a trade union or not to belong to any trade union at all. It is the choice of a worker to join any trade union in their occupation since there is more than one trade union in each occupation. In June 2006, talks concerning
7854-429: The Volcanic Eifel there are about 75 maars. Both lake-filled and dry maars are typical, though the latter are more common. The last eruptions took place at least 11,000 years ago, and many maars are older, as evidenced by their heavy erosion and less obvious shapes and volcanic features. In the Eifel and Volcanic Eifel there are numerous dry maars: The following volcanic features are often colloquially referred to as
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#17327721945428008-441: The luminiferous aether in 1905, just as Newton had questioned Descartes' Vortex theory in 1687 after Jean Richer 's pendulum experiment in Cayenne , French Guiana . Furthermore, special relativity changed conceptions of time and mass , while general relativity changed that of space . According to Newton, space was Euclidean , infinite and without boundaries and bodies gravitated around each other without changing
8162-475: The wettest places on earth, part of the Cross-Sanaga-Bioko coastal forests . The South Cameroon Plateau rises from the coastal plain to an average elevation of 650 metres (2,133 ft). Equatorial rainforest dominates this region, although its alternation between wet and dry seasons makes it less humid than the coast. This area is part of the Atlantic Equatorial coastal forests ecoregion . An irregular chain of mountains, hills, and plateaus known as
8316-514: The 17th CGPM in 1983 replaced the definition of the metre with its current definition, thus fixing the length of the metre in terms of the second and the speed of light : This definition fixed the speed of light in vacuum at exactly 299 792 458 metres per second (≈ 300 000 km/s or ≈1.079 billion km/hour ). An intended by-product of the 17th CGPM's definition was that it enabled scientists to compare lasers accurately using frequency, resulting in wavelengths with one-fifth
8470-413: The 1860s, at the initiative of Carlos Ibáñez e Ibáñez de Ibero who would become the first president of both the International Geodetic Association and the International Committee for Weights and Measure , to remeasure the arc of meridian from Dunkirk to Formentera and to extend it from Shetland to the Sahara . This did not pave the way to a new definition of the metre because it was known that
8624-418: The 1950s, leading to the national liberation insurgency fought between French and UPC militant forces until early 1971. In 1960, the French-administered part of Cameroon became independent, as the Republic of Cameroun, under President Ahmadou Ahidjo . The southern part of British Cameroons federated with it in 1961 to form the Federal Republic of Cameroon. The federation was abandoned in 1972. The country
8778-434: The 19th century by the modernist impetus of Muhammad Ali who founded in Sabtieh, Boulaq district, in Cairo an Observatory which he was keen to keep in harmony with the progress of this science still in progress. In 1858, a Technical Commission was set up to continue, by adopting the procedures instituted in Europe, the cadastre work inaugurated under Muhammad Ali. This Commission suggested to Viceroy Mohammed Sa'id Pasha
8932-416: The Anglophone region as the Federal Republic of Ambazonia . The government responded with a military offensive, and the insurgency spread across the Northwest and Southwest regions. As of 2019 , fighting between separatist guerillas and government forces continues. During 2020, numerous terrorist attacks—many of them carried out without claims of credit—and government reprisals have led to bloodshed throughout
9086-411: The Association, which asked the French geodesists to take part in its work. It was only after the Franco-Prussian War , that Charles-Eugène Delaunay represented France at the Congress of Vienna in 1871. In 1874, Hervé Faye was appointed member of the Permanent Commission which was presided by Carlos Ibáñez e Ibáñez de Ibero. The International Geodetic Association gained global importance with
9240-408: The Atlantic Ocean. Tourist literature describes Cameroon as "Africa in miniature" because it exhibits all major climates and vegetation of the continent: coast, desert, mountains, rainforest, and savanna. The country's neighbours are Nigeria and the Atlantic Ocean to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea , Gabon and the Republic of
9394-437: The British Cameroons, the question was whether to reunify with French Cameroon or join Nigeria; the British ruled out the option of independence. On 1 January 1960, French Cameroun gained independence from France under President Ahmadou Ahidjo as the Republic of Cameroon. On 1 October 1961, the formerly British Southern Cameroons gained independence from the United Kingdom by vote of the UN General Assembly and merged into
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#17327721945429548-428: The CNU and tried to run the country from behind the scenes until Biya and his allies pressured him into resigning. Biya began his administration by moving toward a more democratic government, but a failed coup d'état nudged him toward the leadership style of his predecessor. In 1987, Dja Faunal Reserve , Cameroon's first world heritage site , was inscribed on the list by UNESCO . An economic crisis took effect in
9702-413: The Central European Arc Measurement (German: Mitteleuropaïsche Gradmessung ) on the initiative of Johann Jacob Baeyer in 1863, and by that of the International Meteorological Organisation whose president, the Swiss meteorologist and physicist, Heinrich von Wild would represent Russia at the International Committee for Weights and Measures (CIPM). In 1834, Hassler, measured at Fire Island
