Encyclopædia Britannica Australia -

Encyclopedias since 1768

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lead-210 dating ... Lebachia

lead-210 dating: method of age determination that makes use of the ratio of the radioactive lead isotope lead-210 to the stable isotope lead-206. The method has been applied to the ores of uranium. In the series of unstable products from the radioactive ...
Leadbelly: American folk-blues singer, songwriter, and guitarist whose ability to perform a vast repertoire of songs, in conjunction with his notoriously violent life, made him a legend.
Leadville: city, seat (1878) of Lake county, central Colorado, U.S., located 103 miles (166 km) west of Denver and 38 miles (61 km) south of Vail. It is situated in the upper Arkansas River valley in an area of national forests, ...
leadwork: sculpture, ornamental objects, and architectural coverings and fittings made of lead. Although the ease with which lead is smelted from lead ores ensured its early discovery, the softness of the metal restricted its use until Roman times. The earliest known ...
leaf: in botany, any usually flattened green outgrowth from the stem of a vascular plant. Leaves manufacture food for plants, which in turn ultimately nourish and sustain all land animals. Botanically, leaves are an integral part of the stem system, and ...
leaf beetle: any member of the 25,000 species of leaf-feeding insects of the family Chrysomelidae (order Coleoptera). Leaf beetles occur throughout the world but are concentrated in the tropics. They are oval and short-legged and tend to be less than 12 mm ...
leaf blister: worldwide disease of many woody plants and ferns caused by fungi of the genus Taphrina. Following cold, wet weather at budbreak, leaves become swollen, crinkled, and distorted with yellow, red, purple, brown, whitish, or gray blisters. Such leaves usually die ...
leaf cactus: the genus Epiphyllum, of about 15 species, family Cactaceae, native to tropical and subtropical America, including the West Indies. The plants are mostly epiphytes (perched on other plants) but sometimes grow from the ground.
leaf fibre: hard, coarse fibre obtained from leaves of monocotyledonous plants (flowering plants that usually have parallel-veined leaves, such as grasses, lilies, orchids, and palms), used mainly for cordage. Such fibres, usually long and stiff, are also called "hard" fibres, distinguishing them ...
leaf fish: any of about 10 species of fishes in the family Nandidae (order Perciformes). All live in fresh water, although some species may enter brackish water. Their geographic distribution is circumtropical, including the Amazon River basin, western Africa, India, southeastern Asia, ...
leaf insect: any of about 25 species of flat, green insects with a leaflike appearance that belong to the order Phasmatodea. The female has large leathery forewings (tegmina) that lie edge to edge on the abdomen and resemble, in their vein pattern, ...
leaf miner: any of a number of insect larvae that live and feed within a leaf. Leaf miners include caterpillars (order Lepidoptera), sawfly larvae (order Hymenoptera), beetle and weevil grubs or larvae (order Coleoptera), and maggots (larvae) of two-winged flies (order Diptera).
leaf monkey: species of langur (q.v.).
leaf roller moth: any member of the worldwide insect family Tortricidae (order Lepidoptera), named for the characteristic leaf rolling habit of the larvae. The name bell moth arises from the shape of the adult's folded, squarish forewings. These moths are characterized by their ...
leaf-cutter bee: any of the insects in the family Megachilidae (order Hymenoptera), particularly certain species in the genus Megachile. Leaf-cutter bees differ from related species in that they collect pollen on their abdomens rather than on their hind legs. The solitary female, ...
leaf-nosed bat: any of almost 250 species of New World and Old World bats belonging to the families Phyllostomidae and Hipposideridae that have a flat projection on the muzzle that often resembles a leaf. The purpose of the leaf structure is not ...
leaf-nosed snake: any of four species of small burrowing snakes of the family Colubridae that have the nose shield enlarged and flattened, with free edges. Several subspecies of each also exist. The two members of the genus Phyllorhynchus are found in creosote-bush ...
leaf-rolling grasshopper: (family Gryllacrididae), any of a group of orthopteran insects that are wingless or nearly wingless and have long cerci and antennae. The California leaf roller (Camptonotus carolinensis), about 15 mm (0.5 inch) long, is active at night, as are other ...
leaf-rolling weevil: any of the beetles of the subfamily Attelabidae of the family Curculionidae (order Coleoptera), so named because of the way in which females protect their newly laid eggs by rolling them up inside a growing leaf. After hatching, the larvae ...
leafbird: (genus Chloropsis), any of about eight species of short-legged, grass-green birds (family Irenidae, order Passeriformes), from Southeast Asia and the Philippines. Some authorities place the leafbird in the bulbul family (Pycnonotidae).
leafcutter ant: any of 39 ant species abundant in the American tropics, easily recognized by their foraging columns composed of hundreds or thousands of ants carrying small pieces of leaves. These moving trails of cut foliage often stretch over 30 metres (100 ...
leafhopper: any of the small, slender, often beautifully coloured and marked sap-sucking insects of the large family Cicadellidae (Jassidae) of the order Homoptera. They are found on almost all types of plants; however, individual species are host specific. Although a single ...
leafy liverwort: any of numerous species of liverworts (class Hepaticae), generally of the order Jungermanniales, in which the plant body is prostrate and extends horizontally in leaflike form with an upper and lower surface. About three-quarters of all liverworts species belong to ...
league: any of several European units of measurement ranging from 2.4 to 4.6 statute miles (3.9 to 7.4 km). In English-speaking countries the land league is generally accepted as 3 statute miles (4.83 km), although varying lengths from 7,500 feet to ...
