Richard Dixon Oldham was a British geologist and seismologist who discovered evidence for the existence of the Earth’s core. After training at the Royal School of Mines, Oldham joined the Geological Survey of India in 1879, eventually serving as superintendent (until 1903). His study of the Assam

meteorite: Achondrites: …calcium as the sulfide mineral oldhamite (CaS) rather than in its more usual silicate and carbonate forms.

Oldman River, river in southern Alberta, Canada, one of the major headstreams of the South Saskatchewan River. Rising in the Canadian Rocky Mountains from several sources, it flows eastward through Lethbridge, past Taber Provincial Park, and joins the Bow River to form the South Saskatchewan River,

Gary Oldman is an English film actor known for his chameleonic ability to evince characters ranging from nebbishes to snarling villains. His notable films include Sid and Nancy (1986), Tinker, Tailor, Soldier, Spy (2011), and several Harry Potter movies. For his portrayal of Winston Churchill in

Gary Oldman is an English film actor known for his chameleonic ability to evince characters ranging from nebbishes to snarling villains. His notable films include Sid and Nancy (1986), Tinker, Tailor, Soldier, Spy (2011), and several Harry Potter movies. For his portrayal of Winston Churchill in

Oldowan industry, toolmaking tradition characterized by crudely worked pebble (chopping) tools from the early Paleolithic, dating to about 2 million years ago and not formed after a standardized pattern. The tools are made of pebbles of quartz, quartzite, or basalt and are chipped in two directions

Czechoslovak history: The Hussite preponderance: …determined by the efforts of Oldřich of Rožmberk, the most powerful Bohemian magnate, and his allies, who undermined George’s plans.

mechanics of solids: Viscoelasticity: …after the British applied mathematician James Gardner Oldroyd showed in 1950 how viscoelastic stress-strain relations of a memory type could be generalized to a flowing fluid. This requires that the constitutive relation, or rheological relation, between the stress history and the deformation history at a material “point” be properly invariant…

human nervous system: Reward and punishment: …made in 1954, Canadian researchers James Olds and Peter Milner found that stimulation of certain regions of the brain of the rat acted as a reward in teaching the animals to run mazes and solve problems. The conclusion from such experiments is that stimulation gives the animals pleasure. The discovery…

Ransom Eli Olds was an American inventor and automobile manufacturer, designer of the three-horsepower, curved-dash Oldsmobile. This was the first commercially successful American-made automobile and the first to use a progressive assembly system, which foreshadowed modern mass-production methods.

Sharon Olds is an American poet best known for her powerful, often erotic, imagery of the body and her examination of the family. Olds grew up in San Francisco, the daughter of an abusive alcoholic father and a weak compliant mother; her anger at her parents would influence her poetry. She studied

Ransom Eli Olds: …designer of the three-horsepower, curved-dash Oldsmobile. This was the first commercially successful American-made automobile and the first to use a progressive assembly system, which foreshadowed modern mass-production methods.

Olduvai Gorge: The Olduvai fossil beds accumulated in a lake basin between 4 and 9 miles (7 and 15 km) in diameter. The lake is underlain by volcanic rocks of the Pliocene Epoch (5.3 million to 2.6 million years ago) and, farther below, by metamorphic deposits of Precambrian…

Olduvai Gorge, paleoanthropological site in the eastern Serengeti Plain, within the boundaries of the Ngorongoro Conservation Area in northern Tanzania. It is a steep-sided ravine consisting of two branches that have a combined length of about 30 miles (48 km) and are 295 feet (90 metres) deep.

Homo habilis: The fossil evidence: Those two skulls are called OH 13 and OH 16.

Homo habilis: The fossil evidence: …are called OH 13 and OH 16.

