Chapter M: M. J. SUTHERLAND, D.Sc., F.I.C (4)

DIJON (d[=e]-zh[=o]n; Lat. _Castrum Divonense_), a town in Eastern France, capital of the department of C[^o]te-d'Or, in a fertile plain, at the foot of a range of vine-clad slopes, formerly surrounded by ramparts, which now furnish beautiful promenades. At some distance it is surrounded by a series of forts. Some of the buildings belong to the period when Dijon was capital of the dukedom of Burgundy, the chief being the cathedral of St. B['e]nigne, a building of vast extent with a lofty wooden spire above 300 feet high; the churches of N[^o]tre Dame and St. Michael; the ancient palace of the Dukes of Burgundy, now used as the h[^o]tel de ville and museum; and the _palais de justice_, formerly the Parliament House of Burgundy. Dijon is the birth-place of Bossuet. It has important educational institutions and a valuable library. Industries: woollens, hosiery, candles, mustard, vinegar, chemicals, paper-hangings, tanneries, foundries, machine factories, cotton- and oil-mills. The trade is considerable, particularly in the wines of Burgundy. Pop. 76,847.

DIKE, or DYKE (connected with the Gr. _teichos_, wall), a word variously used in different localities to represent a ditch or trench, and also an embankment, rampart, or wall. It is specially applied to an embankment raised to oppose the incursions of the sea or of a river, the dikes of Holland being notable examples of work of this kind. These are often raised 40 feet above the high-water mark, and are wide enough at the top for a common roadway or canal, sometimes for both. The Helder Dike, one of the largest, is about 6 miles in length and costly in upkeep. See _Embankment_.

DIKE, or DYKE, in geology, a term applied to intrusive igneous masses, such as basalt, which fill up veins and fissures in the other rocks, and sometimes project on the surface like walls through their superior resistance to weathering.

DILAPIDATION, in English ecclesiastical law, is where an incumbent of a church living suffers the parsonage-house or outhouses to fall down, or be in decay for want of necessary repairs; or it is the pulling down or destroying any of the houses or buildings belonging to a spiritual living, or destroying of the woods, trees, &c., appertaining to the same. An outgoing incumbent (or his heirs) is liable for dilapidation to his successor. In general, the term is applied to the act of allowing or causing any lands, houses, &c., to become waste or to decay.

DILEM'MA (from Gr. _di-_, double, and _l[=e]mma_, proposition, assumption), in logic, a form of argument used to prove the falsehood or absurdity of some assertion, as in the following instance: If he did so he must be either foolish or wicked; but we know he is neither foolish nor wicked; therefore he cannot have done so. The two suppositions, which are equally untenable, are called the 'horns' of the dilemma.

DILETTANTE (di-let-t[.a]n't[=a]), an Italian expression, signifying a lover of the arts and sciences, who devotes his leisure to them as a means of amusement and gratification, being thus nearly equivalent to _amateur_. It is also used in reference to the trifler and dabbler in art and science. In 1734 a number of gentlemen founded in London a Dilettanti Society, which published a splendid work on _Ionian Antiquities_, 1769, 1881 (4 vols.); _Specimens of Ancient Sculpture_, 1809, 1835.

DILKE, Sir Charles Wentworth, English writer and politician, son and grandson of men well known in their day, was born in 1843, died in 1911. He graduated at Cambridge, and was called to the Bar. His first work, _Greater Britain_, the result of a tour round the world from 1866 to 1867, became very popular. In 1868 he was elected member of Parliament for Chelsea, and he remained so up to 1885. After a few years' retirement (due to a divorce case) he became member of Parliament for Forest of Dean. He was Under-Secretary for Foreign Affairs, President of the Local Government Board, &c. He succeeded his father as owner of the _Athenaeum_, and became the proprietor of _Notes and Queries_. _The Present Position of European Politics_, and _Problems of Greater Britain_, are among his works.

DILL, an umbelliferous plant, _An[=e]thum grave[)o]lens_, a native of the southern countries of Europe, the fruits, commonly but erroneously called seeds, of which are moderately warming, pungent, and aromatic, and are employed medicinally as a carminative.

DILLENIA'CEAE, an order of plants, chiefly fine trees, inhabiting the East Indies, allied to Ranunculaceae and Magnoliaceae.

DILLINGEN (dil'ing-en), an old town, Bavaria, on the Danube, formerly the seat of a Jesuit university. Pop. 6291.

DILLON, John, Irish politician and agitator, born in Dublin in 1851, the son of John Blake Dillon (1816-66), a leader of the Young Ireland party. Educated at the Catholic University of Dublin and at the Royal College of Surgeons, he became a doctor of medicine. He identified himself with the Parnellite movement, and entered Parliament for Tipperary in 1880. An ardent Nationalist, not hesitating to incite his compatriots to lawlessness, he was sent to prison in 1888. Without a seat in Parliament from 1883 to 1885, he was returned in the latter year for East Mayo, which he represented thereafter. In 1918, after the death of John Redmond, he was elected chairman of the Irish Nationalist party, which, however, owing to the rise of the Sinn Fein party, was a nominal distinction only.

DILMAN', a town, Persia, province of Azerbijan, 75 miles west of Tabreez. Pop. estimated at 15,000.

DILO'LO, a small lake in Angola, near the southern boundary of Belgian Congo, lat. 11deg 22' S.; long. 22deg 34' E.: regarded as the source of the Zambesi.

DIL'UENTS (Lat. _diluere_, to wash away), in medicine, are those substances which are taken to increase the proportion of fluid in the blood. They consist of water and watery liquors.

DILU'VIUM, the name formerly given by geologists to certain gravels and comparatively recent deposits, which seemed to have been the result of a rush of water or deluge.

DIME (Fr. _d[^i]me_, Lat. _decimus_, tenth), the term for the tenth part of a dollar or ten-cent piece in the United States of America, a silver coin whose English equivalent is about 5d. Hence the phrases _dime novels_, _dime museums_, &c.

