a1x+b1y=c1,a2x+b2y=c2,
a1x+b1y=c1,a2x+b2y=c2,
a1x+b1y=c1,
a2x+b2y=c2,
is given by
x(a1b2-a2b1) =c1b2-c2b1,y(a1b2-a2b1) =a1c2-a2c1.
x(a1b2-a2b1) =c1b2-c2b1,y(a1b2-a2b1) =a1c2-a2c1.
x(a1b2-a2b1) =c1b2-c2b1,
y(a1b2-a2b1) =a1c2-a2c1.
Herexandyhave the same coefficienta1b2-a2b1. This is called a determinant of the second order, and is written
|a1,b1||a2,b2|.
|a1,b1||a2,b2|.
|a1,b1|
|a2,b2|.
We may now write
Similarly with three equations,
a1x+b1y+c1z=d1,a2x+b2y+c2z=d2,a3x+b3y+c3z=d3,
a1x+b1y+c1z=d1,a2x+b2y+c2z=d2,a3x+b3y+c3z=d3,
a1x+b1y+c1z=d1,
a2x+b2y+c2z=d2,
a3x+b3y+c3z=d3,
we find
x{a1(b2c3-b3c2) +a2(b3c1-b1c3) +a3(b1c2-b2c1)}=d1(b2c3-b3c2) +d2(b3c1-b1c3) +d3(b1c2-b2c1)
x{a1(b2c3-b3c2) +a2(b3c1-b1c3) +a3(b1c2-b2c1)}=d1(b2c3-b3c2) +d2(b3c1-b1c3) +d3(b1c2-b2c1)
x{a1(b2c3-b3c2) +a2(b3c1-b1c3) +a3(b1c2-b2c1)}
=d1(b2c3-b3c2) +d2(b3c1-b1c3) +d3(b1c2-b2c1)
The coefficient ofx, and the right-hand member, are here determinants of the third order, and the result is written
When the coefficient ofxis expanded fully, it consists of six terms, half of them positive and half negative, each term being the product of three letters, one from each row and one from each column. Thus in every term, such as the leading terma1b2c3, the three lettersa,b,c, and the three suffixes 1, 2, 3, all occur once and once only. With regard to the signs, we note that if the lettersa,b,care always kept in this order, an interchange of two suffixes changes the sign. Thus, e.g. we may start from +a1b2c3, interchange the suffixes 2 and 3, and thus find -a1b3c2. Again, if in the latter term -a1b3c2we interchange the suffixes 1 and 3, we find +a3b1c2. It is easy to verify that after any number of interchanges of this kind a particular term will always come up with the same sign.
Thus the interchange of two rows (and similarly of two columns) changes the sign of the determinant. It follows that if two rows (or two columns) are identical, the determinant is zero. It is now easy to define functions ofn2letters, arranged in a square array ofnrowsandncolumns, with similar properties to those observed above in the case of determinants of the third order. Determinants are very extensively used in higher algebra, co-ordinate geometry, and other branches of mathematics. See alsoElimination.—Bibliography:C. Smith,Algebra; T. Muir,Theory of Determinants.
Determinants, in biology, the name applied by Weismann to hypothetical particles contained in the nuclei of germ-cells, which determine the existence and nature of the various parts of the body of the embryo. The theory of determinants is part of an elaborate attempt to explain the facts of heredity on a mechanical basis. Although it may serve as a working hypothesis, it is regarded with disfavour by many experts, and may be regarded as an elaboration of the 'provisional theory of pangenesis' advanced by Darwin.
Deter´minism, a term employed by recent writers, especially since J. Stuart Mill, to denote a philosophical theory which holds that the will is not free, but is invincibly determined either—according to the older form of the theory—by a motive furnished by Providence, or—according to the modern form—by the aggregation of inherited qualities and tendencies. Biological determinism maintains that each of our voluntary acts finds its sufficient and complete cause in the physiological conditions of the organism. Psychological determinism ascribes efficiency to the psychical antecedents. Opposed to determinism is the doctrine of indeterminism or indifferentism. SeeFree-will.
Det´inue, in law, the form of action whereby a plaintiff seeks to recover a chattel personal unlawfully detained.
Det´mold, a town, Germany, capital of Lippe-Detmold, on the left bank of the Werra, 50 miles south-west of Hanover, with a new and an old palace (or castle), good public library, and museum. In the vicinity a colossal statue has been erected to the Hermann or Arminius who overthrew the Roman general Varus and his legions in a battle which was fought near this place. The Senner race of horses is bred near Detmold. Pop. 14,295.
