Britannica Concise 2005

Santarem

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SERRADESAO MAMEDE NATURE PARK

Cape

Carvoeiro

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Setubal rs

Bayl'g

Sines* ^

N-Alqueua |j? Reservoir

Portimao* Faro t Cape

Saint Vincent

Gulf of Cddiz\{f

© 2002 Encyclopaedia Britannica, Inc.

ATLANTIC

OCEAN

people are Portuguese. Language: Portu¬ guese (official). Religion: Christianity (predominantly Roman Catholic). Cur¬ rency: euro. Administratively, the Atlantic islands of the Azores and Madeira are part of Portugal. Portugal is divided roughly in half by the Tagus River; the highlands rise mostly north of the Tagus and stretch northeast into Spain. Portugal has an industrialized economy in which both public and private sectors participate. Major industries were nationalized after a military coup in 1974, but many were returned to the private sector beginning in the late 1980s. Although motor vehicle manufacture is significant, light industries predominate; important products include textiles and clothing, paper and wood products, and chemicals. Portugal is a republic with a unicameral legislature; the chief of state is the president, and the head of government is the prime minister. In the 1st millennium bc, Celtic peoples settled the Iberian Peninsula. They were conquered c. 140 bc by the Romans, who ruled until the 5th century ad, when the area was invaded by Germanic tribes. A Muslim invasion in 711 left only the northern part

PORTUGAL

of Portugal in Christian hands. In 1179 it became the kingdom of Portu¬ gal and expanded as it reconquered the Muslim-held sectors. The bound¬ aries of modern continental Portugal were completed under King Afonso III (reigned 1248-79). From 1580 to 1640 Portugal was united with Spain. In the 15th and 16th centuries the monarchy encouraged exploration that took Portuguese navigators to Africa, India, Indonesia, China, the Middle East, and South America. Although Portugal established several colonies, they achieved independence over the years (see Brazil; Goa; Cape Verde; East Timor; Angola; Guinea-Bissau; Mozambique; Macau). Antonio de Oliveira Salazar ruled Portugal as a dictator from 1932 to 1968. The coun¬ try’s dictatorship was overthrown in the April 25, 1974, Revolution of the Carnations. A new constitution was adopted in 1976, and civilian rule resumed. Portugal was a charter member of NATO and is a member of the European Union (EU). In 1999 the government adopted the euro as the country’s official monetary unit and returned Macau, its last overseas ter¬ ritory, to Chinese rule.

Portuguese East Africa See Mozambique Portuguese Guinea See Guinea-Bissau

Portuguese language Romance language spoken by about 170 mil¬ lion people in Portugal, Brazil, and other former Portuguese colonies. The first literary works in Portuguese date from the 13th—14th century. Stan¬ dard Portuguese is based on the dialect of Lisbon. Dialectal variation in Portugal is limited, but the differences between Brazilian and European Portuguese are more extensive, including changes in phonology, verb conjugation, and syntax. The four major dialect groups are Northern (Gali¬ cian, spoken in northwestern Spain), Central, Southern (including the Lisbon dialect), and Insular (including Brazilian and Madeiran) Portu¬ guese.

Portuguese man-of-war Any of various floating, warm-water marine cnidarians (genus Physalia, class Hydrozoa) found worldwide but mostly in the Gulf Stream and the Indian and Pacific oceans. The medusa- form body consists of a translucent, jellylike, gas-filled float, which may be 3-12 in. (9-30 cm) long. Polyps beneath the float bear hanging ten¬ tacles up to 165 ft (50 m) long. Nematocysts on some polyps paralyze fish and other prey. Other polyps then attach to, spread over, and digest the victim. A third type of polyp is involved in reproduction. The painful sting of Physalia can cause fever, shock, or disruption of heart and lung function.

Portuguese West Africa See Angola

Poseidon \po-'sI-d3n\ Greek god of water and the sea, son of Cronus and Rhea. His brothers were Zeus and Hades. When the three brothers deposed their father, the kingdom of the sea fell by lot to Poseidon.

Unpredictable and sometimes vio¬ lent, he was also god of earthquakes, and he was closely associated with horses. Most of his offspring were giants and savage creatures. By Medusa he was the father of the winged horse Pegasus. The Isthmian Games were held in his honor. In art he was often shown holding a trident and accompanied by a dolphin and tuna. The Romans identified him with Neptune.

Posen See Poznan

positivism Any philosophical sys¬ tem that confines itself to the data of experience, excludes A priori or meta¬ physical speculations, and empha¬ sizes the achievements of science.

Positivism is closely connected with EMPIRICISM, PRAGMATISM, and LOGICAL positivism. More narrowly, the term designates the philosophy of Auguste Comte, who held that human thought had passed inevitably through a theological stage into a metaphysical stage and was passing into a positive, or scientific, stage. Believing that the religious impulse would survive the decay of revealed religion, he projected a worship of mankind, with churches, calendar, and hierarchy.

Poseidon, marble statue from Melos, 2nd century bc; in the National Archaeological Museum, Athens.

AUNARI-ART RESOURCE/EB INC.

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1534 I positron ► postmodernism

positron Vpa-z3-,tran\ Subatomic particle having the same mass as an electron but with an electric charge of+1 (an electron has a charge of -1). It constitutes the antiparticle (see antimatter) of an electron. The existence of the positron was a consequence of the electron theory of P. A. M. Dirac (1928), and the particle was discovered in cosmic rays by Carl D. Ander¬ son (1905-1991) in 1932. Though they are stable in a vacuum, positrons react quickly with the electrons of ordinary matter, producing gamma rays by the process of annihilation. They are emitted in positive beta decay of proton-rich radioactive nuclei and are formed in pair production.

positron emission tomography (PET) Imaging technique used in diagnosis and biomedical research. A chemical compound labeled with a radioactive isotope (see radioactivity) that emits positrons is injected into the body, and detectors measure their activity in the tissues as they com¬ bine with electrons and are annihilated. Computers analyze, integrate, and reconstruct the data to produce images of the organs scanned. PET is par¬ ticularly useful for studying brain and heart functions.

possession, adverse See adverse possession

possible world Conception of a total way the universe might have been. It is often contrasted with the way things actually are. In his Theod¬ icy (1710), G.W. Leibniz used the concept of a possible world in his pro¬ posed solution to the theological problem of the existence of evil, arguing that an all-perfect God would actualize the best of all possible worlds; this idea was later satirized by Voltaire in his comic novel Candide (1759). Philosophers have since constructed several different formalizations of the concept of a possible world.

possum or phalanger \f3-Tan-jor, 'fa-.lan-jarX Any of several species (family Phalangeridae) of nocturnal, arboreal marsupials of Australia and New Guinea. They are 22-50 in. (55-125 cm) long, including the long prehensile tail, and have woolly fur. All species eat fruits, leaves, and blossoms; some also eat insects and small vertebrates. Possums grasp branches with their hind feet. Most species bear their young in tree hol¬ lows and unused birds’ nests; a few build leafy nests. Several species are endangered because of predation, fur trapping, or habitat loss, but the common brush-tailed possum is considered a pest. See also opossum.

Post, C(harles) W(illiam) (b. Oct. 26,1B54, Springfield. Ill., U.S.—d. May 9,1914, Santa Barbara, Calif.) U.S. manufacturer of breakfast cereals. In the 1880s Post became a patient of John H. Kellogg at a health sanitarium in Battle Creek, Mich., where he became interested in producing healthful foods like those Kellogg served. In 1895 he founded Postum Cereal Co., the precursor to General Foods Corp. His first product, the cereal beverage Postum, was followed by Grape Nuts and Post Toasties.

Post, Emily orig. Emily Price (b. Oct. 27, 1872 or Oct. 3, 1873, Bal¬ timore, Md., U.S.—d. Sept. 25,

1960, New York, N.Y.) U.S. author¬ ity on etiquette. She was educated in private schools in New York City. At the turn of the century her straitened circumstances compelled her to begin writing light fiction and maga¬ zine articles. At her publisher’s sug¬ gestion, she undertook her major work, Etiquette: The Blue Book of Social Usage (originally Etiquette in Society, in Business, in Politics and at Home), in 1922; unlike earlier writers on the subject, she directed her commonsense views to the ordi¬ nary person of moderate means. The book appeared in 10 editions and 90 printings in her lifetime. The out¬ pouring of letters it provoked inspired her newspaper column, which became widely syndicated.

post-and-beam system In

building construction, a system in which two upright members, the posts, hold up a third member, the beam, laid horizontally across their top sur¬ faces. In Britain it is called post-and-lintel system, but in the U.S. “lin¬ tel” is usually reserved for a short beam that spans a window or door opening. The post and beam formed the basis of architecture from pre¬ historic to Roman times, and is illustrated by such ancient structures as

Stonehenge. All structural openings evolved from this system, which is seen in pure form only in colonnades and in framed structures, the posts of doors, windows, ceilings, and roofs usually being hidden in walls. The beam must bear loads that rest on it as well as its own load without deforming or breaking. Post-and-beam construction has largely been sup¬ planted by the modern steel frame.

Post-Impressionism Movement in Western painting that represented both an extension of Impressionism and a rejection of its limitations. The term was coined by Roger Fry for the works of Paul Cezanne, Georges Seurat, Vincent van Gogh, Paul Gauguin, Henri de Toulouse-Lautrec, and others. Most of these painters first pursued Impressionism, a style based, in its strictest sense, on the objective recording of nature in terms of the fugitive effects of colour and light. The Post-Impressionists rejected this aim in favour of more ambitious expression, admitting their debt, how¬ ever, to the pure, brilliant colours of Impressionism, its freedom from tra¬ ditional subject matter, and its technique of defining form with short brushstrokes of broken colour. Each painter in the movement pursued unique, personal subject matter and, while sharing stylistic goals with the other Post-Impressionists, had a personal form of expression. For example, Cezanne abandoned the Impressionists’ virtuoso depiction of evanescent light effects in order to pursue his preoccupation with the underlying structures of natural forms and the problem of unifying sur¬ face patterns with spatial depth. Both Gauguin and van Gogh rejected the indifferent objectivity of Impressionism in favour of a more personal, spiritual expression. The Post-Impressionists often exhibited together but, unlike the Impressionists, who were a close-knit and convivial group, they painted mainly alone. In general, Post-Impressionism led away from a naturalistic approach and toward the two major movements of early 20th- century art that followed it: Cubism and Fauvism. See also Neo-Impressionism.

post-traumatic stress disorder (PTSD) Psychological reaction occurring after a highly stressful event and typically characterized by flashbacks, recurrent nightmares, and avoidance of reminders of the event; depression and anxiety are often present. Traumatic events that can lead to PTSD include automobile accidents, rape or assault, military combat, tor¬ ture, and such natural disasters as floods, fires, or earthquakes. Long-term effects can include marital and family problems, difficulties at work, and abuse of alcohol and other drugs. Antidepressant medication and psycho¬ therapy, including group therapy, are used in treating the disorder.

postal system System that allows persons to send letters, parcels, or packages to addressees in the same country or abroad. Postal systems are usually government-run and paid for by a combination of user charges and government subsidies. There are early references to postal services in Egypt c. 2000 bc and in Zhou-dynasty China c. 1000 bc. The Roman Empire developed various centralized methods of relaying messages. In the Middle Ages there were no centralized postal services. Private postal systems developed with the rise of nation-states during the Renaissance; subsequently, postal services became government monopolies. Charges based on weight rather than distance and the use of prepaid stamps were first proposed in 1837. The General Postal Union (1875; later Universal Postal Union) improved international mail delivery by allowing member countries to retain the postage they collected on outgoing international mail and requiring them to treat incoming international mail as they did domestic mail. Airmail and automated mail handling were developed in the 20th century. See also e-mail.

poster Eye-catching printed paper announcement or advertisement that is exhibited to promote a product, event, or idea. Posters were popularized by the mid-19th-century invention of lithography, which allowed coloured posters to be produced cheaply and easily. Henri de Toulouse-Lautrec was noted for his poster art, which often advertised Parisian cabaret performers. Poster art flourished with the rise of the Art Nouveau style, as seen in the work of Alphonse Mucha. During World War I posters were used for recruit¬ ing and propaganda, and the industrial boom of the early 20th century gave rise to advertising posters for every conceivable product and event. The later rise of film and television advertising led to an eclipse in poster art.

postmodernism Any of several artistic movements since about the 1960s that have challenged the philosophy and practices of modern arts or literature. In literature this has amounted to a reaction against an ordered view of the world and therefore against fixed ideas about the form and meaning of texts. In its reaction against Modernist ideals (see Modernism) such as autotelic art and the original masterpiece, postmodern writing and art emphasize devices such as pastiche and parody and the stylized tech-

Emily Post.

BROWN BROTHERS

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postmortem ► Potok I 1535

nique of the antinovel and magic realism. Postmodernism has also led to a proliferation of critical theories, most notably deconstruction and its off¬ shoots, and the breaking down of the distinction between “high” and “low” culture.

postmortem See autopsy

poststructuralism Movement in literary criticism and philosophy begun in France in the late 1960s. Drawing upon the linguistic theories of Ferdinand de Saussure, the anthropology of Claude Levi-Strauss (see struc¬ turalism), and the deconstructionist theories of Jacques Derrida (see decon¬ struction), it held that language is not a transparent medium that connects one directly with a “truth” or “reality” outside it but rather a structure or code, whose parts derive their meaning from their contrast with one another and not from any connection with an outside world. Writers asso¬ ciated with the movement include Roland Barthes, Jacques Lacan, Julia Kristeva, and Michel Foucault.

Potala Palace Vpo-to-loV Religious and administrative complex, near Lhasa, Tibet, China. It covers 5 sq mi (13 sq km) atop a hill 425 ft (130 m) above the Lhasa River valley. Potrang Karpo (the White Palace, com¬ pleted 1648) once served as the seat of the Tibetan government and the main residence of the Daai Lama; from the mid-18th century it was used as a winter palace. Potrang Marpo (the Red Palace, 1694) houses several chapels, sacred statues, and the tombs of eight Dalai Lamas; it remains a major pilgrimage site for Tibetan Buddhists. The complex, which has a total of 1,000 rooms, was declared a world heritage site in 1994.

potash \'pat-,ash\ Name used for various inorganic compounds of potas¬ sium, chiefly the carbonate (K 2 C0 3 ), a white crystalline material formerly obtained from wood ashes. They are used to make special types of glass, potassium silicate (a dehydrating agent), pigments, printing inks, and soft soaps; for washing raw wool; and as a lab reagent and general-purpose food additive. Potassium hydroxide is frequently called caustic potash, and in the fertilizer industry, potassium oxide is called potash.

potash mica See muscovite

potassium Chemical element, one of the alkali metals, chemical symbol K, atomic number 19. It is a soft, silvery white metal, not found free in nature and rarely used as the metal (except as a chemical reagent) because of its extreme reactivity. Potassium is essential for life and is present in all soils. Potassium ions (K + ) and sodium ions act at cell membranes in electrochemical impulse transmission and in transport. Potassium in com¬ pounds has valence 1. The chloride is used as a fertilizer and a raw mate¬ rial for producing other compounds, and the hydroxide for making liquid soaps and detergents and in preparing various salts. The iodide is added to table salt to protect against iodine deficiency. The nitrate is also called saltpetre, and the carbonate is called potash.

potassium-argon dating Method for determining the age of igne¬ ous rocks based on the amount of argon-40 in the rock. Radioactive potassium-40 decays to argon-40 with a half-life of about 1.3 billion years, making this method useful for dating rocks that are billions of years old. A more sophisticated method, called argon-argon dating, provides a more accurate estimate of the original potassium-40 content by means of the ratio of argon-40 to argon-39 in the rock, thus yielding a more accurate age determination. See also dating.

potato Herbaceous annual (Solatium One of the world’s main food crops, the potato differs from other food crops in that the edible portion is a tuber. Highly digestible, potatoes are prepared for eating in many ways and are a major source of starch as well as amino acids, protein, vitamin C, and B vitamins. The stem grows 20^10 in. (50-100 cm) tall, sprouting spi¬ rally arranged compound leaves.

Underground, stems extend as sto¬ lons, the ends of which enlarge into 1-20 tubers of variable shape and size. The tubers have spirally arranged buds (eyes) that may remain dormant after the tuber is fully grown for up to 10 weeks or more; they grow into plants identical to the par¬

ent plant. A native of the Andes, the potato (also known as the common potato, white potato, or Irish potato) was carried by Spaniards into Europe during the 16th century. A century later, it had become the major food crop in Ireland; disastrous damage to the crop by a fungal blight caused the Irish potato famine in the mid-1800s. See also sweet potato.

potato beetle Destructive species (Lema trilineata) of leaf beetle (fam¬ ily Chrysomelidae). Less than 0.25 in. (6 mm) long, it is yellow and has three black stripes on its wing covers. Eggs are laid on the underside of a potato leaf, on which both larvae and adults feed. The larvae are cam¬ ouflaged by excrement the beetles pile on their back. Two generations are produced each year; the second overwinters in the ground in the pupal stage. See also Colorado potato beetle.

potato bug See Colorado potato beetle

Potemkin \p9-'tyem-kin\, Grigory (Aleksandrovich) (b. Sept. 24, 1739, Chizovo, Russia—d. Oct.

16, 1791, near Ia§i, Moldavia) Rus¬ sian army officer. He entered the horseguards (1755) and helped bring Catherine II to power (1762). He fought with distinction in the Russo- Turkish War (1768-74), then became Catherine’s lover (1774-76) and was made governor-general of “New Russia” (southern Ukraine). In 1783 she made him prince of Tauris. As a field marshal from 1784, he intro¬ duced reforms in the army, built the harbour of Sevastopol, and con¬ structed a fleet in the Black Sea. He attempted to colonize the Ukrainian steppes, but he underestimated the costs, leaving many projects half- complete; his successful disguising of the weak points of his adminis¬ tration led to the claim that he erected mere facades—“Potemkin villages”—to show Catherine on her tour of the region. He commanded the Russian army in the second Russo- Turkish War.

potential, electric See electric potential

potential energy Energy stored by an object by virtue of its position. For example, an object raised above the ground acquires potential energy equal to the work done against the force of gravity; the energy is released as kinetic energy when it falls back to the ground. Similarly, a stretched spring has stored potential energy that is released when the spring is returned to its unstretched state. Other forms of potential energy include electrical potential energy, chemical energy, and nuclear energy.