9856-410: The Congo to the south. Cameroon is divided into five major geographic zones distinguished by dominant physical, climatic, and vegetative features. The coastal plain extends 15 to 150 kilometres (9 to 93 mi) inland from the Gulf of Guinea and has an average elevation of 90 metres (295 ft). Exceedingly hot and humid with a short dry season , this belt is densely forested and includes some of
10010-476: The Earth was the unit to which all celestial distances were to be referred. Indeed, Earth proved to be an oblate spheroid through geodetic surveys in Ecuador and Lapland and this new data called into question the value of Earth radius as Picard had calculated it. After the Anglo-French Survey , the French Academy of Sciences commissioned an expedition led by Jean Baptiste Joseph Delambre and Pierre Méchain , lasting from 1792 to 1798, which measured
10164-456: The Equator . When the final result was known, a bar whose length was closest to the meridional definition of the metre was selected and placed in the National Archives on 22 June 1799 (4 messidor An VII in the Republican calendar) as a permanent record of the result. In 1816, Ferdinand Rudolph Hassler was appointed first Superintendent of the Survey of the Coast . Trained in geodesy in Switzerland, France and Germany , Hassler had brought
10318-424: The French Academy of Sciences a report drafted by Otto Wilhelm von Struve , Heinrich von Wild , and Moritz von Jacobi , whose theorem has long supported the assumption of an ellipsoid with three unequal axes for the figure of the Earth, inviting his French counterpart to undertake joint action to ensure the universal use of the metric system in all scientific work. In the 1870s and in light of modern precision,
10472-472: The German born, Swiss astronomer, Adolphe Hirsch conformed to the opinion of Italy and Spain to create, in spite of French reluctance, the International Bureau of Weights and Measures in France as a permanent institution at the disadventage of the Conservatoire national des Arts et Métiers . At that time, units of measurement were defined by primary standards , and unique artifacts made of different alloys with distinct coefficients of expansion were
10626-410: The Greek verb μετρέω ( metreo ) ((I) measure, count or compare) and noun μέτρον ( metron ) (a measure), which were used for physical measurement, for poetic metre and by extension for moderation or avoiding extremism (as in "be measured in your response"). This range of uses is also found in Latin ( metior, mensura ), French ( mètre, mesure ), English and other languages. The Greek word
10780-423: The Kanem and its successor state, the Bornu Empire . Kingdoms, fondoms , and chiefdoms arose in the west. Portuguese sailors reached the coast in 1472. They noted an abundance of the ghost shrimp Lepidophthalmus turneranus in the Wouri River and named it Rio dos Camarões ( Shrimp River ), which became Cameroon in English. Over the following few centuries, European interests regularised trade with
10934-449: The Magnetischer Verein, the first international scientific association, in collaboration with Alexander von Humboldt and Wilhelm Edouard Weber . The coordination of the observation of geophysical phenomena such as the Earth's magnetic field, lightning and gravity in different points of the globe stimulated the creation of the first international scientific associations. The foundation of the Magnetischer Verein would be followed by that of
11088-654: The North Pole to the Equator was then extrapolated from the measurement of the Paris meridian arc between Dunkirk and Barcelona and was determined as 5 130 740 toises. As the metre had to be equal to one ten-millionth of this distance, it was defined as 0.513074 toise or 3 feet and 11.296 lines of the Toise of Peru, which had been constructed in 1735 for the French Geodesic Mission to
11242-584: The Republic of Cameroon to form the Federal Republic of Cameroon. The federal republic was composed of two federated states, East Cameroon and West Cameroon , each with their own legislatures, governments, and prime ministers. 1 October is now observed as Unification Day , a public holiday . Ahidjo used the ongoing war with the UPC to concentrate power in the presidency, continuing with this even after
11396-789: The Spanish standard had been compared with Borda 's double-toise N° 1, which served as a comparison module for the measurement of all geodesic bases in France, and was also to be compared to the Ibáñez apparatus. In 1954, the connection of the southerly extension of the Struve Geodetic Arc with an arc running northwards from South Africa through Egypt would bring the course of a major meridian arc back to land where Eratosthenes had founded geodesy . Seventeen years after Bessel calculated his ellipsoid of reference , some of
11550-642: The Swiss physicist Charles-Edouard Guillaume , was granted the Nobel Prize in Physics in 1920. Guillaume's Nobel Prize marked the end of an era in which metrology was leaving the field of geodesy to become a technological application of physics . In 1921, the Nobel Prize in Physics was awarded to another Swiss scientist, Albert Einstein , who following Michelson–Morley experiment had questioned
11704-591: The Toise of Peru, one for Friedrich Georg Wilhelm von Struve , a second for Heinrich Christian Schumacher in 1821 and a third for Friedrich Bessel in 1823. In 1831, Henri-Prudence Gambey also realized a copy of the Toise of Peru which was kept at Altona Observatory . In the second half of the 19th century, the creation of the International Geodetic Association would mark the adoption of new scientific methods. It then became possible to accurately measure parallel arcs, since