Det´onating Powders, certain chemical compounds which, on being exposed to heat or suddenly struck, explode with a loud report, owing to one or more of the constituent parts suddenly assuming the gaseous state. The chloride and iodide of nitrogen are very powerful detonating substances. Mercuric fulminate or fulminating mercury (C2HgN2O2) explodes violently when forcibly struck or when heated to 180°F. It is used for making percussion caps, and in detonators for exploding guncotton and nitroglycerin preparations. Silver fulminate (C2Ag2N2O2) explodes even more violently.
Detonating Tube, a species of eudiometer, being a stout glass tube used in chemical analysis for detonating gaseous bodies. It is generally graduated into centesimal parts, and perforated by two opposed wires for the purpose of passing an electric spark through the gases which are introduced into it, and which are confined within it over mercury and water.
Detroit(de-troit´; Fr.détroit, a strait or channel), a flourishing port and city of the United States, the largest town in Michigan, situated on the Detroit River, connecting Lakes Erie and St. Clair. The site rises gradually from the river, and the city is generally well built. Among the chief edifices are the city hall, the house of correction, post office, and opera-house. Detroit has increased very rapidly, a fact which is due to its admirable position for trade, and to its connections with a region into which a constant tide of emigration is flowing. Among the industrial establishments are saw-mills, flour-mills, building-yards for ships and boats, foundries, tanneries, blast-furnaces, pork-packing establishments, tobacco and cigar manufactories, and locomotive works. The harbour is one of the finest in the United States, and has a depth of water sufficient for the largest vessels. Detroit owes its origin to the French, who visited the site in 1648 and erected the Fort Pontchartrain in 1701. Pop. 688,028 (1919).
Detroit River, orStrait of St. Clair, a river or strait of North America which runs from Lake St. Clair to Lake Erie. It is 28 miles long, and of sufficient depth for the navigation of large vessels. It is about ¾ mile wide opposite Detroit and enlarges as it descends.
Dettingen(det´ing-en), the name of several places in Germany, amongst which is a village of Bavaria, on the right bank of the Main, famous for the victory gained by the English and Austrians under George II of England over the French in 1743.
Deuca´lion, in Greek mythology, the son of Prometheus and father of Hellen, ancestor of the Hellenes. According to tradition he saved himself and his wife, Pyrrha, from a deluge which Zeus had sent upon the earth, by building a ship which rested upon Mount Parnassus. To repair the loss of mankind they were directed by an oracle to throw stones behind them; the stones thrown by Deucalion became men, those thrown by Pyrrha women.
Deus ex Machinâ(mak´i-na; Lat., 'a god out of the machine'), a phrase used to designate the resorting to supernatural causes to explain phenomena that one is not able to account for by natural means. The phrase is taken from the practice on the classical stage of introducing a god from above by means of some mechanical contrivance in order to effect a speedydénouementof the plot.
Deuteronomy(Gr.deuteronomion, the second law), the name of the fifth book of thePentateuch(q.v.). Until the seventeenth century it was believed to have been written by Moses, but now it is generally held to be a compilation, the bulk of it having been written in the reign of Manasseh, or according to other scholars in the reign of Josiah. At any rate the book was discovered or rediscovered while Josiah was king (2 Kings, xxii). It represents the latest phase in the development of the teaching of Moses. Its chief aim is to combat idolatry, and to concentrate the religious life of the country at Jerusalem. It has a lofty moral tone. Of one passage (vi, 4 and 5) Christ said: "On these two commandments hang all the law and the prophets" (Matt.xxii, 40), and all His answers to the Tempter in the Wilderness are taken from the book ofDeuteronomy.
Deutz(doits), a town in Prussia, on the right bank of the River Rhine, opposite the city of Cologne, with which it communicates by a bridge. It is strongly fortified as part of the defences of Cologne, in which it is now incorporated. There are some manufactories of porcelain and glass, also an iron-foundry and machine-works. Pop. 17,060.
Deut´zia, a genus of plants, nat. ord. Saxifragaceæ, containing seven or eight species, all of which are interesting from the beauty of their flowers, some of them favourite garden and greenhouse plants. They are small shrubs indigenous to China and Japan, and Northern India.
De Valera, Eamon, Irish Republican, born at New York in 1883, his father being a Spaniard, and his mother an Irishwoman. Educated at the Royal University of Ireland, he early became known for his revolutionary activities. In 1917 he was elected president of the Gaelic League and was arrested as an agitator. Elected to Parliament in 1918, while he was in prison, he refused to take his seat. He was elected 'President' of the so-called 'Irish Republic' soon afterwards, and in Feb., 1919, escaped from prison and reached New York, where he started an active propaganda and began to raise funds for the Irish cause. He returned to Ireland in 1921.