Homo habilis: The fossil evidence: One intriguing specimen is OH 24, which was also from Olduvai and dated to about 1.8 mya. This cranium is more complete than others from Olduvai. Because some of the bones are crushed and distorted, however, the face and braincase are warped. OH 24 may differ from Australopithecus in…

Olduvai Gorge: …Zinjanthropus boisei (later reclassified as Paranthropus boisei). Officially labeled OH 5 (Olduvai Hominid 5) but dubbed “Nutcracker Man” because of its huge molars (indicative of a vegetarian diet), the skull was dated to about 1.75 million years ago. The discovery indicated that hominins evolved in Africa. Specimens of Homo habilis,…

Homo habilis: The fossil evidence: 8 mya and called OH 62. Although the skull is shattered, enough of the face is preserved to suggest similarities to early Homo. The find is especially important because of the limbs, which show that OH 62 was a very small hominin. The arm is long relative to the…

Homo habilis: The fossil evidence: … from a juvenile individual called Olduvai Hominid 7 (OH 7), additional fossils from Olduvai have been ascribed to H. habilis. Pieces of another thin-walled cranium along with upper and lower jaws and teeth came to light in 1963. Just a month later a third skull was found, but the bones…

Homo erectus: African fossils: This fossil, catalogued as OH 9, was excavated by Louis S.B. Leakey and is probably about 1.2 million years old. Olduvai Gorge has since yielded additional cranial remains, jaws, and limb bones of H. erectus. Much of this material is fragmentary, but gaps in our knowledge of East African…

Olduvai Gorge, paleoanthropological site in the eastern Serengeti Plain, within the boundaries of the Ngorongoro Conservation Area in northern Tanzania. It is a steep-sided ravine consisting of two branches that have a combined length of about 30 miles (48 km) and are 295 feet (90 metres) deep.

perciform: Annotated classification: Family Enoplosidae (oldwives) Eocene to present. Body laterally compressed; spinous and soft dorsal fins elevated anteriorly, as is anal fin; general appearance gives impression in side view of 2 separate bodies joined together at midpoint; pelvic fins large. 1 species (Enoplosus armatus) in rocky areas of Australian…

German literature: The post-1945 period: Stunde Null: Ole Bienkopp), a novel about an old man who establishes a peasant commune, and Christa Wolf’s Der geteilte Himmel (1963; Divided Heaven), in which a young woman decides to return to East Germany after having experienced the lures of the West, are good examples of…

University of Mississippi, public, coeducational institution of higher learning based in Oxford, Mississippi, U.S., with its Medical Center in Jackson and regional campuses at Tupelo and Southaven. Academically divided into one college and eight schools (including the Medical Center), it offers

olive, (Olea europaea), subtropical broad-leaved evergreen tree (family Oleaceae) and its edible fruit. The olive fruit and its oil are key elements in the cuisine of the Mediterranean and are popular outside the region. The tree’s beauty has been extolled for thousands of years. The edible olive

Oleaceae, the olive family, belonging to the order Lamiales and named for the economically important olive tree (species Olea europaea). A number of plants in the family are of economic or aesthetic importance: the olive tree is the source of olives and olive oil; the ashes (genus Fraxinus) are

gastropod: Classification: Superfamily Oleacinacea Carnivorous (Oleaciniidae) and herbivorous (Sagdidae) snails of the Neotropical region. Superfamily Helicacea Land snails without (Oreohelicidae and Camaenidae) or with (Bradybaenidae,

gastropod: Classification: Oleacinacea Carnivorous (Oleaciniidae) and herbivorous (Sagdidae) snails of the Neotropical region. Superfamily Helicacea Land snails without (Oreohelicidae and Camaenidae) or with (Bradybaenidae, Helminthoglyptidae, and Helicidae

Olean, city, Cattaraugus county, western New York, U.S. It lies along the Allegheny River at the mouth of Olean Creek, 60 miles (97 km) southeast of Buffalo. First settled in 1804 as a lumber camp, its name is derived from the word oleum (i.e., oil) for the oil deposits found in the vicinity; the

Potter: violinist Ole Bornemann Bull founded Oleona (located south of present-day Carter Camp) for Norwegian colonists in 1852, but the settlement foundered as a result of financial and legal problems. To the east of Coudersport (the county seat) is the Coudersport Ice Mine (discovered 1894), a cave in Ice Mountain that…

oleander, any of the ornamental evergreen shrubs of the genus Nerium, belonging to the dogbane family (Apocynaceae) and having a poisonous milky juice. The best known is the common oleander (N. oleander), often called rosebay. A native of the Mediterranean region, this plant is characterized by its

fern: Annotated classification: Family Oleandraceae Plants in soil, on rock, or climbing (hemiepiphytic); rhizomes long-creeping, sometimes with elongate, ascending, or climbing branches, scaly; leaves undivided, the petioles jointed to short, persistent stubs (phyllopodia) along the rhizomes, the blades scaly; sori round, the indusia kidney-shaped to nearly U-shaped; sporangia mixed…

