overstocked the market that few of the English houses were able to stand up against it.-Beside their use as ornaments, diamonds are applied to several practical purposes. Those that are unfit from their imperfections for jewelry, are sold under the technical name of bort. They are crushed to fine powder in a steel mortar, and used for coating the metallic disks employed by lapidaries for producing flat surfaces on precious stones of great hardness. The fine splinters are made into drills, for piercing small holes through rubies and other hard stones. The property possessed by the diamond of cutting glass is due not merely to its extreme hardness, but to the peculiarity of its crystallization in rounded faces and curvilinear edges. The natural crystal only is suitable for this purpose. According to Dr. Wollaston, many hard stones, and even flint cut in this form, possess the same property, but soon lose it in use, for want of hardness. Small microscopes of a single lens, and of great power and clearness, have been cut out of diamonds.-The diamond exhibiting the physical properties of matter in their highest state of perfection, and proving after all to be of the simplest chemical composition, it has been a matter of no little scientific interest to study the peculiarities of its construction, and to determine if possible the secret processes by which nature has elaborated the most perfect gem from so homely a substance as charcoal. Its high value has stimulated these researches, in the hope of individual profit by its artificial production. But though more complicated forms of matter have been successfully reproduced, carbon has not yet been made to attain the simple perfection of the diamond, unless it be in crystals invisible to the naked eye; nor have we yet learned from what department of nature's works the material has been taken, that has been so beautifully perfected. The vegetable kingdom may have furnished it, after itself receiving it from the atmosphere, or it may have been unlocked from those repositories of carbon shut up from remote geological periods in the carbonic acid of the calcareous rocks, or from such collections of fossilized plants as are now seen in various stages of change to mineral substance. But if the direct object of these researches has not been attained, the forces which have acted upon it to give to it some of its peculiarities have been partially determined, as also a previous condition in which it must have existed. Sir David Brewster, from the exhibition of polarized light around the minute and irregular cavities in diamonds, has concluded that the substance has once been in a soft state, and compressed in these parts by the expansive action of a gas or fluid contained in the cavities; and as various circumstances indicate that this softness was not the effect of either solvents or heat, he is of opinion that, like amber, the diamond is a vegetable substance, slowly consolidated into a crystalline form. The nearest approach to its reproduction has been in the experiments of M. Desprétz, announced in the

year 1853. By long continued voltaic action, carbon free from every trace of mineral substance, prepared from crystallized sugar candy, was made to deposit microscopic crystals in black octahedrons, in colorless translucent octahedrons, and in colorless and translucent plates, the whole of which had the hardness of the powder of the diamond, and which disappeared in combustion without leaving any perceptible residue. Being, however, only in powder, it was impossible to isolate and weigh these crystals, or to determine their index of refraction and angles of polarization. It is said that a similar result has been obtained by decomposing a mixture of chloride of carbon and alcohol by weak galvanic currents.-The principal English works on the subject are D. Jeffrey's "Treatise on Diamonds and Pearls" (8vo., London, 1750); I. Mawe's "Treatise on Diamonds and Precious Stones" (8vo., London, 1826).

DIAMOND DISTRICT, a part of the district of Serro Frio, in the province of Minas Geraes, Brazil, famous for the production of diamonds. It is a mountainous tract, not far from Villa do Principe, extending about 16 leagues from N. to S. and 8 from E. to W. The diamonds were first discovered here by a company of gold miners in 1730. At first they were ignorant of the value of the gems, and threw away many of them as useless. Others were sent to the governor of Brazil, who supposed them to be curious crystals. A few of the stones having been carried to Lisbon were shown to the Dutch consul, who recognized them as diamonds, and had them transmitted to Holland. Immense numbers of the gems were now exported from Brazil, and the Portuguese government soon took measures to secure a monopoly of the val uable trade. The district was surrounded by lines of demarkation, which were guarded with the utmost strictness. No one was permitted to pass these in either direction without a permit from the intendant of the mines, and travellers leaving the diamond ground were obliged to submit to a thorough examination of their persons, baggage, and horses. A peculiar system of police was established for the regulation of the district, and stringent laws were passed to provide for the registering of the inhabitants, the admission of settlers, the erection of inns and shops, and the punishment of infringements of the government monopoly. The diamond mines were at first rented to private individuals, but the frauds and violations of contract of which these persons were constantly guilty induced the government to take the matter into its own hands, and the mines were long worked under the direction of officers of the crown. precious stones are found in a kind of gravel, called cascalhão, which is dug up and removed to a convenient place for washing. A shed, about 25 or 30 yards long and 15 wide, consist ing simply of upright posts and a thatched roof, is erected over the spot where the heaps of cascalhão are to be deposited. Through the centre of this shed is conducted a stream of