Dev´enter, an old town in Holland, province of Overijssel, 8 miles north from Zutphen, at the confluence of the Schipbeek and Ijssel. Its industries embrace carpets, cast-iron goods, printed cottons, hosiery, and a kind of cake calledDeventer Koek. It has a large export trade in butter. Pop. 32,483 (1918).
Dev´eron, a river of Scotland belonging to Aberdeenshire and Banffshire, 60 miles long. It flows into the Moray Firth at Banff.
Deviation of the Compass, the deflection of a ship's compass needle from the magnetic meridian, caused by adjacent iron. Hard iron is very retentive of a magnetic state, and is specially liable to become magnetized during a hammering process, as in the building of the ship. Soft iron easily receives or loses magnetism, and its magnetic state varies with every shifting of the ship's head. The effect of the former can be counteracted by magnets suitably placed near the compass, that of the latter by spheres of soft iron. The ship is swung, and the compass errors found in the various positions. The effects of the several contributing causes can then be separated, and the nature of the correctors necessary inferred with considerable accuracy. When these have been provided, the small residual errors for different positions of the ship are determined, and a table is constructed from which the navigator may read the slight correction to apply to the indication of his compass in steering any desired course.
Device´, a name common to all figures, ciphers, characters, rebuses, and mottoes which are adopted by a person or a family by way of badge or distinctive emblem, often a representation of some natural body, with a motto or sentence applied in a figurative sense.
Devil(Gr.,diabolos, a slanderer or accuser), in theology, the name given to a fallen angel, who is the instigator of evil, and the ruler of darkness. Most of the old religions of the East acknowledge a host of devils. The doctrine of Zoroaster, who adopted an evil principle called Ahriman, opposed to the good principle and served by several orders of inferior spirits, spread the belief in such spirits among the people. The Greek mythology did not distinguish with the same precision between good and bad spirits. With the MohammedansEblis, or the devil, was an archangel whom God employed to destroy a pre-Adamite race ofjinns, or genii, and who was so filled with pride at his victory that he refused to obey God. The Satan of the New Testament is also a rebel against God. He uses his intellect to entangle men in sin and to obtain power over them. But he is not an independent self-existent principle like the evil principle of Zoroaster, but a creature subject to omnipotent control. The doctrine of Scripture on this subject soon became blended with numerous fictions of human imagination, with the various superstitions of different countries, and the mythology of the pagans. The excited imaginations of hermits in their lonely retreats, sunk as they were in ignorance and unable to account for natural appearances, frequently led them to suppose Satan visibly present; and innumerable stories were told of his appearance, and his attributes—the horns, the tail, the cloven foot,—distinctly described. Theology has always treated the devil from a psychological or ethicalstandpoint. From the New Testament we hardly learn more regarding the devil than that he has a distinct personality; that he is a spirit or angel who in some way fell; that he is devoid of truth and of all moral goodness, always warring against the soul of man and leading him towards evil; that he has demons, spirits, or angels under him who work his will, and enter into or 'possess' men; but of his or their origin, original state, or fall, we really learn nothing.—Bibliography: Mayer,Historia Diaboli; Lecanu,Histoire de Satan, sa chute, son culte, ses manifestations, ses œuvres; Carus,History of the Devil.
Devil-fish, the popular name of various fishes, one of them being the angler. Among others the name is given to several large species of ray (especiallyCeratoptera Vampyruswhich attains the breadth of 20 feet) occasionally captured on the Atlantic and Pacific coasts of America, and much dreaded by divers, whom they are said to devour after enveloping them in their vast wings. During gales of wind or owing to strong currents these immense fish are driven into shoal water, and, being unable to extricate themselves, fall an easy prey to the fishermen, who obtain considerable quantities of oil from their livers. The name is also applied to the larger eight-armed cephalopod molluscs belonging toOctopusand allied genera. A combat with one of these is described in Victor Hugo'sToilers of the Sea.
Devil's Bit, the common name of a British species of scabious (Scabiōsa succīsa), nat. ord. Dipsaceæ. It has heads of blue flowers nearly globular, and a fleshy root, which is, as it were, cut or bitten off abruptly. It flowers from June to October, and is common in meadows and pastures.