American literature: The Off-Broadway ascendancy: …through their language, and in Oleanna (1992) he fired a major salvo in the gender wars over sexual harassment.

oleaster, small deciduous tree of Eurasia, about 4.5 to 6 m (15 to 20 feet) high. It has smooth, dark brown branches that often bear spines and narrow, light green leaves that are silvery on the undersides from a covering of minute scales. The flowers are small, greenish, fragrant, and

Elaeagnaceae, the oleaster family of flowering plants (order Rosales), comprising 45–60 species in 3 genera. The oleaster family is largely composed of shrubs and small trees of the Northern Hemisphere, especially in steppe and coastal regions. The plants have a characteristic silvery or

ulna: …this notch is called the olecranon process; it articulates behind the humerus in the olecranon fossa and may be felt as the point of the elbow. The projection that forms the lower border of the trochlear notch, the coronoid process, enters the coronoid fossa of the humerus when the elbow…

humerus: The two depressions—the olecranon fossa, behind and above the trochlea, and the coronoid fossa, in front and above—receive projections of the ulna as the elbow is alternately straightened and flexed. The epicondyles, one on either side of the bone, provide attachment for muscles concerned with movements of the…

ulna: …this notch is called the olecranon process; it articulates behind the humerus in the olecranon fossa and may be felt as the point of the elbow. The projection that forms the lower border of the trochlear notch, the coronoid process, enters the coronoid fossa of the humerus when the elbow…

olefin, compound made up of hydrogen and carbon that contains one or more pairs of carbon atoms linked by a double bond. Olefins are examples of unsaturated hydrocarbons (compounds that contain only hydrogen and carbon and at least one double or triple bond). They are classified in either or both

Oleg was a semilegendary Viking (Varangian) leader who became prince of Kiev and is considered to be the founder of the Kievan Rus state. According to The Russian Primary Chronicle of the 12th century, Oleg, after succeeding his kinsman Rurik as ruler of Novgorod (c. 879), went down the Dnieper

Oleg was a semilegendary Viking (Varangian) leader who became prince of Kiev and is considered to be the founder of the Kievan Rus state. According to The Russian Primary Chronicle of the 12th century, Oleg, after succeeding his kinsman Rurik as ruler of Novgorod (c. 879), went down the Dnieper

oleic acid, the most widely distributed of all the fatty acids, apparently occurring to some extent in all oils and fats. In oils such as olive, palm, peanut, and sunflower, it is the principal acid obtained by saponification. Oleic acid, CH3(CH2)7CH=CH(CH2)7CO2H, like other fatty acids, does not

Lena River: Physiography: …after the junction with the Olyokma River, and the width of the river reaches 1 mile (1.6 km). From the mouth of the Vitim to the Olyokma, the river skirts the Patom Plateau, on the right bank, forming an enormous bend; the width of the valley increases in places to…

Oleksandr Usyk is a Ukrainian professional boxer who became the two-time undisputed heavyweight world champion by unanimous decision on July 19, 2025. Nicknamed “the Cat” for his agility, quick footwork, and slick technical skills in the ring, Usyk is considered among the greatest heavyweight

Zaporizhzhya, city, southeastern Ukraine, on the Dnieper River just below its former rapids. It is the administrative centre of Zaporizhzhya oblast (province). In 1770 the fortress of Oleksandrivsk was established to ensure government control over the Zaporozhian Cossacks, whose headquarters were

Oleksandriya, city, south-central Ukraine, on the Inhulets River. Founded as Usivka in the early 18th century, it was renamed Becheyu (also Becha, or Bechka) in the 1750s, Oleksandriysk in 1784, and Oleksandriya shortly thereafter. The nearby lignite (brown coal) field was used beginning in the

Oleksandriya, city, south-central Ukraine, on the Inhulets River. Founded as Usivka in the early 18th century, it was renamed Becheyu (also Becha, or Bechka) in the 1750s, Oleksandriysk in 1784, and Oleksandriya shortly thereafter. The nearby lignite (brown coal) field was used beginning in the

Clara Hughes: Speed skating: …medal total was surpassed by Penny Oleksiak in 2021.