DIMENSIONS, ALGEBRAICAL. There are three dimensions in space: length, breadth, and height or depth. An area is said to be of two dimensions because it has length and breadth only; a volume is of three dimensions. In algebra terms like x^2, xy are said to be of two dimensions because there are two letters multiplied together, and their product would measure an area if each letter denoted a length. Similarly, x^3, xyz are said to be of three dimensions, and the meaning is extended to cover the product of any number of letters. An expression of more than one term is said to be of the same degree as its term of highest dimensions. For example, 3x^2y^2z^2 + 5xyz + 6x^3 + 3x^2y^2 is said to be of the sixth degree because x^2y^2z^2 = x x x x y x y x z x z is of six dimensions.

DIMENSIONS, PHYSICAL. One of the aims of physical science is to express all its measurements in terms of the three fundamental units of length, mass, and time. A velocity, for example, is specified by the number of units of length traversed in the unit of time, so that we may write v = l / t, or v = lt^{-1}. On this account velocity is said to have the dimensions LT^{-1}. Similarly, acceleration, being velocity added per unit time, has the dimensions of velocity / time, or LT^{-2}; and force, being proportional to mass and acceleration jointly, has the dimensions MLT^{-2}.

When a physical law is expressed as an equation connecting the numbers of units of the quantities involved, every term in this equation must be of the same dimensions in any one of the fundamental units. This is the _Principle of Dimensions_, first stated by Joseph Fourier, founder of the theory of the conduction of heat. In order to see its truth, we have only to observe that an equation containing terms of different dimensions would give inconsistent results if the unit of length were varied. Suppose it to be suggested, for example, that the period of vibration t of a simple pendulum of length l is given by the formula t = 2[pi]l/g, where g denotes the acceleration of a falling body. The dimensions of the expression on the right are L / (LT^{-2}), or T^2, whereas the term t on the left has dimensions T^1. Suppose the unit of length is the foot and the unit of time the second, so that g = 32, and let l = 3. We find in this case t = 6[pi]/32, so that the period is 3[pi]/16 seconds. But if we change the unit of time to one minute, g becomes 32 x 60 x 60, and the formula gives t = 6[pi]/(32 x 60 x 60), so that the period is 3[pi]/(16 x 60 x 60) minutes.

The two results are obviously inconsistent. If, however, we take the correct formula, namely t = 2[pi][sqrt](l/g), we find on trial that we obtain the same value for the period however we change the unit of time or the unit of length. Both sides are in this case of dimensions T^1.

The principle of dimensions provides therefore a useful check on the accuracy of formulae. But it does much more than this. It often gives very valuable information about the relations of physical phenomena in cases where these relations are far too complicated to be completely worked out by mathematical analysis. To mention but one example, it is by the use of this principle that modern naval architecture is able to predict the behaviour of ocean-going ships from experiments in ponds on small-scale models.

DIMIN'UTIVE, in grammar, a word having a special affix which conveys the idea of littleness, and all other ideas connected with this, as tenderness, affection, or contempt. The opposite of _diminutive_ is _augmentative_. In Latin, diminutives almost always ended in _-lus_, _-la_, or _-lum_; as _Tulliola, meum corculum_, little Tullia my dear, or little heart; _homunculus_, a manikin. The Italian is particularly rich in diminutives and augmentatives, such compound diminutives as _fratellinucciettinetto_ (a diminutive of _frate_, brother) being sometimes employed. Among English diminutive affixes are _-kin_, as in _manikin_, a little man; _pipkin_, a little pipe; _-ling_, as in _gosling_, a little goose; darling, that is, _dearling_, or little dear; and _-et_, as in _pocket_, from _poke_, a bag or pouch; _tablet_, a little table. Diminutives are not confined to nouns, and _dandle_, _scribble_, _tipple_, are examples of diminutive verbs, and _greenish_, _whitish_, are diminutives of adjectives. Diminutives are also formed, in colloquial and familiar language, by adding _-y_ or _-ie_ to the names, as _Charley_, _Mousie_, &c.

DIM'ITY, a stout cotton fabric, ornamented in the loom either by raised stripes or fancy figures. It is usually employed white, as for bed and bedroom furniture.

DIMORPH'ISM, in crystallography, the crystallization of a body in forms belonging to two different systems, or in incompatible forms of the same system, a peculiarity exhibited by sulphur, carbon, &c.

DIMORPHISM, in botany. See _Heterostyly_.

DINAJPUR', a town, Hindustan, Bengal, capital of a district of same name, 205 miles north of Calcutta; pop. 12,500.--The district covers an area of about 4118 sq. miles; pop. 1,687,860.

DINAN (d[=e]-n[:a]n), a town, France, department of C[^o]tes-du-Nord (Brittany), on the Rance, 14 miles south of St. Malo. It was besieged and captured by the English under the Duke of Lancaster in 1359, but retaken by Du Guesclin. It stands on a steep hill nearly 200 feet above the river, is surrounded by high old walls pierced with four gates, and is a picturesque and interesting old place. In the cathedral of St. Sauveur the heart of Bertrand du Guesclin is buried. Pop. 11,410.

DINANT (d[=e]-n[:a]n), a town, Belgium, in the province and 14 miles S. of Namur; picturesquely and strongly situated on the Meuse; a place of antique appearance. The town house was once the palace of the Princes of Li['e]ge. The town was destroyed by the Germans in 1914. It is one of the most popular Belgian summer resorts. Pop. 7690.

DINA'PUR, a town, Hindustan, Patna district, Bengal, on the right bank of the Ganges, about 12 miles north-west of Patna, cantonment and military head-quarters of the district, with extensive barracks. The environs are studded with handsome bungalows. Pop. 31,025.

DINAR (Lat. _denarius_), formerly an Arab gold coin, also a Persian coin; at present the chief Serbian coin, value one franc.

DI'NAS BRICKS, an infusible kind of brick made of a peculiar rock, containing 98 per cent of silica, with a little alumina, which occurs at Dinas, in the Vale of Neath, in Glamorganshire, S. Wales. The rock is crushed, moistened with water, and moulded by a machine.

DINDIGUL, a town of India, Madura district, Madras, with a fort on a rocky height; manufactures cigars. Pop. 21,000.

