plover Vplo-vor, 'plo-vorX Any of about 36 species (family Charadriidae, order Charadriiformes) of plump-breasted shorebirds found almost world¬ wide. Plovers are 6-12 in. (15-30 cm) long and have long wings, long-
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1514 I plow ► Pluto
ish legs, a short neck, and a straight, short bill. Many species are plain brown, gray, or sandy above and whitish below. Others, including the golden and black-bellied plovers, are finely patterned above and black below in breeding season. Many spe¬ cies run along the shoreline, snap¬ ping up small aquatic invertebrates.
They have a melodious whistled call.
Both parents incubate the two to five eggs and care for the young. See also KILLDEER.
plow or plough Most important agricultural implement since the beginning of history, used to turn and break up soil, to bury crop residues, and to help control weeds. The forerunner of the plow is the prehistoric digging stick. The earliest plows were undoubtedly digging sticks with handles for pulling or pushing. By Roman times, plows were pulled by oxen or horses, and today they are drawn by tractors.
plum Any of various trees in the genus Prunus of the rose family, and their edible fruits. In the U.S. and Europe, plums are the most extensively distributed of the stone (drupe) fruits, most varied in native and cultivated kinds, and most adapted to a wide range of soils and climatic conditions. The fruits show a wide range of size, flavour, colour, and texture. They are widely eaten fresh, cooked, or baked in pastries. In full bloom, plum trees are covered with densely packed, showy flower clusters. The smooth-skinned fruit has a fleshy, juicy exterior and a hard interior stone or pit. Plum varieties that can be or have been dried without resulting in fermentation are called prunes.
plumbago See graphite
plumbing System of pipes and fixtures installed in a building for the distribution of potable water and the removal of waterborne wastes. Plumbing is usually distinguished from water and sewage systems, which serve a group of buildings or a city. Improvement in plumbing systems was very slow, with virtually no progress made from the time of the Roman system of aqueducts and lead pipes until the 19th century. Even¬ tually the development of separate, underground water and sewage sys¬ tems eliminated open sewage ditches. Present-day water pipes are usually made of steel, copper, brass, plastic, or other nontoxic material. A build¬ ing’s waste-disposal system has two parts: the drainage system and the venting system. The drainage portion comprises pipes leading from vari¬ ous fixture drains to the central main, which is connected to the sewage system. The venting system consists of pipes leading from an air inlet (usually on the roof) to various points within the drainage system; by pro¬ viding the circulation of air within the system, it protects the trap seals of fixtures from siphonage and back pressure. See also sewage system, water pollution, water-supply system. See illustration opposite.
Plunket, Saint Oliver (b. 1629, Loughcrew, County Meath, Ire.—d. July 1, 1681, London, Eng.; canonized 1975; feast day July 11) Irish prel¬ ate, the last man to suffer martyrdom for the Catholic faith in England. He was ordained in Rome, where he taught theology and represented the Irish bishops at the Holy See. In 1669 he was appointed archbishop of Armagh and primate of Ireland, and he worked to restore the disorga¬ nized church in Ireland. Renewed persecution forced him into hiding in 1673. In the anti-Catholic hysteria caused by the Titus Oates plot (1678), he was betrayed and imprisoned in Dublin in 1679. After a farcical trial in London, he was convicted of treason and was hanged, drawn, and quartered. His head, originally sent to Rome, is preserved at Drogheda, and his body is at Downside Abbey, near Bath.
pluralism In political science, the view that in liberal democracies power is (or should be) dispersed among a variety of economic and ideo¬ logical pressure groups and is not (or should not be) held by a single elite or group of elites. Pluralism assumes that diversity is beneficial to soci¬ ety and that the disparate functional or cultural groups of which society is composed—including religious groups, trade unions, professional orga¬ nizations, and ethnic minorities—should be autonomous. Pluralism was stressed most vigorously during the early 20th century by a group of English writers that included Frederic W. Maitland and Harold J. Laski; it was defended in the later 20th century by the American scholars Robert Dahl and David B. Truman.
The basic components of a plumbing fixture include the water-supply pipes, a valve or faucet for controlling the flow of water, and a drainpipe to carry wastewater away. An air chamber may be added to the supply line to cushion the effects of water hammer. A trap in the drain line leaves a plug of water in the pipe to prevent unwanted sewer gases from entering the room via the drain.
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pluralism In metaphysics, the doctrine opposed to monism. Whereas monists such as Parmenides, Benedict de Spinoza, and G.W.F. Hegel main¬ tain that reality consists of only one ultimate substance, pluralists assert that reality consists of manifold entities of many different types and that the diversity of things is more striking and important than their unity. In A Pluralistic Universe (1909), William James held that it is characteristic of empirically minded thinkers to note the changeability of things, the multiplicity of their being and their relations with one another, and the unfinished character of the world.
plurality system Electoral process in which the candidate who polls more votes than any other candidate is elected. It is distinguished from the majority system, in which, to win, a candidate must receive more votes than all other candidates combined. It is the most common method of selecting candidates for public office. Its chief advantage is that it avoids the need for runoffs to produce a winner. Its chief disadvantage is that it may result in a winner who has received a minority of the votes cast. It operates best in a two-party system, where the small vote for any third party will rarely result in an outcome seriously at odds with the voters’ will.
Plutarch Vplii-.tarkV Greek Plutarchos Latin Plutarchus (b. ad 46,
Chaeronea, Boeotia—d. after 119) Greek biographer and author. The son of a biographer and philosopher, Plutarch studied in Athens, taught in Rome, traveled widely, and made many important friends before returning to his native town in Boeotia. His literary output was immense, but his popularity rests primarily on his Parallel Lives, a series of pairs of biographies of famous Greeks and Romans. Displaying impressive learning and research, the Lives exhibit noble deeds and characters and provide model patterns of behaviour. The Moralia, or Ethica, contains his surviving writings on ethi¬ cal, religious, physical, political, and literary topics. His works profoundly influenced the evolution of the essay, biography, and historical writing in 16th-19th-century Europe, especially through translations such as Sir Tho¬ mas North’s Lives of the Noble Grecians and Romanes (1579), William Shakespeare’s source for his Roman history plays.
Pluto Ninth planet from the Sun. It was discovered in 1930 by Clyde W. Tombaugh (1906-97) and named after the Greek god of the underworld. It is usually the outermost of the known planets, averaging about 3.7 billion
Golden plover (Pluvial is apricaria).
KENNETH W. FINK-ROOT RESOURCES
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plutonium ► Pobedonostsev I 1515