11858-565: The UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein expressed deep concern about reports of violations and abuses in the English-speaking Northwest and Southwest regions of Cameroon. According to OCHA, more than 1.7 million people require humanitarian assistance in the northwest and southwest regions. OCHA also estimates that at least 628,000 people have been internally displaced by violence in
12012-655: The accession of Chile , Mexico and Japan in 1888; Argentina and United-States in 1889; and British Empire in 1898. The convention of the International Geodetic Association expired at the end of 1916. It was not renewed due to the First World War . However, the activities of the International Latitude Service were continued through an Association Géodesique réduite entre États neutres thanks to
12166-444: The administration of an elected Regional Council . Each region is headed by a presidentially appointed governor. These leaders are charged with implementing the will of the president, reporting on the general mood and conditions of the regions, administering the civil service, keeping the peace, and overseeing the heads of the smaller administrative units. Governors have broad powers: they may order propaganda in their area and call in
12320-580: The army, gendarmes , and police. All local government officials are employees of the central government's Ministry of Territorial Administration, from which local governments also get most of their budgets. The regions are subdivided into 58 divisions (French départements ). These are headed by presidentially appointed divisional officers ( préfets ). The divisions are further split into sub-divisions ( arrondissements ), headed by assistant divisional officers ( sous-prefets ). The districts, administered by district heads ( chefs de district ), are
12474-748: The coast, and the North-West ( Nord-Ouest ) and West ( Ouest ) regions are in the western grassfields. At 475,442 square kilometres (183,569 sq mi), Cameroon is the world's 53rd-largest country. The country is located in Central Africa , on the Bight of Bonny , part of the Gulf of Guinea and the Atlantic Ocean. Cameroon lies between latitudes 1° and 13°N , and longitudes 8° and 17°E . Cameroon controls 12 nautical miles of
12628-674: The coastal peoples, and Christian missionaries pushed inland. In 1896, Sultan Ibrahim Njoya created the Bamum script , or Shu Mom, for the Bamum language . It is taught in Cameroon today by the Bamum Scripts and Archives Project . Germany began to establish roots in Cameroon in 1868 when the Woermann Company of Hamburg built a warehouse. It was built on the estuary of the Wouri River. Later, Gustav Nachtigal made
12782-416: The colonial system of forced labour. The British administered their territory from neighbouring Nigeria . Natives complained that this made them a neglected "colony of a colony". Nigerian migrant workers flocked to Southern Cameroons, ending forced labour altogether but angering the local natives, who felt swamped. The League of Nations mandates were converted into United Nations Trusteeships in 1946, and
12936-435: The country rock with the maar being " the crater cut into the ground and surrounded by an ejecta ring ". A 2011 geological clarification of a maar is " Maar volcanoes are distinguished from other small volcanoes in having craters with their floor lying below the pre-eruptive surface ". Maar lakes , also referred to simply as maars , occur when groundwater or precipitation fills the funnel-shaped and usually round hollow of
13090-636: The country. Since 2016, more than 450,000 people have fled their homes. The conflict indirectly led to an upsurge in Boko Haram attacks, as the Cameroonian military largely withdrew from the north to focus on fighting the Ambazonian separatists. More than 30,000 people in northern Cameroon fled to Chad after ethnic clashes over access to water between Musgum fishermen and ethnic Arab Choa herders in December 2021. The President of Cameroon
13244-508: The creation of an Ambazonian state in the English-speaking territories escalated into open warfare . Large numbers of Cameroonians live as subsistence farmers . The country is often referred to as "Africa in miniature" for its geological, linguistic, and cultural diversity. Its natural features include beaches , deserts , mountains , rainforests , and savannas . Cameroon's highest point, at almost 4,100 metres (13,500 ft),
13398-540: The creation of the Office of Standard Weights and Measures in 1830. In continental Europe , Napoleonic Wars fostered German nationalism which later led to unification of Germany in 1871. Meanwhile, most European countries had adopted the metre. In the 1870s, German Empire played a pivotal role in the unification of the metric system through the European Arc Measurement but its overwhelming influence
13552-589: The creation of the Office of Standard Weights and Measures as an office within the Coast Survey contributed to the introduction of the Metric Act of 1866 allowing the use of the metre in the United States, and preceded the choice of the metre as international scientific unit of length and the proposal by the European Arc Measurement (German: Europäische Gradmessung ) to establish a "European international bureau for weights and measures". In 1867 at
13706-406: The data available at the time, Ritter came to the conclusion that the problem was only resolved in an approximate manner, the data appearing too scant, and for some affected by vertical deflections , in particular the latitude of Montjuïc in the French meridian arc which determination had also been affected in a lesser proportion by systematic errors of the repeating circle . The definition of