Potenza \po-'tent-sa\ ancient Potentia City (pop., 2001 prelim.: 69,295), capital of the Basilicata region, southern Italy. Located at 2,684 ft (819 m) above sea level in the Apennines, the Roman city Potentia was founded in the 2nd century bc and became an important road junction and flourishing community. In medieval times it had a succession of feudal overlords. In 1860 it was the first town in southern Italy to expel the Bourbon rulers of the Kingdom of the Two Sicilies. The town has been rebuilt several times after earthquake damage. It is an agricultural centre and ships fruit and vegetables.

potestas patria See patria potestas

potlatch Ceremonial distribution of property and gifts practiced among the American Indians of the Northwest Pacific coast, particularly the Kwakiutl. A potlatch is given by an heir or successor to assert and vali¬ date his newly assumed social position. Ceremonial formalities are observed in inviting guests, in speech making, and in distributing goods according to the social rank of the recipients. Great feasts and generous hospitality accompany the potlatch. The ceremony has been much stud¬ ied by anthropologists for the light it sheds on the nature of property, wealth, prestige, and social status. See also gift exchange.

Potok \'po-tak\, Chaim orig. Herman Harold Potok (b. Feb. 17, 1929, New York, N.Y., U.S.—d. July 23, 2002, Merion, Pa.) U.S. rabbi and novelist. The son of Polish immigrants, he was reared in an Ortho-

tuberosum ) in the nightshade family.

Potato (Solanum tuberosum).

GRANT HEILMAN

Grigory Potemkin, engraving by James Walker, 1789, after a portrait by Johann Baptist Lampi.

REPRODUCED BY COURTESY OF THE TRUSTEES OF THE BRITISH MUSEUM; PHOTOGRAPH, J.R. FREEMAN & CO., LTD.

© 2006 Encyclopaedia Britannica, Inc.

1536 I Potomac River ► Pound

dox Jewish home and was ordained a Conservative rabbi. He taught until he began a career as an editor and writer of scholarly and popular articles and reviews in the 1960s. His novels, which have introduced to Ameri¬ can fiction the spiritual and cultural life of Orthodox Jews, include The Chosen (1967; film, 1981), The Promise (1969), and My Name Is Asher Lev (1972). Three connected novellas, Old Men at Midnight, appeared in 2001. Notable among Potok’s nonfiction writings are Wanderings: Chaim Potok’s History of the Jews (1978), in which the author combines impres¬ sive scholarship with dramatic narrative, and The Gates of November (1996), a chronicle of a Soviet Jewish family and the rise and fall of the Soviet Union.

Potomac \p3-'to-m9k\ River River, east-central U.S. Rising in the Appalachian Mountains of West Virginia, it is about 287 mi (462 km) long. It flows southeast through the District of Columbia into Chesapeake Bay. It is navigable by large vessels to Washington, D.C., above which it descends in a series of rapids and falls, including Great Falls. Noted for its beauty, the Potomac is also rich in history. Mount Vernon, home of George Washington, is on its banks below Washington, D.C. The Chesa¬ peake and Ohio Canal National Historical Park parallels the river.

Potosi \,po-t6-'se\ City (pop., 2001: 132,966), southwestern Bolivia. Founded in 1545 after the discovery of silver in a neighbouring moun¬ tain, it grew to be the most populous city in Latin America. After the mid- nth century, its population declined drastically when silver production waned but expanded in the 19th-20th century with the introduction of other industries, including tin mining. One of the highest cities in the world, at an elevation of about 13,700 ft (4,200 m), it is a major Boliv¬ ian industrial centre. The historic city was designated a UNESCO World Heritage site in 1987.

Potsdam City (pop., 2002 est.: 130,435), capital of Brandenburg state, Germany. It is located on the Havel River southwest of Berlin. First men¬ tioned in 993 as a Slav settlement, it was chartered in 1317. It became the electoral residence of the margrave of Brandenburg in 1640 under Frederick William, the Great Elector. It was the Prussian royal residence under Frederick II, during whose reign it was a military and intellectual centre. It was severely damaged during World War II, but many monu¬ ments survived and others have been restored. In 1945 it was the site of the Potsdam Conference. Its large, beautifully landscaped parks were named a World Heritage site by UNESCO in 1990. Industries include administration, retailing, education, film production, and tourism. It is the site of several scientific and technical institutions.

Potsdam Conference (July 17-Aug. 2, 1945) Allied conference held in the Berlin suburb of Potsdam after Germany’s surrender in World War II. Harry Truman, Joseph Stalin, and Winston Churchill (later replaced by Clement R. Attlee) met to discuss European peace settlements, the admin¬ istration of defeated Germany, the demarcation of the boundaries of Poland, the occupation of Austria, the definition of the Soviet Union’s role in eastern Europe, the determination of reparations, and the further prosecution of the war against Japan. The four occupation zones of Ger¬ many conceived at the Yalta Conference were set up, each to be admin¬ istered by the commander-in-chief of the Soviet, British, U.S., or French army of occupation. Poland’s boundary became the Oder and Neisse riv¬ ers in the west, and the country received part of former East Prussia. Sta¬ lin refused to let the Western powers interfere with his control of eastern Europe.

Potter, (Helen) Beatrix (b. July 28, 1866, South Kensington, Mid¬ dlesex, Eng.—d. Dec. 22, 1943, Sawrey, Lancashire) English author and illustrator of children’s books. In her childhood Potter spent holidays in Scotland and the English Lake District, which inspired her love of animals and stimulated her imagina¬ tive and technically superb waterco¬ lour drawings. The illustrated animal stories she sent to a sick child when she was 27 were published as The Tale of Peter Rabbit (1902), which became one of the best-selling chil¬ dren’s books of all time. More than 20 sequels followed, featuring such

Beatrix Potter, 1913

PICTORIAL PARADE /LONDON DAILY EXPRESS, REPRODUCED BY PERMISSION OF FREDERICK WARNE & CO.

original characters as Jeremy Fisher, Squirrel Nutkin, Jemima Puddle- Duck, and Mrs. Tiggy-Winkle.

Potter, Dennis (Christopher George) (b. May 17, 1935, Berry Hill, Gloucestershire, Eng.—d. June 7, 1994, Ross-on-Wye, Hereford¬ shire) British dramatist. Educated at Oxford, he thereafter devoted him¬ self to writing, especially of television plays. His innovative serial Pennies from Heaven (1978) combined fantasy sequences and musical interludes in which actors lip-synched to old recordings of period songs. His best- known teleplay, the eight-part The Singing Detective (1986), an autobio¬ graphical account of his crippling bouts of psoriatic arthropathy, combined humour, pathos, and fantastic musical numbers. His other teleplays include the allegedly sacrilegious Brimstone and Treacle (1976, televised 1987) and Lipstick on Your Collar (1993). His movie screenplays include Gorky Park (1983) and Dreamchild (1985).

pottery One of the oldest and most widespread of the decorative arts, consisting of objects (mostly useful ones, such as vessels, plates, and bowls) made of clay and hardened with heat. Earthenware is the oldest and simplest form; stoneware is fired at a high temperature to cause it to vitrify and harden; and porcelain is a fine, generally translucent form of pottery. The Chinese began their sophisticated production of pottery in the Neolithic period and produced porcelain as early as the 7th century ad. Chinese porcelain, or “china,” was widely exported to Europe and had a profound influence on European manufacturers and on taste. Clas¬ sical Greece and Islamic cultures are also known for their artistic and technical innovations in pottery.

Poujade \pu-'zhad\, Pierre (-Marie) (b. Dec. 1, 1920, Saint-Cere, France—d. Aug. 27, 2003, La Bastide-l’Eveque) French political leader. The owner of a bookstore in Saint-Cere, in 1953 he organized a local shopkeepers’ strike to protest high taxation. Expanding his activities to other towns, he enrolled 800,000 members in his Union for the Defense of Tradesmen and Artisans. His right-wing movement, known as Pou- jadism, attracted discontented farmers and merchants; in 1956 it won 52 seats in the National Assembly. Poujade’s influence soon waned, but in the 1970s he founded an organization for nonunion workers.

Poulenc Vpu-.laqkV Francis (Jean Marcel) (b. Jan. 7, 1899, Paris, Fr.—d. Jan. 30, 1963, Paris) French composer. In his teens he studied piano with Ricardo Vines (1875-1943). Influenced by Erik Satie, Poulenc and five other like-minded young composers became known as Les Six. Poulenc wrote piano compositions, orchestral music, and chamber music, but he is best known for his vocal music, including many admired songs, the operas The Breasts of Tiresias (1944), Dialogues of the Carmelites (1956), and La voix humaine (1958), and such sacred choral works as Mass in G Major (1937), the Stabat Mater (1950), and the Gloria (1959), reflecting his devout Catholicism.

poultry farming Raising birds commercially or domestically for meat, eggs, and feathers. Chickens, ducks, turkeys, and geese are the birds of primary commercial importance. Guinea fowl and squabs are chiefly of local interest. Though chickens have been domesticated for at least 4,000 years, their meat and eggs have been mass-production commodities only since c. 1800.

pound Unit of weight in the avoirdupois system, the traditional Euro¬ pean system of weight (incorporated into the British Imperial system and the U.S. system of weights and measures), equal to 16 oz, 7,000 grains, or 0.4536 kg. It is also a unit of weight in the troy and apothecaries’ sys¬ tems (two other traditional systems of weight), equal to 12 troy or apoth¬ ecaries’ oz, 5,760 grains, or 0.37 kg. Its Roman ancestor, the libra, is the source of the abbreviation lb. The troy pound is used for precious met¬ als, the apothecaries’ pound for drugs. The British monetary pound is linked historically with the minting of silver coins (sterlings). Large pay¬ ments were reckoned in “pounds of sterlings,” later shortened to “pounds sterling.” See also gram; International System of Units; measurement; metric system; ounce.

Pound, Ezra (Loomis) (b. Oct. 30,1885, Hailey, Idaho, U.S.—d. Nov. 1, 1972, Venice, Italy) U.S. poet and critic. Pound attended Hamilton College and the University of Pennsylvania, where he studied various languages. In 1908 he sailed for Europe, where he would spend most of his life. He soon became a leader of Imagism and a dominant influence in Anglo-American verse, helping promote writers such as William Butler Yeats, James Joyce, Hilda Doolittle, Ernest Hemingway, Robert Frost, D.H. Lawrence, and T.S. Eliot, whose The Waste Land he brilliantly edited. After

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Pound ► Powell I 1537

World War I he published two of his most important poems, “Homage to Sextus Propertius” (1919) and “Hugh Selwyn Mauberley” (1920). He also began publishing The Cantos, an attempt at an epic sequence of poems, which would remain his major poetic occupation throughout his life. With the onset of the Great Depression, he increasingly pursued his interest in history and economics, became obsessed with monetary reform, and declared his admiration for Benito Mussolini. In World War II he made pro-fascist radio broadcasts; detained by U.S. forces for treason in 1945, he was initially held at Pisa; The Pisan Cantos (1948, Bollingen Prize), written there, are notably moving. He was subsequently held in an Ameri¬ can mental hospital until 1958, when he returned to Italy. The Cantos (1970) collects his 117 completed cantos.

Pound, Roscoe (b. Oct. 27, 1870, Lincoln, Neb., U.S.—d. July 1, 1964, Cambridge, Mass.) U.S. legal educator and botanist. After studying botany at the University of Nebraska and law at Harvard University (1889-90), he was admitted to the Nebraska bar, and he practiced law while also teaching at the state uni¬ versity (1890-1903). At the Univer¬ sity of Nebraska he directed the state botanical survey (1892-1903) and discovered a rare fungus (. Rosco- poundia). He later taught at several law schools, most notably Harvard (1910-37), where he also served as dean (1916-36), instituting many reforms. He was perhaps the chief U.S. advocate of sociological juris¬ prudence, which holds that statutes and court decisions are affected by social conditions; his ideas appar¬ ently influenced the New Deal pro¬ grams of Pres. Franklin D. Roosevelt. After World War II he helped reorganize the judicial system of Taiwan.

Poussin \pii-'sa n \, Nicolas (b. 1594, Villers, France—d. Nov. 19,1665, Rome, Papal States) French painter. Except for two years as court painter to Louis XIII, he spent his entire career in Rome, where he became an admirer of ancient Roman civilization. In early works, he depicted themes from Classical mythology in a painterly style reminiscent of such Vene¬ tian masters as Titian. Turning to Raphael for inspiration, he began in the mid 1630s to develop a style marked by Classical clarity and monumen- tality. His late masterworks, such as Holy Family on the Steps (1648), employ a style calculated to express virtue and rectitude, featuring only a few figures painted in harsh colours against a severe background. In his landscapes, such as Landscape with Polyphemus (1649), the disorder of nature is reduced to the order of geometry. His austere and highly ordered compositions influenced generations of French painters, including Jacques-Louis David, J.-A.-D. Ingres, and Paul Cezanne.

powder metallurgy Fabrication of metal objects from a powder rather than casting from molten metal or forging at softening tempera¬ tures. In some cases the powder method is more economical, as in mak¬ ing metal parts such as gears for small machines, in which casting would involve considerable scrap loss. In other cases, melting is impractical (e.g., because the melting point of the metal is too high). Powder metal¬ lurgy is also used to produce a porous product that will allow a liquid or gas to pass through it. See also metallurgy, sintering.

Powder River River, northern Wyoming and southeastern Montana, U.S. It rises in the foothills of the Bighorn Mountains in Wyoming and flows north 486 mi (782 km) to join the Yellowstone River near Terry, Mont. Tributaries include the Little Powder River and Crazy Woman Creek.

Powderly, Terence V(incent) (b. Jan. 22, 1849, Carbondale, Pa., U.S.—d. June 24, 1924, Washington, D.C.) U.S. labour leader. The son of Irish immigrants, he became a railroad worker at age 13 and a machin¬ ist’s apprentice at 17. He joined the Machinists’ and Blacksmiths’ Union in 1 87 1 . Three years later he joined the secret order of the Knights of Labor, and in 1879 he was chosen for its highest post, grand master workman. He presided over the union in its period of greatest membership, but attacks by opponents such as Jay Gould caused membership to decline.

Powderly became absorbed in internal disputes and finally resigned in 1893. See also labour union; Uriah Smith Stephens.

Powell, Adam Clayton, Jr. (b. Nov. 29, 1908, New Haven, Conn., U.S.—d. April 4, 1972, Miami, Fla.) U.S. politician. In 1937 he succeeded his father as pastor of the Abyssinian Baptist Church in Harlem, New York City, and built its membership to 13,000. Elected to the New York City Council in 1941, he became the first African American to serve on that body. In the U.S. House of Representatives (1945-67, 1969-71), he spon¬ sored much social-welfare legislation, including a minimum wage act, antipoverty acts, and bills providing federal aid to education. Known for his flamboyance and his lack of concern for House decorum, he was the target of a libel suit and was investigated for financial misconduct. In 1967 the House voted to exclude him, but the U.S. Supreme Court later ruled that the House’s action was unconstitutional.

Powell Vpo-ol, 'pau(-9)l\, Anthony (Dymoke) (b. Dec. 21, 1905, London, Eng.—d. March 28, 2000, near Frome, Somerset) British nov¬ elist. He published his first novel.

Afternoon Men (1931), while work¬ ing in a London publishing house.

He worked in journalism and served in World War II before publishing the first of 12 novels in the autobio¬ graphical and satiric series A Dance to the Music of Time (1951-75). His best-known work, it reflects his out¬ look and experiences of English society in the decades before and after the war. His later novels include The Fisher King (1986).

Powell, Bud orig. Earl Powell

(b. Sept. 27, 1924, New York, N.Y.,

U.S.—d. Aug. 1, 1966, New York City) U.S. jazz pianist and composer.

Powell played in Cootie Williams’s big band (1942^14) before becoming part of the burgeoning activity of bebop in the late 1940s. His style became the predominant approach for post-swing era pianists: he did away with most accepted functions of the left hand, reducing it to playing brief, syn¬ copated chords supporting long melody lines by the right hand. He moved to Paris in 1959 and returned to the U.S. in 1964. His career was inter¬ rupted several times due to nervous breakdowns thought to derive from head injuries sustained in a racially motivated attack in 1945.

Powell, Colin (Luther) (b. April 5, 1937, New York, N.Y., U.S.) U.S. general and statesman. The son of Jamaican immigrants, he entered the U.S. Army after college and served in the Vietnam War (1962-63, 1968— 69). After holding various posts in the Pentagon and elsewhere, he was appointed senior military assistant to the secretary of defense in 1983. In 1987 he joined the staff of the National Security Council; in that same year Pres. Ronald Reagan appointed him assistant to the president for national security affairs. In 1989 Powell was promoted to four-star gen¬ eral and, appointed by Pres. George Bush, became the first African Ameri¬ can to serve as chairman of the Joint Chiefs of Staff. He helped plan the invasion of Panama (1989) and the military operations of the First Persian Gulf War. Under Pres. George W. Bush he served as secretary of state (2001-05), the first African American to hold that post.

Powell, John Wesley (b. March 24, 1834, Mount Morris, N.Y., U.S.—d. Sept. 23, 1902, Haven, Maine) U.S. geologist and ethnologist. Powell took many expeditions (1871-79) down the Colorado River, describing the earliest of these in Exploration of the Colorado River of the West and Its Tributaries (1875). He developed the first comprehensive classification of American Indian languages (1877) and was the first direc¬ tor of the Smithsonian Institution’s Bureau of American Ethnology (1879— 1902). In 1881 he became director of the U.S. Geological Survey, where he worked extensively on mapping water sources and advancing irriga¬ tion projects.

Powell, Lewis F(ranklin), Jr. (b. Sept. 19, 1907, Suffolk, Va., U.S.—d. Aug. 25, 1998, Richmond, Va.) U.S. jurist. After studying law at Washington and Lee University and Harvard University, he returned to practice law in Virginia. As chairman of the Richmond school board, he oversaw peaceful school integration in 1959; he later chaired the state

Anthony Powell, 1974

FAY GODWIN

© 2006 Encyclopaedia Britannica, Inc.

1538 I Powell ► Poznan

board of education and served as president of the American Bar Associa¬ tion. Widely respected in legal circles, he was nominated to the Supreme Court of the United States by Pres. Richard Nixon in 1971; he took his seat in 1972 and served until 1987. He adopted moderate-to-liberal positions on civil rights, affirmative action, and separation of church and state, though his views on law enforcement were conservative.