DINDINGS, THE, properly two small islands, also called PANGKOR ISLANDS, in the Straits of Malacca, belonging to the Straits Settlements, off the coast of Perak (British). The name now includes a strip of territory on the Malay Peninsula opposite; total area about 265 sq. miles, two-thirds of which is covered by dense forests. Coco-nuts, coffee, and pepper are grown with success. Lumut, on the mainland, has a fine natural harbour.

DIN'DORF, Karl Wilhelm, German classical scholar, born 1802, lived most of his life at Leipzig, and died 1883. His chief publications were editions of the Greek dramatists (_Poetae Scenici Graeci_) and works elucidative of them and other Greek writers.

DINGO, the native wild dog of Australia (_Canis Dingo_), of a wolf-like appearance and extremely fierce. The ears are short and erect, the head elongated, the tail rather bushy, and the hair of a reddish-dun colour. In habit the dingo is rather fox-like, usually lying concealed throughout the day and making predatory expeditions at night. It is very destructive to sheep, killing more than it eats. It was probably introduced by prehistoric man.

DING'WALL, a royal and parliamentary burgh and seaport of Scotland, county town of Ross and Cromarty, situated at the head of Cromarty Firth. This town, erected into a royal burgh in 1227, unites with Wick and other places in returning a member to Parliament. Pop. 2590.

DINO'CERAS (Gr. _deinos_, terrible, _keras_, a horn), a fossil mammal found in the Eocene strata of North America, in some respects akin to the elephant and of equal size, but without a proboscis. Its bones were very massive; it had two vertical tusks in the upper jaw, three pairs of horns, and the smallest brain, proportionally, of any known mammal.

DINOR'NIS (Gr. _deinos_, terrible, _ornis_, a bird), an extinct genus of large wingless birds--classed with the small existing Apteryx. The bones of several species have been found in New Zealand. The largest must have stood 12 feet in height, several of its bones being at least twice the size of those of the ostrich. The body seems to have been even more bulky in proportion, the tarsus being short and stout in order to sustain its weight. They do not appear to have become extinct until the seventeenth or eighteenth century, and are spoken of as _moas_ by the natives, who buried the eggs (more than 1 foot long) with their dead as provision for their journey to the other world.

DINOSAU'RIA (Gr. _deinos_, terrible, and _sauros_, a lizard), a group of extinct reptiles, allied in skeletal structure both to the lizards and the birds. While some were only 3 feet long, a large number attained gigantic size. Atlantosaurus being 115 feet long. Many were carnivorous, but some of the large heavy forms were herbivorous, and protected by bony spines or plates. The Dinosaurs were the dominant land animals of the Jurassic and Cretaceous periods.

DINOTHE'RIUM (Gr. _deinos_, terrible, _th[=e]rion_, beast), a genus of extinct gigantic proboscidean mammals, precursors of the elephants, the remains of which occur in Miocene formations in several parts of Europe. The type-species (_D. giganteum_) is calculated to have attained the length of 18 feet. It had a proboscis and also two tusks placed at the anterior extremity of the lower jaw, and curved downwards somewhat after the manner of those in the upper jaw of the walrus. The skull is best known from that found in 1835 at Eppelsheim; but the skeleton can now be pieced together from remains in various localities. The vertebrae resemble those of mastodon. Dinotherium may have inhabited rivers or estuaries.

DI'OCESE (Gr. _dioik[=e]sis_, administration), the circuit or extent of a bishop's jurisdiction. Each English diocese is divided into archdeaconries, each archdeaconry (nominally) into rural deaneries, and each deanery into parishes. In the Eastern Churches the term _eparchy_ is used for diocese. See _Bishop_.

DIOCLE'TIAN (Gaius Valerius Diocletianus, surnamed _Jovius_), a man of mean birth, a native of Dalmatia, proclaimed Emperor of Rome by the army A.D. 284. He defeated Carinus in Moesia (286), conquered the Allemanni, and was generally beloved for the goodness of his disposition, but was compelled by the dangers threatening Rome to share the government with M. Aurelius Valerius Maximian. In 292 Galerius and Constantius Chlorus were also raised to a share in the empire, which was thus divided into four parts, of which Diocletian administered Thrace, Egypt, Syria, and Asia. As the result of his reconstitution of the empire there followed a period of brilliant successes in which the barbarians were driven back from all the frontiers, and Roman power restored from Britain to Egypt. In 305, in conjunction with Maximian, he resigned the Imperial dignity at Nicomedia, and retired to Salona, in Dalmatia, where he cultivated his garden in tranquillity until his death in 313. In the latter part of his reign he was induced to sanction a persecution of the Christians.--BIBLIOGRAPHY: Gibbon, _Decline and Fall_; P. Allard, _La Pers['e]cution de Diocl['e]tien_; A. J. Mason, _The Persecution of Diocletian_.

DIODA'TI, Giovanni, Italian Protestant divine, born at Lucca, about 1576, of a noble Catholic family. He was for some time professor, first of Hebrew, then of theology, at Geneva, and in 1619 represented the Genevan clergy at the Synod of Dort, and aided in drawing up the Belgic confession of faith. He is most celebrated for a translation of the Bible into Italian (1607), which is superior to his translation of it into French. He died at Geneva in 1649.

DIODO'RUS of Agyrium, in Sicily, and therefore called SICULUS; a Greek historian in the time of Julius Caesar and Augustus. His universal history, in the composition of which he travelled through a great part of Europe and Asia, occupied him thirty years, and consisted of 40 books, but only books 1-5 and 11-20, with certain fragments, are now extant.

DIOECIOUS (Gr. _di_, double, _oikos_, a house), in botany, a term applied to plants which have flowers with stamens on one individual and those with pistils on another; as opposed to _monoecious_. The willow, the yew, the poplar, &c., are dioecious.