13860-414: The definition of a second in terms of the caesium frequency Δ ν Cs . This series of amendments did not alter the size of the metre significantly – today Earth's polar circumference measures 40 007 .863 km , a change of about 200 parts per million from the original value of exactly 40 000 km , which also includes improvements in the accuracy of measuring the circumference. Metre
14014-418: The difference in longitude between their ends could be determined thanks to the invention of the electrical telegraph . Furthermore, advances in metrology combined with those of gravimetry have led to a new era of geodesy . If precision metrology had needed the help of geodesy, the latter could not continue to prosper without the help of metrology. It was then necessary to define a single unit to express all
14168-527: The direction of the National Anti-Corruption Observatory . There are several high corruption risk areas in Cameroon, for instance, customs, public health sector and public procurement. However, the corruption has gotten worse, regardless of the existing anti-corruption bureaus, as Transparency International ranked Cameroon 152 on a list of 180 countries in 2018. President Biya's Cameroon People's Democratic Movement (CPDM)
14322-624: The distance between a belfry in Dunkirk and Montjuïc castle in Barcelona at the longitude of the Paris Panthéon . When the length of the metre was defined as one ten-millionth of the distance from the North Pole to the Equator , the flattening of the Earth ellipsoid was assumed to be 1 / 334 . In 1841, Friedrich Wilhelm Bessel using the method of least squares calculated from several arc measurements
14476-662: The efforts of H.G. van de Sande Bakhuyzen and Raoul Gautier (1854–1931), respectively directors of Leiden Observatory and Geneva Observatory . After the French Revolution , Napoleonic Wars led to the adoption of the metre in Latin America following independence of Brazil and Hispanic America , while the American Revolution prompted the foundation of the Survey of the Coast in 1807 and
14630-552: The error is explained in the article on measurement uncertainty . Practical realisation of the metre is subject to uncertainties in characterising the medium, to various uncertainties of interferometry, and to uncertainties in measuring the frequency of the source. A commonly used medium is air, and the National Institute of Standards and Technology (NIST) has set up an online calculator to convert wavelengths in vacuum to wavelengths in air. As described by NIST, in air,
14784-459: The event they are charged with high treason or harming national security. Cameroon is viewed as rife with corruption at all levels of government. In 1997, Cameroon established anti-corruption bureaus in 29 ministries, but only 25% became operational, and in 2012, Transparency International placed Cameroon at number 144 on a list of 176 countries ranked from least to most corrupt. On 18 January 2006, Biya initiated an anti-corruption drive under
14938-459: The fall of bodies at the surface of the Earth. He also observed the regularity of the period of swing of the pendulum and that this period depended on the length of the pendulum. Kepler's laws of planetary motion served both to the discovery of Newton's law of universal gravitation and to the determination of the distance from Earth to the Sun by Giovanni Domenico Cassini . They both also used
15092-570: The first baseline of the Survey of the Coast, shortly before Louis Puissant declared to the French Academy of Sciences in 1836 that Jean Baptiste Joseph Delambre and Pierre Méchain had made errors in the meridian arc measurement , which had been used to determine the length of the metre. Errors in the method of calculating the length of the Paris meridian were taken into account by Bessel when he proposed his reference ellipsoid in 1841. Egyptian astronomy has ancient roots which were revived in
15246-696: The government suppresses the freedoms of opposition groups by preventing demonstrations, disrupting meetings, and arresting opposition leaders and journalists. In particular, English-speaking people are discriminated against; protests often escalate into violent clashes and killings. In 2017, President Biya shut down the Internet in the English-speaking region for 94 days, at the cost of hampering five million people, including Silicon Mountain startups. Freedom House ranks Cameroon as "not free" in terms of political rights and civil liberties. The last parliamentary elections were held on 9 February 2020. Cameroon
15400-462: The idea of buying geodetic devices which were ordered in France. While Mahmud Ahmad Hamdi al-Falaki was in charge, in Egypt, of the direction of the work of the general map, the viceroy entrusted to Ismail Mustafa al-Falaki the study, in Europe, of the precision apparatus calibrated against the metre intended to measure the geodesic bases and already built by Jean Brunner in Paris. Ismail Mustafa had
15554-521: The independence of Cameroon. The National Assembly makes legislation. The body consists of 180 members who are elected for five-year terms and meet three times per year. Laws are passed on a majority vote. The 1996 constitution establishes a second house of parliament, the 100-seat Senate . The government recognises the authority of traditional chiefs, fons, and lamibe to govern at the local level and to resolve disputes as long as such rulings do not conflict with national law. Cameroon's legal system
15708-468: The legal basis of units of length. A wrought iron ruler, the Toise of Peru, also called Toise de l'Académie , was the French primary standard of the toise, and the metre was officially defined by an artifact made of platinum kept in the National Archives. Besides the latter, another platinum and twelve iron standards of the metre were made by Étienne Lenoir in 1799. One of them became known as