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water, on one side of which is a range of sloping troughs, each about 3 feet wide, and communicating with the stream at the upper end. Opposite to the troughs are high chairs placed at equal distances for the overseers, or feitores. A slave stations himself in each trough, and with a short-handled rake draws up a pile of 50 or 80 pounds of cascalhão. He lets in water upon this, to wash away the earthy particles, and after throwing out the largest stones, examines the rest with great care for diamonds. As soon as he finds one, he stands upright, claps his hands, and holding it between his finger and thumb shows it to the overseer, who receives it from him, and places it in a bowl half full of water, suspended from the centre of the structure. The mines are now open to all who choose to invest their capital in them, and the cost of working them has been estimated at about $8 per carat. They give employment and support to about 10,000 persons.

DIAMOND HARBOR, a roadstead in the river Hoogly, presidency of Bengal, British India, 29 m. below Calcutta. It was the first place in Bengal acquired by the East India company, and is now a shipping depot. The climate is very unhealthy; the neighboring swamps exhale the most noxious vapors, and the night dews are remarkably heavy. An excellent road and an electric telegraph connect the place with Calcutta.

DIANA, an ancient Italian divinity, identified by the Romans with the Artemis of the Greeks. Servius Tullius is said to have introduced her worship at Rome, dedicating to her a temple on the Aventine. As goddess of light she represented the moon. The root of her name seems to be the same as that of the word dies. In images and legends of a later period she fully answers to the Grecian Artemis. (See ARTEMIS.)

DIANA OF POITIERS, duchess of Valentinois, mistress of Henry II. of France, born Sept. 3, 1499, died in Anet, April 22, 1566. She was maid of honor to Queen Claude, and when her father, the count of St. Vallier, had been condemned to death for favoring the escape of the constable Bourbon, she so touched the heart of the susceptible Francis I. by her tears and beauty, that the punishment was commuted. At the age of 13 she became the wife of Louis de Brézé, count of Maulevrier, by whom she had 2 daughters. In 1531 her husband died, and Diana, putting on a widow's weeds, expressed a resolve to wear them to her grave; but this did not prevent her when nearly 40 years old from becoming the mistress of the dauphin, afterward Henry II. The duchess of Etampes then possessed the affections of Francis I., and the 2 favorites divided the court until the accession of the dauphin, when Diana's rival was sent into exile. Diana now became almost mistress of the kingdom. The beauty and accomplishments of the young queen, Catharine de' Medici, could not prevail against her influence. The king delighted in giving public tokens of his infatuation, and not content with wearing her colors and blazoning

the palaces and public buildings with her emblems and devices, he admitted her to his councils, and in 1548 created her duchess of Valentinois. She retained her ascendency until Henry's death in 1559, when she retired to the palace built for her by her royal lover at Anet; but in 1561 she was recalled by Catharine de' Medici to exert her influence in detaching the constable de Montmorency from the Châtillons. From that time until her death she remained in retirement, retaining her personal charms, of which she had always taken the most extraordinary care, to the last. Her power over the king, even when she had reached the ripe age of 60, was due no less to her beauty than to her intellectual gifts. She seldom made a bad use of her position, and she spent large sums in charity.

DIAPASON (Gr. dia, through, and was, all), a term employed by the old Greek and Latin musicians to denote the scale or octave. Modern musicians sometimes employ it in a similar manner. The diapason stops of an organ are so called because they run through the whole register of the keyboard.

DIAPER, a linen fabric, said to have been originally made at Ypres in Belgium, and hence known as d'Ypres, whence its present name. It is distinguished by its flowered patterns, and sometimes resembles damask. It is largely manufactured for napkins, table-cloths, &c. Ireland, Germany, and Scotland especially produce excellent qualities of the article.

DIAPHORETICS, or SUDORIFIOS (Gr. diapepew, to carry through), stimulant medicines, which increase the cutaneous transpiration. In this class were formerly included many substances, especially the mints and similar plants, which are only diaphoretic in virtue of the abundant, warm, and watery infusion in which they are administered. There are, however, certain substances, vegetable and mineral, which exert a special action upon the skin, stimulating the sudoriferous glands, and eliminated by the cutaneous surface. Warm water is an excellent diaphoretic, either simple or in the form of the many domestic herb teas; the vapor and warm baths are effectual and natural stimulators of the skin; the cold bath, and the various applications of the hydrotherapic method, are sure but disagreeable and often dangerous sudorifics. Among vegetable remedies of this class are aconite, opium (alone or combined in the form of Dover's powder), dulcamara, guaiacum, sarsaparilla, mezereon, and squill. At the head of the mineral diaphoretics stand the antimonials; others are sulphur and the preparations of ammonia. The ethers, especially the nitrous, are powerfully diaphoretic when the surface is kept warmly covered. Indeed, many of the so-called diaphoretics, if the body be not kept warm, act as diuretics, increasing the urinary secretion; and almost any stimulating medicine will increase the secretion of the skin, if the surface be warmed or prevented from losing its heat by evaporation. Deficient action in the skin is seen in a great variety of complaints,