DIOGENES LAERTIUS, author of a sort of history of philosophy in Greek, appears to have been born at Laerte, in Cilicia, and to have lived towards the close of the second century after Christ; but no certain information exists either as to his life, studies, or age. The work is divided into ten books, and bears in MSS. the title, _On the Lives, Doctrines, and Apothegms of those who have distinguished themselves in Philosophy_. It is full of absurd and improbable anecdotes, but contains valuable information regarding the private life of the Greeks, and many fragments of works now lost. It was the foundation of the earlier modern histories of philosophy. A translation of his work by C. D. Yonge was published in Bohn's Classical Library.

DIOGENES (di-oj'[=e]-n[=e]z) OF APOLLONIA (Crete), known also as the _Physicist_, a Greek philosopher of the fifth century B.C., who belonged to the Ionian school, and considered air as the element of all things. He was a pupil of Anaximenes and a contemporary of Anaxagoras.

DIOGENES OF SINOP[=E] (on the Black Sea), the most famous of the Cynic philosophers, born about 412 B.C., died about 323 B.C. Having been banished from his native place with his father, who had been accused of coining false money, he went to Athens, and thrust himself upon Antisthenes as a disciple. Like Antisthenes he despised all philosophical speculations, and opposed the corrupt morals of his time; but while the stern austerity of Antisthenes was repulsive, Diogenes exposed the follies of his contemporaries with wit and good humour. As an exemplar of Cynic virtue he satisfied his appetite with the coarsest food, practised the most rigid temperance, walked through the streets of Athens barefoot, without any coat, with a long beard, a stick in his hand, and a wallet on his shoulders, and by night, according to the popular story, slept in a tub (or large earthenware vessel). On a voyage to the Island of Aegina he fell into the hands of pirates, who sold him as a slave to the Corinthian Xeniades. The latter emancipated him, and entrusted him with the education of his children. He attended to the duties of his new employment with the greatest care, commonly living in summer at Corinth and in winter at Athens. It is at Corinth that he is said to have had his famous interview with Alexander the Great. The Macedonian conqueror was so struck with the philosopher's self-possession that he went away remarking: "If I were not Alexander, I should wish to be Diogenes". Of the many stories related of him the majority are probably fictions; many, indeed, are chronologically impossible. Concerned with practical wisdom, Diogenes established no system of philosophy. To gain virtue, he maintained, man must avoid physical pleasure, despise the conventions of society, and adopt a simple and natural life. His enemies accused him of various scandalous offences, but there is no ground for supposing him guilty of any worse fault than that of elevating impertinence to the rank of a fine art. See _Cynics_.

DIOMEDES (d[=i]-o-m[=e]'d[=e]z), in Greek mythology, (1) the son of Mars and Cyrene, and King of the Bist[)o]nes in Thrace, who fed his horses on human flesh, and used to throw all strangers who entered his territories to those animals to be devoured. He was killed by Hercules, who carried off the horses. (2) One of the heroes at the siege of Troy, the son of Tydeus and Deipyle, and King of Argos, one of the suitors of Helen. After she was carried off, Diomedes engaged in the expedition against Troy, in which his courage and the protection of Pallas rendered him one of the most distinguished heroes. He wounded Aphrodite and Ares, and thrice assailed Apollo; and by carrying off the horses of Rhoesus from the enemies' tents, and aiding Ulysses in the removal of Philoctetes from Lemnos, he fulfilled two of the conditions on which alone Troy could be conquered. Finally he was one of the heroes concealed in the wooden horse by which the capture of Troy was at length accomplished. Different accounts were given of his after-life. He is often called _Diomede_.

DIONAE'A, a genus of plants, nat. ord. Droseraceae. Only one species is known, _D. muscip[)u]la_ (Venus's fly-trap), a native of the sandy savannas of Carolina and Florida. It has a rosette of root-leaves, from which rises a naked scape bearing a corymb of largish white flowers. The leaves have a dilated petiole and a slightly stalked 2-lobed lamina, with three short stiff bristles on each lobe. The bristles are remarkably irritable, and when touched by a fly, or other insect, the lobes of the leaf suddenly close on and capture the insect. It dissolves the food thus captured by means of digestive fluid similar to ordinary gastric juice.

DION CASSIUS, or DIO CASSIUS, a Greek historian, born about A.D. 155 at Nicaea, in Bithynia. After accompanying his father to Cilicia, of which he held the administration, he came to Rome about 180, and obtained the rank of a Roman Senator. On the accession of Pertinax Dion was appointed Praetor, and in the reign of Caracalla he was one of the Senators whom it had become customary to select to accompany the emperor in his expeditions, of which he complains bitterly. In 219 he was raised to the consulship, and about 224 became Proconsul of Africa. In 229 he was again appointed Consul; but feeling his life precarious under Alexander Severus, he obtained permission to retire to his native town of Nicaea. The period of his death is unknown. The most important of his writings, though only a small part is extant, is a _History of Rome_, written in Greek and divided into eighty books, from the arrival of Aeneas in Italy and the foundation of Alba and Rome to A.D. 229.

DION CHRYSOSTOM, a Greek sophist and rhetorician and a favourite of Trajan; born A.D. 50, died about A.D. 110. Eighty of his orations (in excellent Attic) have been preserved.

DION OF SYRACUSE, in Greek history, a connection by marriage of the elder and the younger Dionysius, tyrants of Syracuse, over whom he long exercised great influence. He attempted to reform the younger Dionysius, but his enemies succeeded in effecting his banishment. He afterwards returned and made himself ruler of the city, but became unpopular, and in 353 B.C. one of his followers, Callipus of Athens, caused him to be assassinated.

DIONYS'IA. See _Bacchanalia_.

DIONYS'IUS, ST., a disciple of Origen, and Patriarch of Alexandria in A.D. 248. He was driven from the city in 250, and in 257 was banished to Libya, but was restored in 260. He died in A.D. 265.

DIONYSIUS OF HALICARNASSUS, in Caria, a Greek critic and teacher of eloquence, born about 70 B.C. He went to Rome about 30 B.C., where he wrote his _Roman Antiquities_, in twenty books, in which he relates (in Greek) the early history of Rome and its government up to the times of the first Punic War. We have the first nine books of this work entire, the tenth and eleventh nearly so, and some fragments of the others. His rhetorical writings are of greater value, especially his essays on the Greek orators. He died about 6 B.C.--Cf. Sir J. E. Sandys, _A History of Classical Scholarship_.

