Populonia ancient Pupluna Ancient Roman city, western coast of central Italy. It was originally Etruscan. Silver and iron ores from the nearby island of Elba supplied its metal-manufacturing industry. During the 5th century bc it became wealthy as the first city in Etruria to coin silver. It was conquered by Romans and suffered during the wars between Sulla and Marius in the 1st century bc.
porcelain Vitrified pottery with a white, fine-grained body that is usu¬ ally translucent. It was first made in China during the Tang dynasty (618— 907) and in its advanced form during the Yuan dynasty (1279-1368). The three main types are true (or hard-paste) porcelain, artificial (or soft-paste) porcelain, and bone china. Attempts by medieval European potters to imi¬ tate true porcelain led to the discovery of soft-paste porcelain, which can be cut with a file. The secret of true porcelain was discovered c. 1707 in Saxony. Standard English bone china was produced c. 1800 when Josiah Spode II (1754-1827) added calcined bones to the hard-paste porcelain formula. Hard-paste porcelain, though strong, chips more readily than bone china. See also Bow porcelain; Chantilly porcelain; Chelsea porcelain; Meissen porcelain; Nymphenburg porcelain; Saint-Cloud porcelain; Sevres porcelain; stoneware.
porch Roofed structure, usually open at front and sides, projecting from the face of a building and used to protect an entrance. If colonnaded, it may be called a portico. A veranda is typically a long porch surrounded by a railing, often extending along more than one side of a building. Simple porches were exceedingly common in the domestic architecture of Britain and the U.S. from the late 18th century. In Gothic cathedrals the porch was often a small gabled structure projecting from the northern or southern walls of the nave. See also loggia, narthex.
porcupine Heavy-bodied, solitary, slow-moving, nocturnal rodent with quills (modified hairs) along the back, tail, and, on certain crested spe¬ cies, the neck and shoulders. The quills are easily detached when touched. The New World species (four genera in family Erethizontidae) are arbo¬ real and have barbed quills; the Old World species (four genera in family Hystricidae) are terrestrial and have unbarbed quills. The North Ameri¬ can porcupine (Erethizon dorsatum ), about 31 in. (80 cm) long with a tail about 12 in. (30 cm) long and quills about 3 in. (8 cm) long, drives its powerful tail against an assailant. For food, it favours the tender tissue beneath tree bark. Crested porcupines, the typical Old World porcupines, run backward, quills erect, into the enemy. They eat roots, fruit, and other vegetation. The African crested porcupine, the largest terrestrial rodent in Europe and Africa, may weigh 60 lb (27 kg) and have quills 14 in. (35 cm) long.
porgy Vpor-je\ Any of about 100 species (family Sparidae) of generally shallow-water fishes found through¬ out tropical and temperate seas. Por- gies, sometimes called sea breams, are typically high-backed, with a single dorsal fin, a small mouth, and teeth strong enough to handle fishes and hard-shelled invertebrates. Most species do not exceed 1 ft (30 cm) long, but some may grow to 4 ft (120 cm). The South African mussel- crackers, popular sport fishes, grow to 100 lbs (45 kg). In Australia and Japan, several species of Chrysophrys are important food fish (called snappers in Australia). The red sea bream inhabits deep European waters. See also sheepshead.
pork Flesh of hogs, usually slaughtered between the ages of six months and one year. The world’s most popular meat, it is consumed fresh in various cuts or preparations, including chops and sausage, or cured or smoked for ham, bacon, dry sausage, or other products. Because pigs may be infected by the parasitic disease trichinosis, fresh pork must be cooked
Northern porgy (Stenotomus chrysops).
RUNK/SCHOENBERGER FROM GRANT HEILMAN
© 2006 Encyclopaedia Britannica, Inc.
pornography ► Porter I 1531
to an internal temperature of 160 °F (71 °C) to destroy the parasite. Pork is proscribed by the dietary laws of Islam and Judaism.
pornography Depiction of erotic behaviour intended to cause sexual excitement. The word originally signified any work of art or literature depicting the life of prostitutes. Though pornography is clearly ancient in origin, its early history is obscure because it was customarily not thought worthy of transmission or preservation. Nevertheless, in the artwork of many historic societies, including ancient India, ancient Greece, and Rome, erotic imagery was commonplace and often appeared in religious contexts. The Art of Love, by Ovid, is a treatise on seduction and sensual arousal. The invention of printing led to the production of ambitious works of pornographic writing intended to entertain as well as to arouse. In 18th-century Europe, pornography became a vehicle for social and politi¬ cal protest through its depiction of the misdeeds of royalty and other aris¬ tocrats, as well as those of clerics, a traditional target. The development of photography and motion pictures in the 19th and 20th centuries con¬ tributed greatly to the proliferation of pornography, as did the advent of the Internet in the late 20th century. During the 20th century, restrictions on pornography were relaxed throughout much of Europe and North America, though regulations remained strict in Asia, the Middle East, and Africa. Child pornography is almost universally prohibited.
porphyrin Vpor-fo-ronX Any of a class of biologically important het¬ erocyclic compounds of a characteristic chemical structure that includes four pyrrole groups (five-membered organic rings each containing a nitro¬ gen atom) linked by additional carbon atoms to form a large flat ring. As biological pigments, they and closely related molecules are responsible for many of the vivid colours in living organisms, where they often occur combined with metal ions and various substituents as coordination com¬ plexes (see compound). These include the magnesium-containing chloro¬ phylls and the iron-containing heme group, a constituent (along with protein) of, e.g., hemoglobin, the cytochromes, and the enzyme catalase. In medicine, porphyrins are used in conjunction with light, often a laser beam, to induce reactions in the body against cancer and other diseases.
porphyry copper deposit \'por-f9-re\ A large body of igneous rock, having distinct crystals in a relatively fine-grained base, that contains chal- copyrite and other sulfide minerals. These deposits contain vast amounts of ore that averages a fraction of 1% copper by weight; although low-grade, the deposits are important because they can be worked on a large scale at low cost. Large porphyry copper deposits are worked in the southwestern U.S. (where molybdenum may be produced as a by-product), the Solomon Islands, Canada, Peru, Chile, Mexico, and elsewhere.
porpoise Any toothed whale in the family Phocoenidae (or, by some authorities, part of the dolphin family Delphinidae). The four species (genus Phocoena) of the common, or harbour, porpoise are primarily fish eaters that travel in pairs or large groups. They are gray or black above and white below. The shy P. phocoena, found throughout the Northern Hemisphere, rarely leaps. The other species of Phocoena are found along Californian and South American coasts. The active, gregarious Dali por¬ poise ( Phocoenoides dalli ) of the North Pacific and the True porpoise (P. truei) of Japan often swim with ships, usually in groups of 2 to 20. Both eat cephalopods and fishes and are black with a large white patch on each side. The black finless porpoise ( Neomeris phocoenoides ), a small, slow animal, inhabits the Pacific and Indian oceans. At most 7 ft (2 m) long, porpoises are shorter and chubbier than dolphins and have a blunt snout. Like the dolphins, they are known for their high intelligence.