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  • “Orbis Sensualium Pictus” (book by Comenius)
    ...he had not yet been able to obtain the necessary woodcuts. He sent the manuscript to Nürnberg in Germany, where the cuts were made. The resulting book, Orbis Sensualium Pictus (1658; The Visible World in Pictures), was popular in Europe for two centuries and was the forerunner of the illustrated schoolbook of later times. It consisted of pictures illustrating Latin sentence...
  • Orbison, Roy (American singer and songwriter)
    American singer-songwriter best remembered for his soaring voice, one of the most operatic in all rock music, and for his carefully crafted ballads of loneliness and heartache....
  • orbit (mechanics)
    A trajectory is the path of a shot, subject to the forces of gravity, drag, and lift. Under the sole influence of gravity, a trajectory is parabolic. (See the animation of projectile motion.) Drag retards motion along the trajectory. Below the speed of sound, the drag is roughly proportional to the square of the velocity; streamlining of the shot tail is effective only at these velocities. At......
  • orbit (astronomy)
    in astronomy, path of a body revolving around an attracting centre of mass, as a planet around the Sun or a satellite around a planet. In the 17th century, Johannes Kepler and Isaac Newton discovered the basic physical laws governing orbits; in the 20th century, Albert Einstein’s general theory of relativity supplied a more exact description....
  • orbit (anatomy)
    The eye is protected from mechanical injury by being enclosed in a socket, or orbit, which is made up of portions of several of the bones of the skull to form a four-sided pyramid the apex of which points back into the head. Thus, the floor of the orbit is made up of parts of the maxilla, zygomatic, and palatine bones, while the roof is made up of the orbital plate of the frontal bone and,......
  • orbital (chemistry and physics)
    in chemistry and physics, a mathematical expression, called a wave function, that describes properties characteristic of no more than two electrons in the vicinity of an atomic nucleus or of a system of nuclei as in a molecule. An orbital often is depicted as a three-dimensional region within which there is a 95 percent probability of finding the electron (see )....
  • orbital angular momentum (physics)
    For atoms in the first three rows and those in the first two columns of the periodic table, the atom can be described in terms of quantum numbers giving the total orbital angular momentum and total spin angular momentum of a given state. The total orbital angular momentum is the sum of the orbital angular momenta from each of the electrons; it has magnitude L(L +......
  • orbital cellulitis (pathology)
    For atoms in the first three rows and those in the first two columns of the periodic table, the atom can be described in terms of quantum numbers giving the total orbital angular momentum and total spin angular momentum of a given state. The total orbital angular momentum is the sum of the orbital angular momenta from each of the electrons; it has magnitude L(L +.......
  • orbital element (astronomy)
    ...corresponds to a circle. If the Sun is at the focus S of the ellipse, the point P at which the planet is closest to the Sun is called the perihelion, and the most distant point in the orbit A is the aphelion. The term helion refers specifically to the Sun as the primary body about which the planet is orbiting. As the points P and A are also called apses,......
  • orbital parameter (astronomy)
    ...corresponds to a circle. If the Sun is at the focus S of the ellipse, the point P at which the planet is closest to the Sun is called the perihelion, and the most distant point in the orbit A is the aphelion. The term helion refers specifically to the Sun as the primary body about which the planet is orbiting. As the points P and A are also called apses,......
  • orbital period (astronomy)
    Neptune’s orbital period of 163.72 years means that by mid-2010 it will have circled the Sun only once since its discovery in September 1846. Consequently, astronomers expect to be making refinements in calculating its orbital size and shape well into the 21st century. Voyager 2’s encounter with Neptune resulted in a small upward revision of the planet’s estimated mean distanc...
  • orbital quantum number (chemistry)
    ...axis, and the magnitude of the angular momentum is limited to the quantum values l(l + 1) (ℏ), in which l is an integer. The number l, called the orbital quantum number, must be less than the principal quantum number n, which corresponds to a “shell” of electrons. Thus, l divides each shell into n subshells.....
