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.
[Illustration: Dipper (_Cinclus aquaticus_)]
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.
[Illustration: Diptera--Diagram of a two-winged insect--a Daddy-long-legs.
Appendages of left side omitted]
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.
[Illustration: Directrix of a Parabola]
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.