valley Elongate depression of the Earth’s surface. Valleys are commonly drained by rivers and may be in a relatively flat plain or between ranges of hills or mountains. Valleys formed by rivers and slope denudation are typically V-shaped; those formerly occupied by glaciers are characteris¬ tically U-shaped. Valley evolution is controlled mainly by climate and rock type. Very narrow, deep valleys cut in resistant rock and having steep, almost vertical sides are called canyons. Smaller valleys of similar appear¬ ance are called gorges.
Valley Forge National Historical Park Preserve, southeastern Pennsylvania, U.S. The 3,468-ac (1,404-ha) park commemorates the site where Gen. George Washington camped with his Continental Army in the winter of 1777-78 during the American Revolution. The park was established in 1976.
Valley of Ten Thousand Smokes See Valley of Ten Thousand Smokes
Valley of the Kings See Valley of the Kings
Valois \val-'wa\ Medieval county and duchy, northern France. It corre¬ sponds to the southeastern quarter of the modem departement of Oise, with an adjacent portion of Aisne. It was under the Merovingian kings (c. 500-751) and their successors, the Carolingians, until it became a heredi¬ tary countship. In 1214 King Philip II Augustus annexed it to the royal domain. The duchy’s last representative, Henry III, was succeeded in 1589 by the house of Bourbon. In 1790 it was abolished in the redivision of France into departement s.
Valois, Ninette de See Ninette de Valois
Valparaiso V.val-po-'ri-zoV City (pop., 2002 est.: 262,000) and port, central Chile. It was founded by the Spanish in 1536; few of its colonial
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1984 I value-added tax ► Van Cortlandt
buildings have survived a succession of pirate raids, storms, fires, floods, and earthquakes. After Chilean independence in 1818, the city’s port developed with the growth of the Chilean navy. In 1884 a treaty was signed there by which Bolivia ceded to Chile a coastal region containing principal nitrate deposits (see War of the Pacific). As Chile’s principal seaport, it handles the bulk of the country’s imports, and it is still a naval facility. It also produces chemicals and textiles. Chile’s bicameral parlia¬ ment, the National Congress, has been situated there since it was rees¬ tablished in 1990.
value-added tax (VAT) Government levy on the amount a firm adds to the price of a goods or services as value is added—that is, at each step of their production and distribution. In the most common method of cal¬ culation, the seller subtracts the sum of taxes paid on items being pur¬ chased from the sum of all taxes that have been collected on the items being sold; the net tax liability is the difference between the tax collected and the tax paid. The burden of the value-added tax, like that of other sales TAxes, tends to be passed on to the consumer. To limit the VAT’s regressiveness, most countries set lower rates for consumer necessities than for luxury items. In 1954 France became the first country to adopt the value-added tax on a large scale. Though complex to calculate, the tax served as an improvement on earlier systems by which a product was taxed repeatedly at every stage of production and distribution. It has since been adopted throughout much of Europe and in many countries in South America, Asia, and Africa. All European Union member countries have a VAT. See also regressive tax.
valve In mechanical engineering, a device for controlling the flow of fluids (liquids, gases, slurries) in a pipe or other enclosure. It exerts con¬ trol by means of a movable element that opens, shuts, or partially blocks an opening in a passageway. Valves are of seven main types: globe, gate, needle, plug (cock), butterfly, poppet, and spool. Some valves operate automatically; check (or nonreturn) valves, for example, are self-acting valves that permit flow in only one direction. Safety valves open at a pre¬ determined pressure; the movable element usually has a weighted lever or a spring strong enough to hold the valve closed until a particular pres¬ sure is reached.
bonnet
seat
A globe valve controls the flow of a fluid through a pipe, inlet, or outlet. To stop the flow completely, the threaded stem is turned to lower a sealing gasket onto the seat.
