Part 5
DIAMOND LORE. In Hellenic, Arabian, Chinese, and other literature the diamond is connected with the eagle and snakes. Diamonds, according to ancient belief, lie in deep valleys infested by snakes, or entirely surrounded by straight, high cliffs. Pieces of flesh are thrown down and eagles seize them. The birds are followed to their nests, where the diamonds that adhered to the flesh are found. Mixed with this legend is the older one regarding the 'eagle stone', which assists parturition. It was believed a woman was easily delivered if the 'eagle stone' were placed on her abdomen. The Chinese legend was imported with the diamond from Fu-lin (Syria). Indian diamond lore is mixed with pearl lore. According to the Buddha birth stories, diamonds are found in the sea. The ancients asserted that the diamond could not be injured by iron, fire, or smoke. Before it could be broken it had to be steeped in ram's blood. The alchemists used lead as a substitute for ram's blood. In Chinese lore diamonds are rulers of gold and have their origin in gold. A similar belief prevailed in mediaeval Europe, adamantine gold being credited with the same virtues as the diamond. Both gold and the diamond were sacred. The diamond is a mediaeval symbol of Christ; in the Far East it is connected with Buddha. The association of the diamond with snakes gave origin to the belief that it was poisonous, the saliva of the snakes clinging to it. Diamond dust is regarded in India as a deadly poison. Like the sacred pearl, the diamond has been credited with nocturnal luminosity. Certain varieties of diamonds when heated, rubbed, or exposed in bright sunshine emit slight rays of light for a short time in darkness. The belief in 'night shining gems', however, had origin in pearl lore, the pearl having been connected with the moon ('the pearl of heaven'). Coral, rhinoceros-horn, fern seed, the mandrake, &c., were likewise connected with the moon-goddess and credited with nocturnal luminosity.
DIAMOND NECKLACE, an affair of some note in French history immediately preceding the Revolution. See _Marie Antoinette_; _La Motte_; and _Rohan, Louis_.
DIAN'A, in Roman mythology, an ancient Italian goddess, in later times identified with the Greek Art[)e]mis, with whom she had various attributes in common, being the virgin goddess of the moon, and of the chase, and having as attributes the crescent moon, bow, arrows, and quiver. The name is a feminine form of Janus. She seems to have been originally the patron divinity of the Sabines and Latins. She was worshipped especially by women, as presiding over births, no man being allowed to enter her temple.
DIANA-MONKEY (_Cercopith[=e]cus Diana_), a species of monkey found in West Africa, and so named from the crescent-shaped band on the forehead resembling the crescent moon, which was the symbol of Diana. Another characteristic feature is the possession of a pointed white beard.
DIANA OF POITIERS, Duchess of Valentinois, born in 1499. She was the mistress of King Henry II of France, and descended from the noble family of Poitiers, in Dauphiny. At an early age she married the Grand-Seneschal of Normandy, Louis de Br['e]z['e], became a widow at thirty-one, and some time after the mistress of the young Duke of Orleans. On his accession to the throne in 1547, as Henry II, Diana continued to exercise an absolute empire over him till his death in 1559. After that event she retired to her castle of Anet, where she died in 1566.--Cf. Capefigue, _Diane de Poitiers_.
DIAPA'SON, in music, the concord of the first and last notes of an octave. The word is also used for the most important foundation-stops of an organ. They are of several kinds, as _open diapason_, _stopped diapason_, _double diapason_. The French use the term as equivalent to pitch in music.
[Illustration: Diaper Ornamentation. Westminster Abbey]
DI'APER, a kind of textile fabric much used for towels and napkins, and formed either of linen or cotton, or a mixture of the two, upon the surface of which a flowered or figured pattern is produced by a peculiar mode of twilling.--As a term in ornamentation diaper is applied to a surface covered with a flowered pattern sculptured in low relief, or to a similar pattern in painting or gilding covering a panel or flat surface.
DIAPHANOSCOPE, (1) an apparatus by means of which transparent positive photographs may be viewed. The name is also given to (2) an instrument employed in obstetrical surgery; electric light, contained in a glass tube or bulb, is introduced into the female internal organs, and, thus illumined, their condition can be examined through the translucent walls of the abdomen.