Torez, city, southeastern Ukraine. The settlement was established as Oleksiyivka by runaway serfs in the 1770s and expanded with the growth of coal mining in the 1860s. In 1867 it was renamed Chystyakove; in 1964 it became Torez in honour of the recently deceased French Communist Party leader

Zoroastrianism: Sources: …India and the treatise entitled ʿOlemā-ye Islām (“The Doctors of Islam”), with decidedly Zurvanite tendencies.

Olenyok River, river rising on the southern slopes of the Bukochan Ridge on the Central Siberian Plateau and flowing mainly through Sakha (Yakutiya), east-central Russia. The total length of the river is 1,424 miles (2,292 km), and it has a drainage basin of 84,500 square miles (219,000 square km).

Olenyok River, river rising on the southern slopes of the Bukochan Ridge on the Central Siberian Plateau and flowing mainly through Sakha (Yakutiya), east-central Russia. The total length of the river is 1,424 miles (2,292 km), and it has a drainage basin of 84,500 square miles (219,000 square km).

Olenekian Stage, upper of two divisions of the Lower Triassic Series, representing those rocks deposited worldwide during Olenekian time (251.2 million to 247.2 million years ago) in the Triassic Period. The stage name is derived from the Olenyok, or Olenek, River of Siberia. The stratotype for the

Olenellus, genus of trilobites (extinct arthropods) common in but restricted to Early Cambrian rocks (542 million to 521 million years ago) and thus a useful guide fossil for the Early Cambrian. Olenellus had a well-developed head, large and crescentic eyes, and a poorly developed, small

Viktor Mikhaylovich Chernov was a founder of the Russian Social Revolutionary Party in 1902, who spent much of his life in exile but was briefly a minister in provisional governments in Russia (May 5–Sept. 1, 1917). A revolutionist from 1893, Chernov became a member of his party’s central

Olenyok River, river rising on the southern slopes of the Bukochan Ridge on the Central Siberian Plateau and flowing mainly through Sakha (Yakutiya), east-central Russia. The total length of the river is 1,424 miles (2,292 km), and it has a drainage basin of 84,500 square miles (219,000 square km).

oleograph, colour lithograph produced by preparing a separate stone by hand for each colour to be used and printing one colour in register over another. The term is most often used in reference to commercial prints. Sometimes as many as 30 stones were used for a single print. The technique was

naval stores: …stores are derived from the oleoresin, a fluid commonly called crude turpentine, that exudes from incisions made in the living trees. Wood naval stores are obtained by the chemical processing of deadwood.

horticulture: …plants for food (pomology and olericulture) and plants for ornament (floriculture and landscape horticulture). Pomology deals with fruit and nut crops. Olericulture deals with herbaceous plants for the kitchen, including, for example, carrots (edible root), asparagus (edible stem), lettuce (edible leaf), cauliflower (edible

Oléron Island, island in the Bay of Biscay, forming part of the Charente-Maritime département, Poitou-Charentes région of France. It is located off the coast of France, south of La Rochelle and north of the Gironde Estuary. Oléron is the second largest French island (after Corsica), with an area of

Moustiers faience: …Moustiers factory was that of Joseph Olerys, founded in 1738 and active until c. 1793. Olerys introduced polychrome decoration, producing faience in the Bérain style painted in purple, soft green, and orange as well as blue. Other polychrome faience wares produced by this factory were decorated with such designs as…

Yury Karlovich Olesha was a Russian prose writer and playwright whose works address the conflict between old and new mentalities in the early years of the Soviet Union. Olesha was born into the family of a minor official. He lived in Odessa from childhood, eventually studying for two years at

Zbigniew Oleśnicki was a Polish statesman and cardinal who was chief councillor to King Władysław II and regent of Poland (1434–47). A member of the Polish noble house of Dębno of Oleśnica, he became the leading member of the royal Privy Council after he saved the king’s life at the Battle of

olethreutid moth, (subfamily Olethreutinae), any of a group of moths in the family Tortricidae (order Lepidoptera) that contains several species with economically destructive larvae. The pale caterpillars roll or tie leaves and feed on foliage, fruits, or nuts. Some examples include Cydia

olethreutid moth, (subfamily Olethreutinae), any of a group of moths in the family Tortricidae (order Lepidoptera) that contains several species with economically destructive larvae. The pale caterpillars roll or tie leaves and feed on foliage, fruits, or nuts. Some examples include Cydia

Heidelberg Catechism: …written in 1562 primarily by Caspar Olevianus, the superintendent of the Palatinate church, and Zacharias Ursinus, a professor of the theological faculty of the University of Heidelberg. It was accepted at the annual synod of the Palatinate church in 1563.