  • orbital rendezvous (spaceflight)
    Rendezvous is the process of bringing two spacecraft together, whereas docking is their subsequent meeting and physical joining. The essential elements of a rendezvous are the matching of orbital trajectories and the movement of one spacecraft within close proximity of the other, typically within 100 metres (330 feet). Ideally, the two spacecraft also should lie in the same orbital plane....
  • orbital resonance (astronomy)
    There are stable configurations in the restricted three-body problem that are not stationary in the rotating frame. If, for example, Jupiter and the Sun are the two massive bodies, these stable configurations occur when the mean motions of Jupiter and the small particle—here an asteroid—are near a ratio of small integers. The orbital mean motions are then said to be nearly......
  • orbital septum (anatomy)
    ...of the thick, and relatively rigid, tarsal plates, bordering directly on the palpebral aperture, and the much thinner palpebral fascia, or sheet of connective tissue; the two together are called the septum orbitale. When the lids are closed, the whole opening of the orbit is covered by this septum. Two ligaments, the medial and lateral palpebral ligaments, attached to the orbit and to the septu...
  • orbital velocity (physics)
    velocity sufficient to cause a natural or artificial satellite to remain in orbit. Inertia of the moving body tends to make it move on in a straight line, while gravitational force tends to pull it down. The orbital path, elliptical or circular, thus represents a balance between gravity and inertia. A cannon fired from a mountaintop will throw a projectile farther if its muzzle...
  • Orbiter, Project (space probe)
    In 1954 a secret army–navy project to launch an Earth satellite, Project Orbiter, was thwarted. The situation was changed by the launching of Sputnik 1 by the Soviet Union on Oct. 4, 1957, followed by Sputnik 2 on November 3. Given leave to proceed on November 8, Braun and his army group launched the first U.S. satellite, Explorer 1, on Jan. 31, 1958....
  • Orbiting Astronomical Observatory (satellites)
    any of a series of unmanned U.S. scientific satellites developed to observe cosmic objects from above the Earth’s atmosphere. OAO-2, launched Dec. 7, 1968, carried two large telescopes and a complement of spectrometers and other auxiliary devices. It weighed more than 4,200 pounds (1,900 kilograms), the heaviest satellite orbited up to that time. OAO-2 was able to photograph young stars tha...
  • Orbiting Geophysical Observatory (satellites)
    any of a series of six unmanned scientific satellites launched by the United States from 1964 to 1969. Equipped with a complex of magnetometers, these orbiting satellites were designed to study the Earth’s magnetosphere (i.e., zone of strong magnetic forces around the planet) and its effect on high-energy particles emitted by the Sun. These studies included investigations of auroral ...
  • orbiting observatory (astronomy)
    Earth-orbiting spacecraft that allows celestial objects and radiation to be studied from above the atmosphere. Astronomy from Earth’s surface is limited to observation in those parts of the electromagnetic spectrum (see electromagnetic radiation) that are not absorbed by the atmosphere. Those parts include visible light and some infrared radiation and radio waves. ...
  • Orbiting Solar Observatory (satellite)
    ...States, Europe, the Soviet Union, and Japan developed a variety of space missions, often in a coordinated fashion. In the United States, early studies of the Sun were undertaken by a series of Orbiting Solar Observatory satellites (launched 1962–75) and the astronaut crews of the Skylab space station in 1973–74, using that facility’s Apollo Telescope Mount. These were follo...
  • Orbivirus (virus)
    ...a core of segmented, double-stranded RNA. Characteristic features of structure, preferred hosts, and chemistry are the basis for dividing reoviruses into several genera, of which Orthoreovirus, Orbivirus, Rotavirus, and Phytoreovirus are among the best known. Although orthoviruses have been found in the respiratory and enteric tracts of animals, they are not generally pathogenic.....
  • Orbom, Eric (American art director and designer)
    ...Sons And LoversCinematography, Color: Russell Metty for SpartacusArt Direction, Black-and-White: Alexander Trauner for The ApartmentArt Direction, Color: Alexander Golitzen and Eric Orbom for SpartacusMusic Score of a Dramatic or Comedy Picture: Ernest Gold for ExodusScoring of a Musical Picture: Morris Stoloff and......