DIONYSIUS THE AREOPAGITE, that is, one of the judges of the Areopagus, at Athens, a convert to Christianity by the Apostle Paul about the middle of the first century, and the first Bishop of Athens, where he suffered martyrdom. Certain writings formerly ascribed to him consist of obscurely written treatises on mystical subjects. Scotus Erigena translated them into Latin. In France, where a certain Dionysius (see _Denis, St._) established the first Christian community at Paris in the third century, they were readily received, this Dionysius being without further inquiry taken for the Areopagite, because the origin of the Gallican Church could thus be carried back to the first century; and France gained a patron who was a martyr and the immediate disciple of an apostle.--Cf. article in Smith's _Dictionary of Christian Biography_.

DIONYSIUS THE ELDER, in Greek history, tyrant or absolute ruler of Syracuse, born about 430 B.C. of obscure parentage. He obtained the rank of general, and afterwards of commander-in-chief; and, gaining the support of the army, he seized the supreme power in Syracuse, though only twenty-five years of age. He extended his rule over other cities in Sicily; and after some successes and reverses in the struggle with the Carthaginians, he gained a complete victory over them under the walls of Syracuse. In his expeditions into Lower Italy he reduced the city of Rhegium by famine (387). After another short war with Carthage he lived some time in peace, occupied with writing poems and tragedies, with which he contended for the Olympian prize. In 368 he commenced a new war against the Carthaginians, but failed to drive them entirely out of Sicily. He is said to have died from a potion administered at the instigation of his son Dionysius the Younger (367 B.C.).

DIONYSIUS THE LITTLE (so called on account of his short stature), a Scythian monk who was abbot of a monastery at Rome in the beginning of the sixth century, and died about the year A.D. 530, according to others about 545, celebrated as the first to introduce the computation of time from the Christian era. This mode of computation, however, was not publicly used until the eighth century.

DIONYSIUS THE YOUNGER, a tyrant of Syracuse, who succeeded his father, Dionysius the Elder, in 367 B.C. For the purpose of recalling him from the excesses to which he was addicted, his kinsman Dion persuaded him to invite Plato to his court, but the influence of the philosopher effected no permanent change. Becoming suspicious of Dion, the tyrant banished him and confiscated his property, but in 357 B.C. Dion made himself master of Syracuse. Dionysius fled to Locri, but after the murder of Dion recovered his power in Syracuse. His misfortunes, however, had rendered him more cruel, and Timoleon, who came to Syracuse with aid from Corinth against the Carthaginians, deposed him in 344 B.C. He was carried to Corinth, where he is said to have gained a living by giving lessons in grammar, or as one of the attendants on the rites of Cybele.

DIONY'SUS, the original Greek name of the god of wine, the name Bacchus, by which he was also called both by the Greeks and the Romans, being at first a mere epithet or surname.--Cf. R. Brown, _The Great Dionysiak Myth_.

DIOON, a genus of Cycads, natives of Mexico, where meal is prepared from the starchy seeds.

DIOPHAN'TUS OF ALEXANDRIA, the first Greek writer on algebra, flourished, according to some authorities, about the middle of the fourth century after Christ. He is called the Father of Algebra, and left behind him thirteen books of _Arithmetical Questions_, of which only six are extant; and a work on _Polygonal Numbers_.

DIOP'SIDE, a calcium magnesium silicate, of the pyroxene series, occurring in igneous rocks and altered limestones, with a vitreous lustre, and of a pale-green, or a greenish- or yellowish-white colour.

DIOP'SIS, a genus of two-winged flies of which the species are native to India and Africa. Each side of the head is drawn out into a long lateral horn, which bears the eye and antenna at its extremity.

DI'OPTASE, emerald copper ore, hydrated silicate of copper, a translucent mineral, occurring crystallized in six-sided prisms. It occurs in Siberia, Hungary, and Chile. It has been used as a gem-stone, notably in Persia and Russia.

DIOPTER, the unit in terms of which the power of a lens or curved mirror can be expressed. It is obtained by taking the reciprocal of the focal length of the lens or mirror in metres. Thus, a lens with focal length 1 metre has a power of 1 diopter. If the focal length is 2 metres, the power is 1/2 diopter. The power may also be obtained by dividing 39.37 by the focal length in inches. The unit is employed in classifying spectacle lenses.

DI'ORITE, a coarsely crystalline igneous rock, sometimes of a whitish colour speckled with black or greenish-black, sometimes very dark in colour, consisting of hornblende and calcium sodium felspar. Dark mica sometimes takes the place of hornblende (mica-diorite). The 'greenstones' of older authors are mostly diorites.

DIOSCOREACEAE, a nat. ord. of monocotyledons, with alternate reticulate-veined leaves, tuberous root-stocks, and twining stems. The flowers are small and unisexual. There are 6 genera, with about 100 species. The typical genus is Dioscorea, which includes the yam. Black bryony is the only British representative.

DIOSCOR'IDES, Pedanius, a Greek physician, born in Cilicia in the first century of the Christian era. He was the author of a celebrated work on _materia medica_, in five books, particularly valuable in regard to botany.

DIOSCU'RI. See _Castor and Pollux_.

DIOS'PYROS, a large genus of trees or shrubs, natives of the warmer regions of the world, nat. ord. Ebenaceae. The trees of this genus supply ebony wood. That from Ceylon is the wood of _D. Eb[)e]num_; from India, of _D. melanoxylon_ and other species; and that from Mauritius, _D. tesselaria_. The Chinese date-plum (_D. kaki_) is an apple-like tree which produces large red fruits resembling tomatoes. In China and Japan this tree is as important as the apple is in Northern Europe.

DIP, of the horizon, the angle of depression of the visible horizon at sea below the true horizontal direction, due to the height of the eye above the level of the sea. The dip in minutes of arc is approximately equal to the square root of the height in feet.--_Dip, magnetic_, or _Inclination_, is the angle which a magnetic needle free to move in a vertical circle in the magnetic meridian makes with the horizon. See _Dipping Needle_.