Devil's Bridge, a name for several bridges in wild situations; one being in Cardiganshire, spanning a gorge of the Mynach; another in Switzerland, over which the St. Gothard Railway crosses the Reuss.
Devil's Parliament, the name given to a Parliament convened by Henry VI, which met at Coventry in 1459 and unjustly accused the Duke of York of high treason.
Devil's Punch-bowl, a small lake of Ireland, near the Lakes of Killarney, between 2000 and 3000 feet above the sea, supposed to be the crater of an ancient volcano. The name is also given to Highcomb Bottom, a glen in Surrey.
Devil's Wall, in the south of Germany, a structure which was originally a Roman rampart, intended to protect the Roman settlements on the left bank of the Danube and on the right bank of the Rhine against the inroads of the Teutonic and other tribes. Remains of it are found from the Danube, in Bavaria, to Bonn, on the Rhine.
Devil-worship, the worship paid to the devil, an evil spirit, a malignant deity, or the personified evil principle in nature, by many of the primitive tribes of Asia, Africa, and America, under the assumption that the good deity does not trouble himself about the world; or that the powers of evil are as mighty as the powers of good, and have in consequence to be bribed and reconciled. There is a sect called devil-worshippers inhabiting Armenia and the valley of the Tigris, who pay respect to the devil, to Christ, and to Allah or the supreme being, and also worship the sun.
Devise, in law, usually the disposition of real estate by will, but also sometimes applied to any gift by will, whether of real or personal estate.
Devitrification.Glass which has been kept for a considerable time at a temperature just below its fusion-point gradually becomes opaque or crystalline in appearance; this phenomenon is spoken of asdevitrification. Poor glass, badly prepared window-glass, and glass which has been subjected to strain tend to devitrify on exposure to air, some of the ingredients separating in a crystalline form.
Devi´zes, a town in England, county of Wilts, giving name to a parliamentary division, finely situated on a commanding eminence, 82 miles west by south of London. The name is derived from the Lat.divisæ(terræ, divided lands), because the ancient castle of Devizes was built at the meeting-place of three different manors. Agricultural engines and implements are made, and malting is carried on. Pop. 6740.
Devon, orDevonshire, a maritime county in the s.w. of England, its northern coast being on the Bristol Channel and its southern on the English Channel; area, 1,671,364 acres, the county being the third largest of England. Its principal rivers are the Torridge and the Taw, flowing north into the Bristol Channel; and the Exe, Axe, Teign, Dart, and Tamar, flowing into the English Channel. From Exeter to the confines of Cornwall extends the wide and barren tract called Dartmoor; but the vale of Exeter, comprising from 120,000 to 130,000 acres, and the south extremity of the county calledSouth Hams, limited by a line drawn from Torbay to Plymouth Sound, are amongst the most fertile districts of England. Tin, lead, iron, copper, manganese, granite, and the clay used by potters and pipe-makers are the chief mineral products. The geological formation of the Old Red Sandstone is so largely developed that the term Devonian has to some extent become its synonym. Agriculture is in a somewhat backward state, owing, probably, to the general preference given to dairy husbandry, for which the extent and richness of its grass-lands make the county mostsuitable. Wheat, barley, beans, pease, and potatoes are the principal crops. About three-fourths of the county is under crops or in pasture. There is a large trade in butter, cheese, and live-stock, and the 'clotted' cream and cider of Devonshire are well known as specialities of the county. There are seven parliamentary divisions, each with one member. Pop. 699,703.—Bibliography:Victoria County History, Devonshire; F. J. Snell,Devonshire, Historical, Descriptive, and Biographical.
Devo´nian System, in geology, a name originally given to rocks in Devonshire and Cornwall, intermediate between the Silurian and Carboniferous strata, and consisting of sandstones, calcareous slates and limestones, &c. They are divided into lower, middle, and upper series, the middle most abounding in fossils, including corals, crinoids, brachiopods, and molluscs. Devonian rocks occupy a large area in Central Europe, as well as in the United States, Eastern Canada, and Nova Scotia. The terrestrial and lacustrine equivalents are known as the Old Red Sandstone.
Dev´onport, formerly a county borough and port of England, county of Devon, contiguous to Plymouth. It is the seat of one of the royal dockyards, and an important naval and military station. A bastioned wall and fosse defend the town on the north-east and south sides, while the sea entrance is protected by heavy batteries on Mount Wise. Connected with the dockyards and fortifications are the gun wharf, foundries, machine-works, rope-walks, store-houses, and naval and military barracks. It has no special trade beyond that connected with the dockyards and Government works. Formerly a parliamentary borough, returning two members to Parliament, Devonport now gives its name to a parliamentary division of Plymouth, with which it is amalgamated since Nov., 1914. Pop. 84,370.