  • Orbs (dance by Taylor)
    ...on shape or line), and “lyric” (“long arms”). His avant-garde works range from Duet (1957), in which he and his partner remained motionless for four minutes, to Orbs (1966), an hour-long composition to Beethoven’s last string quartets. Other well-known dances include Three Epitaphs (1956), Aureole (1962), Scudorama (1963), ...
  • orc (mythological creature)
    a mythical creature (such as a sea monster, a giant, or an ogre) of horrid form or aspect....
  • orca (whale)
    largest member of the dolphin family (Delphinidae). The killer whale is easy to identify by its size and striking coloration: jet-black on top and pure white below with a white patch behind each eye, another extending up each flank, and a variable “saddle patch” just behind the dorsal fin. Despite the fact that this cetacean is a powerful carnivo...
  • Orcades (council area, Scotland, United Kingdom)
    group of more than 70 islands and islets—only about 20 of which are inhabited—in Scotland, lying about 20 miles (32 km) north of the Scottish mainland, across the strait known as the Pentland Firth. The Orkney Islands constitute a council area and belong to the historic county of Orkney....
  • Orcagna, Andrea (Italian painter)
    the most prominent Florentine painter, sculptor, and architect of the mid-14th century....
  • Orcelis (Spain)
    town, Alicante provincia, in the comunidad autónoma (“autonomous community”) of Valencia, southeastern Spain. Orihuela lies in the fertile Vega (flat lowland) del Segura, just northeast of Murcia city. A pre-Roman settlement, it became the Roman Orcelis. Captured by the Moors in 713, it was finally liberated by the Christians in 1264. It was sacked during the di...
  • orchard (horticulture)
    ...of a plant, tree, or vine that are not requisite to growth or production, are no longer visually pleasing, or are injurious to the health or development of the plant. Pruning is common practice in orchard and vineyard management for the improvement of flowering and fruiting. In home gardening (e.g., rose culture), pruning enhances plant shape and flowering potential; new growth emerges.....
  • orchard grass (plant)
    (Dactylis glomerata), perennial pasture, hay, and forage grass of the family Poaceae. It has flat leaf blades and open, irregular, stiff-branched panicles (flower clusters)....
  • orchard oriole (bird)
    ...galbula), which breeds in North America east of the Rockies; it is black, white, and golden orange. In western North America is the closely related Bullock’s oriole (I. bullockii). The orchard oriole (I. spurius), black and chestnut, occurs over the eastern United States and Mexico. Among the tropical forms of icterids are the epaulet oriole (I. cayanensis) an...
  • Orchard, The (work by Saʿdī)
    ...de plume from the name of a local atabeg (prince), Saʿd ibn Zangī. Saʿdī’s best-known works are the Būstān (1257; The Orchard) and the Gulistān (1258; The Rose Garden). The Būstān is entirely in verse (epic metre) and consists of stories aptly illustra...
  • Orchard, William Edwin (British priest)
    English ecumenical priest who strove for a closer understanding between Protestants and Roman Catholics. He entered Westminster College, Cambridge, to prepare for the Presbyterian ministry and in 1904 was ordained and became a minister at Enfield, Middlesex. After receiving a D.D. in 1909, he became minister of the King’s Weigh House Congregational Church, London, in 1914....
  • Orchardson, Sir William Quiller (British artist)
    British portraitist and painter of historical and domestic genre scenes....
  • Orchelimum (grasshopper)
    Orchelimum (see photograph), one of the most abundant and widespread types of meadow grasshoppers, has large orange eyes and a body that is brown on top and green on the bottom. The lesser meadow katydids (Conocephalus) are slender and tend to be small in size compared with other meadow grasshopper genera. The meadow grasshopper produces a song, consisting of clicks and buzzes...
  • Orchésographie (work by Arbeau)
    theoretician and historian of the dance, whose Orchésographie (1588) contains carefully detailed, step-by-step descriptions of 16th-century and earlier dance forms....