DIP, in geology, the inclination or angle at which strata slope or _dip_ downwards into the earth. The degree of inclination or amount of the dip, which is easily measured by a _clinometer_, is the steepest angle made with a horizontal plane by a line drawn in the surface of the stratum. The line of dip is hence perpendicular to the intersection of the stratum with the horizontal, which is called the _strike_.

DIP CIRCLE. See _Dipping Needle_.

DIPHTHE'RIA is an acute infectious disease characterized by the formation of membrane in the throat and air-passages, and associated with severe disturbances affecting especially the heart and nervous system. It is due to a bacillus described by Koch in 1883. It is essentially a disease of the early years of life, and the period between two and twelve years covers the vast majority of cases. The commonest modes of infection are direct and indirect contact, infected milk, and defective drains. Of late years, the domestic cat has been held to be a source of infection. The disease runs a rapid course, beginning with fever, headache, chilliness, lassitude, and occasionally vomiting, while usually there is early complaint of sore throat. The membrane, which appears on the side of the throat, is usually of a dirty yellowish-white colour. It may be limited to a small area, but usually, if untreated, it would spread extensively over the throat, involving the palate and uvula. Diphtheria beginning in the larynx (windpipe) is what is popularly called croup (q.v.). There is danger of death in severe cases during the first few days from early heart failure, and almost any time during convalescence late heart failure may occur. Late heart failure is one of the forms of post-diphtheritic paralysis which arise from disturbances of the nervous system. The other common varieties are paralysis of the palate, of the pharynx, of the eye muscles, and of the respiratory muscles. An effective treatment is found in diphtheric antitoxin, which should be administered as early as possible in the disease. It is given under the skin, and the dose is regulated by the severity of the attack.--BIBLIOGRAPHY: W. F. Litchfield, _Diphtheria in Practice_; W. R. Smith, _Harben Lectures_.

DIPHTHONG (Gr. _di-_, double, and _phthongos_, sound), a coalition or union of two vowels pronounced in one syllable. In uttering a proper diphthong both vowels are pronounced; the sound is not simple, but the two sounds are so blended as to be considered as forming one syllable, as in _void_, _bough_. The term improper diphthong is applied to the union in one syllable of two or more vowels of which only one is sounded, as in _bean_.

DI'PHYODONT, a term applied to those animals which develop two sets of teeth, a deciduous or milk set, and a permanent set--as distinct from the monophyodonts, which develop only one set. The majority of mammals are diphyodont, though the number of teeth replaced may vary: thus in man twenty teeth of the adult are preceded by a milk set.

DIPLACAN'THUS, a genus of ganoid fishes, found only in the Old Red Sandstone. They have small scales, a heterocercal tail, and two dorsal fins with a strong spine in front.

DIPLEI'DOSCOPE, an instrument for indicating the passage of the sun or a star over the meridian, by the coincidence of two images of the object, the one formed by single and the other by double reflection. It consists of an equilateral hollow prism, two of whose sides are silvered on the inside so as to be mirrors, while the third is formed of glass. The prism is adjusted so that one of the silvered sides shall be exactly in the plane of the meridian, and the transparent side towards the object.

DIPLOID PHASE, in botany. See _Generations, Alternation of_.

DIPLO'MA (Gr. _dipl[=o]ma_, from _diplo[=o]_, to double or fold), literally a document folded but once, and therefore divided into two parts. It is used to signify a document signed and sealed, in which certain rights, privileges, or dignities are conferred, especially a university degree.

DIPLO'MACY, the science or art of foreign politics. In a more restricted sense the term denotes the science or art of conducting negotiations and arranging treaties between states and nations; the branch of knowledge which deals with the relations of independent states to one another; the agency or management of envoys accredited to a foreign court; the forms of international negotiations. The word, borrowed from the French, was first used in England in 1796 by Burke. The Cardinal de Richelieu is generally considered as the founder of that regular and uninterrupted intercourse between Governments which exists at present between almost all the Christian powers; though the instructions given by Machiavelli to one of his friends, who was sent by the Florentine Republic to Charles V (Charles I of Spain) show that Richelieu was not the first to conceive the advantages that might be derived from the correspondence of an intelligent agent accredited at the seat of a foreign Government. As a uniform system, however, with a fixed international status, diplomacy was only established in the nineteenth century at the Congresses of Vienna (1815) and Aix-la-Chapelle (1818). Amongst the European powers it is agreed that of ministers of the same rank he who arrives first shall have the precedence over his colleagues.--BIBLIOGRAPHY: D. J. Hill, _History of Diplomacy in the International Development of Europe_; E. C. Grenville-Murray, _Embassies and Foreign Courts: a History of Diplomacy_; P. Pradier-Fod['e]r['e], _Cours de droit diplomatique_; L. Oppenheim, _International Law_; D. P. Heatley, _Diplomacy and the Study of International Relations_.

DIPLOMAT'ICS, originally the science of deciphering ancient MSS. It laid down certain principles for the systematic examination of public documents, and taught the forms and styles adopted in them, and the titles and rank of public officers subscribing them. Among the earliest exponents of diplomatics were Daniel van Papenbroeck, an Antwerp Jesuit (1675), and Mabillon (_De Re Diplomatica_, 1681).