Devonshire, Spencer Compton Cavendish, eighth Duke of, long known as Marquess of Hartington, born in 1833, died 1908. He was the eldest surviving son of the seventh Duke of Devonshire, whom he succeeded in the dukedom in 1891. He was educated at Trinity College, Cambridge, where he graduated asM.A.in 1854. He was attached in 1856 to Earl Granville's Russian mission, and in 1857 was elected as a Liberal one of the members for North Lancashire. In 1863 he was for a short time a Lord of the Admiralty, and he then became Under-Secretary for War, being raised to Cabinet rank as War Secretary in 1866. In 1868 he lost his seat for North Lancashire, but became Postmaster-General under Gladstone, and was returned for the Radnor boroughs. In 1871 he was appointed Chief Secretary for Ireland. He went out with the Gladstone ministry in 1874, and on Gladstone's retirement he became the leader of the Liberal party. On the fall of the Conservative Government in 1880 he was elected for North-East Lancashire, and became Secretary for India under Gladstone, being transferred to the War Office in 1882. In the general election of 1885 he was returned for the Rossendale division of Lancashire. He strenuously opposed Gladstone's Home Rule Scheme of 1886, and became the leader of the Liberal Unionists, but long declined to take office in the Cabinet. In 1895, however, he became Lord President of the Council, and from 1900 to 1902 he was President of the newly-instituted Board of Education. In 1903 he withdrew from co-operating with Mr. Balfour as Premier, mainly because he disliked the fiscal changes proposed by Chamberlain. He then accepted the position of head of the Free-Trade Unionists.
Dewis the name given to the minute drops of water which at certain times appear by night upon grass, flowers, foliage, and other surfaces which readily radiate heat. The first attempts at a scientific explanation of dew were made early in the nineteenth century, when Dr. Wells propounded his theory on the subject. According to this, the origin is to be found in the moisture previously contained in a vaporous state in the atmosphere. During the day the earth both absorbs and emits heat, but by night its supply of warmth is cut off, while it continues, under favouring circumstances, to lose heat by radiation into surrounding space. For any given state of the atmosphere, in respect of the amount of aqueous vapour it contains in a specified volume, there is a certain temperature at which it can hold just that amount and no more in suspension. If it be cooled to that temperature, it begins to deposit its moisture in the liquid form, and if the cooling proceeds further, more and more is deposited. This particular temperature is thedew-pointappropriate to the given state of humidity of the air. If the dew-point is below 32°F., the vapour will, when the dew-point is reached, pass directly into the solid form and be deposited as hoar-frost. While there is a certain amount of truth in the foregoing theory, it does not contain the whole facts of the case. Dr. John Aitken, of Falkirk, Stirlingshire, established by experiments that in most cases probably the dew found on plants does not come mainly from the atmosphere. To some extent it exudes from the plants themselves. They derive moisture from the soil, and in the process of supplying their tissues it passes to their outer surfaces, whence in the daytime it is evaporated into the air. By night the fall of temperature checks evaporation of this moisture, and when it reaches their surfaces, it may remain there in the form of dew-drops. Also, moistureis condensed out of the atmosphere upon the cooler plant surfaces, but even this has more often been yielded not long before to the atmosphere through the medium of the plant tissues, so that upon the whole the plants play a much more important part in the process than had been supposed. Dew is most copiously produced when there is a large difference between the day and night temperatures. Hence it is favoured by the absence of clouds, which would throw back much of the heat radiated from the earth. Other favouring circumstances are a still condition of the atmosphere, good radiating surfaces, and an abundant supply of moisture in the soil.
Dewar(dū´a˙r), Sir James, scientist, born at Kincardine-on-Forth, 1842, educated at Dollar Academy, Edinburgh University—where he was assistant to Lord Playfair when professor of chemistry—and Ghent. In 1873 he was elected Jacksonian professor of experimental philosophy at Cambridge, an office which he still holds, and in 1879 a professorial fellow of St. Peter's College. In the latter year he also became Fullerian professor of chemistry at the Royal Institution, London. He is a fellow of the Royal Society, has been awarded several medals and prizes for his scientific researches, including the Rumford medal in 1894 for his investigations into the properties of matter at its lowest temperatures, this branch of science, with which the liquefaction of air and gases is connected, being peculiarly his own. He was the first to reduce hydrogen gas to the liquid and solid form. Together with Sir F. Abel, he was the discoverer of cordite. He is an honorary graduate of several universities, a late president of the Chemical Society and vice-president of the Royal Society, and was president of the British Association in 1902. He has contributed numerous papers to the proceedings of the learned societies of Great Britain, and was knighted in 1904. His collected papers on spectroscopy appeared in 1915.