15862-421: The length of a metre in the 1790s was founded upon Arc measurements in France and Peru with a definition that it was to be 1/40 millionth of the circumference of the earth measured through the poles. Such were the inaccuracies of that period that within a matter of just a few years more reliable measurements would have given a different value for the definition of this international standard. That does not invalidate
16016-583: The maar depression formed by volcanic explosions. Examples of these types of maar are the three maars at Daun in the Eifel mountains of Germany . A dry maar results when a maar lake dries out, becomes aggraded or silted up . An example of the latter is the Eckfelder Maar . Near Steffeln is the Eichholzmaar (also called the Gussweiher ) which has dried out during the last century and
16170-820: The maars of the White Rock Canyon , Mount Taylor , the Potrillo volcanic fields ( Kilbourne Hole and Hunt's Hole ), and Zuñi Salt Lake in New Mexico. In Central Mexico, the Tarascan volcanic field contains several maars in the states of Michoacán and Guanajuato . In Nicaragua is the maar of Laguna de Xiloa, part of the Apoyeque volcano. From South America, there are known maars in Chile (e.g. Cerro Overo and Cerro Tujle in northern Chile). Jayu Khota
16324-601: The main references for geodesy in Prussia and in France . These measuring devices consisted of bimetallic rulers in platinum and brass or iron and zinc fixed together at one extremity to assess the variations in length produced by any change in temperature. The combination of two bars made of two different metals allowed to take thermal expansion into account without measuring the temperature. A French scientific instrument maker, Jean Nicolas Fortin , had made three direct copies of
16478-452: The meantime, the commission of the French Academy of Sciences calculated a provisional value from older surveys of 443.44 lignes. This value was set by legislation on 7 April 1795. In 1799, a commission including Johan Georg Tralles , Jean Henri van Swinden , Adrien-Marie Legendre and Jean-Baptiste Delambre calculated the distance from Dunkirk to Barcelona using the data of the triangulation between these two towns and determined
16632-536: The measurements of terrestrial arcs and all determinations of the gravitational acceleration by means of pendulum. In 1866, the most important concern was that the Toise of Peru, the standard of the toise constructed in 1735 for the French Geodesic Mission to the Equator , might be so much damaged that comparison with it would be worthless, while Bessel had questioned the accuracy of copies of this standard belonging to Altona and Koenigsberg Observatories, which he had compared to each other about 1840. This assertion
16786-691: The measuring devices designed by Borda and used for this survey also raised hopes for a more accurate determination of the length of this meridian arc. The task of surveying the Paris meridian arc took more than six years (1792–1798). The technical difficulties were not the only problems the surveyors had to face in the convulsed period of the aftermath of the French Revolution: Méchain and Delambre, and later Arago , were imprisoned several times during their surveys, and Méchain died in 1804 of yellow fever, which he contracted while trying to improve his original results in northern Spain. In
16940-462: The melting point of ice. The comparison of the new prototypes of the metre with each other involved the development of special measuring equipment and the definition of a reproducible temperature scale. The BIPM's thermometry work led to the discovery of special alloys of iron–nickel, in particular invar , whose practically negligible coefficient of expansion made it possible to develop simpler baseline measurement methods, and for which its director,
17094-405: The meridian arcs the German astronomer had used for his calculation had been enlarged. This was a very important circumstance because the influence of errors due to vertical deflections was minimized in proportion to the length of the meridian arcs: the longer the meridian arcs, the more precise the image of the Earth ellipsoid would be. After Struve Geodetic Arc measurement, it was resolved in
17248-428: The metre in any way but highlights the fact that continuing improvements in instrumentation made better measurements of the earth’s size possible. It was well known that by measuring the latitude of two stations in Barcelona , Méchain had found that the difference between these latitudes was greater than predicted by direct measurement of distance by triangulation and that he did not dare to admit this inaccuracy. This
17402-553: The metre in replacement of the toise of Bessel, the creation of an International Metre Commission, and the foundation of a World institute for the comparison of geodetic standards, the first step towards the creation of the International Bureau of Weights and Measures . Hassler's metrological and geodetic work also had a favourable response in Russia. In 1869, the Saint Petersburg Academy of Sciences sent to
17556-409: The mid-1980s to late 1990s as a result of international economic conditions, drought, falling petroleum prices, and years of corruption, mismanagement, and cronyism . Cameroon turned to foreign aid, cut government spending, and privatised industries. With the reintroduction of multi-party politics in December 1990, the former British Southern Cameroons pressure groups called for greater autonomy, and
17710-402: The number of wavelengths of laser light of one of the standard types that fit into the length, and converting the selected unit of wavelength to metres. Three major factors limit the accuracy attainable with laser interferometers for a length measurement: Of these, the last is peculiar to the interferometer itself. The conversion of a length in wavelengths to a length in metres is based upon
