Dipping Needle
a magnetized needle, moving in a vertical plane, on an axis which passes at right angles exactly through the center of gravity. When thus mounted it will, if placed anywhere not in the magnetic equator, dip or point downward. The position of the magnetic pole can thus be determined from the intersection of two or more lines formed by making experiments with the dipping needle at various places. The inclination or dip of the magnetized needle was not known to the Chinese, who had discovered its variation during the 12th century. This element of terrestrial magnetism appears to have been discovered by Robert Norman, a compass-maker of Ratcliff, London, who detected the dip, and published the fact in 1576. He contrived the dipping needle, and found the dip at London to be 71° 50'. Sir James Ross reached the magnetic pole, lat 70° 5' 17" N., and lon. 96° 46' 45" W., on June 1, 1831. The amount of dip was 89° 59′.
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Diprotodon
a gigantic pachydermoid marsupal mammal, resembling in most essential respects the kangaroo, the dentition especially showing many points of affinity. It is found in the Pleistocene or Upper Tertiary beds of Australia. DIPSACEÆ, the Teazel family, a natural order of exogenous plants, consisting of herbs or undershrubs. They are found in the S. of Europe, the Levant, and the Cape of Good Hope. Lindley enumerates 6 genera and 160 species.
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Dipsas
a genus of non-venomous serpents of the family Colubriformes. They are nocturnal, arboreal animals, feeding chiefly on lizards, frogs and small birds, and are most abundant in neotropical and Oriental regions.
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Dipsomania
a term denoting an insane craving for intoxicating liquors, when occurring in a confirmed or habitual form. It is often of hereditary origin, but may result from sunstroke, from some injury to the brain, or from disease. The only remedy appears to be seclusion, with enforced abstinence and healthy occupation. Homes for this purpose have been established in Great Britain under the Habitual Drunkards Act of 1879. A number of corresponding institutions have long existed in the United States.
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Diptych
originally signified the same as diploma, something folded; the double tablets of metal, ivory, etc., used by the Greeks and Romans. Diptychs became important in the Christian Church, in them being written the names of Popes, and other distinguished persons, who had deserved well of the Church, to be mentioned in the Church prayers. Diptychs also often contained pictures of Biblical scenes.
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Dipus
the jerboas, a genus of rodents, the type of the family Dipodidæ. It includes about 20 species. D. ægypticus is a native of northeastern Africa, Arabia, and southwestern Asia. It lives in burrows, and is generally gregarious. It is about six inches long, with a tail eight inches long, exclusive of the tuft at the end. Its upper surface is of a grayish sand color, the lower surface white, hite, the tail pale yellowish above, and white beneath; the tip white, with an arrow-shaped black mark on the upper surface.
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Direct Legislation
. See Initiative; Referendum ; Recall
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Directional Wireless
a term used to describe the general system whereby an aviator is kept informed of his position in the air by means of successive wireless signals from some known ECONOMIC DETERMINISM, or the Materialistic Interpretation of History: the doctrine that human institutions and activities, beliefs, morality, and general physiological effects of changes in temperature, humidity, etc., which accompany variations in barometric pressure. It has also been attributed to variations in atmospheric electricity. D point on his route, the direction from which such signals come being indicated by various forms of recording apparatus carried on the airplane. DIRECTION FINDER, or RADIO COMPASS, a term applied to any device by which a radio signal receiver is enabled to determine the direction of the sender. Particularly a device used in aviation in which the pointer responds to the control of radio waves from a certain station, being thus kept constant in one direction. directi A novel application of direction finding is the system of guiding ships through channels recently installed in Ambrose Channel, New York. A cable is laid in the middle of the channel and through this an electric current flows. Sensitive detectors of magnetic waves, attached to the sides of incoming ships, are deflected by any departure from the cable, thus keeping the pilot instructed at each moment whether or not he is close to his course. DISARMAMENT. (See WASHINGTON CONFERENCE, and LEAGUE OF NATIONS, 1921.)
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Directory
the name given to a body of five officers to whom the executive authority in France was committed by the constitution of the year III (1795). The two legislative bodies, called the councils, elected the members of the directory. By the revolution of the 18th Brumaire the directory and the constitution of the year III were abolished. It was succeeded by the consulate.
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Directrix
in mathematics, a line governing the direction of another line. If a point so move that the distance from a given fixed point is to its perpendicular distance from a fixed straight line in a constant ratio, it describes a conic section of which the fixed straight line is termed the directrix, and the fixed point the focus. The constant ratio referred to is termed the eccentricity, and its magnitude determines the nature of the conic.
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Dirge
funeral music or hymn expressing grief or lamentation, usually played or sung at funerals or at services in memory of the dead. The word "dirge" derives its name from a Latin hymn beginning with "Dirige, Domine, Deus meus, in conspectu tuo viam meum." (Direct, O Lord, my God, my ways in "Lycidus," is a well-known dirge.
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Dirhem
a modification of the Greek drachma, the name under the caliphs for of silver equivalent to about 45 a weight grains, and was also used for precious stones and medicine in Abrabia, Persia, Eygpt, and Turkey. As a coin the value under varied, but may be given at 5½d. the caliphs. In Turkey, the name dirhem has been given to the much smaller weight, the French gramme.
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Dirk
a kind of dagger formerly used as a weapon of offense by the Highlanders of Scotland. Dirks are worn by midshipmen and cadets of the royal navy, part of the full Kighland and still form and costume.
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