Dewar Flask, a flask devised by Dewar for the examination of liquefied gases. It consists of an inner vessel surrounded by a vacuum, which much reduces loss or gain of heat by the liquid. The principle now finds practical application in the 'Thermos Flask'.
Dewás, a native state of Central India consisting of two combined states with two chiefs. Total pop. 250,000. Dewás, the chief town, has a pop. of 5200.
Dewberry(Rubus cœsius), a European plant belonging to the ord. of the Rosaceæ, and to the same genus as the bramble, from which it is distinguished by its smaller berries, with fewer grains, and by the bloom, resembling dew, with which they are covered, and from which the plant derives its name. It is common in some parts of England. The Canadian dewberry (R. procumbens) yields a much superior fruit.
De Wet, Christian Rudolf, Boer general, born 1854 in the Orange Free State. His father removing into the Transvaal, he fought as a field-cornet at Majuba. As member of the Volksraad (1889-97) he helped to draw the two Dutch republics together, and in the South African War commanded first in Natal, and then in the west under Cronje, whose rescue at Paardeberg he attempted, but unsuccessfully. After March, 1900, he distinguished himself by his attacks on the British lines of communication, and by his skill in evading capture. He became commander-in-chief of the Free State forces, and was the only undefeated Boer general at the end of the war, after which he, with Louis Botha and Delarey, came to Europe to collect funds for his countrymen. A member of the Legislative Assembly and Minister of Agriculture, Orange Free State, from 1907 to 1914, he joined the rebellion at the outbreak of the European War. Captured at Waterburg on 1st Dec., he was sentenced to a fine of £2000 and six years' imprisonment, but was soon released. He publishedThe Three Years' Warin 1902.
Dewey, George, American naval officer, born at Montpellier, Vermont, 26th Dec., 1837, died 16th Jan., 1917. He began active service in the Mediterranean squadron, and in 1862, under Farragut, he was present at the passage of Forts Jackson and St. Philip. Lieutenant-commander in 1865, commander in 1872, he was in command of the Asiatic squadron in 1898, when he destroyed the Spanish fleet at Manila on 1st May. He was made Admiral of the Navy and was thanked by Congress. From 1900 till his death he was President of the General Board of the Navy.
Dewey, John, American philosopher and psychologist, born at Burlington, Vermont, 20th Oct., 1859. Educated at the University of Vermont, he received his Ph.D. degree from Johns Hopkins University. Professor of philosophy at the Universities of Minnesota, Michigan, and Chicago, where he was also director of the School of Education, he became professor of philosophy at Columbia University in 1904. He is one of the two (William James being the other) American leaders ofpragmatism, a philosophical conception according to which questions that have no bearing on experience and on life have no significance whatever, and are meaningless. (SeePragmatism.) His works include:Outlines of a Critical Theory of Ethics(1881),Study of Ethics(1894),My Pedagogical Creed(1897),The School and Society(1900),Studies in Logical Theory(1903),How we Think(1909),Interest and Effort in Education(1913),Democracy and Education(1916),Letters from China and Japan(1920).
De Wint, Peter, English landscape painter in water-colours, born 1784, died 1849. He studied in the schools of the Royal Academy, where he occasionally exhibited; but most of his pictures were shown in the exhibitions of the Water-colour Society. English scenery was his favourite subject. He occasionally painted in oil with marked success. Several of his pictures are in the National Gallery and the Victoria and Albert Museum.
De Witt, Jan, Grand-Pensionary of Holland, celebrated as a statesman and for his tragical end, was the son of Jacob de Witt, burgomaster of Dort, and was born in 1625. He became the leader of the political party opposed to the Prince of Orange, and in 1652, two years after the death of William II, was made Grand-Pensionary. In 1665 the war with England was renewed, and conducted by De Witt with great ability till its termination in 1665. In 1672 Louis XIV invaded the Spanish Netherlands and involved Holland in war. De Witt's popularity, already on the decline, suffered still further in the troubles thus occasioned, and he felt it necessary to resign his office of Grand-Pensionary. At this time his brother Cornelius, who had been tried and put to torture for conspiring against the life of the young Prince of Orange, lay in prison. Jan de Witt went to visit him, when a tumult suddenly arose amongst the people, and both brothers were murdered, 20th Aug., 1672. De Witt was a man of high character, simple and modest in all his relations.—Cf. Motley,History of the United Netherlands.