17864-455: The obvious consideration of safe access for French surveyors, the Paris meridian was also a sound choice for scientific reasons: a portion of the quadrant from Dunkirk to Barcelona (about 1000 km, or one-tenth of the total) could be surveyed with start- and end-points at sea level, and that portion was roughly in the middle of the quadrant, where the effects of the Earth's oblateness were expected not to have to be accounted for. Improvements in
18018-545: The official languages of former French Cameroons and British Cameroons . Christianity is the majority religion in Cameroon , with significant minorities practising Islam and traditional faiths . It has experienced tensions from the English-speaking territories, where politicians have advocated for greater decentralisation and even complete separation or independence (as in the Southern Cameroons National Council ). In 2017, tensions over
18172-713: The oil-rich Bakassi peninsula. Cameroon and Nigeria share a 1,000-mile (1,600 km) border and have disputed the sovereignty of the Bakassi peninsula. In 1994 Cameroon petitioned the International Court of Justice to resolve the dispute. The two countries attempted to establish a cease-fire in 1996; however, fighting continued for years. In 2002, the ICJ ruled that the Anglo-German Agreement of 1913 gave sovereignty to Cameroon. The ruling called for
18326-833: The over 350 eruption points were only active in the Upper Miocene 17 to 11 million years ago, all the maars, apart from the dry maar, Randecker Maar and the Molach, are only detectable geologically. In the Ore Mountains near Hammerunterwiesenthal , the Hammerunterwiesenthal Maar formed about 30 million years ago during the Oligocene; the maar measures 2 kilometres from east to west and 1.4 kilometres from north to south. The Chaîne des Puys in France contains numerous maars; Lake Albano in
18480-575: The peninsula was left to Cameroon two years later, in 2008. The boundary change triggered a local separatist insurgency , as many Bakassians refused to accept Cameroonian rule. While most militants laid down their arms in November 2009, some carried on fighting for years. In February 2008, Cameroon experienced its worst violence in 15 years when a transport union strike in Douala escalated into violent protests in 31 municipal areas. In May 2014, in
18634-559: The portion of the distance from the North Pole to the Equator it represented. Pierre Méchain's and Jean-Baptiste Delambre's measurements were combined with the results of the Spanish-French geodetic mission and a value of 1 / 334 was found for the Earth's flattening. However, French astronomers knew from earlier estimates of the Earth's flattening that different meridian arcs could have different lengths and that their curvature could be irregular. The distance from
18788-413: The predominantly English-speaking Northwest and Southwest regions of the country have been campaigning for continued use of the English language in schools and courts. People were killed and hundreds were jailed as a result of these protests. In 2017, Biya's government blocked the regions' access to the Internet for three months. In September, separatists started a guerilla war for the independence of
18942-599: The question of independence became a pressing issue in French Cameroon. France outlawed the pro-independence political party, the Union of the Peoples of Cameroon ( French : Union des Populations du Cameroun , UPC), on 13 July 1955. This prompted a long guerrilla war waged by the UPC and the assassination of several of the party's leaders, including Ruben Um Nyobè , Félix-Roland Moumié and Ernest Ouandie . In
19096-610: The relation Cameroon This is an accepted version of this page Cameroon , officially the Republic of Cameroon , is a country in Central Africa . It shares boundaries with Nigeria to the west and north, Chad to the northeast, the Central African Republic to the east, and Equatorial Guinea , Gabon , and the Republic of the Congo to the south. Its coastline lies on the Bight of Biafra , part of
19250-401: The same length, confirming an hypothesis of Jean Le Rond d'Alembert . He also proposed an ellipsoid with three unequal axes. In 1860, Elie Ritter, a mathematician from Geneva , using Schubert's data computed that the Earth ellipsoid could rather be a spheroid of revolution accordingly to Adrien-Marie Legendre 's model. However, the following year, resuming his calculation on the basis of all
19404-458: The scientific means necessary to redefine the units of the metric system according to the progress of sciences. The Metre Convention ( Convention du Mètre ) of 1875 mandated the establishment of a permanent International Bureau of Weights and Measures (BIPM: Bureau International des Poids et Mesures ) to be located in Sèvres , France. This new organisation was to construct and preserve
19558-658: The second General Conference of the International Association of Geodesy held in Berlin, the question of an international standard unit of length was discussed in order to combine the measurements made in different countries to determine the size and shape of the Earth. According to a preliminary proposal made in Neuchâtel the precedent year, the General Conference recommended the adoption of
19712-678: The smallest administrative units. The three northernmost regions are the Far North ( Extrême Nord ), North ( Nord ), and Adamawa ( Adamaoua ). Directly south of them are the Centre ( Centre ) and East ( Est ). The South Province ( Sud ) lies on the Gulf of Guinea and the southern border. Cameroon's western region is split into four smaller regions: the Littoral ( Littoral ) and South-West ( Sud-Ouest ) regions are on
