'IoTopia), written in Greek, divided into 80 books, and containing an account of the rise and progress of the state from the landing of Eneas in Italy until A. D. 229, giving only a slight sketch of events down to the time of Julius Cæsar, but dwelling with more minuteness on the history of later times, and especially on that of the author's own age. Of this work, which is written with clearness, diligence, and general accuracy, but in a faulty style, 20 books (from the 36th to the 54th) remain entire. Fragments of the first 35 have been collected, and there are abridgments of the last 25 and of the entire work. One of the best editions of Dion Cassius is that of Sturz (9 vols. 8vo., Leipsic, 1824'25-'43). An English translation of Xiphilin's abridgment was published in London (2 vols. 8vo., 1704).

DION CHRYSOSTOMUS (i. e., Dion the golden-mouthed), a Greek rhetorician, born in Prusa (now Broussa), in Bithynia, about the middle of the 1st century, died in Rome about A. D. 117. In the practice of his art at Rome, he incurred the hostility of the emperor Domitian, and in consequence of a decree of the senate he was obliged to flee from Italy. In the habit of a beggar, with Plato's "Phædon" and Demosthenes's "Oration on the Embassy" in his pocket, he wandered through Thrace and the countries bordering on the lower Danube, and on receiving intelligence of the death of Domitian (96) used his influence and his oratorical powers with the army stationed on that frontier in favor of Nerva. It is probable that he returned to Rome on the accession of this emperor, from whom as well as from his successor Trajan he received tokens of marked kindness. About A. D. 100 he returned to Prusa, but remained but a short time, and then went back to Rome. He was an essayist rather than an orator, and his writings are distinguished for elegance of style. Of his orations 80 have come down to us. There is a very good critical edition of them by Reiske (2 vols. 8vo., Leipsic, 1784).

DIONEA (D. muscipula, Ellis), Venus's fly trap, a plant inhabiting the savannas around Wilmington, N. C., and extending N. as far as Newbern, N. C. Elliott, on the authority of Gen. Pinckney, says that it grows along the lower branches of the Santee in South Carolina. Mr. Audubon informed Mr. Curtis, with the plant before him, that he had seen it in Florida of enormous size. Specific characters: calyx herbaceous; petals 5, hypogynous on the margin of the dilated receptacle, alternate with the sepals; stamens 10 to 20, hypogynous within the petals, shorter than they; filaments filiform; anthers oblong, of 2 parallel cells without connection; pollen of pretty large grains, composed of 4 united; Ovary depressed, ovoid, one-celled, 5 lobes, the lobes alternate with the petals; style columnar, pretty large, undivided; stigmas 5, corresponding with the lobes of the ovary; ovules indefinite, erect, sessile on and uniformly covering the nearly flat basilar placenta, which occupies the whole bottom of the cell; herb acaulescent,

smooth, with fibrous roots, and a cluster of spreading yellowish green leaves, traversed by a strong midrib bearing on its apex an orbicular herbaceo-coriaceous lamina, emarginate at both ends, fringed with a row of bristles, the 2 sides conduplicate, the upper surface dotted with minute glands, in which the sensitiveness of the leaf chiefly resides. The lobes or sides of the lamina are folded at night, but spread during the day, when if the glands be roughly touched, or an insect alights upon them, the sides suddenly close on the intruder., After remaining contracted for some time, the trap again opens, ready to enclose a new intruder; but by repeated irritation at short intervals its movements become languid, and its sensibility is for the time entirely exhausted. The best popular description of this singular plant is given by Curtis in his enumeration of plants growing spontaneously around Wilmington, N. C., communicated to the Boston society of natural history in 1834, and published in the proceedings of that society. "The leaf," remarks Mr. Curtis, "which is the only curious part, springs from the root, spreading upon the ground or at a little elevation above it. It is composed of a petiole or stem with broad margins like the leaf of the orange tree, 2 to 4 inches long, which at the end suddenly expands into a thick and somewhat rigid leaf, the 2 sides of which are semi-circular, about of an inch across, and fringed around the edge with somewhat rigid cilia or long hairs like eyelashes. It is very aptly compared to 2 upper eyelids joined at their bases. Each side of the leaf is a little concave on the inner side, where are placed 3 delicate hair-like organs in such an order that an insect can hardly traverse it without interfering with one of them, when the 2 sides suddenly collapse and enclose the prey with a force surpassing an insect's efforts to escape. The fringe or hairs of the opposite sides of the leaf interlace, like the fingers of the 2 hands clasped together. The sensitiveness resides only in these hair-like processes on the inside, as the leaf may be touched or pressed in any other part without sensible effects. The little prisoner is not crushed and suddenly destroyed, as is sometimes supposed, for I have often liberated captive flies or spiders, which sped away as fast as fear or joy could hasten them. At other times I have found them enveloped in a fluid of a mucilaginous consistence, which seems to act as a solvent, the insects being more or less consumed by it. This circumstance has suggested the possibility of their being made subservient to the nourishment of the plant, through an apparatus of absorbent vessels in the leaves." The discovery of this plant has led naturalists to make experiments upon plants with the view of ascertaining the possibility of their appropriating animal matter to their own nourishment, with such success as to lead to the belief that the form and organization of the dionaa muscipula is really intended to entrap its insect prey, for the purpose of furnishing a kind of food to the plant, which, although not essential to its