  • Orchesography (work by Weaver)
    Weaver’s writings on dance are of major significance. His Orchesography (1706) was the first English version of the French choreographer Raoul-Auger Feuillet’s Chorégraphie. The work included the most widely adopted dance notation system of the period. Its introduction to an English-speaking audience enabled more widespread com...
  • Orchestia agilis (crustacean)
    The common sand flea (Orchestia agilis or O. platensis), which is found on the coast of Europe and on the eastern Atlantic coasts of the Americas from Greenland to Argentina, is about 1 centimetre (0.4 inch) in length and is mostly dark brown or gray; the tail is bluish, and the antennae are reddish brown. It lives in damp sand....
  • Orchestia platensis (crustacean)
    The common sand flea (Orchestia agilis or O. platensis), which is found on the coast of Europe and on the eastern Atlantic coasts of the Americas from Greenland to Argentina, is about 1 centimetre (0.4 inch) in length and is mostly dark brown or gray; the tail is bluish, and the antennae are reddish brown. It lives in damp sand....
  • orchestra (theatre)
    The outdoor setting for performances of Greek drama traditionally comprised three areas: a large circular dancing floor (orchēstra in Greek) on which the action took place and in the centre of which was an altar to Dionysus; behind this, a scene-building and dressing room (skēne in Greek, whence......
  • orchestra (music)
    instrumental ensemble of varying size and composition. Although applied to various ensembles found in Western and non-Western music, orchestra in an unqualified sense usually refers to the typical Western music ensemble of bowed stringed instruments complemented by wind and percussion instruments that, in the string section at least, has mor...
  • orchēstra (theatre)
    The outdoor setting for performances of Greek drama traditionally comprised three areas: a large circular dancing floor (orchēstra in Greek) on which the action took place and in the centre of which was an altar to Dionysus; behind this, a scene-building and dressing room (skēne in Greek, whence......
  • Orchestra Hall (concert hall, Chicago, Illinois, United States)
    ...(1889) is the site of touring plays, popular concerts, and visiting orchestras and is the home of the Joffrey Ballet, which moved from New York City to Chicago in 1995. A few more blocks north is Symphony Center (formerly Orchestra Hall), home of the Chicago Symphony Orchestra and its training ensemble, the Civic Orchestra of Chicago, as well as a venue for other musical events. Across the......
  • Orchestra, or a Poem of Dancing (work by Davies)
    English poet and lawyer whose Orchestra, or a Poem of Dancing reveals a typically Elizabethan pleasure in the contemplation of the correspondence between the natural order and human activity....
  • orchestral bells (musical instrument)
    series of tuned brass (originally bronze) tubes of graded length, struck with wooden hammers to produce a sound. They first appeared in England in an 1886 performance of Arthur Sullivan’s Golden Legend in Coventry. Large tubular bells were at first used as a substitute for church bells in towers. Smaller tubes were later built to be controlled from an organ man...
  • orchestral chimes (musical instrument)
    series of tuned brass (originally bronze) tubes of graded length, struck with wooden hammers to produce a sound. They first appeared in England in an 1886 performance of Arthur Sullivan’s Golden Legend in Coventry. Large tubular bells were at first used as a substitute for church bells in towers. Smaller tubes were later built to be controlled from an organ man...
  • orchestral drum (musical instrument)
    ...holes in the membrane), or neck lacing (wrapping a cord around the membrane overlap). Double-headed drums were often directly cord-tensioned (i.e., through holes in the skin). Modern European orchestral drums often combine two hoops pressing against each head (one rolled in the skin, the other outside) with indirect lacing (i.e., to the hoops)....
  • orchestral horn (musical instrument)
    the orchestral and military brass instrument derived from the trompe (or cor) de chasse, a large, circular hunting horn that appeared in France about 1650 and soon began to be used orchestrally. Use of the term French horn dates at least from the 17th century. Valves were added to the instrument in the early 19th century. Modern Fre...
  • orchestral marimba (musical instrument)
    The orchestral marimba, with metal resonators, was developed in the United States in the early 20th century by J.C. Deagan and U.G. Leedy. It is a tube-resonated instrument pitched an octave below the orchestral xylophone; its range varies, but 312octaves upward from the C below middle C is common. Players may hold......