Dew-point, the temperature at which the air is saturated with the water-vapour which it contains. If the temperature of the air falls to the dew-point, dew is deposited. The dew-point is determined by means of an instrument called a hygrometer. When the air is 'dry', the dew-point is low, and evaporation proceeds rapidly, whilst a 'moist' atmosphere is one whose temperature is near the dew-point, and in which evaporation takes place slowly.
Dewsbury, a town, England, in the West Riding of Yorkshire, and 30 miles south-west of the town of York, chiefly engaged in the manufacture of heavy woollen cloths, including blankets, carpets, rugs, flannels, and baizes. In 1862 it was made a municipal borough; in 1867 a parliamentary borough, returning one member. Pop. of municipal borough, 53,351.
Dexter chief pointA, Dexter chief point.
A, Dexter chief point.
Dexter, a term meaning on the right-hand side, chiefly used in heraldry. Thedexter chief pointis a point in the right-hand upper corner of the shield, being in the dexter extremity of the chief.
Dex´trine, orBritish Gum, (C6H10O5)x, a generic name applied to soluble gummy substances intermediate between starch and glucose. They are prepared from starch by the aid of dilute mineral acids or of enzymes, and are usually named according to the colour they give with iodine, e.g. erythro-dextrine, &c. When heated with dilute acids, they are transformed into glucose. They are white, odourless substances, and are good substitutes for gum-arabic. Dextrine is used in calico printing for thickening colours; for the preparation of gums, and for stiffening cloth.
Dextro-compounds, bodies which cause the plane of a ray of polarized light to rotate to the right. Dextrine itself, dextro-glucose, naturally occurring tartaric acid, malic acid, cinchonine, and many other bodies have this property; while others, which have the opposite effect, of causing the plane to rotate to the left, are calledlævo-compounds.
Dey, an honorary title formerly bestowed by the Turks on elderly men, and assumed by the rulers (under the Turkish Sultan) of Algiers, Tripoli, and Tunis.
Dhalak(dha˙-la˙k´), an archipelago of the Red Sea, belonging to the Italian territory of Eritrea. It consists of nearly 100 islets, mostly uninhabited, clustering round the Island of Dhalak-el-Kebir, which is about 35 miles long by 30 miles broad. This island possesses a pearl-fishery.
Dhar(dhär), a small native state in Central India, with an area of about 1740 sq. miles. The soil is fertile, and yields wheat, rice, and opium. Pop. 169,474.—The capital is of the same name, is surrounded by a mud wall, and has some striking buildings. Pop. 19,000.
Dhárangaon, a town of Hindustan, in Khandesh district, Bombay. Pop. 15,000.
Dharmsála, a hill station with military cantonments, in Kangra district, Punjab, India. Pop. 6170.
Dharwar, the chief town of Dharwar district, in the Bombay Presidency, Hindustan, a straggling place with some trade. There is a fort well planned and strongly situated, but now falling into ruins, and military cantonments at 2 miles' distance. Pop. 32,000.—The Dharwar district has an area of 4535 sq. miles; pop. 1,051,314.
Dhawala´giri, orDhaulágiri, one of the highest peaks of the Himalayas, in Nepál; height, 26,828 feet.
Dhole(dōl), the Cingalese name for the wild dog of India (Cyon dukhunensis). It is distinguished from the genus Canis or dog proper by its having one molar fewer in either side of the lower jaw. It is of a fox-red or rufous-fawn colour, in size between a wolf and a jackal, and hunts always in packs.
Dholera(dhō-lā´ra), a town of Hindustan,Bombay Presidency, on a stream entering the Gulf of Cambay, an important cotton-mart. Pop. 10,190.
Dholka, a town of Hindustan, Bombay Presidency, probably one of the oldest towns in Gujarat. Pop. 16,700.
Dholpur, native state of Central India, Rájputána; area, 1155 sq. miles; pop. 263,188.—The capital is also called Dholpur. Pop. 9750.
Arab DhowArab Dhow
Dhow(dou), an Arab sea-going vessel, ranging from a comparatively small size up to 200 tons burden, with one mast and a large triangular (lateen) sail. It is used for merchandise and is often employed in carrying slaves from the east coast of Africa to Arabia.
Dhúliá, a town of Hindustan, Khandesh district, Bombay Presidency. Pop. 22,000.
