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aberration of starlight Apparent displacement of a star or other celestial body resulting from Earth’s orbital motion around the Sun. The maximum displacement is about 20.49 seconds of arc. It depends on the ratio of Earth’s orbital speed to the speed of light and Earth’s direction of motion and thus provides confirmation that Earth orbits the Sun rather than the reverse.

Aberystwyth X.a-bo-'ris-.twithX Town (pop., 1991: 11,154) on Cardi¬ gan Bay, western Wales. The medieval walled town was built around a 13th-century fortress. It later became the exporter for the once-flourishing local lead mines. A principal stronghold of Welsh culture, it has grown as a seaside resort.

Abhayagiri \ab-'ya-go-re\ Theravada Buddhist monastic center built at Anuradhapura, then capital of Ceylon, by King Vattagamani Abhaya (r. 29-17 bc). Originally associated with the nearby Mahavihara (“Great Mon¬ astery”), it soon seceded in a dispute over the relations between monks and the lay community and the use of Sanskrit works to augment Pali texts as scripture. It gained wealth and power under the patronage of Gajabahu I (ad 113-35) and flourished until Anuradhapura was abandoned in the 13th cen¬ tury. Two of its main colleges operated into the 16th century.

Abhidhamma Pitaka V.a-bi-'da-mo-'pe-ta-koX Third and latest collec¬ tion of texts comprising the Pali canon (see Tripitaka) of Theravada Bud¬ dhism. The first two collections, Sutta Pitaka and Vinaya Pitaka, are attributed to the Buddha. Abhidhamma Pitaka texts are ascribed to later dis¬ ciples and scholars; they deal with ethics, psychology, and epistemology.

Abhidharmakosa V.a-bi-.dar-mo-'ko-soX Buddhist scholarly work that provides an introduction to the seven Abhidharma treatises in the Sarvastivada canon and a digest of their contents. It was composed by the Buddhist monk Vasubandhu (fl. 4th or 5th century), who lived in north¬ western India. It systematizes Sarvastivada doctrine and shows the influ¬ ence of Mahayana, to which Vasubandhu later converted. It provides much information on doctrinal differences among the ancient Buddhist schools.

abhijna \3-'bij-n9\ In Buddhist philosophy, the miraculous powers obtained through meditation and wisdom. They include the ability to travel any distance or take any form at will, to see everything, to hear everything, to read minds, and to recall former existences. A sixth miracu¬ lous power, available only to Buddhas and arhats (saints), is freedom by undefiled wisdom (Enlightenment). The powers are signs of spiritual progress but their indulgence is a distraction from the path toward Enlight¬ enment.

Abidjan \,a-be-'jan\ Largest city (pop., 1999 est.: 3,199,000) and chief port of Cote d’Ivoire. Abidjan was a rail terminus from 1904; after its lagoon was opened to the sea to create a port (1950), the city became the financial centre of French West Africa. Though it was once the country’s capital and remains its seat of government, the official capital was moved to Yamoussoukro in 1983. Abidjan has a museum of traditional Ivorian art, a national library, and several research institutes.

Abilene Town (pop., 2000: 6,543), Kansas, U.S. It lies on the Smoky Hill River east of Salina. Settled in 1858, it gained importance when it became the railway terminus for overland Texas cattle drives. With the prosperity of the cattlemen came an era of lawlessness; Wild Bill Hickok was its marshal in 1871. Pres. Dwight D. Eisenhower spent his boyhood there and is buried at the Eisenhower Center, which includes his family home and library.

Abilene City (pop., 2000: 115,930), west-central Texas, U.S. Founded in 1881 as the new railhead for the overland Texas cattle drives, it took the business of the previous railhead, Abilene, Kan. It is the site of sev¬ eral educational institutions, the West Texas Fair, and the reconstructed Old Abilene Town.

© 2006 Encyclopaedia Britannica, Inc.