Powell, Michael (Latham) (b. Sept. 30, 1905, Bekesbourne, Kent, Eng.—d. Feb. 19, 1990, Avening, Gloucestershire) British film director. He directed his first movie, Two Crowded Hours, in 1931 and made over 20 low-budget films before Alexander Korda teamed him with screenwriter Emeric Pressburger (1902-88) to make the successful U-Boat 29 (1939). Forming their own production company, they made movies such as The Thief of Bagdad (1940), The Life and Death of Colonel Blimp (1943), Stairway to Heaven (1946), Black Narcissus (1947), The Red Shoes (1948), and The Tales of Hoffmann (1951). Powell made the controver¬ sial Peeping Tom (1960) without Pressburger. Powell’s films were notable for their use of brilliant colour, fantasy, and experimental cinematogra- phy.

Powell, Robert Baden- See Robert S. Baden-Powell

Powell, William (b. July 29, 1892, Pittsburgh, Pa., U.S.—d. March 5, 1984, Palm Springs, Calif.) U.S. film actor. He acted on Broadway from 1912 and made his screen debut in Sherlock Holmes (1922). Powell played villains in the silent movies, and with the coming of sound he moved into light mysteries, playing his first detective in The Canary Mur¬ der Case (1929). An intelligent, debonair leading man, he became a top star as the sophisticated, bemused detective Nick Charles, opposite Myrna Loy, in the hit The Thin Man (1934) and its successful sequels. His later notable films include The Great Ziegfeld (1936), My Man Godfrey { 1936), and Life with Father (1947).

power In science and engineering, the time rate of doing work or deliv¬ ering energy. Power ( P) can be expressed as the amount of work done (W), or energy transferred, divided by the time interval ( t ): P = Wit. A given amount of work can be done by a low-powered motor in a long time or by a high-powered motor in a short time. Units of power are those of work (or energy) per unit time, such as foot-pounds per minute, joules per second (called watts), or ergs per second. Power can also be expressed as the product of the force ( F) applied to move an object and the speed (v) of the object in the direction of the force: P = Fv. See also horsepower.

Power, Charles Gavan (1888-1968) Canadian politician. Born in Sillery, Quebec, he was seriously wounded in World War I. He served in the Canadian House of Commons 1917-55. In W.L. Mackenzie King’s government he served as minister for pensions and national health (1935— 39) and postmaster general (1939^-0). As minister for national defense for air (1940-44), he promoted the interests of Canadian air forces serv¬ ing under British command and created Canadian squadrons in Europe.

Power, Tyrone (Edmund) (b. May 5, 1914, Cincinnati, Ohio, U.S.—d. Nov. 15, 1958, Madrid, Spain) U.S. actor. The descendant of a long line of actors, he toured with a Shakespearean repertory company before making his Broadway debut in Romeo and Juliet (1935). His first film hit was Lloyds of London (1936). He became noted for his action- adventure roles in movies such as The Rains Came (1939), The Mark of Zorro (1940), Blood and Sand (1941), Nightmare Alley (1947), and The Mississippi Gambler (1953), while continuing to act on stage in plays such as Saint Joan (1936), Mister Roberts (1950), and Back to Methuselah

(1958).

power of attorney See power of attorney

Powers, Hiram (b. June 29, 1805, Woodstock, Vt., U.S.—d. June 27, 1873, Florence, Italy) U.S.-bom Italian sculptor. He worked as an artist- assistant in a waxworks museum in Cincinnati, Ohio, then moved to Washington, D.C., where he modeled busts of such figures as Andrew Jackson (1834). In 1837 he settled permanently in Florence. He attracted international notoriety with his marble Greek Slave (1843), an image of a nude young woman in chains, which caused a sensation at Fondon’s Crystal Palace Exposition in 1851. An artist of outstanding technical abil¬ ity, he was one of the most popular sculptors of his time. See photograph opposite.

Powhatan \,pau-3-'tan, pau-'ha-t 3 n\ (d. April 1618, Virginia) American Indian leader, father of Pocahontas. At the peak of his power, he ruled the 13,000 to 34,000 people of the Powhatan empire. He initially acted

ambivalently toward the English settlement at Jamestown, Va., and some¬ times permitted attacks against the colonists. After Pocahontas married an English settler in 1614, however, Powhatan maintained peaceful relations with the colonists until the end of his life.

Powhatan Confederacy of more than 30 North American Indian tribes living in Oklahoma, New Jersey, and Virginia, U.S., and in Canada. Powhatan languages belong to the Algonquian language family. They once occupied most of Tidewater Virginia and the eastern shore of Chesa¬ peake Bay. The confederacy was named for its powerful chief, Powhatan, to whom the tribes provided military support and paid taxes in the form of goods. Many of the villages, consisting of long dwellings covered with bark or reed mats, were palisaded. Powhatan women cultivated corn, beans, and squash; the men hunted and waged war, chiefly against the Iroquois. The intermittent hostilities with the English settlers, often called the Powhatan War (1622-44), ended with the breaking of the confederacy.

powwow American Indian ceremony or gathering of various kinds. Powwows originally were healing ceremonies, but the word could also refer to exuberant celebrations, with dancing and singing, of success in hunting or victory in battle. Meetings of tribal councils were also called powwows. Today the word is used for large-scale Indian social gather¬ ings, often representing more than one tribe, with traditional drumming, singing, and dancing. Modern powwows draw tourists as well as partici¬ pants, and craft items and souvenirs are offered for sale.

Powys Vpo-9s\ County (pop., 2001: 126,344), east-central Wales. The county seat is at Llandridod Wells. It is named after the Welsh princedom

of Powys, located in the border country between Wales and England. At its most powerful in the 12th cen¬ tury, the princedom was unable to gain ascendancy in Wales because it was so close to the border area where the cultures of Wales and England intermingled. Main elements in the landscape are the valley lowlands leading to Shrewsbury and Hereford. There are remains of Iron Age and Roman settlements.

poxvirus Any of a group of viRUSes responsible for a wide range of pox diseases in humans and other ani¬ mals. Poxvirus was the cause of smallpox. (Human chickenpox is caused by varicella-zoster virus.) The virus particle is somewhat brick¬ shaped, and its surface is studded with hollow spikes. It contains DNA. Unlike other DNA viruses, poxvi¬ ruses appear to develop entirely within the cytoplasm of affected cells. The virus of rabbitpox has been used with mixed success in Australia to control the wild rabbit population.

Poyninas \ , poi- 1 nh]z\ / Sir Edward (b. 1459, Southwark?, near London, Eng.—d. October 1521, Westenhanger, Kent) English soldier and administrator. A sup¬ porter of Henry Tudor (later Henry VII), he served as the king’s lord deputy of Ireland (1494-95), where he enacted legislative measures (“Poynings’ Laws”) that applied all English public laws to Ireland and required every act of the Irish parlia¬ ment to be approved by the king and privy council.

Poznan Vp6z-,nan\ German Posen Vpoz- 3 n\ City (pop., 2000 est.: 574,896), west-central Poland. Located on the Warta River, Poznan is one of the oldest cities in Poland,

Hr

5 ?

"Greek Slave," marble statue by Hiram Powers, 1843; in the Corcoran Gallery of Art, Washington, D.C.

© 2006 Encyclopaedia Britannica, Inc.

Practical Learning School ► Prague Spring I 1539

dating from the 9th century ad. It reached the height of prosperity as a trade centre from the 15th to the 17th century but declined after the Sec¬ ond Northern War. In 1793 Poznan was annexed to Prussia, intensifying a Germanization that had begun in the 13th century. In 1918 it reverted to Poland. During World War II it was occupied by the Germans and suf¬ fered extensive damage. Rebuilt after the war, it has become the admin¬ istrative, industrial, and cultural centre of western Poland. It is also an academic centre with scientific and literary institutes. Its varied industries include textile mills, metallurgical works, and chemical plants.

Practical Learning School or Silhak School of thought that arose in 18th-century Korea, dedicated to a practical approach to statecraft. It attacked Neo-Confucianism, particularly its formalism and concern with ritual. Members of the school originated many ideas for social reform and the development of farming. Notable contributors include Yi Ik (1681— 1763), who wrote on land reform and the abolition of class barriers, and Pak Chi-won (1737-1805), who advocated the development of commerce and technology. The school contributed to the wave of modernization that occurred after the introduction of Western culture into Korea in the late 19th century.

practical reason Rational capacity by which (rational) agents guide their conduct. In Immanuel Kant’s moral philosophy, it is defined as the capacity of a rational being to act according to principles (i.e., according to the conception of laws). Unlike the ethical intuitionists (see intuition- ism), Kant never held that practical reason intuits the rightness of particu¬ lar actions or moral principles. For him, practical reason was basically formal rather than material, a framework of formative principles rather than a source of specific rules. This is why he put such stress on his first formulation of the categorical imperative. Lacking any insight into the moral realm, humans can only ask themselves if what they are proposing to do has the formal character of law, namely, the character of being the same for all persons similarly circumstanced.

Prado \'pra-do\ Museum Spain’s national art museum, housing the world’s greatest collection of Spanish painting as well as other European works. Founded in Madrid in 1818 by Ferdinand VII, it was opened to the public in 1819 as the Royal Museum of Painting. Its holdings were formed over three centuries from the various royal collections of the Habsburg and Bourbon monarchs in Spain. In 1868 it became the National Museum of the Prado after the exile of Isabella II. In 1872 it acquired many notable paintings formerly owned by Spanish convents and monasteries. It owns the outstanding collections of the works of El Greco, Diego Velazquez, and Francisco de Goya and numerous works by other Spanish masters such as Jose de Ribera and Francisco Zurbaran. Among its other holdings are col¬ lections of Greco-Roman statuary and many Flemish and Italian master¬ pieces.

Praeneste \pre-'nes-te\ modem Palestrina Ancient city, Latium, cen¬ tral Italy. Praeneste was located on a spur of the Apennines. Founded before the 8th century bc, it saw many battles with Rome before becoming part of the Roman Empire. It was a major centre for the cult of the goddess Fortuna, whose sanctuary and temple oracle were surrounded by an immense complex of buildings. It became a favourite summer resort of wealthy Romans, including Augustus, Hadrian, and Puny the Younger. The modern town is the birthplace of composer Giovanni Pierluigi da Pal¬ estrina.

praetor Vpre-torN In ancient Rome, a judicial officer who had broad authority in cases of equity, was responsible for producing public games, and, in the absence of a consul, exercised extensive authority in the gov¬ ernment. After a one-year term, a praetor typically went on to govern a province. Originally only a patrician magistrate could be a praetor, but from c. 337 bc, the position was also open to plebeians. The number of praetors increased to eight by the 1st century bc, two for civil matters and six for specific courts. It continued to vary under different government leaders and emperors; by the late empire, only the city praetor for public games remained.

Praetorian \pre-'tor-e-3n\ Guard (Latin, cohors praetoria) House¬ hold troops of the Roman emperors. In the 2nd century bc they were bodyguards for Roman generals, their name taken from the general’s tent ( praetorium ). During the civil wars military leaders had personal body¬ guards, but in 27 bc Augustus created a permanent corps to guard the emperor and stationed its members around Rome. In ad 23, with Sejanus as commander, they gained political influence; from then on, they usually had an important voice in the appointment of emperors. They were respon¬

sible for the accession of Claudius (41), the disorders of 68-69, the lynch¬ ing of Domitian’s murderers (97), and the murder of Elagabalus (222). Constantine I disbanded the Praetorian Guard in 312.

Pragmatic Sanction (1713) Decree by Emperor Charles VI requiring the undivided descent of his Habsburg domains. It stipulated that his heri¬ tage go to his eldest son or, in the absence of a son, to his eldest daugh¬ ter. It became law in 1720 within the Habsburg states, and much of Charles’s later reign was directed toward securing acceptance of the sanc¬ tion from the other European powers. Since his son died soon after birth (1716), his daughter Maria Theresa became his heir. On Charles’s death (1740), the sanction was contested by Prussia and Bavaria, which led to the War of the Austrian Succession.

Pragmatic Sanction of Bourges VbUrzh\ (July 7, 1438) Decree issued by King Charles VII of France after the Council of Basel, confirm¬ ing the supremacy of a council over the pope. The decree also confirmed the Council’s assertion of the “liberties” of the Gallican Church, restrict¬ ing the rights of the pope and in many cases making his jurisdiction sub¬ ject to the king’s. Revoked by Louis XI in 1461, the Pragmatic Sanction was reasserted periodically until the 16th century.

pragmatics In linguistics and philosophy, the study of the use of natu¬ ral language in communication; more generally, the study of the relations between languages and their users. It is sometimes defined in contrast with linguistic semantics, which can be described as the study of the rule sys¬ tems that determine the literal meanings of linguistic expressions. Prag¬ matics is then the study of how both literal and nonliteral aspects of communicated linguistic meaning are determined by principles that refer to the physical or social context (broadly construed) in which language is used. Among these aspects are conversational and conventional “impli- catures” (e.g., “John has three sons” conversationally implicates that John has no more than three sons; “He was poor but honest” conventionally implicates an unspecified contrast between poverty and honesty). Other aspects include metaphor and other tropes and speech acts.

pragmatism Philosophical movement first given systematic expres¬ sion by Charles Sanders Peirce and William James and later taken up and transformed by John Dewey. Pragmatists emphasize the practical function of knowledge as an instrument for adapting to reality and controlling it. Pragmatism agrees with empiricism in its emphasis on the priority of expe¬ rience over A priori reasoning. Whereas truth had traditionally been explained in terms of correspondence with reality or in terms of coher¬ ence (see coherentism), pragmatism holds that truth is to be found in the process of verification. Pragmatists interpret ideas as instruments and plans of action rather than as images of reality; more specifically, they are suggestions and anticipations of possible conduct, hypotheses or forecasts of what will result from a given action, or ways of organizing behaviour. See also W.V.O. Quine; Richard Rorty.

Prague Vprag\ City (pop., 2001 est.: 1,178,576), capital of the Czech Republic. Situated on both sides of the Vltava River, the site was settled as early as the 9th century ad. By the 14th century it was one of Europe’s leading cultural and trade centres. It was the focal point of opposition to the Habsburgs in the early 17th century (see Defenestration of Prague). The treaty ending the Austro-Prussian War was signed there in 1866. It became the capital of an independent Czechoslovakia in 1918. Prague was occupied by Germany during World War II and by the U.S.S.R. and other Warsaw Pact military forces in 1968 (see Prague Spring). In 1989 it was the centre of a movement that led to the peaceful overthrow of the com¬ munist government. Prague is the country’s major economic and cultural centre, famous for its music, literature, and architecture.

Prague, Defenestration of (May 23, 1618) Incident of Bohemian resistance to Habsburg authority. In 1617 Catholic officials in Bohemia closed Protestant chapels in violation of the religious-liberty guarantee of 1609. At an assembly called by the Protestants, the imperial regents were found guilty of violating the guarantee and were thrown from the win¬ dows of the council room of Prague Castle. Though the victims were not seriously hurt, the incident sparked the Bohemian revolt against Emperor Ferdinand II and led to the Thirty Years' War.

Prague Spring (1968) Brief period of liberalization in Czechoslova¬ kia under Alexander Dubcek. In April 1968 he instituted agricultural and industrial reforms, a revised constitution to guarantee civil rights, autonomy for Slovakia, and democratization of the government and the Communist Party. By June, many Czechs were calling for more rapid

© 2006 Encyclopaedia Britannica, Inc.

1540 I Praia ► Pratt

progress toward real democracy. Although Dubcek believed he could con¬ trol the situation, the Soviet Union and the Warsaw Pact countries, alarmed by the threat of a social-democratic Czechoslovakia, invaded the country in August, deposed Dubcek, and gradually restored control by reinstalling hard-line communists as leaders.

Praia Vpri-9\ City (pop., 2000: 94,757), port, and capital of Cape Verde. It is located on the southern shore of Sao Tiago (Santiago) Island, in the Atlantic Ocean, about 400 mi (640 km) off the western African bulge. It ships agricultural products, including bananas, coffee, and sugarcane, and it is a submarine cable station.

prairie Level or rolling grassland, especially that found in central North America. Decreasing amounts of rainfall, from 40 in. (100 cm) at the for¬ ested eastern edge to less than 12 in. (30 cm) at the desertlike western edge, affect the species composition of the prairie grassland. The vegeta¬ tion is composed primarily of perennial grasses, with many species of flowering plants of the pea and composite families. The three main types of prairie are the tallgrass prairie; midgrass, or mixed-grass, prairie; and shortgrass prairie, or shortgrass plains. Coastal prairie, Pacific or Califor¬ nia prairie, Palouse prairie, and desert plains grassland are covered pri¬ marily with combinations of mixed-grass and shortgrass species.

prairie chicken Either of two species of North American grouse (genus Tympanuchus) noted for lek displays (group courtship displays). The greater prairie chicken is about 18 in. (45 cm) long and may weigh almost 2 lbs (1 kg). Its brown plumage is strongly barred below, and it has a short, rounded, dark tail. It occurs locally from Saskatchewan to coastal Texas and Louisiana; northernmost birds are somewhat migratory. The eastern subspecies, the heath hen, is extinct. The lesser prairie chicken, smaller and paler, inhabits the arid western central Great Plains. The sharp-tailed grouse ( Pedioecetes ) is locally called prairie chicken.

prairie dog Any of five species (genus Cynomys) of short-legged, ter¬ restrial squirrels, named for their barklike call. Once abundant through¬ out the plains of the western U.S., part of southern Canada, and northern Mexico, they are now found mostly in isolated or protected areas. They are 12-17 in. (30-43 cm) long, including a 1-5-in. (3-12-cm) tail. Their main diet is grass. Colonies consist of well-defined territories defended by a male, several females, and young. The burrows of the black-tailed prairie dog have carefully tended funnel-shaped entry mounds that pre¬ vent flooding and serve as lookout posts. The white-tailed prairie dog inhabits higher altitudes, hibernates, and is less colonial.

Prairie school Group of architects, including Frank Lloyd Wright, who created low-lying “prairie houses” in the U.S. Midwest c. 1900-17. Prai¬ rie houses were generally built of brick, wood, and plaster, with stucco walls and bands of casement windows. The Prairie architects emphasized horizontal lines by using low roofs with wide, projecting eaves. They dis¬ carded elaborate floor plans and detailing for flowing internal spaces orga¬ nized around a central fireplace or hearth. The resulting low, spreading structures are characterized by light, crossing volumes and spaces; they reach out to nature, not to other buildings. Other architects working in the style included George Grant Elmslie (1871-1952) and Barry Byrne

(1883-1967).

