Xochicalco \,sb-che-'kal-ko\ Ancient Toltec city known for its impres¬ sive ruins and feathered-serpent pyramid. It is located on several hilltops near Cuernavaca, Morelos state, Mex. Built mainly in the 8th-9th cen¬ tury, it became an important trading centre and religious centre, and it was turned into a defensive stronghold before the Spanish conquest (c. 1520). The main temple pyramid is known for its lower facing of intri¬ cately carved stones. The reliefs, which show a strong Mayan influence, portray plumed serpents, priests with elaborate headdresses, squatting warriors, calendar glyphs, and fire symbols.
Xu Beihong or Hsu Pei-hung (b. July 19, 1895, Yixing, Jiangsu province, China—d. Sept. 26, 1953, Beijing) Chinese artist and art edu¬ cator. Xu became an itinerant professional painter in his early teens and an art teacher before reaching age 20. He first visited Shanghai in 1912, and over the next few years he studied Western-style painting. In 1918 Xu traveled to Beiping (now Beijing), where he was appointed a teacher at the Beiping University’s Art Research Association. During this period Xu began to teach that only the realist approach from recent Western painting could revive Chinese painting. After studying in Paris and Ber¬ lin, Xu held a large-scale, one-person exhibition in Shanghai in 1926 that firmly established his fame as a modem Chinese master. He was best known for his history paintings, portraits, and pictures of horses, cats, and other animals, and he was competent both in Western media and in the traditional Chinese ink-and-wash method. His rigorous and stylish illus¬ trations of horses were especially highly acclaimed by Chinese critics and connoisseurs and helped gain him an international reputation. In 1927 Xu returned permanently to China, where he continued to teach.
Xu Yue (b. c. 185, Donglai, China—d. c. 227, China) Chinese astrono¬ mer and mathematician. He wrote several books, of which only Shushu jiyi (“Memoir on the Methods of Numbering”) is extant; some scholars question its authenticity. The treatise was used as an auxiliary mathemat¬ ics textbook in the Tang (618-907) and Song (960-1279) state universi¬ ties. Its first part provides three methods of assigning the powers of 10 up to 10 4,096 to traditionally established terms for “large numbers” and alludes to a method of indefinite generation of even larger numbers. The second part contains descriptions of various devices for representing, if not actually manipulating, large numbers. Among them the book men¬ tions a device resembling the abacus, which some scholars believe origi¬ nated in China.
Xuanxue or hsuan-hsueh \'shwan-'shwe\ Chinese "Dark Learn¬ ing" Intellectual movement in China in the 3rd-4th century that arose during a period of disenchantment with Confucianism. Founded by Wang Bi (226-249), the movement drastically reinterpreted Confucian sources and incorporated aspects of Daoism. Wang and his followers tried to deter¬ mine whether the nature of ultimate reality was being or nothingness and sought to discover if the principle underlying a thing was universal or particular. The movement played an important role in the development of Chinese Buddhism.
Xuanzang or Hsuan-tsang \'shwan-'dzaq\ (b. 600, Guoshi, China—d. 664, Chang’an) Chinese Buddhist monk and pilgrim to India. He received a classical Confucian education before converting to Bud¬ dhism. Troubled by discrepancies in the sacred texts, he left for India in 629 to study the religion at its source. He traveled by foot across Central Asia and reached India in 633. After study at the famous Nalanda mon¬ astery, he returned home in 645 to a hero’s welcome, bringing back hun¬ dreds of Buddhist texts, including some of the most important Mahayana scriptures, and spent the rest of his life translating. Influenced by the Yogacara school, he established the Weishi (“Ideation Only”) school of Buddhism, which won many followers in Japan as the Hosso school. The classic novel Xiyou ji was inspired by his life.
Xuanzong or Hsuan-tsung VshiEn-'dzuqX orig. Li Longji (b. 685, Louyang, China—d. April 762, Chang’an) Sixth emperor (r. 712-756) of the Tang dynasty of China, which during his reign achieved its greatest prosperity and cultural brilliance. Xuanzong reformed the bureaucracy, increased tax revenues through reregistering the population, improved the transportation system, and established a permanent military force along China’s northern frontiers. Toward the end of his reign, he withdrew increasingly from government and came under the influence of his con¬ sorts, including the notorious beauty Yang Guifei. The An Lushan Rebel¬ lion of 755-756 forced him to flee the capital, Chang 7 an (modern Xi’an), and he abdicated in favour of the heir apparent.
Xunzi or Hsun-tzu Vshuen-'dzoV (b. c. 300, Zhao kingdom, China—d. c. 230 bce, Lanling, Chu kingdom) Chinese scholar and philosopher. He belonged to the academy of philosophy in the state of Qi before becom¬ ing magistrate of a district in Chu in 255. His major work, the Xunzi, taught that humanity is evil by nature and can become good only through rigorous training. This view provoked much controversy because it opposed the teachings of Mencius, who believed in innate human good¬ ness. Xunzi’s teachings were later eclipsed when the Mencius became a Confucian classic. Xunzi is regarded as one of the three great philoso¬ phers of the classical period of Confucianism in China.
XX, Les See Les Vingt
xylem VzI-lomV Part of a plant’s vascular system that conveys water and dissolved minerals from the roots to the rest of the plant and fur¬ nishes mechanical support. Xylem constitutes the major part of a mature woody stem or root and the wood of a tree, and consists of specialized water-conducting tissues made up mostly of several types of narrow, elongate, hollow cells. Xylem for¬ mation begins when the actively dividing cells of growing root and shoot tips give rise to primary xylem.
Eventually the primary xylem is cov¬ ered by secondary xylem produced by the cambium. The primary xylem cells die, forming a hard skeleton that supports the plant but loses its conducting function. Thus, only the outer part of the wood (secondary xylem) serves in water conduction.
xylophone Percussion instrument consisting of a set of tuned wooden bars that are struck with mallets.
Primitive xylophones may consist of logs of graded length laid across two supporting logs; a pit may be dug underneath to serve as a resonator.
The xylophone has long been one of the principal instruments of African music; it is also important in the Indonesian gamelan. The marimba is a Latin American xylophone. In the modern orchestral xylophone, the bars are laid out on a stand in key¬ board arrangement, with vertical resonating tubes suspended under each bar. See also glockenspiel; vibra¬ phone.
XYZ Affair (1797-98) Diplomatic incident between the U.S. and France. Pres. John Adams sent special envoys Elbridge Gerry and John Marshall to France to help Charles C. Pinckney negotiate an agreement to protect U.S. shipping from French pri¬ vateers. Before the three could meet with Charles-Maurice de Talleyrand, they were approached by three of his agents—called X, Y, and Z in dip¬ lomatic correspondence to Adams—who suggested a bribe of $250,000 to Talleyrand and a loan of $10 million to France as preconditions for negotiations. Adams rejected the French demands and reported the mis¬ sion had failed. When he was forced to reveal the correspondence, pub¬ lic outrage was followed by calls for war with France. The Alien and Sedition Acts were passed to restrict potential French sympathizers. The Convention of 1800 ended a period of undeclared naval warfare between the U.S. and France.
Cross section of oak xylem