DIONYSIUS (OF ALEXANDRIA)

existence, performs an important part in its economy.

DIONYSIUS OF ALEXANDRIA, saint and bishop of the church, born in Alexandria, in Egypt, in the last years of the 2d century, died in that city, A. D. 265. He was of a noble and wealthy family. His parents were pagans; but in the course of his early philosophical studies his attention was turned to the Christian sacred writings, especially the epistles of Paul, and he became a convert. He left the heathen schools, became a pupil of Origen, was ordained priest, and in 232 was chosen to succeed Heraclas as chief of the Alexandrian school of theology. In 248 he was raised to the office of bishop, made vacant by the death of Heraclas. Shortly after this, violent persecutions broke out against the Christians. The populace of Alexandria had been stirred up against them by a certain heathen false prophet, and the edict of Decius, which reached that city A. D. 250, put arms in the hands of the enraged enemies of the Christian name. Dionysius, who had taken an active part in preparing the Christians for the coming trial, was marked for a victim, was arrested, sent to be put to death, rescued by a band of peasants, and he remained concealed more than a year in the Libyan desert, sending continual messages meanwhile to his brethren in the city. In the persecution under Valerian in the year 257, Dionysius was again exiled from his see. After his restoration (A. D. 260), he was more than once called to mediate on occasions of public strife. The writings of Dionysius were numerous, but most of them have been lost. They were mainly controversial. In opposition to Nepos, bishop of Arsinoë, who preached the millennial earthly reign of the Saviour at his second coming, Dionysius wrote 2 books refuting the theory. In opposition to Sabellius, who denied the distinct personality of the members of the Trinity, he wrote several books and epistles, caused the heresy to be condemned by a council, and insisted upon the distinction between the Son and the Father so strongly, that it brought upon him the charge of denying the divinity of Christ, against which he defended himself. According to Basil, he also defended the doctrine of the divinity of the Holy Spirit. In opposition to Paul of Samosata, Dionysius maintained the consubstantial nature of the Son and the Father. The fragments of his writings were collected by Simon de Magistris (Rome, 1796) in a folio, and are also contained in the 3d volume of the Biblio

theca Patrum.

DIONYSIUS THE AREOPAGITE, an Athenian, styled by Suidas a master of Greek erudition, and who was one of the council of the Areopagus when St. Paul appeared before that tribunal. He is said to have studied first at Athens, and afterward at Heliopolis, in Egypt. There is a legend that when he observed in Egypt the darkening of the sun which occurred during the crucifixion of Jesus Christ, he exclaimed: "Either God himself is suffering, or

is sympathizing with some one who is suffering." He was converted by the preaching of Paul, about A. D. 50; is mentioned in the Acts of the Apostles (xvii. 34), and was the first bishop of Athens, having been appointed to that office, it is said, by St. Paul himself. It is probable that he suffered death by martyrdom, but in what year is not known. It is not certain that Dionysius the Areopagite ever wrote any thing, but his name has been given to several theological treatises, imbued with the mystical doctrines of the Alexandrian Platonism. These works, 4 in number, are first mentioned in the 6th century, contain allusions to facts and quotations from authors subsequent to the apostolic age, and were probably written by some NeoPlatonic Christian of the 4th or 5th century. They exercised a great influence upon the development of Christian doctrine in the middle ages, were translated into Latin by Scotus Erigena, and gave the first impulse to that theology which the combined efforts of mystics and schoolmen maintained for centuries. The fact that this Dionysius became confounded with the patron saint of France perhaps invested these writings with an importance which they would not have acquired from their intrinsic merits.