Prajapati \pr9-'ja-p9-te\ Creator figure in the Vedic period of India. In early Vedic literature (see Veda), the name was applied to various primal figures. Later it signified one deity, the “lord of all creatures,” who was said to have produced the universe and all its beings after preparing him¬ self through ascetic practices. Other stories allude to his own creation from the primal waters. His female emanation was Vac, the personifica¬ tion of the sacred word; Usas, the dawn, was identified as his female part¬ ner or his daughter. In the post-Vedic age, Prajapati came to be identified with Brahma.

Prajnaparamita Vpr9g- 1 nya- , par-3-me- l ta\ Body of sutras and their commentaries in Mahayana Buddhism. The main texts, written 100 bce- 150 ce, represent prajna (wisdom) as the supreme perfection and the pri¬ mary avenue to nirvana. The content of this wisdom is the realization that all phenomena are illusory. The name Prajnaparamita also refers to the personification of the literature or of wisdom, often depicted as a woman with her hands in the teaching gesture or holding a lotus and sacred book. See photograph opposite.

prakriti and purusha \'pr3-kri-te...'pu-ru-sh9\ In the Samkhya school of Indian philosophy, material nature and the soul. Prakriti is material nature in its germinal state, eternal and beyond perception. When it comes

into contact with the soul or self (purusha), it starts a process of evolu¬ tion that leads through several stages to the creation of the existing mate¬ rial world. In the Samkhya view, only prakriti is active; the self, trapped in materiality, does nothing but observe and experience. The self escapes from prakriti by recognizing its total difference from and noninvolvement in the material world.

Pramoedya Ananta Toer or Pramudya Ananta Tur

Npra-'mud-ya-a-'nan-ta-'tthA (b. Feb. 20, 1925, Blora, Java, Indon.) Jav¬ anese novelist and short-story writer. While imprisoned by the Dutch (1947-49) for his role in the Indonesian revolt against renewed colonial rule, Pramoedya wrote his first published novel, The Fugitive (1950). After Indonesia gained independence in 1949, he began to produce works written in a rich style that incorporates everyday speech and images from classical Javanese culture. Imprisoned (1965-79) for his role in an attempted communist coup, he wrote a series of four novels — This Earth of Mankind (1980), Child of All Nations (1980), Footsteps (1985), and House of Glass (1988)—that depict Javanese society under Dutch rule. He is the preeminent prose writer of postindependence Indonesia.

Prandtl \'pran-t 3 l\, Ludwig (b. Feb. 4, 1875, Freising, Ger.—d. Aug. 15, 1953, Gottingen, W.Ger.) German physicist, considered the father of aerodynamics. He taught at the University of Gottingen (1904-53). His 1904 discovery of the boundary layer at the surface of a body moving in air or water led to an understanding of skin friction drag and of the way streamlining (see streamline) reduces the drag of airplane wings and other moving bodies. His work on wing theory explained the process of airflow over airplane wings.

prasada Vpro-'sa-dsV In Hinduism, consecrated food offered to the deity and then distributed to worshipers, who consume it as a sign of the god’s favour. Prasada is used both in temple ceremonies, where it may be offered to a god such as Krishna and then distributed by the priests, and at household shrines, where it is offered to the god and then handed out to household members. See also puja.

pratitya-samutpada Xpro-'tet-yo-.ss-mut-'pa-doV In Buddhism, the chain of causation that leads from rebirth to death. Existence is seen as an interrelated flux of transient events that occur in a series, one produc¬ ing another, usually described as a chain of 12 links: (1) ignorance, which leads to (2) faulty perceptions of reality, which provide the structure of (3) knowledge, which addresses (4) name and form, or the principle of individual identity and the sensory perception of an object, experienced through (5) the six domains (the five senses and their object, along with the mind), whose presence leads to (6) contact (between objects and the senses), followed by (7) sensation, which, being pleasant, leads to (8) thirst and then (9) grasping (as of sex partners), which leads to (10) the process of becoming, culminating in (11) birth, and at last (12) old age and death.

Pratt, E(dwin) J(ohn) (b. Feb. 4, 1883, Western Bay, Nfd., Can.—d. April 26, 1964, Toronto, Ont.) Canadian poet. He trained for the ministry

and later taught for many years at the University of Toronto. The early col¬ lection The Titans { 1926) contains his widely read “The Cachalot,” an account of a whale hunt. Brebeufand His Brethren (1940), perhaps his best work, chronicles the martyrdom of Jesuit missionaries. Later collections include Dunkirk (1941), They Are Returning (1945), Behind the Log (1947), and Towards the Last Spike

(1952).

Pratt, Francis Ashbury (b. Feb. 15, 1827, Woodstock, Vt., U.S.—d. Feb. 10, 1902, Hartford, Conn.) U.S. inventor. With Amos Whitney he founded the Pratt & Whitney Co. in Hartford to manufacture machine tools. He was instrumental in bring¬ ing about adoption of a standard sys¬ tem of gauges. He also invented a metal-planing machine (1869), a gear cutter (1884), and a milling machine (1885).

Prajnaparamita, 13th-century stone sculpture from Singosari, East Java; in the Museum Pusat, Jakarta, Indonesia

© 2006 Encyclopaedia Britannica, Inc.

Pratt Institute ► precession I 1541

Pratt Institute Private institution of higher learning in Brooklyn, New York, New York, U.S. It was founded as a trade school in 1887 by the industrialist Charles Pratt (1830-91). It comprises schools of architecture, art and design (for which it is especially renowned), liberal arts and sci¬ ences, professional studies, and information and library science. It has both bachelor’s and master’s degree programs.

pratyaya \pr9t-'ya-y9\ In Buddhism, an auxiliary, indirect cause, as dis¬ tinguished from a direct cause ( hetu ). A seed, for example, is the direct cause of a plant, whereas sunlight, water, and earth are the auxiliary causes. Sometimes pratyaya is used to refer to cause in general. The idea of causation is important in the Buddhist concept of the cycle of death and rebirth (see pratitya-samutpada).

pratyeka-buddha \prot-'ya-k9\ In Buddhism, one who attains enlight¬ enment through his own efforts rather than by listening to the teachings of a buddha. The way of the self-enlightened buddha was retained only in the Theravada tradition. Mahayana Buddhism rejects the path of self¬ enlightenment as too limiting and embraces the ideal of the bodhisattva, who postpones final enlightenment to work for the salvation of others.

Pravda \'prav-da\ Russian "Truth" Former daily newspaper published in Moscow and distributed nationwide, the official organ of the Commu¬ nist Party of the Soviet Union (1918-91). It was founded in St. Peters¬ burg as an underground paper by Vladimir Ilich Lenin and two colleagues in 1912. As a Soviet state newspaper and central source of information and education, it offered well-written articles and analyses on science, economics, cultural topics, and literature as well as materials to indoctri¬ nate and inform readers on communist theory and programs. Topics con¬ cerning international relations were largely left to the government paper Izvestiya. After communist power ended in 1991, most of its readership evaporated; it became the voice of the conservative-nationalist opposition and ceased publication in 1996.

Praxiteles \prak-'si-t 3 l-,ez\ (fl. c. 370-330 bc, Greece) Greek sculptor. His only known surviving work, the marble Hermes Carrying the Infant Dionysus, displays delicate modeling and exquisite surface finish. A few other works survive in Roman copies. His most celebrated work was the Aphrodite of Cnidus, which Pliny the Elder considered the best statue in the world. Through Praxiteles’ influence, figures were increasingly shown standing in graceful, sinuous poses, leaning lightly on some support, a pose further developed by sculptors of the Hellenistic Age. Greatest and most original of the 4th-century Attic sculptors, he profoundly influenced the later course of Greek sculpture.

Prayag Raj See Allahabad

prayer Silent or spoken petition made to God or a god. Prayer has been practiced in all religions throughout history. Its characteristic postures (bowing the head, kneeling, prostration) and position of the hands (raised, outstretched, clasped) signify an attitude of submission and devotion. Prayer may involve con¬ fessions of sin, requests, thanks, praise, offerings of sacrifice, or prom¬ ises of future acts of devotion. In addition to spontaneous private prayer, most religions have fixed for¬ mulas of prayer (e.g., the Lord's Prayer), often recited in group wor¬ ship. The four prophetic religions (Judaism, Christianity, Islam, and Zoroastrianism) prescribe a daily set form of individual prayer, such as the Shema, to be recited twice a day by every male Jew, and the Islamic salat, performed five times a day.

prayer wheel In Tibetan Buddhism, a mechanical device used as an equivalent to the recitation of a man¬ tra. The prayer wheel consists of a

hollow metal cylinder, often beautifully embossed, mounted on a rod and containing a consecrated paper bearing a mantra. Each turn of the wheel by hand is considered equivalent to orally reciting the prayer. Variants to the handheld prayer wheel are large cylinders that can be set in motion by hand or attached to windmills or waterwheels and thus kept in con¬ tinuous motion.

praying mantis See mantis

Pre-Raphaelites X.pre-'ra-fe-a-JItsN Group of young British painters, led by Dante Gabriel Rossetti, William Holman Hunt, and John Everett Mill¬ ais, who banded together in 1848 in reaction against what they considered the unimaginative and artificial historical painting of the 18th and early 19th centuries, seeking to express a new moral seriousness and sincerity in their works. Their name, the Pre-Raphaelite Brotherhood, honoured the simple depiction of nature in Italian art before Raphael; the symbolism, imagery, and mannered style of their paintings often suggest a faux- medieval world. Later members included Edward Burne-Jones and George Frederic Watts (1817-1904). The group also functioned as a school of writers who often used medieval settings, sometimes with shocking effect, as in William Morris’s The Defence ofGuenevere (1858), which deals with issues of love and sex. Though active less than 10 years, the group had a profound influence on the arts.

pre-Socratics Earliest Greek philosophers (those who preceded Socrates) whose attention to questions about the origin and nature of the physical world has led to their being called cosmologists or naturalists. Among the most significant were the Milesians Thales, Anaximander, and Anaximenes, Xenophanes of Colophon, Parmenides, Heracleitus of Ephesus, Empedocles, Anaxagoras, Democritus, Zeno of Elea, and Pythagoras.

Preakness Stakes One of the three classic U.S. horse races making up the Triple Crown. It is held annually in mid-May at Baltimore’s Pim¬ lico Race Course. The course distance is l 3 /i6 mi (1.9 km). The field is limited to 3-year-old Thoroughbreds.

Prebisch Vpra-bishV Raul (b. April 17, 1901, Tucuman, Arg.—d. April 29, 1986, Las Vertientes, near Santiago, Chile) Argentine economist and statesman. Serving in various positions in Argentine government and aca¬ demia, he advised developing countries to stimulate domestic manufac¬ turing to reduce their reliance on imports and thus their dependence on the industrialized nations. He also advocated the economic integration of Latin America to achieve economies of scale and land reform to reduce the income inequalities that impeded the growth of the domestic market. As the influential head of the UN’s Economic Commission for Latin America, he addressed inequities in the trade relationships between wealthy and poor nations.

Precambrian time Interval of geologic time from c. 3.8 billion years ago, the age of the oldest known rocks, to 544 million years ago, the beginning of the Cambrian Period. This interval represents more than 80% of the geologic record and thus provides important evidence of how the continents evolved. The Precambrian is divided into the Archean and Proterozoic eons, with the boundary between them at 2.5 billion years ago. It was originally defined as the era that predated the emergence of life in the Cambrian Period. It is now known, however, that life on Earth had begun by the early Archean. Soft-bodied organisms without skeletons began to appear toward the end of the Precambrian.

precast concrete Concrete cast into structural members under factory conditions and then brought to the building site. A 20th-century develop¬ ment, precasting increases the strength and finish durability of the mem¬ ber and decreases time and construction costs. Concrete cures slowly; the design strength is usually reached 28 days after initial setting. Using pre¬ cast concrete eliminates the lag between the time on-site concrete is placed and the time it can carry loads. Precast concrete components include slabs, beams, columns, walls, stairways, modular boxes, and even kitchens and bathrooms with precast fixtures. See also prefabrication.

precession Phenomenon associated with the action of a gyroscope or a spinning top and consisting of a comparatively slow rotation of the axis of rotation of a spinning body about a line intersecting the spin axis. It arises as a result of external torque acting on the body. One example of precession is the smooth, slow circling of a spinning top (the uneven wobbling is called nutation). Precession of the earth’s axis of rotation is the reason that the positions of celestial bodies appear to drift systemati¬ cally with the passage of time. See also precession of the equinoxes.

Tibetan prayer wheel, gilt silver, 18th— 19th century; in the Seattle (Washing¬ ton) Art Museum.

COURTESY OF THE SEATTLE ART MUSEUM, WASHINGTON, EUGENE FULLER MEMORIAL COLLECTION

© 2006 Encyclopaedia Britannica, Inc.

1542 I precipitation ► prelude

precipitation All liquid and solid water particles that fall from clouds and reach the ground, including drizzle, rain, snow, ice crystals, and hail. The essential difference between a precipitation particle and a cloud par¬ ticle is size; an average raindrop has a mass equivalent to that of about one million cloud droplets. Precipitation elements (ice crystals or drop¬ lets that form around soluble particles such as salt) form directly from the vapour state and get larger through collision and coalescence. Eventually they become large enough to respond to gravity, and they fall to the ground.

Precisionism Smooth, precise technique used primarily in the 1920s by several U.S. painters in representational canvases depicting sharply defined forms, such as urban skylines; the industrial landscape of facto¬ ries and smokestacks, buildings, and machinery; and country landscapes with grain elevators and barns or empty desert and sky. The scenes are always devoid of people or signs of human activity. Precisionism is a “cool” art, which keeps the viewer at a distance. It had its origins in Cub¬ ism, Futurism, and Orphism; in turn it influenced Pop art. Though it was not a school or movement with a formal program, the Precisionist artists, including Charles Demuth and Georgia O'Keeffe, often exhibited together.

predation Form of food getting in which one animal, the predator, eats an animal of another species, the prey, immediately after killing it or, in some cases, while it is still alive. Most predators are generalists; they eat a variety of prey species. Specialist predators, such as anteaters, eat only one or a few prey species. Cannibalism is a type of predation in which an animal eats another of its own species. Seed consumption is also con¬ sidered predation because the entire living embryo of a plant is destroyed.

predestination In Christianity, the doctrine that God has long ago determined who will be saved and who will be damned. Three types of predestination doctrine have developed. One doctrine holds that God singled out the saved because he foresaw their future merits. A second doctrine (often identified with John Calvin) states that from eternity God has determined the saved and the damned, regardless of their merit or lack thereof. A third doctrine, set forth by Thomas Aquinas and Martin Luther, ascribes salvation to the unmerited grace of God but links the lack of grace to sin. In Islam, issues of predestination and free will were argued extensively. The Mutazila held that God would be unjust if he predestined all human actions; the Ashariya advocated a strict predestination that became the mainstream Islamic view.

predicate calculus Part of modern symbolic logic which systemati¬ cally exhibits the logical relations between propositions involving quan¬ tifiers such as “all” and “some.” The predicate calculus usually builds on some form of the propositional calculus and introduces quantifiers, indi¬ vidual variables, and predicate letters. A sentence of the form “All F’s are either G’s or H’s” is symbolically rendered as (Vx)[Fx z> (Gx v Hx)J, and “Some F’s are both G’s and H’s” is symbolically rendered as (3x)[Fx a (Gx a Hx)]. Once conditions of truth and falsity for the basic types of propositions have been determined, the propositions formulable within the calculus are grouped into three mutually exclusive classes: (1) those that are true on every possible specification of the meaning of their predicate signs, such as “Everything is F or is not F”; (2) those false on every such specification, such as “Something is F and not F”; and (3) those true on some specifications and false on others, such as “Something is F and is G.” These are called, respectively, the valid, inconsistent, and contingent propositions. Certain valid proposition types may be selected as axioms or as the basis for rules of inference. There exist multiple complete axi- omatizations of first-order (or lower) predicate calculus (“first-order” meaning that quantifiers bind individual variables but not variables rang¬ ing over predicates of individuals). See also logic.

preeclampsia V.pre-i-'klamp-se-oV and eclampsia Hypertensive conditions unique to pregnancy. Preeclampsia is marked by hypertension, protein in the urine, and hand and face edema, which develop late in preg¬ nancy or soon after. Persistent hypertension compromises the fetus’s blood supply and damages the mother’s kidneys. Monitoring of blood pressure and weight gain may detect it before symptoms (headaches, visual disturbances, stomach pain) begin. Eclampsia follows in about 5% of cases, with convulsions that pose a serious threat to mother and child. It can usually be prevented by special diets, drugs, and limited activity or early delivery.

preemption \pre-'emp-sh3n\ U.S. policy that allowed the first settlers, or squatters, on public land to buy the land they had improved. Since improved land, coveted by speculators, was often priced too high for

squatters to buy at auction, temporary preemptive laws allowed them to acquire it without bidding. The Pre-Emption Act (1841) gave squatters the right to buy 160 acres at $1.25 per acre before the land was auctioned. The Homestead Act (1862) made preemption an accepted part of U.S. land policy. See also Homestead Movement.

prefabrication Assembly of standardized building components at a location other than the building site. Units may include doors, stairs, win¬ dow walls, wall panels, floor panels, roof trusses, room-sized components, and even entire buildings. Prefabrication requires the cooperation of archi¬ tects, suppliers, and builders regarding the size of basic modular units. In the U.S. building industry, the 4-by-8-ft (1.2-by-2.4-m) panel is a stan¬ dard unit; the architect’s drafted building plans and the supplier’s pre¬ fabricated wall units are based on multiples of that module. Advantages of prefabrication include the cost savings of mass production, the oppor¬ tunity to use specialized equipment to produce components, and stan¬ dardization of parts for quick assembly and erection. The major drawback is in assigning responsibility for quality control. See also precast concrete.

prefect In ancient Rome, any of various high officials with primarily judicial and administrative responsibilities. In the early republic, a prefect of the city (praefectus urbi ) took over the consul’s duties during their absence from Rome. The office lost some importance after the introduc¬ tion of praetors (mid 4th century bc). Augustus revitalized the office when he appointed five prefects to supervise the city government, the fire bri¬ gade, the grain supply, and the Praetorian Guard. The praetorian prefects acquired great power and often became virtual prime ministers.

pregnancy Process of human gestation that takes place in the female’s body as a fetus develops, from fertilization to birth (see parturition). It begins when a viable sperm from the male and egg from the ovary merge in the fallopian tube (see fertility; fertilization). The fertilized egg (zygote) grows by cell division as it moves toward the uterus, where it implants in the lining and grows into an embryo and then a fetus. A placenta and umbilical cord develop for nutrient and waste exchange between the cir¬ culations of mother and fetus. A protective fluid-filled amniotic sac encloses and cushions the fetus. Early in pregnancy, higher estrogen and progesterone levels halt menstruation, cause nausea, often with vomiting (morning sickness), and enlarge the breasts and prepare them for lacta¬ tion. As the fetus grows, so does the uterus, displacing other organs. Nor¬ mal weight gain in pregnancy is 20-25 lbs (9-11.5 kg). The fetus’s nutritional needs require the mother to take in more calories and espe¬ cially protein, water, calcium, and iron. Folic-acid supplements are rec¬ ommended during early pregnancy to prevent neural tube defects. Smoking, alcohol, and many legal and illegal drugs can cause congenital disorders and should be avoided during pregnancy. Ultrasound imaging is often used to monitor structural and functional progress of the growing fetus. The due date is estimated as 280 days from the time of last menstruation; 90% of babies are born within two weeks of the estimated date. See also amniocentesis; preeciampsia and eclampsia; premature birth. See illustration on opposite page.

prehistoric religion Religious practices and beliefs of prehistoric peoples, as inferred from archaeological findings. The oldest burials that attest to a belief in life after death date from 50,000-30,000 bc. Corpses were buried with goods such as stone tools and parts of animals, sug¬ gesting an attempt to placate the dead or equip them for the next world. The Middle Paleolithic Period provides the first evidence of animal sacri¬ fices, which may have been offerings to the dead, to a higher power, or to the fertility of the animal species. Prehistoric human sacrifices have also been found, usually of women and children. From the Bronze Age on, weapons and jewelry were often thrown into springs, wells, and other bodies of water as sacrifices (probably of war booty). Animals such as bears were important in prehistoric religion from the Upper Paleolithic Period on, probably seen as guardian spirits and associated with magical powers. Fertility rites were also practiced, as evidenced by small, corpu¬ lent female figures, known as Venus statuettes, with highly emphasized breasts and buttocks.

prelude Musical composition, usually brief, generally played as an introduction to another piece. The prelude originated as short pieces that were improvised by an organist to establish the key of a following piece or to fill brief interludes in a church service. Their improvisatory origins were often reflected in rhythmic freedom and virtuosic runs. A section in this style would often lead to a closing fugal section; in time this turned into a separate movement, and preludes came to be paired with fugues.