and in certain stages of almost all fevers, and the choice of the proper remedy to stimulate its action often requires the highest skill of the physician. Diaphoretics are employed to most advantage in chronic diseases of the skin, in gout and rheumatism, syphilis, dropsy, and catarrhal affections. When we consider the amount of carbonic acid and azotized matters thrown off by the skin, in its vicarious and alternating performance of the offices of the lungs and kidneys, we can understand how necessary it is to keep this surface in a healthy condition. The skin is a most important respiratory organ, and will keep up the standard of animal heat when the lungs are almost destroyed as aërating organs, giving a most valuable therapeutic indication in the treatment of pulmonary affections. According to Mr. Wilson, the total number of pores of the sudoriferous glands on the surface of the human body is about 7,000,000, and the length of the perspiratory tubing connected therewith nearly 28 miles. Such an extensive system as this cannot be neglected in disease with impunity, and the medicines which can stimulate it, when depressed or obstructed, must be among the most useful in the materia medica. It is highly probable that, in many forms of fever, the suppression of the perspiration is the cause of the disordered vascular action; and that deficient action of the cutaneous glandulæ, from want of exercise and inattention to cleanliness, is a frequent source of disease, from the accumulation in the blood of decomposing organic matter whose natural outlet is the skin. The cutaneous surface seems to be the natural channel for the elimination of many morbid products, and the use of diaphoretics to be the only rational method of removing such from the system. The experience of physicians in tropical climates shows that the great art of preserving health there consists in attention to the regular performance of the cutaneous functions, and that the adynamic fevers of those unhealthy regions are best treated by active diaphoretics.

DIAPHRAGM, the transverse muscle which separates the thoracic from the abdominal cavity in mammalian vertebrates. It is flattened in shape, nearly circular, fleshy at the edges, tendinous in the centre, elongated, and ending in a point behind. In front it is attached to the ensiform cartilage of the breast bone, on the sides to the posterior surface of the last 6 ribs, behind to the transverse process of the 1st lumbar vertebra and to the bodies of the first 3 vertebræ of the loins by tendinous slips; the fleshy fibres of the last form the pillars of the diaphragm, and their fasciculi cross each other in such a way as to leave 2 openings, one superior and most anterior, giving passage to the cesophagus and par vagum nerve, the other inferior and more to the left, for the passage of the aorta, thoracic duct, and vena azygos; the tendinous centre has been compared to a leaf of clover. Between the middle and right portion of the tendinous centre is the opening for the

passage of the inferior vena cava. The diaphragm is in relation, above, with the pericardium in the middle, and with the pleuræ, base of the lungs, and walls of the chest on the sides; below, with the aorta in the middle, the kidneys, renal capsules, pancreas, and duodenum; on the right side with the liver, and on the left with the stomach and spleen. The direction of the posterior fibres is nearly vertical; all the others converge toward the tendinous centre. The diaphragm is the great muscle of respiration; when it contracts, its upward convexity becomes a plane surface, the cavity of the chest is enlarged, and air rushes in to expand the lungs during the act of inspiration; when forcibly contracted, it may act as an assistant to the abdominal expiratory muscles by diminishing the size of the base of the chest; by its action on the abdominal viscera it aids in the expulsion of fæces and urine; in ordinarily tranquil breathing the diaphragm is sufficient for the performance of the function. In animals the extent and position of the diaphragm vary according to the number of the ribs; in those whose ribs extend nearly to the pelvis, as in the horse, the thoracic convexity of the diaphragm is much greater than in man. This important muscle is liable to malformations, wounds, and morbid conditions; its total absence is incompatible with any other than intrauterine life, as aërial respiration would be impossible; its partial absence, like dilatation of its natural openings, or laceration of its fibres, is accompanied by the passage of more or less of the abdominal viscera into the chest, impeding the action of the heart, lungs, and digestive organs; in such cases, the liver, stomach, omentum, ileum, cæcum, and part of the colon, have been found above the diaphragm. This partition is also liable to penetrating wounds, and to rupture from external violence, the latter being the most dangerous; in either case, nature alone can remedy the evil. It is sometimes inflamed, and in the rheumatic diathesis is the seat of the most acute pain, increased by every respiratory act, and forcing the patient to breathe almost entirely by means of the abdominal muscles. Spasmodic contractions are familiarly known by the phenomenon of hiccough; this is sometimes merely a nervous affection, and at others is a symptom of peritonitis, strangulated hernia, and other abdominal diseases. Paralysis of the diaphragm is speedily fatal, from the suspension of respiration.