19866-433: The standard both for the unit of length and for the second. These two quantities could then be used to define the unit of mass. About the unit of length he wrote: In the present state of science the most universal standard of length which we could assume would be the wave length in vacuum of a particular kind of light, emitted by some widely diffused substance such as sodium, which has well-defined lines in its spectrum. Such
20020-479: The structure of space. Einstein's theory of gravity states, on the contrary, that the mass of a body has an effect on all other bodies while modifying the structure of space. A massive body induces a curvature of the space around it in which the path of light is inflected, as was demonstrated by the displacement of the position of a star observed near the Sun during an eclipse in 1919. In 1873, James Clerk Maxwell suggested that light emitted by an element be used as
20174-610: The suppression of the UPC in 1971. Ahidjo's political party, the Cameroon National Union (CNU), became the sole legal political party on 1 September 1966, and on 20 May 1972, a referendum was passed to abolish the federal system of government in favour of a United Republic of Cameroon, headed from Yaoundé . This day is now the country's National Day , a public holiday. Ahidjo pursued an economic policy of planned liberalism , prioritising cash crops and petroleum development. The government used oil money to create
20328-456: The task to carry out the experiments necessary for determining the expansion coefficients of the two platinum and brass bars, and to compare the Egyptian standard with a known standard. The Spanish standard designed by Carlos Ibáñez e Ibáñez de Ibero and Frutos Saavedra Meneses was chosen for this purpose, as it had served as a model for the construction of the Egyptian standard. In addition,
20482-589: The then abundant Cameroon ghost shrimp . Today the country's name in Portuguese remains Camarões . Evidence from digs at Shum Laka in the Northwest Region shows human occupation in Cameroon dating back 30,000 years. The longest continuous inhabitants are groups such as the Baka ( Pygmies ). From there, Bantu migrations into eastern, southern and central Africa are believed to have occurred about 2,000 years ago. The Sao culture arose around Lake Chad , c. 500 CE , and gave way to
20636-439: The theoretical definition of the metre had been inaccessible and misleading at the time of Delambre and Mechain arc measurement, as the geoid is a ball, which on the whole can be assimilated to an oblate spheroid , but which in detail differs from it so as to prohibit any generalization and any extrapolation from the measurement of a single meridian arc. In 1859, Friedrich von Schubert demonstrated that several meridians had not
20790-539: The two regions, while more than 87,000 have fled to Nigeria. Same-sex sexual acts are banned by section 347-1 of the penal code with a penalty of from 6 months up to 5 years imprisonment. Since December 2020, Human Rights Watch claimed that Islamist armed group Boko Haram has stepped up attacks and killed at least 80 civilians in towns and villages in the Far North region of Cameroon. The constitution divides Cameroon into 10 semi-autonomous regions, each under
20944-437: The uncertainties in characterising the medium are dominated by errors in measuring temperature and pressure. Errors in the theoretical formulas used are secondary. By implementing a refractive index correction such as this, an approximate realisation of the metre can be implemented in air, for example, using the formulation of the metre as 1 579 800 .762 042 (33) wavelengths of helium–neon laser light in vacuum, and converting
21098-574: The uncertainty involved in the direct comparison of wavelengths, because interferometer errors were eliminated. To further facilitate reproducibility from lab to lab, the 17th CGPM also made the iodine-stabilised helium–neon laser "a recommended radiation" for realising the metre. For the purpose of delineating the metre, the BIPM currently considers the HeNe laser wavelength, λ HeNe , to be 632.991 212 58 nm with an estimated relative standard uncertainty ( U ) of 2.1 × 10 . This uncertainty
21252-424: The violence, many reportedly hiding in forests. Prisons are overcrowded with little access to adequate food and medical facilities, and prisons run by traditional rulers in the north are charged with holding political opponents at the behest of the government. However, since the first decade of the 21st century, an increasing number of police and gendarmes have been prosecuted for improper conduct. On 25 July 2018,
21406-705: The wake of the Chibok schoolgirls kidnapping , presidents Paul Biya of Cameroon and Idriss Déby of Chad announced they were waging war on Boko Haram , and deployed troops to the Nigerian border. Boko Haram launched several attacks into Cameroon, killing 84 civilians in a December 2014 raid , but suffering a heavy defeat in a raid in January 2015 . Cameroon declared victory over Boko Haram on Cameroonian territory in September 2018. Since November 2016, protesters from
21560-436: The wavelengths in vacuum to wavelengths in air. Air is only one possible medium to use in a realisation of the metre, and any partial vacuum can be used, or some inert atmosphere like helium gas, provided the appropriate corrections for refractive index are implemented. The metre is defined as the path length travelled by light in a given time, and practical laboratory length measurements in metres are determined by counting
21714-403: The world. Foulden Maar in Otago , New Zealand , is an important fossil site, but there are many more maars in New Zealand. As already mentioned these include Lake Pupuke , but the Auckland volcanic field has other easily accessible maars such as the Mangere Lagoon , Orakei Basin , Panmure Basin , and Pukaki Lagoon . Elsewhere a recent example, only 4000 years old, is Lake Rotokawau in