Diabase, originally an equivalent of diorite; then used for chloritic igneous rocks of the Intermediate series of various grain; and now usually for a type of dolerite in which the felspar is embedded in augite.
Diabe´tesis a disease characterized by great thirst, a voracious appetite, and the passage of large quantities of saccharine urine, while there is usually marked emaciation and debility. As a rule the skin is dry and the patient does not perspire. Skin irritations (pruritus) of an intense type occur frequently and cause much discomfort. Constipation is the rule, but the digestion usually remains good, and enormous quantities of food are taken without causing disturbance.
Acute and chronic forms are recognized, but there is no essential difference, except that in the former the patients are younger, the course more rapid, and the emaciation more marked. Beyond the large quantity, the outstanding feature of the urine is the presence of sugar, varying from 2 per cent in mild cases to 10 per cent in severe cases.
The disease is due to disturbance in the carbohydrate metabolism, with the result that these carbohydrates are not properly assimilated, but passed as sugar in the urine. Much research has been undertaken to find what organ or organs of the body cause this defect in metabolism, and recent work in connection with the pancreas has established a definite relationship between cells in that organ and the disease.
In treatment the main consideration is to reduce the carbohydrates in the dietary, and many diets have been produced for this purpose.
Diabetic patients may take:—liquids: clear soups, lemonade, coffee, tea, cocoa (without sugar), soda-water, and such like waters or milk (in moderation); animal foods: fish of all sorts, fresh meat, poultry, game, eggs, butter, cream-cheese; vegetables: lettuce, tomatoes, spinach, radishes, asparagus, water-cress, cucumbers, chicory, mustard; fruits: lemons, oranges, and in moderation currants, plums, cherries, pears, apples (tart), melons, raspberries, strawberries, nuts: bread: gluten bread, almond or coco-nut biscuits. A substitute for bread is one of the greatest difficulties, as many gluten foods are very unpalatable.
Further, it is important to observe strict personal hygiene and to take moderate exercise, lead a regular, quiet life in an equable climate, and above all to avoid worries of any sort. In acute cases the disease may run a very rapid course, coma frequently supervening a few days before death, but chronic cases may live for ten to twenty years.
Diabetic Sugar.Sugar is present in normal urine in very small amount—so small that it cannot be detected by the ordinary tests. In diabetes the percentage of sugar in the urine may rise, in mild cases, to 1½ to 2 per cent, and in severe cases it may reach to 10 per cent.
Diablerets(dē-a˙b-lė-rā),Les, a mountain group of the Bernese Alps, Switzerland, between the cantons Vaud and Valais. The highest peak has a height of 10,620 feet.
Diachylon(dī-ak´i-lon), a substance prepared by heating together oxide of lead or litharge, olive-oil, and water, until the combination is complete, and replacing the water as it evaporates. It is used for curing ulcers, and is the basis of many plasters.
Di´adem(Gr.diadein, to bind round), an ancient ornament of royalty. It was originally a head-band or fillet made of silk, linen, or wool, worn round the temples and forehead, the ends being tied behind and let fall on the neck, as seen in old representations of the diadem of the Indian Bacchus. In later times it was usually set with pearls and other precious stones. The term is also used as equivalent to crown or coronet.
Diæ´resis, a separation of one syllable into two, also the mark (¨) by which this separation is distinguished, as inaërial.
Diagno´sis, in medicine, the recognition of diseases by their distinctive signs or symptoms; the discovery of the true nature and seat of a disease.
Diagonal ScaleDiagonal Scale
Diag´onal Scale, a scale which consists of a set of parallel lines drawn on a ruler, with lines crossing them at right angles and at equal distances. One of these equal divisions, namely, that at the extremity of the ruler, is subdivided into a number of equal parts, and lines are drawn through the points of division obliquely across the parallels. With the help of the compasses such a scale facilitates the laying down of lines of any required length to the 200th part of an inch. The length 1·67 inches, for example, is given by EF in the figure. Similarly AB = ·91 inch, CD = ·84 inch.
Diag´oras, ancient Greek poet and philosopher, born in Melos, an island of the Cyclades, and flourished about 425B.C.He spent a great part of his life in Athens. Like his teacher, Democritus, he attacked the prevailing polytheism, and sought to substitute the active powers of nature for the divinities of the Greeks. On this account he had to leave Athens.
Di´agram(Gr.diagraphein, to describe), a figure or geometrical delineation applied to the illustration or solution of geometrical problems, or any illustrative figure in which outlines are chiefly presented, and the details more or less omitted.