6 I Abnaki ► Absaroka

Abnaki See Abenaki

abnormal psychology or psychopathology Branch of psychol¬ ogy. It is concerned with mental and emotional disorders (e.g., neurosis, psychosis, mental deficiency) and with certain incompletely understood normal phenomena (such as dreams and hypnosis). The chief tool used in classifying psychological disorders is the American Psychiatric Assn.’s Diagnostic and Statistical Manual of Mental Disorders 4th edition {DSM- IV).

ABO blood-group system Classification of human blood according to whether red blood cells (erythrocytes) have or lack the inherited anti¬ gens called A (including A1 and A2) and B on their surface. Blood can be type O (lacking both), type A (having only A), type B (having only B), or type AB (having both). The ABO antigens make certain blood types incompatible for transfusion. They are developed well before birth and remain through life. The frequencies of blood groups vary among differ¬ ent racial groups and in different geographic areas. Certain diseases are rarer in persons with particular blood groups.

abolitionism (c. 1783-1888) Movement to end the slave trade and emancipate slaves in western Europe and the Americas. The slave system aroused little protest until the 18th century, when rationalist thinkers of the Enlightenment criticized it for violating the rights of man, and Quaker and other evangelical religious groups condemned it as un-Christian. Though antislavery sentiments were widespread by the late 18th century, they had little immediate effect on the centres of slavery themselves—the West Indies, South America, and the southern U.S. In 1807 the importa¬ tion of African slaves was banned in the U.S. and the British colonies. Slavery was abolished in the British West Indies by 1838 and in the French possessions 10 years later. In the 11 Southern states of the U.S., however, slavery was a social and economic institution. American abolitionism laboured under the handicap that it threatened the harmony of North and South in the Union, and it also ran counter to the U.S. Constitution, which left the question of slavery to the individual states. The abolitionist move¬ ment in the North was led by agitators such as William Lloyd Garrison, founder of the American Anti-Slavery Society, writers such as John Green- leaf Whittier, former slaves such as Frederick Douglass, and Harriet Beecher Stowe. The election of Abraham Lincoln, who opposed the spread of sla¬ very to the West, marked a turning point in the movement. Convinced that their way of life was threatened, the Southern states seceded from the Union (see secession), which led to the American Civil War. In 1863 Lin¬ coln (who had never been an abolitionist) issued the Emancipation Proc¬ lamation, which freed slaves held in the Confederate states; the 13th Amendment to the U.S. Constitution (1865) prohibited slavery through¬ out the country. Slavery was abolished in Latin America by 1888. In some parts of Africa and in much of the Islamic world, it persisted as a legal institution well into the 20th century.

Abominable Snowman Tibetan Yeti Mythical monster believed to inhabit the Himalayas near the snow line. The Yeti is thought to resemble an oversized man covered with shaggy fur. Reported sightings are rare; evidence of its existence consists largely of unusual footprints left in the snow, probably the tracks of bears. At certain gaits, bears place the hind- foot partly over the imprint of the forefoot, thus creating tracks that resemble the footprints of a very large primate heading in the opposite direction.

Aborigine See Australian Aboriginal

abortion Expulsion of a fetus from the uterus before it can survive on its own. Spontaneous abortion at earlier stages of pregnancy is called mis¬ carriage. Induced abortions often occur through intentional medical inter¬ vention and are performed to preserve the woman’s life or health, to prevent the completion of a pregnancy resulting from rape or incest, to prevent the birth of a child with serious medical problems, or because the woman does not believe she is in a position to rear a child properly. The drug RU-486, if taken within a few weeks of conception, will trigger a miscarriage. Up to about 19 weeks of pregnancy, injections of saline solutions or hormones may be used to stimulate uterine contractions that will expel the fetus. Surgical removal of the contents of the uterus may be performed in the second trimester or later. Intact dilation and extrac¬ tion procedures may occur in the third trimester; sometimes critically referred to as “partial-birth abortions,” they have been very controversial. Other abortion procedures include manual vacuum aspiration (extraction by manual syringe) and dilation and suction curettage (extraction by machine-operated suction), both of which can be performed in early preg¬