DIONYSIUS THE ELDER, tyrant of Syracuse, son of Hermocrates, born in 430 B. C., died in 367. While a clerk in a public office, he came forward in the popular assembly as the accuser of the unsuccessful Syracusan commanders, who had suffered Agrigentum and other foremost cities of Sicily to be taken by the Carthaginians. He displayed so much vigor of character, and the condition of Syracuse was so critical, that even men like the historian Philistus saw in him the only safety for the country. He succeeded in obtaining a decree for deposing the obnoxious generals, and for appointing others in their stead, and was himself elected among the new officers. He then brought false accusations against his associates, and the people determined to depose them, and appointed him, 405 B. C., sole general, with full powers, and allowed him to protect himself by a body guard. He now began those measures which made him proverbial in antiquity as a tyrant; and concerning himself no longer for the deliverance of Sicily from the Carthaginians, aimed only to subdue his native city. He induced the Syracusans to double the pay of the soldiers, appointed officers who were in his own interest, and, by marrying the daughter of the patriot Hermocrates, secured the support of the partisans of that leader. He was received as commander-inchief of the Sicilians, who had concentrated their forces at Gela, and he offered battle to the Carthaginians in so unskilful a manner as to make it probable that he did not regret the defeat in which it resulted. He withdrew the inhabitants of Gela and Camarina to Leontini, and left the whole of the western coast to the Carthaginians. This reverse gave a shock to his popularity, and enabled his enemies to raise a revolt in Syracuse, where he was now looked

upon as a manifest traitor. They gained possession of the city, but their plans being disconcerted by the sudden return of Dionysius, they were driven out, though not until his wife had fallen a victim to their cruelty. The Carthaginian generals now besieged Syracuse, but the plague having broken out in their camp, they were satisfied with the immense advantages offered them by Dionysius without storming the place. He was recognized as ruler of Syracuse, and of a district of land around the city, but was to resign all claim to dominion over the island. He availed himself of the peace to establish his tyranny on firmer foundations; and having fortified the isle of Ortygia, and excluded from it all but his immediate dependants, he built upon it a citadel which might serve as an impregnable asylum. The Carthaginians lost the advantages of the peace through negligence. Syracuse had in 6 years recovered her strength, and Dionysius undertook the recapture of the cities which he had surrendered. The immense preparations which he made form an epoch in ancient military history. His machinists invented engines for throwing missiles, and especially devised the catapult, which may be termed the artillery of the ancients. He also constructed ships having 4 or 5 banks of rowers, instead of the old triremes. He gained at first great success in the war, and conquered Motya, the ancient seat of the Carthaginian dominion. His fleet, however, was defeated by that of the Carthaginians, which then ravaged the northern coast of the island, overpowered Messana and Catana, and laid siege to Syracuse. But the plague, or some malady resembling it, breaking out in the camp of the enemy, proved the safety of the city. Nearly the whole Carthaginian army was lost by the fearful pestilence, and the remainder purchased from Dionysius the privilege of a free departure. In the treaty which followed, the restrictions which had been imposed by the last treaty upon the government of Syracuse were removed. Dionysius carried on also a 3d and 4th war with Carthage, the results of which seem to have been only to reestablish the terms of the former peace. The intervals between these wars were harassed by the revolts of his subjects, which he avenged with cruelties; and the frequent attempts upon his life made him suspicious. He dared not trust even his relatives, and his body guard was formed of foreigners. No one was admitted to his presence till after being searched, and often an innocent pleasantry of conversation was punished as a menace. His palace was surrounded by a ditch, which was crossed by a drawbridge, and when he harangued the people it was from the top of a lofty tower. He built the terrible prison of the lautumia, cut deep into the solid rock, and another of his prisons was so arranged that every word spoken within it was reechoed into his chamber; and he is said to have passed entire days listening to the complaints of his victims. Tradition, in making of Dionysius the