  • orchestration (music)
    the arrangement or composition of music for instruments, especially those found in an orchestra. See instrumentation....
  • Orchestre de la Suisse Romande (orchestra)
    ...conducted under two outstanding figures, Felix Mottl and Arthur Nikisch. About 1914 he met Stravinsky and in 1915 he became conductor of Diaghilev’s Ballets Russes. In 1918 he formed the renowned Orchestre de la Suisse Romande, of which he remained the conductor until his retirement in 1967. He frequently toured Europe with the orchestra and made many recordings with it. Ansermet was a.....
  • Orchestre de Paris (orchestra)
    ...then in Australia with the Melbourne and Sydney symphony orchestras. He thereafter was guest conductor in several cities in Europe, Israel, and the United States. He served as music director of the Orchestre de Paris from 1975 to 1989. In 1987 he signed to become musical and artistic director of the new Bastille Opera in Paris, but he fell into disputes with representatives of the socialist......
  • orchestrina di camera (musical instrument)
    any of a group of small keyboard instruments related to the harmonium, invented and made by W.E. Evans of London. He patented them on Oct. 29, 1862....
  • Orchha (state, India)
    former Rājput princely state of central India, founded in about 1500. In the early 17th century it was systematically devastated by the forces of the Mughal emperor Shāh Jahān following the rebellion of the Bundēla chief Jujhār Singh....
  • Orchha (historical town, India)
    historic town, Tīkamgarh district, Madhya Pradesh state, central India, on the Betwa River. The town, surrounded by thick jungle that long made it impregnable, was founded in 1531 and served until 1783 as the capital of the former Orchha princely state. An island in the Betwa, approached by a causeway, contains a large 17th-century fort and palace. Other buildings of historic interest are ...
  • Orchia, Lex (Roman law)
    ...were allowed to wear; in 195, after the crisis, the law was repealed despite Cato’s protests. Later sumptuary laws were motivated not by military crisis but by a sense of the dangers of luxury: the Orchian law (182) limited the lavishness of banquets; the Fannian law (161) strengthened the Orchian provisions, and the Didian law (143) extended the limits to all Italy. A similar sense of t...
  • Orchian law (Roman law)
    ...were allowed to wear; in 195, after the crisis, the law was repealed despite Cato’s protests. Later sumptuary laws were motivated not by military crisis but by a sense of the dangers of luxury: the Orchian law (182) limited the lavishness of banquets; the Fannian law (161) strengthened the Orchian provisions, and the Didian law (143) extended the limits to all Italy. A similar sense of t...
  • orchid (plant)
    The order Orchidales consists of four families. The largest, Orchidaceae, consists of approximately 1,000 genera and 20,000 species distributed throughout the world, especially in wet tropics. The orchids are generally terrestrial or epiphytic herbs (i.e., those not rooted in soil [see photograph]), rarely vines, and occasionally saprophytes. Often, the orchids develop corms or tubers. The......
  • orchid bee (bee tribe)
    any of a large group of brightly coloured, bees important to the ecology of New World tropical forests. Colour combinations include metallic blues, greens, and bronzes. They are noted for their long tongues and their role in the pollination of over 700 species of tropical orchids. Euglossines pollinate many flowers in the forest understory, but they also visit species in the forest canopy such as ...
  • orchid cactus (plant)
    the genus Epiphyllum, of about 15 species, family Cactaceae, native to tropical and subtropical America, including the West Indies. The plants are mostly epiphytic (grow on other plants) but sometimes grow from the ground....
  • orchid flower
    the genus Epiphyllum, of about 15 species, family Cactaceae, native to tropical and subtropical America, including the West Indies. The plants are mostly epiphytic (grow on other plants) but sometimes grow from the ground.......
  • orchid holder (jewelry)
    As coiffure bottles, they were also used in the elaborate headdresses worn by women of that period. In recent times a tubelike version with a pin attached has been known as an orchid holder....