© 2006 Encyclopaedia Britannica, Inc.

premature birth ► prerogative court I 1543

chorionic villi

decidua

basalis

placenta

intervillus space

umbilical

arteries

umbilical cord

chorion amnion

uterus

amniotic cavity

mucus plug

Full-term fetus in the uterus. The amnion, formed from the inner embryonic mem¬ brane, encloses the fetus. The space between the amnion and fetus (amniotic cavity) is filled with the watery amniotic fluid. The outermost embryonic membrane, the chorion, has developed fingerlike projections (villi) on its outer surface, which have enlarged and penetrated the decidua basalis layer of the uterus. The chorionic villi and the decidua basalis form the placenta. Maternal blood fills the spaces around the villi (intervillous spaces); oxygen and nutrients diffuse into the villi and pass on to the fetus via the umbilical vein. Waste materials that leave the fetus via the umbilical arteries diffuse out of the villi into the mother's blood.

© MERRIAM-WEBSTER INC.

In the 17th century, preludes began to be frequently written for lute or harpsichord. In later years the term came to be used for short piano pieces, often in sets, by composers such as Frederic Chopin, Aleksandr Scriabin, and Claude Debussy.

premature birth Birth less than 37 weeks after conception. Infants bom as early as 23-24 weeks may survive but many face lifelong dis¬ abilities (e.g., cerebral palsy, blindness, deafness). Premature infants account for 8-9% of live births but two-thirds of infant deaths. 40-50% of cases have no explanation; other cases can be attributed to such causes as maternal hypertension or diabetes, multiple pregnancy, or placental separation. With good care, about 85% of live-born premature infants should survive. Infants born very early (before 32-34 weeks) lack fully developed lungs and often develop respiratory distress syndrome. They also have problems maintaining body temperature and fighting infection. Most deaths result from breathing problems, infections, and brain or lung hem¬ orrhages. Premature infants are characterized by low birth weight, small size, irregular breathing, absence of subcutaneous fat, and thin skin.

premenstrual syndrome (PMS) Variable group of symptoms occurring before menstruation in 40% of women, severe in about 10% of those. Physical symptoms may include headache, cramps, bloating, and constipation or diarrhea. Emotional symptoms range from irritability, leth¬ argy, and mood swings to hostility, confusion, and depression. Theories as to the cause centre on hormones, nutrition, and stress (known to affect severity). Depending on the symptoms, treatment may involve exercise, stress management, nutritional therapy, or drugs. Dietary measures include low sodium and high protein and complex carbohydrate intake and avoid¬ ance of xanthines (including caffeine). Increasing calcium intake has been shown to prevent or reduce cramps, which are best treated with ibuprofen.

premier See prime minister

Preminger Vpre-min-joiA, Otto (Ludwig) (b. Dec. 5, 1906, Vienna, Austria—d. April 23, 1986, New York, N.Y., U.S.) Austrian-bom U.S. film director. While studying law in his native Vienna, he worked with Max Reinhardt’s theatre and soon became its director. In 1935 he went to the U.S. to direct Libel on Broadway. Invited to Hollywood, he made the suc¬ cessful thriller Laura (1944), which helped establish film noir. Forming his own production company, he defied Hollywood’s Production Code with a series of controversial films and brought about the relaxation of censorship regulations. His landmark films include The Moon Is Blue (1953); the all-African American Carmen Jones (1954); and The Man with the Golden Arm (1955), a tale of drug addiction. His later films include Anatomy of a Murder (1959), Exodus (1960), The Cardinal (1963), and Hurry Sundown (1967). He also worked as a character actor, most nota¬ bly in Billy Wilder’s Stalag 17 (1953).

Prendergast, Maurice (Brazil) (b. Oct. 10, 1859, St. John’s, Nfd., Can.—d. Feb. 1, 1924, New York, N.Y., U.S.) Canadian-born U.S. painter. He moved with his family to Boston in 1868. After study in Paris (1891- 94), he spent much of his career traveling and painting abroad. He was the first U.S. artist to fully absorb French Impressionism and Post- Impressionism. His lively street scenes feature floating geometric areas of brilliant decorative colour with a mosaiclike effect. He produced his most outstanding works in watercolour. In his later years he lived in New York City and exhibited with The Eight and in the 1913 Armory Show.

Prensa Ypren-sa\, La Spanish "The Press" Argentine daily newspa¬ per, widely regarded as the finest Spanish-language newspaper in the world. Founded in Buenos Aires in 1869, it soon broke with the tradi¬ tional emphasis on propaganda to stress professional, accurate news reporting and independence in editorial opinion. It displayed a concern for human welfare that persisted in the face of government harassment, notably in the 1940s under the regime of Juan Peron. In 1951 it was seized and became a Peronist propaganda organ; after Peron’s overthrow, it reap¬ peared as an independent daily in 1956.

Preobrajenska, Olga orig. Olga Yosifovna Preobrazhen¬ skaya (b. Feb. 2, 1871, St. Petersburg, Russia—d. Dec. 27, 1962, Saint- Mande, Fr.) Russian ballerina and teacher. She joined the Mariinsky Ballet (see Mariinsky Theatre) in 1889 and earned the title of prima ballerina in 1900. Her lyrical creativity and love of improvisation were praised by audiences and critics. She also taught at the Imperial Theatre School (1901-02 and 1914-21, during which time the school was renamed the Petrograd State Ballet School). As an instructor, she helped to form the next generation of Russian dancers. In 1922 she emigrated from Russia and taught at her own ballet school in Paris (1923-60).

preparatory school School that prepares students for entrance to a higher school. In Europe, where secondary education has been selective, preparatory schools have been those that catered to pupils wishing to enter the academic secondary schools. In North America, where access to sec¬ ondary education has been less competitive, the term usually refers to pri¬ vate secondary schools that prepare students for college.

Preparedness Movement Pre-World War I campaign to increase U.S. military capabilities and convince the public of the need for U.S. involvement in a future European conflict. Leaders such as Theodore Roosevelt and Gen. Leonard Wood sought to persuade Pres. Woodrow Wilson to strengthen U.S. national defenses, and various organizations sponsored preparedness parades to build public awareness and support. The campaign resulted in passage of the National Defense Act (1916); the U.S. entered World War I the following year.

prerogative court \pri-‘ra-g9-tiv\ In English law, a court through which the powers, privileges, and immunities reserved to the sovereign

© 2006 Encyclopaedia Britannica, Inc.

1544 I Presbyterianism ► pressure gauge

were exercised. Such courts were originally formed during the period when the sovereign’s power was greater than the Parliament’s. The Star Chamber, the High Commission, and the Court of Chancery all achieved importance in the 16th century. By the 17th century they were being chal¬ lenged by the common law courts and competing political interests, and they were soon put out of business. See also Privy Council.

Presbyterianism Form of church government based on rule by elders, or presbyters. The presbyters who govern the church are grouped in a hierarchy of courts, the highest of which is the general assembly. They are elected by the members of the congregation for fixed terms, in a sys¬ tem intended to affirm the equality of all Christians. The term Presbyte¬ rianism also refers to a denomination, the Presbyterian Church. The modern Presbyterian churches trace their origins to the Calvinist churches of the British Isles; in continental Europe such congregations were known as Reformed churches. The Presbyterian Church is strongest in Scotland, where it was founded by John Knox in 1557, but it is also well established in England, Wales, and the U.S. See also Calvinism.

preschool education Childhood education during the period from infancy to age five or six. Institutions for preschool education vary widely around the world, as do their names (e.g., infant school, day care, mater¬ nal school, nursery school, creche, kindergarten). The first systematic theory of early childhood pedagogy was propounded by Friedrich Froebel, the founder of the kindergarten. Other influential theorists include Maria Montessori and Jean Piaget. Of major concern in preschool education is language development; teachers often conduct listening and language games. See also elementary education.

Prescott, Edward C. (b. Dec. 26, 1940, Glens Falls, N.Y., U.S.) U.S. economist. Prescott studied at Swarthmore College (B.A., 1962), Case Western Reserve University (M.S., 1963), and Carnegie Mellon Univer¬ sity (Ph.D., 1967), where he later taught and advised Finn E. Kydland on his doctorate. Working with Kydland, he demonstrated how a declared commitment to a low inflation rate by policy makers might create expec¬ tations of low inflation and unemployment rates. The two men also estab¬ lished the microeconomic foundation for business cycle analyses, demonstrating that technology changes or supply shocks, such as oil price hikes, could be reflected in investment and relative price movements and thereby create short-term fluctuations around the long-term economic growth path. In 2004 Prescott shared the Nobel Prize for Economics with Kydland.

Prescott, William H(ickling) (b. May 4, 1796, Salem, Mass., U.S.—d. Jan. 28, 1859, Boston, Mass.) U.S. historian. Bom to a prosper¬ ous family, Prescott graduated from Harvard University in 1814 but was prevented by poor health and eyesight from a career in law or business. His friends, including Washington Irving, led him to his life’s work: recounting the history of 16th-century Spain and its colonies. He is best known for his History of the Conquest of Mexico (1843) and History of the Conquest of Peru (1847), for which he made rigorous use of original sources, and which earned him a reputation as the first scientific U.S. his¬ torian.

prescription In property law, the effect of the lapse of time in creating and destroying rights. Acquisitive prescription allows an individual, after unequivocal possession for a specific period, to acquire an interest in real property, such as an easement, but not the property itself. See also adverse possession.

prescriptivism In metaethics, the view that moral judgments are pre¬ scriptions and therefore have the logical form of imperatives. Prescrip¬ tivism was first advocated by Richard M. Hare (born 1919) in The Language of Morals (1952). Hare argued that it is impossible to derive any prescription from a set of descriptive sentences, but tried neverthe¬ less to provide a foothold for moral reasoning in the constraint that moral judgments must be “universalizable”: that is, that if one judges a particu¬ lar action to be wrong, one must also judge any relevantly similar action to be wrong. Universalizability is not a substantive moral principle but a logical feature of the moral terms: anyone who uses such terms as “right” and “ought” is logically committed to universalizability.

preservation, food See food preservation

preservative Any of numerous chemical additives used to prevent or slow food spoilage caused by chemical changes (e.g., oxidation, mold growth) and maintain a fresh appearance and consistency. Antimycotics (e.g., sodium and calcium propionate, sorbic acid) inhibit mold growth;

antioxidants (e.g., butylated hydroxytoluene or BHT) delay rancidity in foods containing fats and oils; antibiotics (e.g., tetracyclines) prevent bac¬ terial growth; humectants retain moisture in products like shredded coco¬ nut; and antistaling agents (e.g., glyceryl monostearate) maintain moisture and softness in baked goods. Some preservatives also improve the appear¬ ance of the product (e.g., sodium nitrate and nitrite in meats).

president In government, the officer who serves as head of state and sometimes also as chief executive. In countries where the president is chief of state but not of government, the role is largely ceremonial, with few or no political powers. Presidents may be elected directly or indi¬ rectly, for a limited or unlimited number of terms. In the U.S., the presi¬ dent’s chief duty is to ensure that the laws are faithfully executed, which he does through various executive agencies and with the aid of his cabi¬ net. He also serves as commander in chief of the armed forces, nominates judges to the Supreme Court, and makes treaties with foreign governments (contingent on Senate approval). The office of president is used in gov¬ ernments in South and Central America, Africa, and elsewhere. In west¬ ern Europe executive power is generally vested in a prime minister and his cabinet, and the president, where the office exists, has few responsibili¬ ties (though France is a significant exception).

Presley, Elvis (Aaron) (b. Jan. 8, 1935, Tupelo, Miss., U.S.—d. Aug. 16, 1977, Memphis, Tenn.) U.S. popular singer, the “King of Rock and Roll.” Presley was raised in Memphis, where he sang Pentecostal church music and listened to black bluesmen and Grand Ole Opry broadcasts. In 1954 he began to record for the producer Sam Phillips, who had been searching for a white singer who sounded like a black man. In 1956, under his new manager, “Colonel” Tom Parker, he released “Heartbreak Hotel,” the first of numerous million-selling hits that included “Hound Dog” and “All Shook Up.” In the same year, he appeared in Love Me Tender , the first of 33 mediocre films, and on several TV shows, notably the Ed Sul¬ livan Show. Presley’s intensely charismatic style—including his sexy hip shaking, ducktail haircut, and characteristic sneer—excited young fans, especially females, to wild adulation. After a stint in the army (1958-60) he resumed recording and acting, but his earlier raucous style was mod¬ erated. In 1968 he introduced a Las Vegas-based touring act with orches¬ tra and gospel-type choir. Battling public pressures, weight gain, and drug dependence, he underwent a personal decline. His death at age 42, attrib¬ uted to natural causes, was mourned by hundreds of thousands of fans at Graceland, his Memphis estate, which remains a place of international pilgrimage.

Prespa, Lake Lake on the boundary between Macedonia, Albania, and Greece. It is 14 mi (23 km) long, 8 mi (13 km) wide, 2,800 ft (853 m) above sea level, and it drains northwest into Lake Ohrid through a sub¬ terranean channel. South of it is Little Prespa Lake, which contains the island of St. Achilius; the island was an early capital of Bulgarian Tsar Samuel in the 10th century. It became a tourist and fishing centre in the 1970s.

Pressburg See Bratislava

Pressburg, Treaty of (Dec. 26, 1805) Agreement signed by Austria and France at Pressburg (now Bratislava, Slvk.) after Napoleon’s victo¬ ries at the Battles of Ulm and Austerutz. Austria gave up Venetia to Napo¬ leon’s kingdom of Italy and the Tirol and Vorarlberg to Bavaria. Austria agreed to admit the electors of Bavaria and Wurttemberg, allied with Napoleon, to the rank of kings, which further reduced Austrian influence in Germany. Austria’s influence was also excluded from Italy. The treaty enabled Napoleon to create a ring of French client states beyond France.

pressure Perpendicular force per unit area, or stress at a point within a confined fluid. A solid object exerts pressure on a floor equal to its weight divided by the area of contact. The weight of the Earth’s atmosphere on the surface constitutes atmospheric pressure, which varies from place to place but always decreases with altitude. The pressure exerted by a con¬ fined gas results from the average effect of the forces produced on the walls of the container by the continual, numerous collisions by gas mol¬ ecules. Hydrostatic pressure is the stress, or pressure, exerted equally in all directions at points within a confined fluid. Lithostatic pressure is the stress exerted on a body of rock in the Earth’s crust by surrounding rock, which increases with depth below the surface. The SI unit of pressure is the pascal (Pa), which is equal to one newton of force per square metre.

pressure gauge Instrument for measuring the condition of a fluid (liquid or gas) that is specified by the force the fluid would apply, when

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PresterJohn ► price I 1545

at rest, to a unit area, such as pounds per square inch (psi) or pascals (Pa). The reading on the gauge, called the gauge pressure, is always the dif¬ ference between two pressures. When the lower of the pressures is that of the atmosphere, the total (or absolute) pressure is the sum of the gauge and atmospheric pressures.

Prester John Legendary Christian ruler of the East. He was believed to be a Nestorian and a king-priest (prester being short for presbyter, “elder” or “priest”) reigning in an unspecified part of the Far East. The legend arose during the Crusades in the 12th century, among European Christians who hoped that Prester John would prove an ally in the effort to regain the Holy Land from the Saracens. In the 13th—14th century vari¬ ous missionaries and travelers, including Marco Polo, searched for his kingdom in Asia. After the mid-14th century, Ethiopia was the centre of the quest, as Prester John became identified with the emperor of that Afri¬ can Christian nation.

Prestes \'pras-tas\, Luis Carlos (b. Jan. 3, 1898, Porto Alegre, Rio Grande do Sul, Braz.—d. March 7, 1990, Rio de Janeiro) Brazilian revo¬ lutionary. Beginning in 1924, he led a rebel force on a three-year trek through Brazil’s interior in an effort to spark a rebellion in the country¬ side. Although the effort failed, he became a romantic hero. He went on to lead the Brazilian Communist Party, which advocated ending payments on the national debt, nationalization of foreign-owned companies, and land reform. Imprisoned after a violent uprising in 1935, he was released after World War II and later served briefly as a senator.