DIONYSIUS EXIGUUS

type of cruelty, has doubtless transmitted some unauthenticated stories concerning him; but even a legend like that of Damocles and the sword shows his mind always alarmed, and his hand always raised to defend his imperilled life. Dionysius was long engaged in ambitious projects against the Greek cities of southern Italy. He formed an alliance with the Locrians, and after suffering some_reverses besieged and conquered Rhegium. Italy was now open to him, and he sought by establishing colonies upon the Adriatic to secure for himself a way into Greece. Already his name was known in the Peloponnesus, where he had contracted an alliance with the Lacedæmonians. He was now the recognized master of southern Italy, interfered in the affairs of the Illyrians, sent an army into Epirus, and received an offer of friendship from the Gauls, who had burned Rome. His settlements upon the Adriatic increased his wealth and strengthened his power, but they were his last great undertakings, and henceforth he disappears from history. He was so detested in Greece, that the auxiliaries which he sent to his allies the Spartans only drew upon the latter the hatred of all their countrymen. His reign lasted 38 years, and became milder toward its latter part. He left an immense military force and a powerful empire, and though he had governed as a tyrant, the old republican forms remained. Niebuhr affirms that a republic was as great an impossibility at Syracuse under Dionysius as at Rome under Cæsar, and blames him therefore for not having given to his countrymen institutions suited to them, instead of allowing the old democratic forms to exist in all their impotent absurdity, merely for the purpose of enabling him to carry out his will. Dionysius had a singular passion for literature, wrote lyrics and tragedies, and it was necessary for every one who sat at his table to praise not less the poet than the warrior. It is said, probably as a sarcastic jest, that Philoxenus, one of his guests, chose the penalty of being sent to work in the quarries rather than listen complacently to some of the tyrant's verses.

DIONYSIUS EXIGUUS (the Little), so named from his small stature, a Roman monk in the early part of the 6th century. He was originally from Scythia, but became abbot of a monastery in Rome, where he died in A. D. 540, during the reign of Justinian. He is praised by Cassiodorus, the best authority of the time, for his great erudition, writing in Greek or Latin with equal facility, and having profoundly studied theology. He gave to the western church the first regular collection of ecclesiastical laws, comprising the canons of the apostles and of several councils, and the decrees of some of the popes. But his chronological labors have given him greater celebrity. He is reputed the founder of the era which for more than 10 centuries has been observed by Christian nations. Before him the Christian era had been calculated from the death of Christ; he first fixed the year of the incarnation in the 753d year of Rome, and this,

at least after the 8th century, was universally adopted as the commencement of the era.

DIONYSIUS OF HALICARNASSUS, a Greek historian and rhetorician, born in Halicarnassus, in Caria. He removed to Rome early in the reign of Augustus, and 22 years later, shortly before his death, published his work, entitled Ρωμαϊκή Αρχαιολογια, or " Roman Antiquities.” It was in 20 books, and contained the history of Rome from the earliest mythical times to the era of the Punic wars, where the history of Polybius begins. There remain only the first 11 books, which stop with the year 441 B. C., a few years after the expulsion of the decemvirs. Several fragments and extracts from the last 9 books have been preserved in the collections made by command of the emperor Constantine Porphyrogenitus in the 10th century. The best editions of his works are those of Hudson (Oxford, 1704) and Reiske (Leipsic, 1774-'6). His rhetorical compositions have been published separately by Gross and by Westermann. There is an English translation of the "Roman Antiquities," by Edward Spelman (4 vols. 4to., London, 1758).

