igloo Temporary dome-shaped winter home or hunting-ground dwelling of Canadian and Greenland Inuit (Eskimos), made from blocks of snow. The builder chooses a deep snowdrift of fine-grained, compact snow and cuts it into blocks. After a row of blocks has been laid in a circle, their top surfaces are shaved off in a sloping angle to form the first rung of a spiral. Additional blocks are added to the spiral to draw it inward until a dome is completed, leaving a ventilation hole at the top.
Ignarro, Louis J(oseph) (b. May 31,1941, Brooklyn, N.Y., U.S.) U.S. pharmacologist. He earned a Ph.D. from the University of Minnesota. Along with Robert F. Furchgott and Ferid Murad, Ignarro was awarded a 1998 Nobel Prize for the discovery that nitric oxide acts as a signaling mol¬ ecule in the cardiovascular system. Ignarro concluded that the factor that Furchgott had named endothelium-derived relaxing factor was nitric oxide. This work uncovered an entirely new mechanism by which blood vessels in the body relax and widen. It was the first discovery that a gas could act as a signaling molecule in a living organism. The principle behind the drug Viagra, used to treat impotence, was based upon this research.
Ignatius of Antioch \ig-'na-sh3s\, Saint (d. c. 110, Rome; Western feast day October 17; Eastern feast day December 20) Early Christian martyr. Probably of Syrian origin, he may have been a pagan who per¬ secuted Christians before his conversion. He succeeded St. Peter the Apostle as bishop of Antioch. During the reign of Trajan, Roman authori¬ ties arrested Ignatius and sent him to Rome, where he was tried and executed. He wrote a series of famous letters on the journey to Rome, attempting to encourage his fellow Christians during their persecution. The letters condemn two sets of heretics: the Judaizers, who insisted that Christians continue to follow Jewish law, and the Docetists, who main¬ tained that Jesus only appeared to suffer and die on the cross.
Ignatyev \ig-'nat-yiA, Nikolay (Pavlovich), Count (b. Jan. 29, 1832, St. Petersburg, Russia—d. July 3, 1908, Krupodernitsy estate, Kiev
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igneous rock ► ijtihad I 927
province) Russian politician and diplomat under Tsar Alexander II. A career diplomat, he concluded a treaty with China in 1860 that allowed Russia to construct the city of Vladivostok and become a major power in the northern Pacific. Appointed head of the foreign ministry’s Asian depart¬ ment, he gained jurisdiction over Russia’s relations with the Ottoman Empire as well, and in 1864 he became ambassador to Constantinople. An advocate of Pan-Slavism, he encouraged Serbia and Bulgaria in a revolt that proved unsuccessful. In 1878, after Russia’s victory in the Russo- Turkish War, he negotiated the favourable Treaty of San Stefano. The western European powers replaced it with the Treaty of Berlin, far less favourable to Russia, and he was forced to resign.
igneous rock Any of various crystalline or glassy, noncrystalline rocks formed by the cooling and solidification of molten earth material (magma). Igneous rocks comprise one of the three principal classes of rocks, the others being metamorphic and sedimentary rocks. Though they vary widely in composition, most igneous rocks consist of quartz, feldspars, pyroxenes, amphiboles, micas, olivines, nepheline, leucite, and apatite. They may be classified as intrusive or extrusive rocks.
ignition system In a gasoline engine, the means used for producing an electric spark to ignite the fuel-air mixture in the cylinders to produce the motive force. The ignition system consists of a storage battery recharged by a generator, an induction coil, a device to produce timed high-voltage discharges from the induction coil, a distributor, and a set of spark plugs. The battery provides an electric current of low voltage, usually 12 volts, that is converted by the system to some 40,000 volts. The distributor routes the successive bursts of high-voltage current to each spark plug in the proper firing order.
iguana \i-'gwa-n3\ Any of about 13 of the larger members of the lizard family Iguanidae. Best known is the common iguana {Iguana iguana ), which ranges from Mexico southward to Brazil. It reaches a maximum length of 6 ft (1.8 m). It lives in trees, especially trees overhanging water, into which it will plunge if disturbed. It is greenish, with brown bands that form regular rings on the tail. It primarily eats tender leaves and fruits but will also eat small birds and crustaceans. Species of the southwestern U.S. and Mexico include the chuckwalla {Sauromalus obesus) and desert iguana {Dipsosaurus dorsalis).
Iguazu Falls or Iguacu \,e-gw3-'su\ FaWs, formerly Victoria Falls
A series of cataracts on the Iguazu River near the border between Argen¬ tina and Brazil. The horseshoe-shaped falls were discovered by Alvar Nunez Cabeza de Vaca in 1541. They vary between 200 and 269 ft (60 and 82 m) in height and extend for 1.7 miles (2.7 km)—nearly three times wider than North America’s Niagara Falls —and are divided into 275 waterfalls or cataracts. The scenic beauty and wildlife of the falls are pro¬ tected by two separate national parks: Iguazu National Park (1939) in Brazil and Iguazu National Park (1934) in Argentina. Both parks were designated UNESCO World Heritage sites in 1984 and 1986, respectively.
Iguazu Falls on the Iguazu River at the Argentina-Brazil border.
© R. MANLEY/SUPERSTOCK
Iguazu River or Iguacu River River, southern Brazil and northeast¬ ern Argentina. It winds westward for 820 mi (1,320 km) before joining
the Parana River at the point where Argentina, Brazil, and Paraguay meet. Although sections of the river are navigable, it is known chiefly for the scenic Iguazu Falls. Near the falls a major portion of the river tumbles into a chasm called the Garganta del Diablo (“Devil’s Throat”), which has been described as “an ocean plunging into an abyss.”
Iguvine \I-'gu-v!n\ Tables Set of seven inscribed bronze tables writ¬ ten in the Umbrian language and found in 1444 at Iguvium (modern Gub- bio, Italy). Some are written in the Umbrian script and others in the Latin alphabet; they probably date from the 3rd to 1st century bc. The tables record liturgy, sacred rites, and regulations of the Fratres Atiedii, a broth¬ erhood of priests, and are of great value for the study of ancient Italic language and religion.
Ihara Saikaku \e- , ha-ra- , sl-,ka-ku\ or Ibara \e-'ba-ra\ Saikaku known as Saikaku orig. Hirayama Togo (b. 1642, Osaka, Japan—d. Sept. 9, 1693, Osaka) Japanese poet and novelist. He first won fame for his speed in composing haikai (humorous linked-verse poems), once pro¬ ducing 23,500 in a day. He is best known for his novels, including The Life of an Amorous Man (1682) and Five Women Who Loved Love (1686) in which he enchanted readers with racy accounts of the amorous and financial affairs of the merchant class and the demimonde. He was one of the brilliant figures of the 17th-century revival in Japanese literature.
li Naosuke \'e-e-na-'os-ka\ (b. Nov. 29, 1815, Hikone, Japan—d. March 24, 1860, Edo [now Tokyo]) Japanese daimyo and statesman who made the last attempt to reassert the traditional political role of the sho- gunate (military ruler). In response to Commodore Matthew Perry’s demand that Japan end its centuries-old policy of isolation, Ii favoured developing relations. The Tokugawa shogun signed the Perry Convention (1854), which opened two ports to U.S. ships, exposing the country to Western influence, and began negotiations with Townsend Harris over trade. In an unusual move, the shogunate had sought the emperor’s con¬ sent to the treaty; when antitreaty forces blocked approval, Ii, as head of the shogunal governing body, authorized the signing. This outraged many daimyo; when Ii silenced them, he was beheaded by assassins. See also Tokugawa period; Meiji Restoration.