Preston City and borough (pop., 2001: 129,642), county seat of Lan¬ cashire, England. On the River Ribble, Preston grew near the site of a Roman fort and received its first charter in 1179. As a market centre, it became known for its wool and linen weaving and its cotton mills. It was the site of the Lancashire Royalist headquarters during the English Civil Wars. The Royalists were defeated there by Oliver Cromwell in 1648. Despite the decline of the cotton textile industry, the economy has remained strong through diversification, and it produces aircraft and motor vehicles.

prestressed concrete Concrete reinforced by either pretensioning or posttensioning, allowing it to carry a greater load or span a greater dis¬ tance than ordinary reinforced concrete. In pretensioning, lengths of steel wire or cables are laid in the empty mold and stretched. The concrete is placed and allowed to set, and the cables are released, placing the con¬ crete into compression as the steel shrinks back to its original length. In posttensioning, the steel in the concrete is stretched after the curing pro¬ cess. Prestressing places a concrete member in compression; these com¬ pressive stresses counteract the tensile bending stresses of an applied load. The process was developed by the French engineer Eugene Fressinet in the early 20th century.

Pretoria \pri-'tor-e-9\ City (pop., 2005 est.: metro, area, 1,282,000), administrative capital of the Republic of South Africa. Founded in 1855, it became the capital of the Transvaal in 1860, the administrative capital of South Africa in 1910, and a city in 1931. In 1899, during the South African War (1899-1902), Winston Churchill was imprisoned there until his escape. Pretoria is primarily a seat of government, and most people are employed in the service sector. It is also an important rail centre, with an industrial economy based on iron and steel. Its educational institutions include the University of South Africa (1873) and the University of Pre¬ toria (1908). Pretoria became part of the Tshwane Metropolitan Munici¬ pality in 2000. See also Bloemfontein; Cape Town.

Pretorius Xpro-'tii-re-iBsV Andries (Wilhelmus Jacobus) (b. Nov. 27, 1798, near Graaff-Reinet, Cape Colony—d. July 23, 1853, Magalies- berg, Transvaal) Boer leader in the Great Trek. Pretorius’ s forces defeated the Zulu at Blood River in 1838 and at Magono in 1840. In 1842 he led an unsuccessful fight with the British over the annexation of Natal. Fol¬ lowing British annexation of Transvaal in 1848, his forces again attacked and were again defeated. In 1852 he participated in the Sand River Con¬ vention, where Transvaal independence was recognized. He led negotia¬ tions for independence of the Orange River Sovereignty, finally guaranteed by the Bloemfontein Convention of 1854. His son Marthinus Wessel Pretorius (1819-1901) was the first president of the South Afri¬ can Republic (1857, 1864, 1869) and president of the Orange Free State (1859-63). After British annexation of the Transvaal, Marthinus joined insurgent Boer leaders and helped win recognition of its independence. He was a member of the ruling triumvirate until the election of Paul Kruger as president in 1883.

preventive medicine Efforts toward disease prevention in the com¬ munity and the individual. It covers patient interviews and testing to detect risk factors; sanitary measures in homes, communities, and medical facili¬ ties; patient education; and diet and exercise programs as well as preven¬ tive drugs and surgery. It has three levels: primary (e.g., prevention of coronary heart disease in a healthy person), secondary (e.g., prevention of heart attack in a person with heart disease), and tertiary (e.g., preven¬ tion of disability and death after a heart attack). The first is by far the most economical. Important advances in preventive medicine include vac¬ cination (see vaccine), antibiotics, diagnostic imaging, and recognition of psychological factors. See also epidemiology, immunology, industrial medi¬ cine, QUARANTINE.

Prevert \pra-'ver\, Jacques (-Henri-Marie) (b. Feb. 4, 1900, Neuilly-sur-Seine, France—d. April 11, 1977, Omonville-la-Petite) French poet and screenwriter. A shop worker, he began writing after his military service. Influenced by the Symbolist movement, he renewed the ancient tradition of oral poetry, creating “song poems” about Paris street life, collected in the anthology Words (1945). Many were put to music and became extremely popular. His excellent screenplays for Marcel Carne include The Children of Paradise (1945), Spectacle (1951), and Things and Other Things (1972). He also worked for French television and on animated films for children.

Previn \'pre-vin\, Andre (George) orig. Andreas Ludwig Pri-

win (b. April 6, 1929, Berlin, Ger.) German-born U.S. pianist, composer, and conductor. He fled Nazi persecution with his family and moved to Los Angeles in 1939. He orchestrated and arranged music for MGM in the 1940s and ’50s and thereafter scored films for several studios. Mean¬ while he had become a noted classical and jazz pianist and started con¬ ducting. He served as principal conductor of the Houston Symphony, London Symphony, Pittsburgh Symphony, Los Angeles Philharmonic, and Royal Philharmonic orchestras. He also composed a symphony, con¬ certos, and the opera A Streetcar Named Desire (1998), as well as popu¬ lar songs. He was knighted in 1996.

Prevost d'Exiles \pra-,vo-dag-'zel\, Antoine-Francois, Abbe

known as Abbe Prevost (b. April 1, 1697, Hesdin, France—d. Nov. 25, 1763, Chantilly) French novelist. From an early age Prevost alternated between enlistments in the army and entries into the religious life, which he eventually fled in 1728. Subsequent years were marked by numerous love affairs and debt. His fame rests entirely on one work— Manon Les- caut (1731), a sentimental novel about a young man of good family who ruins his life for a courtesan, which became the basis of two famous operas, Jules Massenet’s Manon and Giacomo Puccini’s Manon Lescaut.

PRI See Institutional Revolutionary Party

Priam \'pri-3m\ In Greek mythology, the last king of Troy. He succeeded his father Laomedon as king and gradually expanded Troy’s control over the Hellespont. By his wife, Hecuba, he had many children, including Hector and Paris. He reigned during the Trojan War; in its final year he lost 13 sons, three of whom were killed by Achilles in a single day. Hec¬ tor’s death broke his spirit, and he went humbly to Achilles to ask for the corpse. When Troy fell, Achilles’ son Neoptolemus killed the elderly Priam on an altar.

Priapus \pri-'a-p3s\ Greek god of animal and vegetable fertility. He was represented in a caricature of the human form, grotesquely misshapen, with an enormous phallus. The ass was sacrificed in his honor, probably because it symbolized lecherousness and was associated with the god’s sexual potency. His father was Dionysus and his mother was either a local nymph or Aphrodite. In Hellenistic times the worship of Priapus spread throughout the ancient world, and he was adopted as the god of gardens.

Pribilof Vpri-bo-.lofN Islands Group of islands, southeastern Bering Sea, Alaska, U.S. It includes St. Paul, St. George, and three islets, and it lies about 300 mi (500 km) west of the mainland. Control of the islands was transferred from Russia to the U.S. with the Alaska Purchase (1867). The islands are hilly and treeless with no harbours. They are breeding grounds from April to November for most of the world’s fur seals. Commercial harvesting of seals was discontinued in 1986. The islands are also home to enormous numbers of birds and both blue and white phases of Arctic foxes. The indigenous population is made up of Aleuts.

price Amount of money that has to be paid to acquire a given good, ser¬ vice, or resource. Operating as a measure of value, prices perform a sig¬ nificant economic function, distributing the scarce supply of goods.

© 2006 Encyclopaedia Britannica, Inc.

1546 I Price ► Priestley

services, and resources to those who most want them through the adjust¬ ments of supply and demand. Prices of resources are called wages, interest, and rent. This system, known as the price mechanism, is based on the principle that only by allowing prices to move freely will the supply of any given commodity match demand. If supply is excessive, prices will be low and production will be reduced; this will cause prices to rise until there is a balance of demand and supply. If supply is inadequate, prices will be high, prompting an increase in production that in turn will lead to a reduction in prices until supply and demand are in equilibrium. A totally free price mechanism does not exist in practice; even in free-market economies, monopolies or government regulation may limit the efficiency of price as a determinant of supply and demand. In centrally planned economies, the price mechanism may be supplanted by centralized gov¬ ernment control. Attempts to operate an economy without a price mecha¬ nism usually result in surpluses of unwanted goods, shortages of desired products, black markets, and stunted economic growth.

Price, (Mary Violet) Leontyne (b. Feb. 10, 1927, Laurel, Miss., U.S.) U.S. soprano. She was trained at the Juilliard School. After her debut in a revival of Four Saints in Three Acts in 1952, she made her name in the international tour of Porgy and Bess (1953-55). She sang in Aida at Milan’s La Scala in 1960 and made her Metropolitan Opera debut in 1961. Price was one of the Met’s most popular stars for more than two decades and was the first African American singer to achieve an international reputation in opera. She gave her farewell performance of A'ida at the Met in 1985 but continued to give recitals.

Price, Vincent (Leonard) (b. May 27, 1911, St. Louis, Mo., U.S.—d. Oct. 25, 1993, Los Angeles, Calif.) U.S. actor. He first appeared onstage in a London production of the play Chicago and then played the leading role as Prince Albert in Victoria Regina (1935), which he reprised on Broadway. In 1938 he went to Hollywood, where he became known for his cultivated manner and silken voice. He played historical roles in The Private Lives of Elizabeth and Essex (1939), Hudson’s Bay (1941), and The Three Musketeers (1948). He was the menacing villain in horror movies such as House of Wax (1953) and The Abominable Dr. Phibes (1971) as well as a series of Roger Corman movies adapted from Edgar Allan Poe stories, including The Masque of the Red Death (1964). He accepted occasional film and television roles throughout his later years; his performances in The Whales of August (1987) and Edward Scis- sorhands (1990) were particularly memorable.

price discrimination Practice of selling goods or services at differ¬ ent prices to different buyers, even though sales costs are the same for all the transactions. Buyers may be discriminated against on the basis of income, ethnicity, age, or geographic location. For price discrimination to succeed, other entrepreneurs must be unable to purchase goods at the lower price and resell them at a higher one.

price index Measure of change in a set of prices, consisting of a series of numbers arranged so that a comparison of the values for any two peri¬ ods or places will show the change in prices between periods or the dif¬ ference in prices between places. Price indexes were first developed to measure changes in the cost of living in order to determine the wage increases necessary to maintain a constant standard of living. There are two basic types. Laspeyres-type indexes define a market basket of goods in a base period, then use the prices for those goods to examine change over space and time. In its simplest form, this is simply the ratio of what those goods cost today to what they cost in the base period. The two most familiar indexes of this type are the consumer price index (CPI) and the producer price index (PPI). The CPI measures changes in retail prices in such component parts as food, clothing, and shelter. The PPI (formerly called the wholesale price index) measures changes in the prices charged by manufacturers and wholesalers. Paasche-type indexes define a market basket of goods in the current period, then use the prices of those goods from past periods. The most familiar index of this type is the GDP defla¬ tor, used in the U.S. in the national income accounting to differentiate amounts in constant dollars from those in current dollars.

prickly pear Any of a group of flat-stemmed, spiny opuntia cacti (see cactus), native to the Western Hemisphere, or the edible fruit of certain species. Engelmann prickly pear ( Opuntia engelmannii) and beaver tail cactus ( O . basilaris ) commonly occur in the southwestern U.S. The Indian fig ( O. ficus-indica) is an important food in tropical and subtropical coun¬ tries. Because their stems have a high water content, prickly pears can be

used as forage crops and emergency stock feed during drought. Some species are cultivated as ornamentals and valued for their large flowers.

Pride, Sir Thomas (b. Somer¬ set?, Eng.—d. Oct. 23, 1658,

Worcester House, Surrey) English soldier. Joining the Parliamentary army in the English Civil Wars, he commanded a regiment in the Battle of Naseby (1645), then served with Oliver Cromwell and helped rout the invading Scots at Preston (1648).

When the army, dominated by the Independents, occupied London later that year, Pride arrested or expelled about 140 Presbyterian members from the House of Commons (“Pride’s Purge”). He was a member of the commission that tried King Charles I.

Pridi Phanomyong Vpre-de-'pa-nom-.yoqV or Luang Pradist Manudharm Uu-'aq-pra-'dist-.ma-nu-'darnA (b. May 11, 1900, Ayut- thaya, Siam—d. May 2, 1983, Paris, France) Thai political leader and prime minister. He earned a doctorate in law in France, where he was influenced by socialism and where, with Luang Phibunsongkhram and oth¬ ers, he plotted to overthrow the absolute monarchy in Siam (Thailand). Pridi participated in the Promoters Revolution and helped write the con¬ stitution of December 1932. He engineered the downfall of Phibun- songkhram’s pro-Japanese government (1944) and in 1946 became Thailand’s first popularly elected prime minister. Unjustly held respon¬ sible for the assassination of King Ananda that year, he was forced to resign and flee the country in 1947. He lived in China until 1970, when he moved to France.

Priene \pri-'e-ne\ Ancient city of Ionia, north of the Menderes (Maean- der) River, southwestern Anatolia. According to Strabo, it was founded by Ionians and Thebans. It was sacked in the 7th century bc but regained its position in the 6th century bc. It prospered under the Romans and Byz¬ antines but gradually declined. After passing into Turkish hands in the 13th century ad, it was abandoned. Archaeological excavations revealed a Greek town built on terraces; atop a nearby hill is a temple of Athena Polias that was dedicated by Alexander the Great in 334 bc.

priesthood Office of a spiritual leader expert in the ceremonies of wor¬ ship and the performance of religious rituals. Though chieftains, kings, and heads of households have sometimes performed priestly functions, in most civilizations the priesthood is a specialized office. The priest’s duties are concerned less with magic than with the right performance of ritual acts required by the divine powers. Many African societies, for example, differentiated between shamans and the priests responsible for the wor¬ ship of tribal ancestors. Sacrifice is often one of the most important duties of the priesthood. Not every highly developed religion possesses a priest¬ hood, the most notable exception being Islam. The idea of the “priesthood of all believers” was also a cardinal doctrine of the Reformation, and the Protestant belief that priests are not needed as intermediaries between church members and the Holy Spirit is seen most clearly in sects such as the Society of Friends.

Priestley, Joseph (b. March 13, 1733, Birstall Fieldhead, near Leeds, Yorkshire, Eng.—d. Feb. 6, 1804, Northumberland, Pa., U.S.) English theologian, political theorist, and physical scientist. He worked as a teacher and lecturer in various subjects before joining the ministry in 1767. His early scientific studies resulted in his History and Present State of Electricity (1767), which became a fundamental text in the field. His Essay on Government (1768) influenced later utilitarianism. He did impor¬ tant work in the field of chemical reactions and change. He is considered the discoverer of nitrogen, carbon monoxide, ammonia, and several other gases, and in 1774 he became the first to identify oxygen; his report led Antoine Lavoisier to repeat the experiment, deduce oxygen’s nature and role, and name it. His theological works include History of the Corrup¬ tions of the Christian Church (1782), burned as sacrilegious in 1785, and A General History of the Christian Church, 6 vol. (1790-1802). His non¬ conformist religious views and his political activities, particularly in sup-

Engelmann prickly pear (Opuntia sngelmannii)

3RANT HEILMAN PHOTOGRAPHY

© 2006 Encyclopaedia Britannica, Inc.

primary education ► Prince Albert National Park I 1547

port of the French Revolution, made him increasingly controversial in England, and he immigrated to the U.S. in 1794.

primary education See elementary education

primary election Electoral device for choosing a party’s candidates for public office. The formal primary system is peculiar to the U.S., where it came into widespread use in the early 20th century. Most U.S. states use it for elections to statewide offices and to the national presidency; in presi¬ dential elections, delegates are selected to attend a national convention, where they vote for the candidate to whom they are pledged. A closed-vote primary is restricted to party members; an open-vote primary is open to all voters in the district. Names can be placed on a ballot by an eligible citi¬ zen’s declaration of candidacy, by nomination at a pre-primary convention, or by a petition signed by a required number of voters. In the late 20th and early 21st centuries political parties in some countries (e.g., the United Kingdom and Israel) adopted similar procedures for the election of the national party leader. See also electoral system; party system.

primate Any of more than 300 species of the order Primates, including monkeys, apes, humans, and others. Primates are distinguished from other mammals by one or more of the following traits: unspecialized structure, specialized behaviour, a short muzzle, comparatively poor sense of smell, prehensile five-digit hands and feet possessing flat nails instead of claws, acute vision with depth perception due to forward-facing eyes, a large brain, and prolonged pre- and postnatal development. Most species bear a single young and live in troops headed by a male. The primates are one of the most diverse orders of mammals on Earth. They include the lemurs (more than 70 species in six families), the LORises (three or more species in one subfamily), the tarsiers (six or more species in one family), the New World monkeys (almost 100 species in five families), the Old World monkeys (more than 100 species in one family), and the apes and humans (about 20 species in two families). The oldest known fossil remains of primates are about 60 million years old.

Primaticcio V.pre-mo-'tet-choV, Francesco (b. April 30, 1504, Bolo¬ gna, Emilia—d. 1570, Paris, France) Italian-born French painter, sculp¬ tor, and architect. In 1532 Francis I invited him to help redecorate the Fontainebleau Palace, and Primaticcio became one of the principal artists in France; he remained there the rest of his life, making only brief trips to Italy. His decorative style in painting and stucco sculpture stressed the human figure; the exaggerated musculature and active, elongated forms of his figures greatly influenced 16th-century French art. One of the first artists in France to replace religious themes with those of Classical mythology, he brought a quiet French elegance to Italian Mannerism.

prime minister or premier \pri-'mir, pri-'mynA Head of the execu¬ tive branch of government in states with a parliamentary system (see par¬ liamentary democracy). The prime minister is the leader of the political party or coalition with a governing majority, and is formally appointed by the head of state. The office was developed in Britain by Robert Walpole; its powers were consolidated by William Pitt the Younger. The British prime ministry has served as a model for the heads of government in many Commonwealth countries, Europe, and Japan. The prime minister has appointive powers and is responsible for the government’s legislative program, budget, and other policies. His term of office lasts until the next scheduled election or until he loses legislative support. In France, which has both a president and a prime minister, the president wields greater power but the prime minister controls the domestic legislative agenda. See also chancellor.

prime number Any positive integer greater than 1 and exactly divis¬ ible only by 1 and itself. The sequence of prime numbers begins 2, 3, 5, 7, 11, 13, 17, 19, 23, 29... but follows no discernible pattern. The issues of the regularities and irregularities in the distribution of primes are among the most important questions in number theory. Primes have been recog¬ nized at least since Pythagoras. It has been known that there are infinitely many of them at least since Euclid. The prime-number factors of an inte¬ ger are the prime numbers whose product is that integer (see fundamental THEOREM OF ARITHMETIC).