DIONYSIUS THE YOUNGER Succeeded his father Dionysius the Elder, as tyrant of Syracuse, 367 B. C. At that time he was a reckless young man, educated in luxury, and unused to public affairs. He hastened to conclude a peace with the Carthaginians, abandoned his father's projects of foreign settlements and power, and devoted himself to pleasure. The philosopher Dion was his uncle, and undertook to excite him to a noble career. He conversed with him of the doctrines of Plato, and through his influence that philosopher was invited to visit the court of Syracuse. On coming, Plato proposed an amendment to the constitution, changing the government from nominal democracy and real despotism to a confederate authority, in which the sovereignty should reside in all the members of the ruling family, who should form together a college of princes. The monarch rejected this proposal, and soon after took up his residence in Locri, and gained some advantages against the Lucanians; but the wild orgies to which he surrendered himself drew upon him the contempt both of his subjects and of foreigners. With a small band of exiles, and with two vessels laden with arms, Dion landed in Sicily (359 B. C.), and was joined by thousands as he marched toward Syracuse. Dionysius had instantly returned from Locri, but his troops were defeated, and he was obliged to retreat to the citadel; and finding it impossible to retain his power, he collected his most valuable property, and sailed away to Italy, while his friends still kept possession of the stronghold. In 346 he availed himself of internal dissensions to recover his power in the city, and continued to reign there during the next 3 years. But the former Syracusan empire was now in fragments; and even the garrison which defended the tyrant in the citadel was rebellious. Timoleon now appeared upon the stage, marched against Syracuse in 343, and

Dionysius consented to an arrangement, by which he was allowed to depart in safety to Corinth. He passed the remainder of his life in a private condition, with low associates, performing, according to various traditions, the parts of schoolmaster, actor, and mendicant priest of Cybele.

DIONYSUS. See BACCHUS.

DIOPHANTUS OF ALEXANDRIA, the only Greek writer on algebra, first mentioned by John, patriarch of Jerusalem, in the 8th century, unless he be identical with the astronomer Diophantus, on whose work Hypatia is said by Suidas to have written a commentary. There are no more definite indications of his era. When his MSS. came to light in the 16th century, 13 books of his Apidμerika were announced, only 6 of which have been produced. Another treatise by him, Пeр тwv Арidμwv Пoλvywvwv ("On Polygonal Numbers"), is extant. These books contain a system of reasoning on numbers with the use of general symbols, and are therefore algebraical treatises, though the demonstrations are written out at length in common language. The term Diophantine was applied by some modern mathematicians, as Gauss and Legendre, to the peculiar analysis employed in investigating the theory of numbers. The similarity of the Diophantine and Hindoo algebra renders it probable that both had a common origin, or that one was derived from the other. The best edition of his works is that of Fermat, in Greek and Latin, published posthumously (Toulouse, 1670). They were translated into German by Schulz (Berlin, 1821). The 6 books of the "Arithmetic" were translated into French by Stévin and Girard (Paris, 1625). A complete translation of his works into English was made by the late Miss Abigail Lousada, but has not been published.

DIOPTRICS, that part of optics which treats of refracted light. See OPTIOS.

DIOSCORIDES, PEDACIUS or PEDANIUS, & medical and botanical writer of the 1st or 2d century A. D., probably a native of Anazarbus in Cilicia. He made collections of plants in Italy, Gaul, Greece, and Asia Minor, and wrote a treatise in 5 books on materia medica (Пept 'Yλns Iarpins), a work which enjoyed the highest reputation until the 17th century. It is now chiefly valuable as illustrating the opinions of physicians in ancient times, and as giving us some idea of their attainments in natural history. It has been translated into the Arabic, Italian, Spanish, French, and German languages, and many editions of it have been published in Latin and Greek.

DIP, in geology, the inclination of a stratum of rock from a horizontal line. The angle of inclination is measured by an instrument called a clinometer, and the magnetic needle which is commonly with it gives the point of the compass toward which the rock slopes or dips.-In terrestrial magnetism, it is the inclination which a needle makes from a horizontal line after it has been magnetized, when before this it was