League of Women Voters: nonpartisan American political organization that has pursued its mission of promoting active and unhampered participation in government since its establishment in 1920.
Leah: in the Old Testament (primarily in Genesis), first wife of Jacob (later Israel) and the traditional ancestor of five of the 12 tribes of Israel. Leah was the mother of six of Jacob's sons: Reuben, Simeon, Levi, Issachar, Zebulun, and ...
Leahy, Frank: American college gridiron football coach whose teams at the University of Notre Dame won 87 games, lost 11, and tied 9. His career winning percentage of .864 (107-13-9) ranks second in the history of first-division college football to that of ...
Leahy, William Daniel: American naval officer who served as personal chief of staff to President Franklin D. Roosevelt during World War II.
Leakey, Louis S.B.: Kenyan archaeologist and anthropologist whose fossil discoveries in East Africa proved that human beings were far older than had previously been believed and that human evolution was centred in Africa, rather than in Asia, as earlier discoveries had suggested. Leakey ...
Leakey, Mary Douglas: English-born archaeologist and paleoanthropologist who made several fossil finds of great importance in the understanding of human evolution. Her early finds were interpreted and publicized by her husband, the noted anthropologist Louis S.B. Leakey.
Leakey, Richard: Kenyan anthropologist, conservationist, and political figure who was responsible for extensive fossil finds related to human evolution and who campaigned publicly for responsible management of the environment in East Africa.
Lean, Sir David: British film director whose literate, epic productions featured spectacular cinematography and stunning locales.
Leaning Tower of Pisa: medieval structure in Pisa, Italy, that is famous for the settling of its foundations, which caused it to lean 5.5 degrees (about 15 feet [4.5 metres]) from the perpendicular by the late 20th century. The bell tower, begun in 1173 ...
leap of faith: metaphor used by the 19th-century Danish philosopher Soren Kierkegaard in his Afsluttende uvidenskabelig Efterskrift (1846; Concluding Unscientific Postscript) to describe commitment to an objective uncertainty, specifically to the Christian God. For Kierkegaard, God is totally other than man; between God ...
leap year: year containing some intercalary period, especially a Gregorian year having a 29th day of February instead of the standard 28 days. The astronomical year, the time taken for the Earth to complete its orbit around the Sun, is about 365.242 ...
Lear: legendary British king and central character of William Shakespeare's King Lear. One of the most moving of Shakespeare's tragic figures, Lear grows in self-awareness as he diminishes in authority and loses his illusions. Lear at the outset presents the very ...
Lear, Edward: English landscape painter who is more widely known as the writer of an original kind of nonsense verse and as the popularizer of the limerick. His true genius is apparent in his nonsense poems, which portray a world of fantastic ...
Lear, William P: self-taught American electrical engineer and industrialist whose Lear Jet Corporation was the first mass-manufacturer of business jet aircraft in the world. Lear also developed the automobile radio, the eight-track stereo tape player for automobiles, and the miniature automatic pilot for ...
learning: the alteration of behaviour as a result of individual experience. When an organism can perceive and change its behaviour, it is said to learn.
learning theory: any of the proposals put forth to explain changes in behaviour produced by practice, as opposed to other factors, e.g., physiological development.
Leary, Timothy: American psychologist and author who was a leading advocate for the use of LSD and other psychoactive drugs.
lease: a contract for the exclusive possession of property (usually but not necessarily land or buildings) for a determinate period or at will. The person making the grant is called the lessor, and the person receiving the grant is called the ...
least squares approximation: in statistics, a method for estimating the true value of some quantity based on a consideration of errors in observations or measurements. In particular, the line (function) that minimizes the sum of the squared distances (deviations) from the line to ...
leather: animal skins and hides that have been treated to preserve them and make them suitable for use.
leatherleaf: (Chamaedaphne calyculata), evergreen shrub of the heath family (Ericaceae). The name is also sometimes applied to a stiff-leaved fern.
Leaud, Jean-Pierre: French screen actor who played leading roles in some of the most important French New Wave films of the 1960s and '70s, particularly ones by Francois Truffaut.
leavening agent: substance causing expansion of doughs and batters by the release of gases within such mixtures, producing baked products with porous structure. Such agents include air, steam, yeast, baking powder, and baking soda.
Leavenworth: city, seat (1855) of Leavenworth county, northeastern Kansas, U.S. It lies on the Missouri River. First settled as Fort Leavenworth in 1827 by Colonel Henry H. Leavenworth to protect travelers on the Santa Fe and Oregon trails, the town was ...
Leavis, F.R.: English literary critic who introduced a new seriousness into a field still influenced by the informal narrative approach taken by George Saintsbury and other English critics.
Leavitt, Henrietta Swan: American astronomer known for her discovery of the relationship between period and luminosity in Cepheid variables, pulsating stars that vary regularly in brightness in periods ranging from a few days to several months.
Lebachia: a genus of extinct cone-bearing plants known from fossils of the Late Carboniferous and Early Permian epochs (from about 320 to 258 million years ago). Lebachia and related genera in the family Lebachiaceae, order Coniferales (sometimes family Voltziaceae, order Voltziales), ...