Ethiopia: Challenges to the regime: …southern Ethiopia, where the long-dormant Oromo Liberation Front (OLF) became active. By May 1991, with EPRDF forces controlling Tigray, Welo, Gonder, Gojam, and about half of Shewa, it was obvious that the army did not have sufficient morale, manpower, weapons, munitions, and leadership to stop the rebels’ advance on Addis…

smell, the detection and identification by sensory organs of airborne chemicals. The concept of smell, as it applies to humans, becomes less distinct when invertebrates and lower vertebrates (fish and amphibians) are considered, because many lower animals detect chemicals in the environment by

olfactory bulb, structure located in the forebrain of vertebrates that receives neural input about odours detected by cells in the nasal cavity. The axons of olfactory receptor (smell receptor) cells extend directly into the highly organized olfactory bulb, where information about odours is

chemoreception: Fish: …on accessory cells in the olfactory epithelium. In contrast, in rockfish and some other benthic fish, the volume changes produced in the mouth by respiratory movements compress and expand accessory chambers that are associated with the olfactory epithelium, causing water to move into and out of the nasal cavity. The…

human nervous system: Olfactory nerve (CN I or 1): Bipolar cells in the nasal mucosa give rise to axons that enter the cranial cavity through foramina in the cribriform plate of the ethmoid bone. These cells and their axons, totaling about 20 to 24 in number, make up…

nasal tumour: Olfactory neuroblastoma is a highly malignant tumour that originates in the olfactory (smell) receptor cells, located in the upper rear portion of the nose. This tumour is one of the few that can generally be obliterated with radiation treatment.

nose: …respiratory tract and contains the olfactory organ. It provides air for respiration, serves the sense of smell, conditions the air by filtering, warming, and moistening it, and cleans itself of foreign debris extracted from inhalations.

olfactory receptor, protein capable of binding odour molecules that plays a central role in the sense of smell (olfaction). These receptors are common to arthropods, terrestrial vertebrates, fish, and other animals. In terrestrial vertebrates, including humans, the receptors are located on

smell, the detection and identification by sensory organs of airborne chemicals. The concept of smell, as it applies to humans, becomes less distinct when invertebrates and lower vertebrates (fish and amphibians) are considered, because many lower animals detect chemicals in the environment by

olfactory system, the bodily structures that serve the sense of smell. The system consists of the nose and the nasal cavities, which in their upper parts support the olfactory mucous membrane for the perception of smell and in their lower parts act as respiratory passages. The bony framework of the

Langjökull: …rivers, including the Hvítá and Ölfusá. Haga Lake (Hagavatn) is at the foot of the glacier.

For someone who needed a teammate’s misfortune to even make the team in 1972, tiny Soviet gymnast Olga Korbut had little trouble snagging the sport’s spotlight and endearing herself to millions. Korbut, 4 feet 11 inches (1.5 metres) tall and 85 pounds (38 kilograms), qualified as an alternate, but

Olgas, group of tors (isolated weathered rocks) in southwestern Northern Territory, Australia. The Olgas are a circular grouping of some 36 red conglomerate domes rising from the desert plains north of the Musgrave Ranges. They occupy an area of 11 square miles (28 square km) within Uluru–Kata

Olgas: …National Park) and culminate at Mount Olga, 1,500 feet (460 metres) above the plain and 3,507 feet above sea level. Mount Olga is the most westerly of Australia’s three giant tors; the others are Uluru/Ayers Rock and Mount Conner (Artilla). They were visited and named in 1872 after Queen Olga…

St. Olga ; feast day July 11) was the princess who was the first recorded female ruler of the Rus and the first member of the ruling family of Kyivan Rus to adopt Christianity. She was canonized as the first Kyivan saint of the Orthodox Church and is the patron saint of widows and converts. Olga