perfectly balanced in a horizontal position. In the northern hemisphere the north pole of the needle dips toward the north pole of the earth, and in the southern hemisphere the south pole is depressed toward the south pole of the earth. The line called the magnetic equator, upon which a needle continues in the same horizontal plane before and after it is magnetized, is a curved line, not varying from the geographical equator. From this toward either pole the dip increases in intensity, and by means of a needle constructed with great delicacy, and furnished with a graduated vertical arc, called a dipping needle, the angle is measured and determined for different places upon the surface of the earth. It is found, however, not to be constant in any place, but to follow the motion of the magnetic poles, which appear to move westward at an annual rate of about 11' 4". The position of these poles is ascertained by comparison of the angles given by the dipping needle in different latitudes. In 1831 Commander Ross succeeded in reaching the spot in the northern hemisphere calculated to be the N. magnetic pole, lat. 70° 5′ 17′′ N., long. 96° 46′ 45" W., where he found the dipping needle to take a position within 1' of the vertical, and the compass needles to be as perfectly indifferent to polarity as if they possessed no magnetic properties. For compasses intended to be used over a wide range of latitude, provision has to be made to counteract the effect of dip, in order that the needle may retain a horizontal position. This is effected by a small weight, so adjusted as to be slid along the bar as may be required. In passing from the northern to the southern hemisphere, it must be taken off the south pole of the needle and placed upon the north end. Dipping needles require to be made with the nicest accuracy, and to be free as possible from friction and every other impediment to their motion. By means of a universal joint, or by reference to a variation compass, the needle is made to move always in a vertical plane coinciding with the magnetic meridian of the place. -The dip of the horizon is the angle which a line to the visible horizon makes with a horizontal plane; its magnitude depends upon the height to which the observer's eye is elevated.

DIPHTHERIA (Gr. dipepa, skin), the most recent name of a disease of the mucous membranes first described by Bretonneau as diphtherite, characterized by the exudation of a thick leathery membrane in the throat; it may occupy also any portion of the air passages even to the bronchi, the gastro-intestinal surfaces, the points of junction of the skin and mucous membrane, and the skin itself where it is delicate or deprived of its epidermis. It is allied to some forms of scarlatinous inflammation, to croup, and to quinsy, with which it is often confounded. It is probably, as it has occurred during the last few years in France and England, only an intense epidemic form of an old disease, manifesting itself in various forms of throat disease. In the formation of firm con

cretions and in its tendency to spread when epidemic, it resembles in some respects the disease of infants known as muguet. Various causes have been assigned for it, and it is generally admitted to be a specific disease. Dr. Laycock and others regard it as due to the oidium albicans, a parasitic fungus, whose sporules and mycelium have been found on the mucous membrane of the mouth, fauces, and alimentary canal; its irritation induces in the enfeebled membranes an increased secretion of epithelial scales and exudation corpuscles, which with the fungus constitute the membrane or pellicle; it seems to act upon the capillaries of the subjacent tissue, which is red and bleeding. Syphilitic, scarlatinic, or rubeolic inflammation may take on the diphtheritic form during an epidemic, and the fungus may excite an irritation without forming a pellicle; it is not vesicular nor ulcerative like aphthæ, and the redness is deeper. These microscopic parasitic organisms doubtless cause more diseased conditions than physicians are as yet aware of, and the question naturally arises whether the fungous growth is the primary process, or whether it is secondary, requiring the nidus of a previously diseased membrane for its development. From the occurrence of similar growths in a variety of diseases, they would seem a consequence rather than a cause, springing up wherever they find a suitable nidus, complicating and often masking the original disease; the fungus of diphtheria, however, is said to be peculiar, and different from other similar parasites. The sporules may and do pass from one person to another, and the disease is consequently contagious, rendering necessary the isolation of the sick. It is most common in the foul districts of the large cities of France and England, and is attributed to the action of putrid effluvia on the fauces, especially the foul air of sewers and cess-pools; according to the report of the registrar-general, in March, 1858, 2,000,000 of the people of London live over such subterranean structures, so imperfectly secured that any variation in the pressure of the atmosphere forces up the foul air and sends it along every street and into every house, as if it were an apparatus specially contrived for passing currents of poisonous vapor steadily over the people. The same authority states that in 1857 15,000 deaths in London were attributed to the aggregate effects of impure air and other sanitary defects, and recommends the conducting off of the effluvia of these receptacles through pipes running as high as the chimneys. It is altogether probable that many epidemics in this country have had a similar origin, and from the account of the symptoms and successful treatment of the recent epidemic of singular throat disease in Albany, it would seem that it was diphtheria; it was found in all parts of the city, and in almost every block, and raged for several months with a mortality of about 5 per cent.-As diphtheria most severely attacks debilitated constitutions, in addition to hygienic and sanitary measures, the general treatment should be by