© MERRIAM-WEBSTER INC.
vampire In popular legend, a bloodsucking creature that rises from its burial place at night, sometimes in the form of a bat, to drink the blood of humans. By daybreak it must return to its grave or to a coffin filled with its native earth. Tales of vampires are part of the world’s folklore, most notably in Hungary and the Balkan Peninsula. The disinterment in Serbia in 1725 and 1732 of several fluid-filled corpses that villagers claimed were behind a plague of vampirism led to widespread interest and imaginative treatment of vampirism throughout western Europe. Vampires are supposedly dead humans (originally suicides, heretics, or criminals) who maintain a kind of life by biting the necks of living humans
and sucking their blood; their vic¬ tims also become vampires after death. These “undead” creatures cast no shadow and are not reflected in mirrors. They can be warded off by crucifixes or wreaths of garlic and can be killed by exposure to the sun or by an oak stake driven through the heart. The most famous vampire is Count Dracula from Bram Stoker’s novel Dracula (1897).
vampire bat Any of three species (family Desmodontidae) of tailless, brown, blood-eating bats native to the New World tropics. They grow to 2-3.5 in. (6-9 cm) long and weigh 0.5-2 oz (15-50 g). They run swiftly and leap with agility. They live in colonies in caves, hollow trees, and culverts, leaving after dark to forage low on the ground. They feed on quietly resting birds and mammals, including the occasional human, mak¬ ing a small cut with their sharp incisor teeth, often without disturbing the prey, and lapping the blood. The wounds are not serious but may trans¬ mit rabies or other diseases.
Van City (pop., 1997: 226,965), eastern Turkey, on the eastern shore of Lake Van. The ruins of stone buildings there date from the 8th century bc, when it was the chief centre of the kingdom of Urartu. After the fall of Nineveh (612 bc), it was occupied in succession by the Medes, the kings of Pontus, Arabs (7th century ad), and Armenians (8th century ad). It fell to the Seljuq dynasty after 1071 ad and to the Ottoman Empire in 1543. Russian forces held it (1915-17) during World War I. It has a large Kurdish population. It once had a large Armenian population that was brutally expelled following the war (see Armenian massacres). Van is a shipping point for hides, grains, fruits, and vegetables.
Van, Lake Salt lake, eastern Anatolia. The largest lake in Turkey, it covers an area of 1,434 sq mi (3,713 sq km) and is more than 74 mi (119 km) across at its widest point. Its greatest depth exceeds 330 ft (100 m). It is fed by precipitation and meltwater as well as by several small tribu¬ taries. It has no apparent outlet, and its brackish waters are unsuitable for either drinking or irrigation.
Van Allen radiation belts Two doughnut-shaped zones of highly energetic charged particles (see electric charge) trapped at high altitudes in Earth’s magnetic field. Named for James A. Van Allen (b. 1914), who discovered them in 1958, they are most intense over the Equator and effectively absent above the poles. The two zones merge gradually, with the flux of charged particles showing two regions of maximum density. The inner one, mostly protons thought to be produced by primary cosmic rays striking the atmosphere, is centred about 3,700 mi (6,000 km) above Earth’s surface. The outer region includes some helium ions from the solar wind and is centred about 12,500 mi (20,000 km) above Earth’s sur¬ face. Intense solar activity (see solar cycle) causes disruptions of the belts, linked in turn with such phenomena as auroras and magnetic storms.
Van Buren, Martin (b. Dec. 5, 1782, Kinderhook, N.Y., U.S.—d. July 24, 1862, Kinderhook) Eighth president of the U.S. (1837-41). He served in the New York Senate (1812-20) and as state attorney general (1816-19). An informal group of his political supporters came to be known as the Albany Regency because they dominated state politics even while Van Buren was in Washington. He was elected to the U.S. Senate (1821-28), where he supported states' rights and opposed a strong central government. After John Quincy Adams became president, he joined with Andrew Jack- son and others to form a group that later became the Democratic Party. He was elected governor of New York (1828) but resigned to become U.S. sec¬ retary of state (1829-31). He was nominated for vice president at the first Democratic Party convention (1832) and served under Jackson (1833-37). As Jackson’s chosen successor, he defeated William H. Harrison to win the 1836 election. His presidency was marked by an economic depression, the Maine-Canada border dispute (see Aroostook War), the Seminole Wars in Florida, and debate over the annexation of Texas. He was defeated in his bid for reelection and failed to win the Democratic nomination in 1844 because of his antislavery views. In 1848 he was nominated for president by the Free Soil Party but failed to win the election and retired.