Olgas, group of tors (isolated weathered rocks) in southwestern Northern Territory, Australia. The Olgas are a circular grouping of some 36 red conglomerate domes rising from the desert plains north of the Musgrave Ranges. They occupy an area of 11 square miles (28 square km) within Uluru–Kata

Algirdas was the grand duke of Lithuania from 1345 to 1377, who made Lithuania one of the largest European states of his day. His son Jogaila became Władysław II Jagiełło, king of united Poland and Lithuania. Algirdas was one of the sons of the country’s ruler, Gediminas, and he began his long

Jainism: Festivals: …is the Shvetambara fasting ceremony, oli, which is celebrated for nine days twice a year (in March–April and September–October) and which corresponds to the mythical celestial worship of the images of the Tirthankaras. The most significant time of the Jain ritual year, however, is the four-month period, generally running from…

Nepal: Federal republic: In mid-October parliament elected Khadga Prasad Sharma Oli as prime minister, succeeding Koirala, and at the end of the month the legislators chose a woman, Bidhya Devi Bhandari, as the country’s new president. Oli resigned in July 2016, after his government coalition collapsed and before he was to face…

Páros: …is the once-attached island of Andíparos (Antiparos), the ancient Oliarus, whose limestone cavern is a tourist attraction. Pop. (2001) town, 4,463; municipality, 12,514; (2011) town, 4,326; municipality 13,715.

frankincense, aromatic gum resin containing a volatile oil that is used in incense and perfumes. Frankincense was valued in ancient times in worship and as a medicine and is still an important incense resin, particularly in Roman Catholic and Eastern Orthodox churches. The resin is also used in

conquistador: …by Pedro de Alvarado and Cristóbal de Olid, respectively, were sent to Mayan Guatemala and the Gulf of Honduras.

New Year’s Food Traditions from Around the World: Oliebollen—Netherlands:

Jean-Jacques Olier was the founder of the Sulpicians, a group of secular priests dedicated to training candidates for the priesthood. Ordained a priest in 1633, Olier soon came under the influence of St. Vincent de Paul, founder of a congregation of missionaries known as Lazarists. In 1641 Olier

oligarchy, government by the few, especially despotic power exercised by a small and privileged group for corrupt or selfish purposes. Oligarchies in which members of the ruling group are wealthy or exercise their power through their wealth are known as plutocracies. Read about the rise of the

iron law of oligarchy, sociological thesis according to which all organizations, including those committed to democratic ideals and practices, will inevitably succumb to rule by an elite few (an oligarchy). The iron law of oligarchy contends that organizational democracy is an oxymoron. Although

oligonucleotide, a short chain of nucleotides (nitrogen-containing units linked to a sugar and a phosphate group) that consist of either single- or double-stranded DNA or RNA. Oligonucleotides originally were used almost exclusively in laboratory research, being synthesized and used generally as

arthritis: Spondyloarthropathies: Patients typically develop acute oligoarthritis (two to four joints affected) of the lower extremities within weeks of gastrointestinal infection or of acquiring a sexually transmitted disease. Reiter arthritis is not considered an infectious arthritis, because the joint space is actually free of bacteria. Instead, an infection outside the joint…

Oligocene Epoch, third and last major worldwide division of the Paleogene Period (65.5 million to 23 million years ago), spanning the interval between 33.9 million to 23 million years ago. The Oligocene Epoch is subdivided into two ages and their corresponding rock stages: the Rupelian and the

oligochaete, any worm of the subclass Oligochaeta (class Clitellata, phylum Annelida). About 3,500 living species are known, the most familiar of which is the earthworm (q.v.), Lumbricus terrestris. Oligochaetes are common all over the world. They live in the sea, in fresh water, and in moist soil.

oligochaete, any worm of the subclass Oligochaeta (class Clitellata, phylum Annelida). About 3,500 living species are known, the most familiar of which is the earthworm (q.v.), Lumbricus terrestris. Oligochaetes are common all over the world. They live in the sea, in fresh water, and in moist soil.

oligoclase, the most common variety of the feldspar mineral plagioclase

oligodendrocyte, a type of neuroglia found in the central nervous system of invertebrates and vertebrates that functions to produce myelin, an insulating sheath on the axons of nerve fibres. Oligodendrocytes are subdivided into interfascicular and perineuronal types and have few cytoplasmic fibrils