wall-attachment effect: see Coanda effect.

wall, in architecture, protective, enclosing, or dividing vertical structure. Its thickness is determined by the material, height, and stress. It may be of studding and lath, either boarded or plastered; adobe; rammed earth; brickwork or stonework; concrete; tile; or of steel in combination with one or more of the preceding materials. The wall serves two functions. A bearing wall is used as a support, e.g., for the floors and roof. Usually raised on foundations, it is thicker at the bottom than at the top and is often buttressed. A nonbearing wall, such as a partition screen or curtain wall, is used to separate and define spaces and is generally much thinner. A party wall is one common to two adjoining buildings, and a gable wall is one at right angles to the roof ridge. A fire wall, or bulkhead, separates hazardous equipment from the rest of a structure to prevent the spreading of fire; in ships the bulkhead is also watertight. The front wall or face of a building is termed the facade. Exterior walls may be finished with stucco or graffito and enhanced by bas-relief, tile, mosaic, or painted decoration. Arcade, rustication, and vermiculated work are means of ornamenting brick and stone masonry. In engineering a retaining wall either of Cyclopean or of wet masonry protects an embankment from washing; a sea wall, or breakwater, is for harbor protection; and a dam is an earth, masonry, or concrete wall to stop the natural flow of a stream to conserve a water supply or create power. The defensive walls of a city or other political division (see Great Wall of China) are frequently two or three concentric ramparts, often including fortification and watchtowers. Great portals form the gateways. Notable walls of antiquity were those of Thebes, Troy, Jericho, and Babylon; an example of a medieval wall is that at Carcassonne in France.

long-wall mining: see coal mining.

Wall, Richard, 1694-1778, Spanish statesman. Born in France of Irish parents, Wall entered the Spanish military service as a young man and later held important diplomatic posts. He helped negotiate the Treaty of Aix-la-Chapelle (1748) ending the War of the Austrian Succession, and he cemented friendly Anglo-Spanish relations as ambassador in London (1748-52). In Madrid, he served (1752-64) as minister of state under Ferdinand VI and Charles III.

Wall Street, narrow street in the lower part of Manhattan island, New York City, extending E from Broadway to the East River. It is the center of one of the greatest financial districts in the world, and by extension the term "Wall St." has come to designate U.S. financial interests. In the district, which extends several blocks N and S of Wall St., are the New York and the American Stock Exchanges as well as commodity exchanges and the homes of numerous commercial and investment banks, and "Wall St." law firms. Facing Wall St., on the west side of Broadway, is Trinity Church (founded 1696). Federal Hall National Memorial (see National Parks and Monuments, table), one block east, was erected on the site of the former Federal Hall, where George Washington was inaugurated in 1789 and where the first Congress met. Wall St. received its name from a stockade, or wall, built in 1653 by Dutch colonists to protect the settled area south of it from assault by the English and by the native population.

Hadrian's Wall, ancient Roman wall, 73.5 mi (118.3 km) long, across the narrow part of the island of Great Britain from Wallsend on the Tyne River to Bowness at the head of Solway Firth. It was mainly built from c.A.D. 122 to 126 under Emperor Hadrian and was extended by Emperor Severus a century later. The wall demarcated the northern boundary and defense line of Roman Britain. Fragments of the wall, 6 ft (1.8 m) high and 8 ft (2.4 m) thick, and many of the "mile stations" (stone blockhouses along the wall constructed every Roman mile) remain. Hadrian's Wall, which has been preserved, is one of the largest and most significant remains of the Roman occupation.

Great Wall of China, fortifications, c.1,500 mi (2,400 km) long, winding across N China from Gansu prov. to Hebei prov. on the Yellow Sea. The wall, running mostly along the southern edge of the Mongolian plain, was erected to protect China from northern nomads. It is an amalgamation of many walls built in ancient times; the first unified wall was built in the 3d cent. B.C. by the Ch'in dynasty. Laborers were conscripted from all over China to build it, and many of them died during the project. The wall's present form dates substantially from the Ming dynasty (1368-1644), and wall building was particularly intense in the late Ming period. The wall averages 25 ft (7.6 m) in height and is 15 to 30 ft (4.6-9.1 m) thick at the base, sloping to 12 ft (3.7 m) at the top. Guard stations and watchtowers are placed at regular intervals. The eastern part of the wall is earth and stone faced with brick, but in the west it is merely a tamped earth mound. Successive invasions of China from the north demonstrated that the Great Wall had little military utility. The Ch'ing (Manchu) dynasty (1644-1912) did not use the wall and largely abandoned it. Since 1949 two sections N of Beijing have been reconstructed and are open to visitors.

China, Great Wall of: see Great Wall of China.

Berlin Wall, 1961-89, a barrier first erected in Aug., 1961, by the East German government along the border between East and West Berlin, and later extended along the entire border between East Germany and West Germany. It was built to halt large numbers of defections and to prevent E. Berliners commuting to the West. Erected at a time of growing tension between East and West, the barbed wire was eventually replaced by concrete topped with wire. In 1989, after hundreds of thousands of East Germans had fled westward via Hungary and Czechoslovakia, on Nov. 9, the beleaguered East German regime lifted travel restrictions, and days later dismantling of the wall began. Built to keep people in, the wall was dismantled in a failed gamble by the Communists to keep power. By Jan., 1990, the regime was selling large slabs of the wall for hard currency, and had set December for its total demolition. In Oct., 1990, however, East Germany was formally reabsorbed into the Federal Republic of Germany and only short sections of the wall remained standing, as memorials.