DIAPHORET'ICS (Gr. _diaphorein_, to carry through) are agents used in medical practice to produce perspiration. The Turkish bath, hydropathic treatment, diluent drinks, &c., are employed for this purpose. The degree of perspiration produced is more than normal, but less than in sweating. See _Sudorifics_.
DIAPHRAGM (d[=i]'a-fram), in anatomy, a muscular membrane placed transversely in the trunk, and dividing the chest from the abdominal cavity. In its natural situation the diaphragm is convex on the upper side and concave on its lower, but when the lungs are filled with air it becomes almost flat. It is the principal agent in respiration, particularly in inspiration. A complete diaphragm is found only in Mammalia.
DIARBEK'IR, a town in Armenia, formerly in Asiatic Turkey, capital of the vilayet of same name, on a high bank overlooking the Tigris, and surrounded by a lofty massive wall. It has manufactures of iron- and copper-ware, leather, silk, woollen, and cotton goods, and a considerable trade. Pop. about 38,000.--The province of Diarbekir has an area of 14,480 sq. miles, and a pop. of 471,500.
DIARRHOE'A is morbidly frequent evacuation of the bowels. Several forms are recognized. _Choleraic diarrhoea_; this form is acute, and is marked by great frequency, with serous stools, and accompanied by vomiting and collapse. _Critical diarrhoea_ occurs at the crisis of a disease. _Lienteric diarrhoea_ is marked by the passage of fluid stools containing scraps of undigested food. _Mucous diarrhoea_ is marked by the presence of mucous in the stools. _Summer diarrhoea_ occurs chiefly among young children and infants, most frequently in late summer. It is usually acute in type and associated with marked prostration. In epidemic form it may give rise to a high mortality in crowded districts and in institutions. _Nervous diarrhoea_ is produced by some emotional cause. The treatment, whatever the type, is to get rid of the cause of the irritation, and to avoid further irritation in the intestinal tract. For this purpose purgatives are given, and all solid food forbidden. This is followed by gastro-intestinal sedatives and a gradual return to normal diet--substances causing least digestive difficulty being first given.
DIASTASE is an unorganized ferment or enzyme produced in the germination of barley, oats, &c. It is soluble in water, and the solution has the property of inducing fermentation or hydrolysis of starch into dextrine and glucose. To prepare diastase, barley is allowed to germinate; germination is then interrupted by raising the temperature, and the grain is treated with a mixture of water and alcohol under pressure, and filtered. Diastase, being soluble, is obtained in the filtrate.
DIATHER'MANCY, the property that is possessed in various degrees by different substances, of transmitting radiant heat. Bodies that are equally transparent, that is, bodies which have equal power of transmitting rays of light, are very different in their power of transmitting heat-rays. Thus a thin plate of glass and a thin plate of rock-salt may be nearly equally transparent, but the plate of rock-salt has far superior power of transmitting rays of heat. The latter, it has been found, allows 92 per cent of the total heat from most sources to pass; glass and other substances transmit a much smaller proportion, and the amount varies with the source. Rock-salt is diathermanous to heat from nearly all sources. It has been shown that rock-salt is extremely opaque or athermanous to the radiations from a piece of heated rock-salt. The diathermancy of the plates in every case decreases very rapidly as their thickness is increased. See _Radiation_.
DIATH'ESIS is the term given in medicine to a constitutional predisposition to a disease; thus uratic diathesis is a tendency to gout; aneurysmal diathesis is an inherent predisposition to aneurysms.
DIATOMA'CEAE, a family of Algae, consisting of microscopic unicellular plants with brown chromatophores found in fresh, brackish, and salt water, and on damp ground. The cell wall contains a very large quantity of silica, and is formed in each cell into three portions, viz. two generally symmetrical valves and a connecting hoop. The species consist of single free cells, or the cells remain connected so as to form usually linear colonies, sometimes enclosed in a transparent gelatinous sheath. The ordinary method of increase is by cell division. A sexual process resembling that of the conjugatae also occurs. Diatoms constitute an important source of food for the lower marine animals, and thus indirectly for the food-fishes. Diatomaceae are found fossil, forming considerable deposits of tertiary age, as at Bilin, Richmond in the United States, &c. Fossil polishing-powders, as tripoli and bergmehl, are composed of them; also kieselguhr, which, impregnated with nitroglycerine, forms dynamite. They are abundant in guano.