DIPLOMATIC SERVICE, THE, as now existing, may be said to have originated in the Venetian Republic, which employed ambassadors as early as the thirteenth century. At first these officials had a very brief term of office, rarely remaining at their post in a foreign country for more than two or three months. By the middle of the fifteenth century, however, a permanent Milanese embassy had been established at Genoa, followed by one at Paris in 1494; while two years later Venice was officially represented at London. The clergy, who for the most part alone possessed the requisite accomplishments for such work, were the usual ambassadors of the Middle Ages; but by the sixteenth century lawyers, or not seldom merchants, were employed. It was not till two hundred years later that the modern attach['e]s, junior officials of an embassy, came into being. The diplomatic service of Great Britain, controlled by the Foreign Office, includes (1) ambassadors, and (2) envoys and ministers plenipotentiary, both of which ranks represent the person of their sovereign and enjoy numerous special privileges in the country to which they are sent. Of lower standing are (3) ministers resident and (4) charg['e]s d'affaires; the last-named are accredited, not to a sovereign, but to his foreign minister, and frequently act merely as temporary substitutes for an ambassador. Secretaries of more than one grade, with naval, military, and, of late years, commercial attach['e]s, also form members of an embassy. Candidates for the British diplomatic service require a nomination from the Foreign Secretary, must be between the ages of nineteen and twenty-five, are subjected to an examination, and are almost invariably young men of good birth and position. The service is distinguished and affords a pleasant, if to some extent an idle life; but it does not offer any prospect of financial fortune. Lord Stratford de Redcliffe (the 'Great Elchi') and Lord Lyons rank high among distinguished British ambassadors. See _Civil Service_.

DIPLOZO'ON, a parasitic trematode worm which infests the gills of the bream, and which appears to be formed of two distinct bodies united in the middle, and resembling an [X] or St. Andrew's cross, two sexually mature individuals being thus united.

DIP'NOI, mud-fishes or lung-fishes, an ancient order now represented by three genera--Neoceratodus, Protopterus, and Lepidosiren. Like some adult Amphibia they possess both gills and lungs, the latter corresponding to a specialized swim-bladder. The heart has two auricles instead of one only, as in all other fishes. The single species of Neoceratodus (_N. forsteri_) is a large form with paddle-like fins and large overlapping cycloid scales. It is native to the Burnett and Mary Rivers of Queensland. Protopterus is represented by three African species, which inhabit rivers and swamps from the Senegal to the Zambezi. It is smaller than Neoceratodus, somewhat eel-shaped, with very narrow fins, and small cycloid scales embedded in the skin. It spends the summer in a torpid condition, buried in the mud, and is dug up by the natives as an article of food. Lepidosiren includes a single South American species (_L. paradoxa_) ranging from the Amazon to Paraguay. It is closely related to Protopterus, which it resembles in shape and the character of the fins.

DIPPEL, Johann Conrad, German theologian and alchemist, born 1672, died 1734. He studied theology, defended the orthodox party against the Pietists, led a turbulent life at Strasbourg, and then joined the Pietists until an unfortunate tractate placed him in disfavour with both parties. He then turned his attention to alchemy, and during a residence at Berlin produced the oil called after him, from which indirectly followed the discovery of Prussian or Berlin blue. After various adventures and wanderings in Sweden, Denmark, and Germany, he died at Berleburg.

DIPPEL'S OIL, a pharmaceutical preparation obtained by the destructive distillation of animal matter, such as horn, ivory, blood. The crude form was refined by Dippel, and at one time was a good deal used in medicine as a diaphoretic and hypnotic. It is a form of bone oil, a product obtained in the manufacture of bone-black, or animal charcoal, by the distillation of bones. Crude bone oil has a most offensive smell. It contains the carbonate and other salts of ammonium, and a large variety of organic substances.

DIPPER, a bird of the genus Cinclus, allied to the wrens. The common dipper, water-ouzel, or water-crow (_Cinclus aquaticus_), is a familiar European bird; it is about 7 inches in length, with a very short tail, small rounded wings, and large powerful feet; the bill is of moderate length, straight, and slender. The male has the upper part of the body dark brown, the throat and breast white, belly rusty. The dipper frequents streams, and feeds largely on water-insects and larvae. It can dive and walk under water, effecting its progress by grasping the stones with its feet. The song is sweet and lively. Other species are found in North Asia, America, and North Africa.

DIPPING-NEEDLE, or INCLINATION COMPASS, an instrument for showing the direction of the earth's magnetic force. In essentials the instrument consists of a light magnetized steel bar supported on a horizontal axis which passes, as nearly as possible, through the centre of inertia of the bar. When a needle thus mounted is placed anywhere not in the magnetic equator, it dips or points downward; and if the vertical plane, in which it moves, coincides with the magnetic meridian the position of the needle shows at once the direction of the magnetic force. The angle between the magnetic axis of the dipping-needle and the horizontal is called the dip or inclination. This varies from 90deg at the magnetic poles to 0deg at the magnetic equator. The dip is 70deg at Glasgow, and varies slowly with the passage of time. In the northern hemisphere, the north-seeking pole of the dipping-needle dips downwards, the reverse being the case south of the magnetic equator.

DIPRO'TODON, a gigantic fossil marsupial from Pleistocene beds in Australia, allied to the kangaroos. The skull is 3 feet long.

DIPSAS, a genus of tree-snakes of which the species are native to tropical South America. Some of the hinder teeth in the upper jaw are grooved for the conduction of poison, but this is not sufficiently deadly to be dangerous to human beings. The related genus Dipsadomorphus includes a number of Indian species.

DIPSOMA'NIA (Gr. _dipsa_, thirst, and _mania_, madness), a term used to denote an insane craving for intoxicating liquors, when occurring in a confirmed or habitual form. It is a form of acute alcoholism seen in persons with a strong hereditary tendency to drink. The only remedy appears to be seclusion, with enforced abstinence and healthy occupation. Homes for this purpose have been established in Britain under the Habitual Drunkards Act of 1879 and Inebriates Act of 1888. There are corresponding institutions in the United States.

DIP'TERA, two-winged flies, an order of insects embracing a vast number of species, of which about 40,000 have been named. The two transparent wings correspond to the fore-wings of other insects, the hind-wings being often represented by small club-shaped structures (halteres or balancers). See diagram, p. 42. There are two large compound eyes, and the mouth-parts are often modified for piercing and sucking. There is a well-marked metamorphosis, the larvae being usually limbless maggots. The Diptera include many agricultural and horticultural pests, and a number are notorious as disease carriers. See _Blow-fly_; _Bot-fly_; _Crane-fly_; _Gnat_; _House-fly_; _Hover-fly_; _Midge_; _Mosquito_; _Tsetse-fly_.