Primo de Rivera Vpre-mo-tha-ri-'ver-oX, Jose Antonio (b. April 24, 1903, Madrid, Spain—d. Nov. 20, 1936, Alicante) Spanish politician. Son of the dictator Miguel Primo de Rivera, he began a legal career in 1925. In 1933 he founded the Spanish fascist party, the Falange, and was elected to the Cortes (parliament). He expounded his views in his periodicals F.E. (1934) and Arriba (1935) and made speeches across Spain. After the left¬

ist Popular Front came to power (1936), he was arrested, given a sum¬ mary trial, and executed at age 33. He was treated as a martyr by Francisco Franco’s Nationalist movement.

Primo de Rivera, Miguel (b. Jan. 8, 1870, Cadiz, Spain—d. March 16, 1930, Paris, France) Spanish general and dictator of Spain (1923-30). A military officer from 1888, he served as military governor of Cadiz (1915-19), Valencia (1919-22), and Barcelona (1922-23), where he firmly suppressed disorder. Believing the parliamentary system to be cor¬ rupt, he took power in a coup in 1923, dissolved the Cortes (parliament), and suspended constitutional guarantees. He successfully ended the Moroccan War (1927), settled labour disputes, and undertook public works, but he failed to implement agrarian reforms. Increasing discontent with his repressive government and lack of support from the army forced him to resign in 1930. Jose Antonio Primo de Rivera was his son.

primogeniture \ l pri-mo- , je-n3-,chur\ Preference in inheritance that is given by law or custom to the eldest son and his issue. The motivation for such a practice has usually been to keep the estate of the deceased, or some part of it, whole and intact, and to acknowledge the importance of age-seniority within the social hierarchy. It is no longer a recognized principle of inheritance in most jurisdictions.

primrose Any flowering plant of the genus Primula, one of 28 genera of the family Primulaceae. Primula includes more than 500 species, which occur chiefly in the Northern Hemisphere in cool or mountainous regions. The plants are low-growing, usually perennial herbs; a few are biennials. Most species grow 25-50 cm (10-20 inches) tall, but some are as short as 5 cm and others as tall as 120 cm. Many species are cultivated for their attractive, five-petaled flowers, which may be red, pink, purple, blue, white, or yellow. Other plants in the primrose family include cyclamens and pimpernels. The evening primrose (family Onagraceae) is not a true primrose.

Primus Vpri-mosV Pearl (b. Nov. 29, 1919, Port of Spain, Trin.—d. Oct. 29, 1994, New Rochelle, N.Y., U.S.) U.S. dancer, choreographer, and anthropologist. Her family moved to New York City when she was two years old. She made her dance debut as the first black member of the New Dance Group in 1943 and formed her own company the next year. Her anthropological research in Africa and the Caribbean led her to choreo¬ graph works such as African Ceremonial (1944) and The Wedding (1961), and she obtained a Ph.D. from Columbia University.

Prince orig. Prince Rogers Nelson (b. June 7, 1958, Minneapolis, Minn., U.S.) U.S. singer and songwriter. The son of a jazz pianist, he taught himself several instruments and formed his own bands as a teen¬ ager. At age 19 he released his first album, on which he played all the instruments. His second album, Prince (1979), was followed by many others, including the best-selling 1999 (1982), the soundtrack of the film Purple Rain (1983), in which he also starred, and Diamonds and Pearls (1991). In 1993 he changed his name to an unpronounceable symbol and became known as “the artist formerly known as Prince,” but in 2000 he resumed his previous name. In 2004 he was inducted into the Rock and Roll Hall of Fame.

prince European title of rank, usually denoting a person exercising com¬ plete or almost complete sovereignty or a member of a royal family. The wife of a prince is a princess. In Britain, the title was not used until 1301, when Edward I invested his son, the future Edward II, as prince of Wales. From Edward Ill’s time, the king’s (or queen’s) eldest son and heir has usually been so invested.

Prince, Hal orig. Harold Smith Prince (b. Jan. 30, 1928, New York, N.Y., U.S.) U.S. theatrical producer and director. He worked for the pro¬ ducer George Abbott before coproducing the successful musical The Pajama Game (1954). He went on to produce or coproduce over 30 hit musicals, including Damn Yankees (1955), West Side Story (1957), A Funny Thing Happened on the Way to the Forum (1962), and Fiddler on the Roof( 1964). Frequently working with Stephen Sondheim, he won Tony Awards for his direction of the musicals Cabaret (1966), Company (1970), Follies (1971), Candide (1974), Sweeney Todd (1979), Evita (1979), The Phantom of the Opera (1986), and Show Boat (1995).

Prince Albert National Park Park, central Saskatchewan, Canada. Its main entrance is northwest of the city of Prince Albert. Established in 1927, it has an area of 1,496 sq mi (3,875 sq km) and is mostly wood¬ land and lakes, interlaced with streams and nature trails. It is a sanctuary for birds, moose, elk, caribou, and bears.

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1548 I Prince Edward Island ► Pripet River

Prince Edward Island Province (pop., 2000 est.: 138,900), Canada. One of the Maritime Provinces and Canada’s smallest province, it is an island in the southern Gulf of St. Lawrence, separated from Nova Scotia and New Brunswick by the Northumberland Strait. Its capital is Charlot¬ tetown. Discovered by Jacques Cartier in 1534, it was used by Micmac Indians for fishing and hunting. It was colonized by the French in 1720, then ceded to the British in 1763. Known as the “Cradle of Confedera¬ tion,” it was the site of the Charlottetown Conference of 1864, which led to the federation of Canada. It became a province in 1873. It has good natural harbours on its eastern and southern sides. There has been little industrial development, and more than half of the island is used for agri¬ culture. Fishing and tourism are also of economic importance. In 1997 a bridge opened between Prince Edward Island and the mainland.

Prince of Wales Strait Narrow channel between Banks Island and northwestern Victoria Island in the southwestern Arctic Archipeago of the Northwest Territories, Canada. It is about 170 mi (274 km) long and forms part of the Northwest Passage between the Atlantic and Pacific oceans. It was discovered in 1850 by the Irish explorer Robert McClure.

Prince Rupert's Land See Rupert's Land

Prince William Sound Inlet of the Gulf of Aaska, southern Alaska, U.S. It lies east of the Kenai Peninsula and spans 90-100 mi (145-160 km). It was named by the British captain George Vancouver in 1778 to honour a son of George III. In 1989 one of the most disastrous oil spills in history occurred when the tanker Exxon Valdez ran aground on Bligh Reef and lost 10.9 million gallons of crude oil into the sound.

princeps Latin "first one," "leader" Unofficial title used by Roman emperors from Augustus (r. 27 bc-ad 14) to Diocletian (r. 284- 305), a period called the principate. The title originated during the Roman republic, when it was held by the leading member of the Senate. Its use by Augustus strengthened his claim to be the restorer of republican insti¬ tutions and virtues, though he and his successors were in fact autocrats. See also prince.

Princeton, Battles of Trenton and See Battles of Trenton and Prin¬ ceton

Princeton University Private university in Princeton, New Jersey, U.S., a traditional member of the Ivy League. Founded as the College of New Jersey in 1746, it is the fourth oldest university in the U.S. and one of the most prestigious. Woodrow Wilson served as university president (1902-10). In addition to an undergraduate college and a graduate school, Princeton has a school of engineering and applied science and a school of architecture and urban planning. Its Woodrow Wilson School of Pub¬ lic and International Affairs continues a long Princeton tradition of train¬ ing government officials. The university has admitted women since 1969.

Princip Vprent-sep\, Gavrilo (b. July 25, 1894, Obljaj, Bosnia—d. April 28, 1918, Theresienstadt, Austria) Serbian nationalist and assassin of Archduke Francis Ferdinand. A Bosnian Serb, he sought to unite the southern Slavic peoples and destroy Austro-Hungarian rule in the Bal¬ kans and was trained in terrorism by the Back Hand society. When the Austro-Hungarian archduke made an official visit to Sarajevo in June 1914, Princip shot him and his wife, Sophie. The assassinations precipi¬ tated World War I. Princip was sentenced to 20 years in prison, where he died after the amputation of his arm.

Principe See Sao Tome and Principe

Pringle, Sir John (b. April 10,1707, Stitchel, Roxburgh, Scot.—d. Jan. 18, 1782, London, Eng.) British physician. As physician general to the British armed forces (1740-48), he applied his knowledge to hospitals and army camps. In Observations on the Diseases of the Army (1752), he outlined procedures for hospital ventilation and camp sanitation. He rec¬ ognized the various forms of dysentery as one, equated hospital and jail fevers, and coined the term influenza. His suggestion that military hospi¬ tals be respected as sanctuaries by both sides in a conflict led to the estab¬ lishment of the Red Cross.

printed circuit Electrical device in which the wiring and certain com¬ ponents consist of a thin coat of electrically conductive material applied in a pattern on an insulating substrate. Printed circuits replaced conven¬ tional wiring after World War II in much electronic equipment, greatly reducing size and weight while improving reliability and uniformity over the hand-soldered circuits formerly used. They are commonly used to mount integrated circuits on boards for use as plug-in units in computers.

televisions, and other electronic devices. Mass-produced printed circuit boards allow automated assembly of electronic components, considerably reducing their cost.

printer, computer Electronic device that accepts text files or images from a computer and transfers them to a medium such as paper or film. It can be connected directly to the computer or indirectly via a network. Printers are classified as impact printers (in which the print medium is physically struck) and non-impact printers. Most impact printers are dot¬ matrix printers, which have a number of pins on the print head that emerge to form a character. Non-impact printers fall into three main categories: laser printers use a laser beam to attract toner to an area of the paper; ink-jet printers spray a jet of liquid ink; and thermal printers transfer wax- based ink or use heated pins to directly imprint an image on specially treated paper. Important printer characteristics include resolution (in dots per inch), speed (in sheets of paper printed per minute), colour (full-colour or black-and-white), and cache memory (which affects the speed at which a file can be printed).

printing Process for reproducing text and illustrations, traditionally by applying ink to paper under pressure, but today including various other methods. In modern commercial printing, three basic techniques are used. Letterpress printing relies on mechanical pressure to transfer a raised inked image to the surface to be printed. Gravure printing transfers ink from recessed cells of varying depths. In offset printing the printing and non¬ printing areas of the plate differ not in height but in wettability.

printmaking Art form consisting of the production of images, usually on paper but occasionally on fabric, parchment, plastic, or other support, by various techniques of multiplication, under the direct supervision of or by the hand of the artist. Such fine prints are considered original works of art, even though they can exist in multiple copies. The major techniques are relief printing, where the background is cut away, leaving a raised image; intaglio printing, where the image is incised directly into the plate; surface printing such as lithography, where the image is painted or drawn onto a stone; and stencil printing, where the design is cut out and printed by spraying paint or ink through the stencil. The history of printmaking parallels the history of art and is one of the oldest art forms. Though he had several predecessors, the first important engraver was a 15th-century German, Martin Schongauer. In the 16th century Albrecht Durer created prints of the highest quality, and in the 17th century the etchings of Rem¬ brandt were especially fine. Japanese printmaking originated in the 17th century with the ukiyo-e school of woodcuts; the best-known artists were Hokusai and Hiroshige. Important 18th-century Western artists who made prints include William Hogarth, Francisco Goya, and Giambattista Piranesi. Among the works of 19th-century printmakers, those of Honore Daumier and of many of the French Impressionists are notable. Experimentation in new styles and new directions proliferated in the 20th century, with art¬ ists from the century’s major movements—including Expressionism, Sur¬ realism, Pop art, Minimalism, and Neo- Expressionism —all pursuing printmaking. See also engraving; etching; mezzotint; woodcut.

prion Vpre-,an\ Disease-causing agent, discovered by Stanley Prusiner, responsible for various fatal neurodegenerative diseases called transmis¬ sible spongiform encephalopathies. An abnormal form of a normally harmless protein found in mammals and birds, the disease-causing prion can enter the brain through infection, or it can arise from a mutation in the gene that encodes the protein. Once present in the brain it causes nor¬ mal proteins to refold into the abnormal shape. As prion proteins multi¬ ply, they accumulate within nerve cells, destroying them and eventually causing brain tissue to become riddled with holes. Diseases caused by prions include Creutzfeldt-Jakob disease, mad cow disease, and scrapie. Pri¬ ons are unlike all other known disease-causing organisms in that they appear to lack nucleic acid (DNA or RNA).

Pripet Vpri-.peA Marshes Vast marsh region, southern Belarus and northwestern Ukraine. The largest swamp of the European continent, the marshes lie in the thickly forested basin of the Pripet River. They cover an area of about 104,000 sq mi (270,000 sq km). Densely wooded and largely uninhabited, the region has supported a diversified lumber industry. A vast amount of land reclamation took place during the 20th century, including the regulation of water drainage, permitting the development of agricul¬ tural areas.

Pripet \'pri-,pet\ River Belarusian Prypyats' River Ukrainian Pryp'yat River River, northwestern Ukraine and southern Belarus. Rising in northwestern Ukraine near the Polish border, it flows east

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Priscian ► Privy Council I 1549

through the Pripet Marshes to Mazyr, then joins the Dnieper River in the Kiev Reservoir after a course of 480 mi (775 km). It is navigable for 300 mi (483 km) and is connected by canals with the Bug and Neman rivers.

Priscian Vpri-shsn \ Latin Priscianus Caesariensis (b. c. 500, Cae¬ sarea, Mauretania) Latin grammarian. He used the writings of Apollonius Dyscolus on Greek grammar as a guide in producing his own classic works on Latin grammar. His Institutiones grammaticae (“Grammatical Foun¬ dations”), with citations from Latin authors, became the standard work for teaching grammar in the Middle Ages. His other writings include trea¬ tises on weights and measures and on the metres of Terence.

prism Piece of glass or other transparent material cut with precise angles and plane faces. Prisms are useful for analyzing and refracting light (see refraction). A triangular prism can separate white light into its constitu¬ ent colours by refracting each different wavelength of light by a different amount. The longer wavelengths (those at the red end of the spectrum) are bent the least, the shorter ones (those at the violet end) the most. The result is the spectrum of visible light, or the rainbow. Prisms are used in certain kinds of spectroscopy and in various optical systems.

prison Institution for the confinement of people convicted of crimes. Prisons are administered by state, provincial, or national governments and house inmates for relatively long terms. They thus differ from jails, which usually are under local jurisidiction and house inmates serving short sen¬ tences. Until the late 18th century, prisons were used mainly for the con¬ finement of debtors who could not meet their obligations, of accused persons waiting to be tried, and of convicts who were waiting for their sentences of death or banishment to be put into effect. Later, imprison¬ ment itself came to be accepted as a means of punishing convicted crimi¬ nals. In early U.S. prisons, prisoners were kept in isolation; in the 19th century, they were permitted to work together, but only in silence. At the end of the 19th century, prison reformers successfully advocated segre¬ gation of criminals by type of crime, age, and sex; rewards for good behaviour; indeterminate sentencing; vocational training; and parole. In the late 20th century, prison populations in many countries began to explode as arrests for violent offenses and for possession of small amounts of illegal drugs increased.

prisoner's dilemma Imaginary situation employed in game theory. One version is as follows. Two prisoners are accused of a crime. If one confesses and the other does not, the one who confesses will be released immediately and the other will spend 20 years in prison. If neither con¬ fesses, each will be held only a few months. If both confess, they will each be jailed 15 years. They cannot communicate with one another. Given that neither prisoner knows whether the other has confessed, it is in the self-interest of each to confess himself. Paradoxically, when each prisoner pursues his self-interest, both end up worse off than they would have been had they acted otherwise. See egoism.

Pristina Vpresh-te-,na\ City (pop., 2000 est.: 186,611), Kosovo region, Serbia, Serbia and Montenegro. It is the capital of the Kosovo region (administered by the UN from mid-1999). Pristina was the capital of the Serbian state before the Turks defeated the Balkan Christian armies in 1389 at the Battle of Kosovo. It is also a cultural centre for Kosovar Alba¬ nians, though it lost many of its ethnic Albanian inhabitants in 1999 when they were driven out by the Serbian campaign of “ethnic cleansing” (see Kosovo conflict). Many returned after a peace accord was signed in June 1999, however.

Pritchett, Sir V(ictor) S(awdon) (b. Dec. 16, 1900, Ipswich, Suf¬ folk, Eng.—d. March 20, 1997, London) British novelist, short-story writer, and critic. A full-time journalist from 1922 and a literary critic for the New Statesman (1928—65), Pritchett became known for his perceptive essays and reviews and for his penetrating and finely crafted short stories. His collections, which offer lively, ironic portraits of middle-class life, include You Make Your Own Life (1938), Blind Love (1969), and A Care¬ less Widow (1989). He also wrote novels, travel books, and the admired memoirs A Cab at the Door (1968) and Midnight Oil (1971).

Prithvi Narayan \'prit-ve-'na-ra-yan\ Shah (b. 1723?—d. 1775) Founder of the modem state of Nepal. A member of the ruling Shah fam¬ ily of Gurkha (Gorkha) principality, he conquered the three Malla king¬ doms (see Malla era) and consolidated them. After unifying Nepal, he annexed territory in northern India, as well as large portions of the Pla¬ teau of Tibet and of the valleys of the Inner Himalayas. He sealed Nepal’s border and maintained peaceful but distant relations with the British.