DIAT'OMITE (Ger. _kieselguhr_), a diatomaceous earth (see _Diatomaceae_) generally found underlying peat. In Skye, at Loch Quire, it is found about 18 inches below the surface, and extends downward for about 7 feet, and in some places to a much greater depth. Another important area is north of Toome Bridge in the county of Antrim. Diatomite is principally used for the manufacture of dynamite on account of its value as an absorbent. It is described also as extremely well adapted for the manufacture of silicate paints, siliceous glazings, porcelain, boiler-coatings, and for isolating felt and bricks for cold-storage buildings.
DIATON'IC, a term originally applied by the Greeks to one of their three genera of music. In modern music it is applied to the natural scale, and to the intervals, chords, melodies, or harmony characteristic of it. A diatonic chord is a chord having no note chromatically altered. A diatonic interval is an interval formed by two notes of the diatonic scale unaltered by accidentals. A diatonic melody is a melody composed of notes belonging to one scale only.
DIAZ, Bartolommeo, a celebrated Portuguese navigator of the fifteenth century, named in 1486 commander of one of that long succession of exploratory expeditions which the Portuguese court had during this century become distinguished for promoting. The two vessels composing the expedition sailed along the African coast till they reached Cape Negro (lat. 15deg 50' S.), where Diego Cam, a previous explorer, had stopped. At 29deg S. they anchored at a point to which they gave the name of Angra das Voltas (Bay of Detours). In sailing south from this point they doubled the Cape of Good Hope without knowing it, and landed at a bay on the east coast. Diaz now wished to continue his voyage in order to discover the country of Prester John, but the sailors refused to accompany him. In again doubling the Cape he gave it the name of Cabo Tormentoso (Cape of Storms), which the king changed to its present designation. In 1500 Diaz had command of a vessel in the expedition of Cabral which discovered Brazil. In returning home the vessel which he commanded was lost, 29th May, 1500.
DIAZO COMPOUNDS, or DIAZONIUM COMPOUNDS, a name given to substances containing the chemical group - N:N -; thus diazo-benzene chloride, C_6H_5 - N:N.Cl, or diazo-toluene sulphate, C_6H_4(CH_3) - N:NH.SO_4, &c.
These substances are formed from the aromatic amines by treatment with nitrous acid at low temperatures. Primary amines all react with nitrous acid at moderate temperatures when the amino group (NH_2) is replaced by a hydroxyl group (OH); thus ethylamine (C_2H_5NH_2) reacts with nitrous acid (HNO_2), yielding alcohol (C_2H_5OH), C_2H_5NH_2 + HNO_2 - C_2H_5OH + N_2 + H_2O. The aromatic amines, however, if treated below 0deg C. with nitrous acid, yield diazo compounds, and not hydroxy compounds, e.g. aniline treated with nitrous acid in hydrochloric acid solution yields diazo-benzene chloride, C_6H_5NH_2.HCl + HONO = C_6H_5 - N:N.Cl + 2(H_2O). Diazo salts are crystalline compounds soluble in water, sparingly soluble in alcohol, and are unstable, decomposing explosively if struck or suddenly heated. In solution in water they decompose as the temperature rises, liberating nitrogen, and forming hydroxy compounds, C_6H_5N:NCl + H_2O = C_6H_5OH + N_2 + HCl. Diazo salts are valuable in the synthesis of different classes of compounds, as the - N:N - group reacts readily with other groups. For this purpose it is usually only necessary to prepare a solution containing the diazo compound. In the preparation of the azo dyes the starting-point is a primary amine; the amino group is 'diazotized', i.e. treated with a solution of sodium nitrite and dilute mineral acid at low temperature. A diazo salt is formed, and is then made to react in solution with a hydroxy compound or an amino compound, &c., with the formation of a highly coloured azo compound. The diazo compound is then said to be coupled. Diazo compounds are therefore important intermediate substances in the manufacture of azo dyes.
The diazo group may also be exchanged for the hydroxyl group by warming the solution with water, or for the cyanogen group by warming with a solution of potassium cyanide, e.g. diazo-benzene chloride warmed with potassium cyanide solution is converted into the nitrile of benzoic acid, C_6H_5 - N:NCl + KCN = C_6H_5CN + KCl + N_2; or transformed into halogen derivatives of hydrocarbons by warming with cuprous chloride, e.g. diazo-benzene chloride is transformed into chlorobenzene, C_6H_5 - N:NCl + Cu_2Cl_2 = C_6H_5Cl + N_2 + Cu_2Cl_2. These reactions, where nitrogen is eliminated from the compound, and a group or element replaces the two atoms of nitrogen, afford a means of synthesizing a variety of compounds.