Antoninus, Wall of, ancient Roman wall extending across N Britain from the Firth of Forth to the Firth of Clyde. It was built by the Roman governor Lollius Urbicus in the reign of Emperor Antoninus Pius—probably in A.D. 140-42. Intended as a defense against the peoples to the north, it was built out of turf, with a ditch on the north and 19 forts along its southern side. The wall was 37 mi (60 km) long. It was abandoned c.185 when the Romans retreated to Hadrian's Wall.

Painting applied to and made integral with the surface of a wall or ceiling. Its roots can be found in the universal desire that led prehistoric peoples to create cave paintings—the desire to decorate their surroundings and express their ideas and beliefs. The Romans produced large numbers of murals in Pompeii and Ostia, but mural painting (not synonymous with fresco) reached its highest degree of creative achievement in Europe with the work of such Renaissance masters as Masaccio, Fra Angelico, Leonardo da Vinci, Michelangelo, and Raphael. In the 20th century, the mural was embraced by artists of the Cubist and Fauve movements in Paris, revolutionary painters in Mexico (e.g., Diego Rivera, José Clemente Orozco, David Alfaro Siqueiros), and Depression-era artists under the sponsorship of the U.S. government (e.g., Ben Shahn, Thomas Hart Benton).

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Any of various upright constructions used to divide or enclose a room or building. In traditional masonry construction, bearing walls supported the weight of floors and roofs, but modern steel and reinforced-concrete frames, as well as heavy timber and other skeletal structures, require exterior walls only for shelter. Some urban buildings dispense with walls on the ground floor, extending outdoor plazas under the building and permitting easier access to elevators, escalators, and stairs. In masonry construction, all types of floors and roofs except domes are most easily supported on straight, parallel walls. Nonbearing walls, used when loads are carried by girders, beams, or other members, can be either curtain walls or infill of brick, block, or other material. Seealso cavity wall, retaining wall, shear wall.

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or revetment

Wall constructed to hold in place a mass of earth or prevent the erosion of an embankment. It may also be battered, with the face inclined toward the load it is bearing. The most basic type of reinforced retaining wall is the massive concrete gravity wall, which is prevented from falling over by the sheer weight and volume of its mass. A cantilever (L-shaped) retaining wall resists overturning by means of cantilever footings, spread footings (see foundation) shaped to resist overturning and sliding.

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Street in New York City where many major U.S. financial institutions are located. The street, in southern Manhattan, is narrow and short and extends only about seven blocks from Broadway to the East River. It was named for an earthen wall built by Dutch settlers in 1653 to repel an expected English invasion. Even before the Civil War it was recognized as the nation's financial capital, and it remains a worldwide symbol of high finance. The Wall Street, or financial, district contains the New York Stock Exchange, the American Stock Exchange, and the Federal Reserve Bank of New York. The district is also the headquarters for many investment banks, securities dealers, utilities and insurance companies, and brokerage firms.

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Continuous Roman defensive barrier. Begun by Hadrian in AD 122, the wall guarded the northwestern frontier of the province of Britain from barbarian (particularly Celtic) invaders. It extended 73 mi (118 km) from coast to coast, from Wallsend (Segedunum) to Bowness. It had towers, gates, and forts at regular intervals; a ditch fronted it and an earthwork (the vallum) ran behind it. It was briefly abandoned in favour of the Antonine Wall, but it returned to use until circa 410. Portions remain visible today.

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Chinese Wanli Changcheng

Defensive wall, northern China. One of the largest building-construction projects ever carried out, it runs (with all its branches) about 4,500 mi (7,300 km) east to west from the Bo Hai (Gulf of Chihli) to a point deep in Central Asia. Large parts of the fortification date from the 7th to the 4th century BC. In the 3rd century BC the emperor Shihuangdi connected existing defensive walls into a single system fortified by watchtowers. These served both to guard the rampart and to communicate with the capital, Xianyang (near modern Xi'an) by signal—smoke by day and fire by night. Originally constructed partly of masonry and earth, it was faced with brick in its eastern portion. It was rebuilt in later times, especially in the 15th and 16th centuries. The basic wall is about 23–26 ft (7–8 m) high; at intervals towers rise above it to varying heights. It was designated a UNESCO World Heritage site in 1987.

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Barrier surrounding West Berlin that closed off East Germans access to West Berlin from 1961 to 1989 and served as a symbol of the Cold War's division of East and West Germany. The barrier was built in response to the flight of about 2.5 million East Germans to West Germany in the years 1949–61. First erected on the night of Aug. 12–13, 1961, it developed into a system of concrete walls topped with barbed wire and guarded with watchtowers, gun emplacements, and mines. It was opened in the 1989 democratization that swept through eastern Europe and has been largely torn down.

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