21868-425: Was Elie Ness. Active maar volcanoes are mainly known outside Europe. In the US there are numerous maar areas, such as in Alaska ( Ukinrek maars , Nunivak in the Bering Sea ); in Washington ( Battle Ground Lake ); in Oregon ( Fort Rock basin with the maars of Big Hole , Hole-in-the-Ground , Table Rock ); in Death Valley National Park , California ( Ubehebe Crater ); in Nevada ( Soda Lakes ); as well as
22022-409: Was a way to determine the figure of the Earth , whose crucial parameter was the flattening of the Earth ellipsoid . In the 18th century, in addition of its significance for cartography , geodesy grew in importance as a means of empirically demonstrating the theory of gravity , which Émilie du Châtelet promoted in France in combination with Leibniz's mathematical work and because the radius of
22176-403: Was determined astronomically. Bayer proposed to remeasure ten arcs of meridians and a larger number of arcs of parallels, to compare the curvature of the meridian arcs on the two slopes of the Alps , in order to determine the influence of this mountain range on vertical deflection . Baeyer also planned to determine the curvature of the seas, the Mediterranean Sea and Adriatic Sea in the south,
22330-429: Was discovered that the length of a seconds pendulum varies from place to place. Christiaan Huygens found out the centrifugal force which explained variations of gravitational acceleration depending on latitude. He also mathematically formulated the link between the length of the simple pendulum and gravitational acceleration. According to Alexis Clairaut , the study of variations in gravitational acceleration
22484-486: Was later explained by clearance in the central axis of the repeating circle causing wear and consequently the zenith measurements contained significant systematic errors. Polar motion predicted by Leonhard Euler and later discovered by Seth Carlo Chandler also had an impact on accuracy of latitudes' determinations. Among all these sources of error, it was mainly an unfavourable vertical deflection that gave an inaccurate determination of Barcelona's latitude and
22638-412: Was mitigated by that of neutral states. While the German astronomer Wilhelm Julius Foerster , director of the Berlin Observatory and director of the German Weights and Measures Service boycotted the Permanent Committee of the International Metre Commission, along with the Russian and Austrian representatives, in order to promote the foundation of a permanent International Bureau of Weights and Measures ,
22792-419: Was necessary to carefully study considerable areas of land in all directions. Baeyer developed a plan to coordinate geodetic surveys in the space between the parallels of Palermo and Freetown Christiana ( Denmark ) and the meridians of Bonn and Trunz (German name for Milejewo in Poland ). This territory was covered by a triangle network and included more than thirty observatories or stations whose position
22946-424: Was originally defined in 1791 by the French National Assembly as one ten-millionth of the distance from the equator to the North Pole along a great circle , so the Earth's polar circumference is approximately 40 000 km . In 1799, the metre was redefined in terms of a prototype metre bar, the bar used was changed in 1889, and in 1960 the metre was redefined in terms of a certain number of wavelengths of
23100-402: Was particularly worrying, because when the primary Imperial yard standard had partially been destroyed in 1834, a new standard of reference was constructed using copies of the "Standard Yard, 1760", instead of the pendulum's length as provided for in the Weights and Measures Act of 1824, because the pendulum method proved unreliable. Nevertheless Ferdinand Rudolph Hassler 's use of the metre and
23254-429: Was renamed the United Republic of Cameroon in 1972 and back to the Republic of Cameroon in 1984 by a presidential decree by President Paul Biya . Biya, the incumbent president, has led the country since 1982 following Ahidjo's resignation; he previously held office as prime minister from 1975 onward. Cameroon is governed as a unitary presidential republic . The official languages of Cameroon are French and English,
23408-467: Was the first to tie experimentally the metre to the wave length of a spectral line. According to him the standard length might be compared with that of a wave of light identified by a line in the solar spectrum . Albert Michelson soon took up the idea and improved it. In 1893, the standard metre was first measured with an interferometer by Albert A. Michelson , the inventor of the device and an advocate of using some particular wavelength of light as
23562-443: Was the only legal political party until December 1990. Numerous regional political groups have since formed. The primary opposition is the Social Democratic Front (SDF), based largely in the Anglophone region of the country and headed by John Fru Ndi . Biya and his party have maintained control of the presidency and the National Assembly in national elections, which rivals contend were unfair. Human rights organisations allege that
23716-441: Was ultimately decided that the metre would be based on the Earth quadrant (a quarter of the Earth's circumference through its poles), Talleyrand proposed that the metre be the length of the seconds pendulum at a latitude of 45°. This option, with one-third of this length defining the foot , was also considered by Thomas Jefferson and others for redefining the yard in the United States shortly after gaining independence from
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