  • Orchid Man (French boxer)
    French boxer who was world light-heavyweight champion (1920–22) and a European champion at four weight classes....
  • orchid order (plant order)
    orchid order of monocotyledonous flowering plants, a division of the subclass Liliidae....
  • orchid peat (plant anatomy)
    fern genus of the family Osmundaceae, with divided fronds and often growing to a height of 1.5 metres (5 feet). The matted fibrous roots of these abundant ferns are called osmunda fibre, osmundine, or orchid peat; they are broken up and used as a rooting medium for epiphytic orchids; i.e., those that derive moisture and nutrients from the air. For information on the Osmunda......
  • Orchidaceae (plant)
    The order Orchidales consists of four families. The largest, Orchidaceae, consists of approximately 1,000 genera and 20,000 species distributed throughout the world, especially in wet tropics. The orchids are generally terrestrial or epiphytic herbs (i.e., those not rooted in soil [see photograph]), rarely vines, and occasionally saprophytes. Often, the orchids develop corms or tubers. The......
  • Orchidales (plant order)
    orchid order of monocotyledonous flowering plants, a division of the subclass Liliidae....
  • Orchidantha (plant genus)
    The curious genus Orchidantha consists of rather small plants found in Malaysian forests. One species has quite large flowers with dull purplish sepals and creamy white labellum, both as long as 12 centimetres. The flowers have a strong unpleasant odour and probably attract flies, but no observations on pollination have been made and few fruits have been found. The ovary has a long solid......
  • orchiectomy (medical procedure)
    ...and radiation therapy, depending on the type and spread of the original cancer. Virtually all testicular cancer is diagnosed and treated initially by surgically removing the affected testis (orchiectomy). Fortunately, the removal of one testis usually does not affect fertility. If the cancer has spread into the pelvic region or beyond, radiation or chemotherapy may be added to the......
  • orchil (dye)
    a violet dye obtained from some lichens by fermentation. It is also the term for any lichen that yields orchil (Roccella, Lecanora, Ochrolechin, and Evernia) and refers to any colour obtained from this dye....
  • Orchis (plant genus)
    genus of orchids, family Orchidaceae, containing as many as 100 species native to Eurasia and North America. Each plant bears a single flower spike with many flowers and has egg-shaped, lobed, or forked tuberous roots. Most species have several leaves at the base. The petals and sepals often form a helmetlike structure, and the flower lip usually is several lobed. The monkey orchid (O. simia...
  • Orchis mascula (plant)
    The root of the early purple orchid (O. mascula) and several other species contain a nutritive starch. In southern Europe they are softened by soaking to produce a drink called salep. The green-winged orchid (O. morio) is widely distributed throughout Eurasia. Other Eurasian species of Orchis include some known as marsh orchids and others as......
  • Orchis militaris (plant)
    ...roots. Most species have several leaves at the base. The petals and sepals often form a helmetlike structure, and the flower lip usually is several lobed. The monkey orchid (O. simia) and the soldier, or military, orchid (O. militaris) are two European species the flowers of which resemble helmeted human figures....
  • Orchis morio (plant)
    ...root of the early purple orchid (O. mascula) and several other species contain a nutritive starch. In southern Europe they are softened by soaking to produce a drink called salep. The green-winged orchid (O. morio) is widely distributed throughout Eurasia. Other Eurasian species of Orchis include some known as marsh orchids and others as spotted orchids. The showy......
  • Orchis simia (plant)
    ...egg-shaped, lobed, or forked tuberous roots. Most species have several leaves at the base. The petals and sepals often form a helmetlike structure, and the flower lip usually is several lobed. The monkey orchid (O. simia) and the soldier, or military, orchid (O. militaris) are two European species the flowers of which resemble helmeted human figures....
  • Orchis spectabilis (plant)
    ...The green-winged orchid (O. morio) is widely distributed throughout Eurasia. Other Eurasian species of Orchis include some known as marsh orchids and others as spotted orchids. The showy orchis (O. spectabilis) is the most well known of the three North American species of Orchis. It has pink or purple flowers and ranges in height from 6 to 20 centimetres (2 to 8......