Pritzker Architecture Prize World’s most prestigious honour in the field of architecture. Established through the philanthropic efforts of the Pritzkers, a prominent Chicago business family, the prize, first awarded in 1979, bestows an annual award of $100,000 on an architect whose built contributions to the field and to society are judged worthiest. The inter¬ national jury has included architects, artists, historians, academicians, crit¬ ics, and business executives.

privacy, right of Right of a person to be free from intrusion into mat¬ ters of a personal nature. Although not explicitly mentioned in the U.S. Constitution, a right to privacy has been held to be implicit in the Bill of Rights, providing protection from unwarranted government intrusion into areas such as marriage and contraception. A person’s right to privacy may be overcome by a compelling state interest. In tort law, privacy is a right not to have one’s intimate life and affairs exposed to public view or oth¬ erwise invaded. Less broad protections of privacy are afforded public officials and others defined by law as “public figures” (e.g., movie stars).

privateer Privately owned vessel commissioned by a state at war to attack enemy ships, usually merchant vessels. All nations engaged in pri¬ vateering from the earliest times until the 19th century. Crews were not paid by the government but were entitled to receive portions of the value of any cargo they seized. Limiting privateers to the activities laid down in their commissions was difficult, and the line between privateering and piracy was often blurred. In 1856, by the Declaration of Paris, Britain and other major European countries (except Spain) declared privateering ille¬ gal; the U.S. finally repudiated it at the end of the 19th century, and Spain agreed to the ban in 1908. See also buccaneer, Francis Drake, William Kidd, Jean Laffite.

privatization Transfer of government services or assets to the private sector. State-owned assets may be sold to private owners, or statutory restrictions on competition between privately and publicly owned enter¬ prises may be lifted. Services formerly provided by government may be contracted out. The objective is often to increase government efficiency; implementation may affect government revenue either positively or nega¬ tively. Privatization is the opposite of nationalization, a policy resorted to by governments that want to keep the revenues from major industries, especially those that might otherwise be controlled by foreign interests.

privet Vpri-V9t\ Any of about 40-50 species of shrubs and small trees in the genus Ligustrum of the olive family that are widely used for hedges, screens, and ornamental plantings. Native to Europe, Asia, Australia, and the Mediterranean, these evergreen or deciduous plants have usually oval, smooth-edged leaves; creamy-white, often odorous clusters of flowers; and black berries. The hardy common privet (L. vulgare), native to north¬ eastern Europe and Britain and naturalized in northeastern North America, is used widely as a hedge plant. Mock privets belong to the genus Phillyrea (same family) and bear small, bright-red fruits that turn purple- black as they mature.

privileged communication or confidential communication

In law, communication between parties to a confidential relation such that the communication’s recipient is exempted from disclosing it as a wit¬ ness. Communications between attorney and client are privileged and do not have to be disclosed to the court. The right to privileged communi¬ cation also exists between husbands and wives, as neither is required to testify against the other in court, and between physicians and patients, though doctors may be required to disclose such information if the right of the defendant to receive a fair trial outweighs the patient’s right to con¬ fidentiality. Members of the clergy have limited rights to refuse to testify in court, and reporters have been accorded a limited right to privileged communication concerning the sources of their information, though they can be ordered to divulge information in certain circumstances.

Privy Vpri-ve\ Council Historically, the British sovereign’s private council. Once powerful, the Privy Council has long ceased to be an active body, having lost most of its judicial and political functions since the middle of the 17th century. It grew out of the medieval curia ( curia regis ), which comprised the king’s tenants in chief, household officials, and other advisers. The curia performed all the functions of government in either small groups, which became the king’s council, or large groups, which grew into the great council and Parliament. It now is chiefly concerned with issuing royal charters, conducting government research, and serving as an appeals body for ecclesiastical and other lesser courts. See also pre¬ rogative court.

© 2006 Encyclopaedia Britannica, Inc.

1550 I PrixdeRome ► proctoscope

Prix de Rome Vpre-ds-'rorrA in full Grand Prix de Rome Art

scholarship awarded by the French government. First established in 1666 by Louis XIV and Charles Le Brun, it enables young French painters, sculp¬ tors, architects, engravers, and musicians to study in Rome. Grand-prize winners in each artistic category study at the Academie de France in Rome for four years. Many of the greatest French artists and musicians of past centuries have been prizewinners, including Jean-Honore Fragonard, Jacques-Louis David, Hector Berlioz, and Claude Debussy. The prizes are still being awarded, though their prestige has diminished.

prize cases (1863) Legal dispute in which the U.S. Supreme Court upheld Pres. Abraham Lincoln’s seizure of ships (prizes). In April 1861, three months before Congress declared a state of war, Lincoln authorized a blockade of Confederate ports. In that three-month period, several mer¬ chant ships ran the blockade and were captured by the Union navy. The legality of the seizures was challenged in court; on appeal, the Supreme Court ruled that the president had acted legally to resist insurrection, sanctioning presidential use of emergency powers.

probability theory Branch of mathematics that deals with analysis of random events. Probability is the numerical assessment of likelihood on a scale from 0 (impossibility) to 1 (absolute certainty). Probability is usu¬ ally expressed as the ratio between the number of ways an event can hap¬ pen and the total number of things that can happen (e.g., there are 13 ways of picking a diamond from a deck of 52 cards, so the probability of picking a diamond is 13 /s 2 , or Va). Probability theory grew out of attempts to understand card games and gambling. As science became more rigor¬ ous, analogies between certain biological, physical, and social phenom¬ ena and games of chance became more evident (e.g., the sexes of newborn infants follow sequences similar to those of coin tosses). As a result, probability became a fundamental tool of modern genetics and many other disciplines. Probability theory is also the basis of the insurance industry, in the form of actuarial statistics.

probate In law, the process of proving in a court (probate court) that an instrument is the valid last will and testament of a deceased person. The term also refers broadly to the process of administering an estate. Unless it is contested or shown to contain obvious anomalies, a document purporting to be a will requires little authenticating proof for certification (admission to probate). Probate courts also often supervise the adminis¬ tration of estates by executors and oversee the guardianship of minors and others lacking capacity under the law.

probation Conditional suspension of an offender’s sentence upon the promise of good behaviour and agreement to accept supervision and abide by specified requirements. It differs from parole in that the offender is not required to serve any of his sentence. Those convicted of serious offenses and those previously convicted of other offenses are usually not consid¬ ered for probation. Studies in several countries show that 70 to 80% of probationers successfully complete their probation; additional limited evi¬ dence suggests that recidivism may be less than 30%.

problem play or thesis play Type of drama that developed in the 19th century to deal with controversial social issues in a realistic manner, expose social ills, and stimulate thought and discussion. It is exemplified by the works of Henrik Ibsen, who exposed hypocrisy, greed, and hidden coiTuption of society in a number of masterly plays. His influence encour¬ aged others to use the form. George Bernard Shaw brought it to an intel¬ lectual peak with his plays and their long, witty prefaces. More recent examples include works of Sean O'Casey, Athol Fugard, Arthur Miller, and August Wilson.

problem solving Process involved in finding a solution to a problem. Many animals routinely solve problems of locomotion, food finding, and shelter through trial and error. Some higher animals, such as apes and cetaceans, have demonstrated more complex problem-solving abilities, including discrimination of abstract stimuli, rule learning, and application of language or languagelike operations. Humans use not only trial and error but also insight based on an understanding of principles, inductive and deductive reasoning (see deduction; induction; and logic), and diver¬ gent or creative thinking (see creativity). Problem-solving abilities and styles may vary considerably by individual.

proboscis monkey Xprs-'ba-sos, pro-'bas-kosV Species (Nasalis lar- vatus, family Cercopithecidae) of long-tailed arboreal Old World monkey of swampy mangrove forests on Borneo. Diurnal vegetarians, they live in groups of about 20. They are red-brown with pale underparts; the young

monkey has a blue face. The male’s nose is long and pendulous, the female’s is smaller, and the young’s is upturned. Males are 22-28 in. (56-72 cm) long, have a 26-29-in. (66-75-cm) tail, and weigh 26-53 lbs (12-24 kg); females are smaller and much lighter.

procedural law Law that prescribes the procedures and methods for enforcing rights and duties and for obtaining redress (e.g., in a suit). It is distinguished from substantive law (i.e., law that creates, defines, or regu¬ lates rights and duties). Procedural law is a set of established forms for conducting a trial and regulating the events that precede and follow it. It prescribes rules relative to jurisdiction, pleading and practice, jury selec¬ tion, evidence, appeal, execution of judgments, representation of counsel, costs, registration (e.g., of a stock offer), prosecution of crime, and con¬ veyancing (transference of deeds, leases, etc.), among other matters.

process philosophy 20th-century school of philosophy that empha¬ sizes the elements of becoming, change, and novelty in experienced real¬ ity and opposes the traditional Western philosophical stress on being, permanence, and uniformity. Reality, including both the natural world and the human sphere, is essentially historical in this view, emerging from (and bearing) a past and advancing into a novel future. Hence, it cannot be grasped by old static spatial concepts that ignore the temporal and novel aspects of the universe given in human experience. The foremost contributors to process philosophy have been Henri Bergson and Alfred North Whitehead.

Proclamation of 1763 Proclamation by Britain at the end of the French and Indian War that prohibited settlement by whites on Indian ter¬ ritory. It established a British-administered reservation from west of the Appalachians and south of Hudson Bay to the Floridas and ordered white settlers to withdraw. It formalized Indian land titles and forbade land pat¬ ents without a purchase from, or treaty agreement with, the title-holding tribe. After American colonists and pioneers objected, the proclamation was replaced by the Treaties of Fort Stanwix.

proconsul In the ancient Roman republic, a consul whose powers had been extended for a definite period beyond his regular one-year term. These extensions were necessitated by such events as long periods of war. The extension of a chief magistrate’s term was originally voted by the people, but the power was soon assumed by the Senate. Provincial gov¬ ernors were usually magistrates whose terms had been extended. Under the empire (after 27 bc), governors of senatorial provinces were called proconsuls.

Procopius \pr3-'ko-pe-3s\ (b. probably between 490 and 507, Caesarea, Palestine) Byzantine historian. He advised Belisarius on his first Persian campaign (527-531) and fought the Vandals in Africa until 536. He was in Sicily with Belisarius and fought the Goths in Italy until 540, and he described the plague in Constantinople in 542. His books Polemon (“Wars”), Peri Ktismaton (“Buildings”), and Anecdota (“Secret History”) are valuable sources for his period’s history.

Procter, William (Cooper) (b. Aug. 25, 1862, Glendale, near Cin¬ cinnati, Ohio, U.S.—d. May 2, 1934, Cincinnati) U.S. manufacturer. A grandson of the founder of Procter & Gamble Co., he started working at the company in 1883. He served as president from 1907 to 1930, during which time sales rose from $20 million to over $200 million. Under his leadership the company pioneered in labour relations: he introduced a profit-sharing plan for employees (1887), guaranteed them 48 weeks of work a year (1920), and introduced a disability pension plan, a life- insurance plan, and employee representation on the board of directors.

Procter & Gamble Co, Major U.S. manufacturer of soaps, cleansers, and other household products. It was formed in 1837 when William C. Procter, a British candlemaker, and James Gamble, an Irish soapmaker, merged their businesses in Cincinnati. The company supplied soap and candles to the Union Army in the Civil War and continued to prosper when the war was over. Among its products were Ivory soap (1879), Crisco shortening (1911), Tide, the first synthetic laundry detergent (1946), and Joy, the first liquid synthetic detergent (1949). In 1932 Procter & Gamble also sponsored the first radio soap opera. The company later began to make personal-care items such as toothpaste, shampoo, and deodorant; food products such as cake mixes and coffee; and miscellaneous products such as cellulose pulp and chemicals.

proctoscope \'prak-t9-,skop\ Lighted tube used to inspect the rectum and lower colon. It is 10 in. (25 cm) long, allowing the entire rectal lin¬ ing to be examined for evidence of disease. It is inserted into the anal

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Prodi ► programming language I 1551

canal and advanced as far as is comfortable for the patient. Modern fibre- optic proctoscopes allow more extensive observation with less discom¬ fort. Proctoscopy is standard in physical examinations of older persons. See also endoscopy.

Prodi, Romano (b. Aug. 9, 1939, Scandiano, Italy) Italian prime min¬ ister (1996-98) and president of the European Commission (1999-2004), one of the governing bodies of the European Union (EU). Prodi graduated from Catholic University in Milan in 1961 and did postdoctoral work at the London School of Economics. After serving as a professor of eco¬ nomics at the University of Bologna, he entered government as minister of industry in 1978. In 1996, after two productive stints as chairman of the Institute for Industrial Reconstruction (1982-89 and 1993-94), he was narrowly elected prime minister as head of the centre-left Olive Tree coa¬ lition. During his 28 months in office, Prodi privatized telecommunica¬ tions and reformed the government’s employment and pension policies. Budget disputes with members of his own party led to his resignation in October 1998. During his five-year term as president of the European Commission, the EU expanded beyond its western European roots to include Malta, Cyprus, and eight eastern and central European members.

producer goods or capital goods or intermediate goods

Goods manufactured and used in further manufacturing, processing, or resale. Intermediate goods either become part of the final product or lose their distinct identity in the manufacturing stream, while capital goods are the plant, equipment, and inventories used to produce final products. The contribution of intermediate goods to a country’s gross domestic product may be determined through the value-added method, which calculates the amount of value added to the final consumer good at each stage of pro¬ duction. This series of values is summed to estimate the total value of the final product.

product rule Rule for finding the derivative of a product of two func¬ tions. If both/and g are differentiable, then (fg)' =fg' +f'g-

production function Equation that expresses the relationship between the quantities of productive factors (such as labour and capital) used and the amount of product obtained. It states the amount of product that can be obtained from every combination of factors, assuming that the most efficient available methods of production are used. The production func¬ tion can thus measure the marginal productivity of a particular factor of production and determine the cheapest combination of productive factors that can be used to produce a given output.

production management or operations management Plan¬ ning, implementation, and control of industrial production processes to ensure smooth and efficient operation. Production management techniques are used in both manufacturing and service industries. Production man¬ agement responsibilities include the traditional “five M’s”: men and women, machines, methods, materials, and money. Managers are expected to maintain an efficient production process with a workforce that can readily adapt to new equipment and schedules. They may use indus¬ trial engineering methods, such as time-and-motion studies, to design effi¬ cient work methods. They are responsible for managing both physical (raw) materials and information materials (paperwork or electronic docu¬ mentation). Of their duties involving money, inventory control is the most important. This involves tracking all component parts, work in process, finished goods, packaging materials, and general supplies. The produc¬ tion cycle requires that sales, financial, engineering, and planning depart¬ ments exchange information—such as sales forecasts, inventory levels, and budgets—until detailed production orders are dispatched by a production-control division. Managers must also monitor operations to ensure that planned output levels, cost levels, and quality objectives are met. See also productivity.

productivity In economics, a measure of productive efficiency calcu¬ lated as the ratio of what is produced to what is required to produce it. Any of the traditional factors of production— land, labour, or capital —can be used as the denominator of the ratio, though productivity calculations are actually seldom made for land or capital since their capacity is dif¬ ficult to measure. Labour is in most cases easily quantified—for example, by counting workers engaged on a particular product. In industrialized nations, the effects of increasing productivity are most apparent in the use of labour. Productivity can be seen not only as a measure of efficiency but also as an indicator of economic development. Productivity increases as a primitive extractive economy develops into a technologically sophisti¬ cated one. The pattern of increase typically exhibits long-term stability

interrupted by sudden leaps that represent major technological advances. Productivity in Europe and the U.S. made great strides following the development of such technologies as steam power, the railroad, and the gasoline motor. Later in the 20th century, advances in productivity stemmed from a number of innovations, including assembly lines and auto¬ mation, COMPUTER-INTEGRATED MANUFACTURING, DATABASE MANAGEMENT SYSTEMS, just-in-time manufacturing, and just-in-time inventory management. Increases in productivity have tended to lead to long-term increases in real wages.

proenzyme See zymogen

profiler Machine tool for cutting complex, irregular shapes, invented by Frederick W. Howe. A rapidly rotating cutter is guided by a finger that traces around the outline of a pattern. The profiler was an important com¬ ponent of the American System of manufacture that made mass production possible.

profit In business usage, the excess of total revenue over total cost dur¬ ing a specific period of time. In economics, profit is the excess over the returns to capital, land, and labour. Since these resources are measured by their opportunity costs, economic profit can be negative. There are vari¬ ous sources of profit: an innovator who introduces a new production tech¬ nique can earn entrepreneurial profits; changes in consumer tastes may bring some firms windfall profits; or a firm may restrict output to prevent prices from falling to the level of costs (monopoly profit).

profit sharing System by which employees are paid a share of the profits of the business enterprise in which they are employed, in keeping with a plan outlined in advance. These payments, which may vary accord¬ ing to salary or wage, are in addition to regular earnings. Profit-sharing plans were probably first developed in France in the early 19th century as worker incentives. Today such plans are used by businesses in West¬ ern Europe, the U.S., and parts of Latin America. Profit shares may be distributed on a current or deferred basis or through some combination of the two. Under current distribution, profits are paid out to employees immediately in the form of cash or company stock. In deferred-payment plans, profit shares may be paid into a trust fund from which employees can draw annuities in later years.

progeria \pro-'jir-e-3\ Disorder with characteristics of premature aging. Affected persons have thin skin, go bald or gray early, and develop dis¬ eases of aging decades earlier than normal individuals. Not all systems are affected; there is no senility, no aging in the central nervous system. There are two major types. In the extremely rare Hutchinson-Gilford syn¬ drome, children look 60 years old by age 10 and die at an average age of 13. The unrelated Werner syndrome is a recessive hereditary disease that begins in young adulthood and makes patients look 30 years older than they are; their average life span is 47 years.

progesterone \pro-'jes-t9-,ron\ Steroid hormone secreted by the female reproductive system that functions mainly to regulate the condition of the endometrium (see uterus), preparing it to accept a fertilized egg. If the egg is not fertilized, the level of progesterone drops, the uterine lining breaks down, and menstruation ensues. If the egg is fertilized (see pregnancy), the placenta produces progesterone, whose effects include preparing the mam¬ mary glands for lactation. Many forms of oral contraception use a syn¬ thetic progesterone.

program, computer Set of ordered instructions that enable a com¬ puter to carry out a specific task. A program is prepared by first formu¬ lating the task and then expressing it in an appropriate programming language. Programmers may work in machine language or in assembly lan¬ guages. But most applications programmers use one of the high-level lan¬ guages (such as BASIC or C++) or fourth-generation languages that more closely resemble human communication. Other programs then translate the instructions into machine language for the computer to use. Programs are stored on permanent media (such as a hard disk), and loaded into RAM to be executed by the computer’s processor, which executes each instruc¬ tion in the program, one at a time. Programs are often divided into appli¬ cations and system programs. Applications perform tasks such as word processing, database functions, or accessing the Internet. System programs control the functioning of the computer itself; an operating system is a very large program that controls the operations of the computer, the transfer of files, and the processing of other programs.

programming language Language in which a computer program¬ mer writes instructions for a computer to execute. Some languages, such

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