DIB'DIN, Charles, an English dramatic manager and poet, composer and actor, born in 1745, died in 1814. At the age of fifteen he made his appearance on the stage, and was early distinguished as a composer. He invented a new kind of entertainment, consisting of music, songs, and public declamations, which he wrote, sang, composed, and performed himself, and by this means succeeded in amusing the public for twenty years. In 1769 he composed some of the music for the Shakespeare jubilee at Stratford-on-Avon. His patriotic songs were very popular, and his sea-songs, amongst which are _Tom Bowling_, _Poor Jack_, and _The Trim-built Wherry_, are still favourites in the British navy. He also wrote a _History of the Stage_, and the novels _The Devil_ and _Hannah Hewitt_.--His son, Charles Dibdin, composed and wrote many small pieces and occasional songs.--Another son, Thomas, early displayed the same dramatic tastes as his father, was connected with various theatres, and wrote a great many songs and a number of dramas.
DIBDIN, Thomas Frognall, an English bibliographer, born in 1776, died in 1847, was the son of the elder brother of Charles Dibdin the celebrated naval song-writer. After studying law and practising as a provincial counsel, he took orders and became a popular preacher in London. Here his bibliographical tastes developed themselves, and the Roxburghe Club being established in 1812, he became its first vice-president. Among his numerous writings may be noted: _Bibliomania_, _Bibliographical Decameron_, _Typographical Antiquities of Great Britain_, and _The Library Companion_.
DIBRANCHIA'TA. See _Cephalopoda_.
DICE, cubical pieces of bone or ivory, marked with dots on each of their six faces, from one to six, according to the number of faces. They are shaken in a small box and then thrown on the table. Dice are often loaded or falsified in some way so as to make the high or the low sides turn down. The origin of dice is ascribed to Palamedes of Greece (1244 B.C.), although Herodotus attributes the invention of knuckle-bones and of dice to the Lydians. Dice were well known amongst the ancient Egyptians and Greeks, and are still very popular in Japan, China, India, and other Asiatic countries.
DICEN'TRA. See _Dielytra_.
DICHASIUM. See _Cyme_.
DICHLAMYDEOUS (d[=i]-klam-id'i-us), in botany, said of plants that have both calyx and corolla.
DICHOGAMY, in flowers, the condition in which anthers and stigmas ripen at different times, whereby self-pollination is effectually prevented. If the anthers ripen first, as in borage, columbine, crocus, Caryophyllaceae, Compositae, Labiatae, &c., the flower is said to be protandrous; protogynous flowers, with stigmas ripening and withering before the pollen is shed, occur, e.g. in Christmas rose, Colchicum, horse-chestnut, and in the majority of wind-pollinated plants.
DICHOTOMY (d[=i]-kot'o-mi), a cutting in two; a division by pairs. Hence, in botany, a mode of branching by constant forking, each branch dividing into two others. See _Branching_.
DICHROIC, or more generally PLEOCHROIC, CRYSTALS (d[=i]-kr[=o]'ik), crystals that have the property of exhibiting different colours, according to the direction in which they are traversed by rays of light. When polarized light is passed through a transparent plate of a pleochroic mineral, the colour will vary with the direction in which the light-vibrations take place. Hence, _face-pleochroism_, the colour of the plate, may be distinguished from the colours given by _axis-pleochroism_, the colours given by light vibrating parallel with certain optical directions in the crystal.
DICHROITE (d[=i]'kro-[=i]t), or IOLITE, a mineral, a silicate of magnesium, iron, and aluminium, which readily undergoes modifications and passes into hydrous silicate. It exhibits marked pleochroism, whence the name.
DICK, Thomas, LL.D., a Scottish author of popular scientific works, born at Dundee in 1774, died 29th July, 1857. He was for many years a teacher at Perth, but subsequently resided at Broughty-Ferry, where he devoted himself to astronomical science, especially in its relations to religion. Some years before his death a small pension was granted to him by the Government. Amongst his works are: _The Christian Philosopher_ (1823), _The Philosophy of Religion_ (1825), _The Philosophy of a Future State (1828)_, and _Celestial Scenery_ (1838).