  • orchitis (pathology)
    inflammation and swelling of the testes as a result of infection or physical injury. The testes are a pair of organs located in the scrotum of the male; they produce sperm cells for reproduction. Connected to the back of each testis is the epididymis, which serves as a storage duct for sperm awaiting release. The tube that conducts sperm away from the testis ...
  • Orchoë (ancient city, Iraq)
    ancient Mesopotamian city located northwest of Ur (Tall Al-Muqayyar) in southeastern Iraq. The site has been excavated from 1928 onward by the German Oriental Society and the German Archeological Institute. Erech was one of the greatest cities of Sumer and was enclosed by brickwork walls about 6 miles (10 km) in circumference, which according to legend were built by the mythical hero Gilg...
  • Orchomenos (ancient town, Greece)
    ancient Boeotian town on a promontory on the north of the Copiac plain. The northernmost Mycenaean fortified town, it was a seat of the Minyae dynastic family and controlled a large part of Boeotia. In the Archaic period, Orchomenus was a member of the Calaurian League, but political supremacy in Boeotia passed to Thebes. Among the first Boeotian cities to coin money (c. 550 bc...
  • Orchomenus (ancient town, Greece)
    ancient Boeotian town on a promontory on the north of the Copiac plain. The northernmost Mycenaean fortified town, it was a seat of the Minyae dynastic family and controlled a large part of Boeotia. In the Archaic period, Orchomenus was a member of the Calaurian League, but political supremacy in Boeotia passed to Thebes. Among the first Boeotian cities to coin money (c. 550 bc...
  • Orchon River (river, Asia)
    river in north-central Mongolia. The river lies entirely within Mongolia and rises from the heavily forested slopes of the Hangayn Mountains. It flows east out of the mountains and then turns north, past Karakorum, the ancient capital of the Mongol empire. The Orhon is separated from the Selenge River by a massif. Both rivers flow northeast to meet at Sühbaatar, a trade centre just south of...
  • Orcinus citonensis (whale)
    The evolutionary record of the genus Orca is scanty. The earliest fossil identified as a killer whale is Orcinus citonensis from the Pliocene Epoch (5.3 million to 1.8 million years ago) in Italy. This small mammal was about 4 metres long and had 14 teeth—more like a typical dolphin. This implies that the......
  • Orcinus orca (whale)
    largest member of the dolphin family (Delphinidae). The killer whale is easy to identify by its size and striking coloration: jet-black on top and pure white below with a white patch behind each eye, another extending up each flank, and a variable “saddle patch” just behind the dorsal fin. Despite the fact that this cetacean is a powerful carnivo...
  • Orcus (Roman god)
    (Latin: Rich Father), in Roman religion, god of the infernal regions, the equivalent of the Greek Hades, or Pluto (Rich One). Also known to the Romans as Orcus, he was believed to be the brother of Jupiter and was greatly feared. His wife, Proserpina (a Roman corruption of the Greek Persephone []), was identified with vegetation, being regarded as a goddess o...
  • Orcutt, Maureen (American golfer)
    American golfer who captured more than 65 amateur golf championships and often covered the events that she participated in as a sportswriter (1937–72) for the New York Times. When her own accomplishments on the greens merited mention in her column, her byline was deleted. Orcutt played (1932–38) on four U.S. Curtis Cup teams, and she was runner-up for the U.S. amateur title i...
  • Orczy, Baroness Emmuska (Hungarian author)
    Hungarian-born British novelist, chiefly remembered as author of The Scarlet Pimpernel, one of the greatest popular successes of the 20th century....
  • Ord River (river, Western Australia, Australia)
    river in the Kimberley plateau region, northeastern Western Australia. It rises in the Albert Edward Range and follows an easterly and northerly course for 300 miles (500 km) to Cambridge Gulf. Chief tributaries are the Denham, Stirling, Panton, Wilson, Bow, Nicholson, and Elvire. Its upper reaches cut through deep gorges, which give way to grasslands and forests along its middl...