DIPTERIS, a genus of Leptosporangiate ferns, section Mixtae, formerly included in Polypodium, but now recognized as the sole living genus of the Dipteridineae, a family which was largely developed in Mesozoic times. They are Indo-Malayan ferns with creeping rhizomes and long-stalked, fan-shaped, forked, leathery fronds.

DIPTEROCARPACEAE, an important order of Asiatic dicotyledonous trees, allied to the mallows (Malvaceae). The different species produce a number of resinous, oily, and other substances; one, a sort of camphor; another, a fragrant resin used in temples; and others, varnishes; while some of the commonest produce pitches, and sal (_Shorea robusta_) yields valuable timber.

DIPTYCH (dip'tik), in Greek originally signified the same as _diploma_, something folded; the double tablets of metal, ivory, &c., 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.--Cf. Sir W. Smith, _A Dictionary of Greek and Roman Antiquities_.

DIPYRE (d[=i]'p[=i]r), or MIZZONITE, a mineral--aluminium calcium sodium silicate--of the scapolite series. Its name indicates the double effect of fire upon it (Gr. _di_, double, _pyr_, fire) in producing first phosphorescence, and then fusion.

DIRAE, one of the names under which the Eumenides were known to the Romans. See _Furies_.

DIRECTORS, persons elected to meet together at short fixed intervals and consult about the affairs of corporations or joint-stock companies, and to advise and assist the manager. These are termed _Ordinary Directors_, as in many companies there is a body called _Extraordinary Directors_, who have little or no business functions, and are chosen as a rule on account of their social position imparting a degree of distinction to the concern. Directors are appointed by a general meeting of the shareholders in the undertaking, and a certain number of them, usually a third, retire every year. Ordinary directors are granted a certain remuneration for their services. The duties and responsibilities of directors are defined by the constitution of the company, or by the various Acts of Parliament affecting joint-stock and other companies.

DIREC'TORY, 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: one member was obliged to retire yearly, and his place was supplied by election. This body was invested with the authority which, by the Constitution of 1791, had been granted to the king. By the Revolution of the 18th Brumaire the Directory and the Constitution of the year III were abolished. It was succeeded by the Consulate, with Napoleon as First Consul.

DIREC'TRIX, a fixed line that is required for the description of a curve. The term is chiefly used in connection with the parabola, ellipse, and hyperbola, which are the loci of points that move so that their distances from a fixed point (the focus) are in a constant ratio to their distances from the directrix. The directrix of a parabola is a line perpendicular to the axis produced, and at a distance from the vertex equal to the distance of the vertex from the focus. Thus AB is the directrix of the parabola VED, of which F is the focus.

DIRK, a kind of dagger formerly used as a weapon of offence by the Highlanders of Scotland. Dirks are worn by midshipmen and cadets of the Royal Navy, and still form part of the full Highland costume.

DIRK-HARTOG ISLAND, on the west coast of Australia, 45 miles long, north to south, and 10 miles broad.

DIRT-BEDS, in geology, layers of ancient soil, such as those in the Oolitic strata of the Isle of Purbeck (Dorset), which contain the stumps of trees that once grew in them.

DISABILITY, in law, incapacity to do any legal act. It is either _absolute_, which wholly disables the person, such as outlawry or excommunication--or _partial_, such as infancy, coverture, insanity, or drunkenness.

DISBARRING, or DISBARMENTS, expelling a barrister from the Bar, a prerogative which, in England, is possessed by the benchers of each of the four Inns of Court. The party disbarred may lodge an appeal with the judges in their capacity of visitors.

DISC, or DISK, the central part of the capitulum of compositae, surrounded by the ray. Also a part of a flower, sometimes cup-shaped, at the base of the stamens, consisting in some cases of rudimentary stamens, in others of the modified receptacle.--In astronomy the term is applied to the visible face or figure exhibited by the sun, moon, or a planet. In the case of the moon and certain planets it may be of gibbous, semicircular, or crescent form.

DISCHARGING ARCH, an arch formed in the substance of a wall to relieve the part which is below it from the superincumbent weight. Such arches are commonly used over lintels and flat-headed openings.

DISCIPLINE, BOOKS OF, two books connected with the Church of Scotland. The _First Book of Discipline_ was drawn up by John Knox and four other ministers, and laid before the General Assembly in 1560. Though not formally ratified by the Privy Council, it was secretly subscribed by the greater part of the nobility and barons who were members of the Council. Another similar document, the _Second Book of Discipline_, was prepared and sanctioned by the General Assembly of 1578, and has from that time been recognized as the authorized standard of the Church of Scotland in respect of government and discipline.

DISCLAIM'ER, in its stricter legal sense, a plea containing renunciation or a denial of some claim alleged to have been made by the party pleading.

DISCOMYCETES, a large section of the ascomycetous Fungi, distinguished by the fact that the hymenium covers the surface of an open, disc-like or cup-shaped fruit-body called an _apothecium_. It includes many important genera, such as Dasyscypha, Peziza, and Sclerotinia.

DISCOPHO'RA, (1) a sub-class of the Hydrozoa, comprising most of the organisms known as sea-jellies, jelly-fishes, and sea-nettles; (2) leeches (q.v.).

DIS'COUNT, the charge made by a banker for interest of money advanced by him on a bill or other document not presently due. In advancing money on such a security the banker deducts the charge for interest on his advance from the total amount represented on the security, pays the difference, which is called the _proceeds_ of the bill, to the person parting with it, and collects the full amount to reimburse himself for outlay and interest at maturity. Popularly the term _discount_ is applied to any deduction from the full amount of an account made by the party to whom it is paid, especially on prompt or early payment. When a bill which has been _discounted_ is paid by the acceptor before it is due, the discount allowed for prepayment is called _rebate_.

DISCOV'ERY, in law, the act of revealing or making known any matter by a defendant in his answer to a bill in chancery. The word is also used in reference to the disclosure by a bankrupt of his property for the benefit of his creditors, and to the right of a party to a lawsuit to obtain from his adversary, on oath, full disclosure of the facts within his knowledge, and production of the documents in his possession, pertinent to the action.