  • Ord River Dam (dam, Western Australia, Australia)
    Formed by the Ord River Dam (1972), it has a storage capacity of 204,719,140,000 cubic feet (5,797,000,000 cubic m). The dam, fed by the 300-mile (480-kilometre) Ord River, measures 325 feet (99 m) high and 1,119 feet (341 m) long. Lake Argyle is the main reservoir in the Ord River Irrigation Scheme, a public works project dating from 1945 and designed to irrigate the surrounding plains. The......
  • Ord River Diversion Dam (dam, Western Australia, Australia)
    ...to drought. The Kimberley Research Station decided in 1945 that irrigated agriculture would be possible in this area, and plans were formed for the development of a large area of farmland. The Kununurra Diversion Dam, completed in 1967, allowed for the cultivation of the first portion of this land under the project. Kununurra town was built nearby as the service and residential centre. A......
  • Ord River Irrigation Scheme (project, Western Australia, Australia)
    ...cubic feet (5,797,000,000 cubic m). The dam, fed by the 300-mile (480-kilometre) Ord River, measures 325 feet (99 m) high and 1,119 feet (341 m) long. Lake Argyle is the main reservoir in the Ord River Irrigation Scheme, a public works project dating from 1945 and designed to irrigate the surrounding plains. The controversial project was troubled with economic and agricultural problems,......
  • Orda (Mongol prince)
    ...that his son was plotting his death, but Jöchi died before he could take any action. Genghis Khan died six months later, and Jöchi’s lands were divided among his sons. His eldest son, Orda, founded the White Horde, his second son, Batu, the Golden Horde....
  • Ordainer (English history)
    one of a committee of 21 nobles and prelates who opposed Edward II and framed a body of “Ordinances” intended to regulate his household and power....
  • Ordaz, Diego de (Spanish explorer)
    ...penetrated the Llanos southward across the Apure and Meta rivers. From the east, several Spanish expeditions ascended the river from its mouth without much success. In 1531 the Spanish explorer Diego de Ordaz voyaged up the river, and that same year another Spanish explorer, Antonio de Berrio, descended the Casanare and Meta rivers and then descended the Orinoco to its mouth....
  • ordeal (trial method)
    a trial or judgment of the truth of some claim or accusation by various means based on the belief that the outcome will reflect the judgment of supernatural powers and that these powers will ensure the triumph of right. Although fatal consequences often attend an ordeal, its purpose is not punitive....
  • ordeal by combat (trial process)
    In ordeal by combat, or ritual combat, the victor is said to win not by his own strength but because supernatural powers have intervened on the side of the right, as in the duel in the European Middle Ages in which the “judgment of God” was thought to determine the winner. If still alive after the combat, the loser might be hanged or burned for a criminal offense or have a hand cut.....
  • ordeal by divination (trial process)
    The main types of ordeal are ordeals by divination, physical test, and battle. A Burmese ordeal by divination involves two parties being furnished with candles of equal size and lighted simultaneously; the owner of the candle that outlasts the other is adjudged to have won his cause. Another form of ordeal by divination is the appeal to the corpse for the discovery of its murderer. The ordeal......
  • ordeal by fire (trial process)
    The ordeal by physical test, particularly by fire or water, is the most common. In Hindu codes a wife may be required to pass through fire to prove her fidelity to a jealous husband; traces of burning would be regarded as proof of guilt. The practice of dunking suspected witches was based on the notion that water, as the medium of baptism, would “accept,” or receive, the innocent......
  • ordeal by physical test (trial process)
    The ordeal by physical test, particularly by fire or water, is the most common. In Hindu codes a wife may be required to pass through fire to prove her fidelity to a jealous husband; traces of burning would be regarded as proof of guilt. The practice of dunking suspected witches was based on the notion......
  • ordeal by water (trial process)
    The ordeal by physical test, particularly by fire or water, is the most common. In Hindu codes a wife may be required to pass through fire to prove her fidelity to a jealous husband; traces of burning would be regarded as proof of guilt. The practice of dunking suspected witches was based on the notion that water, as the medium of baptism, would “accept,” or receive, the innocent......
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