DIARBEKIR, DIYAR-BEKR, or DIARBEKR, a town of Turkey in Asia, formerly capital of an ancient pashalic of the same name, on a rocky eminence a short distance from the right bank of the river Tigris, in lat. 37° 55′ 30′′ N., long. 39° 52′ E. A fertile and well cultivated plain surrounds the city, which is encompassed by walls pierced by 4 gates, and surmounted by many towers. In the N. E. portion of the town are the ruins of the citadel, formerly the residence of the pasha. The town was once a very flourishing place, and contained, it is said, 200,

000 inhabitants; but owing to the predatory disposition of the Koords, who by their attacks have rendered unsafe the intercourse with Bagdad and Aleppo, its prosperity has declined, and it now contains no more than 40,000 inhabitants, the greater part Turkish, the rest mostly Armenian. Some trade is, however, carried on with Aleppo, and the manufacture of cotton and silk goods, though much diminished, is still continued. The streets, like those of other eastern cities, are narrow and dirty, and most of the houses are constructed of rough stone covered with a plaster composed of mud and straw. The town contains many mosques, an Armenian cathedral and other Christian churches, numerous baths, caravansaries, and bazaars, and is well supplied with water, which is introduced by a fine aqueduct, and distributed through the city in numerous stone fountains. The walls are built of a dark-colored basalt, quarried in the neighborhood, and many of the principal buildings of the city are constructed of the same material, whence the Turks call the place Kara Amid, or Black Amid; Amida being the ancient name of the town. A British consul resides here.

DIARRHEA (Gr. diappew, to flow through), a disease characterized by the occurrence of frequent, loose, alvine discharges. In a proper system of nosology diarrhoea would scarce find a place; it is a symptom rather than a disease, and is produced by a number of different pathological conditions. It is present in the course of typhoid fever, is a frequent accompaniment of phthisis, and is sometimes an attendant upon albuminuria and other forms of blood poisoning; it is caused by inflammation and ulceration of the bowels. Those slighter forms of the complaint only will be noticed here which are independent of constitutional causes, and which are produced by a temporary irritation or sub-inflammation of the intestinal mucous membrane. Diarrhoea is often caused by the use of crude and indigestible food, or even by food ordinarily wholesome taken in too great quantity or variety. Fruit, particularly when acid and unripe, uncooked vegetables, as cucumbers and salads, food in a state of incipient decomposition, the flesh of immature animals, as young veal, &c., are all liable to act upon the bowels. Certain articles, as mushrooms, shellfish, the richer varieties of ordinary fish, as salmon, from peculiarity of habit disagree with particular individuals and produce diarrhoea. The same is true of a total change of diet; food perfectly wholesome to those accustomed to it, and the water used habitually in certain districts of country, often cause bowel complaints in the stranger. Emotions of the mind, particularly grief and anger, in some persons promptly occasion an attack of diarrhoea; others are affected in the same way by sudden changes of temperature, wet feet, or exposure to cold. Where diarrhoea is caused by the ingestion of food rendered irritating by its quantity or quality, the purging itself soon removes the cause of irrita

tion and the diarrhoea ceases; if this should not be the case, a moderate opiate or an anodyne combined with an astringent are all that will be found necessary. When diarrhoea is dependent on exposure to cold, a bland, unirritating diet, the warm bath, and the use of opium or of opium and ipecacuanha in small doses, may be had recourse to; in such cases the patient is generally benefited by wearing a flannel bandage around the abdomen.-Young infants at the breast sometimes suffer from bowel complaint; here it is commonly caused by over-feeding. Ordinarily nature provides against this by the facility with which the infant vomits; the stomach frees itself from the excess of food, and no mischief is done; but when the infant does not vomit, diarrhoea is caused, and undigested curd is present in large quantity in the evacuations. The obvious remedy is a prolongation of the intervals at which the child is suckled. During dentition in infants, from the large quantity of blood sent to the digestive organs, and the rapid evolution which they are undergoing, the bowels are irritable, and diarrhoea often supervenes; this is best guarded against by care in the diet and a proper observance of hygienic regulations. The severer forms of the complaint which occur in large cities, from the combined effect of an impure atmosphere and the excessive heat of our summers, are spoken of under the head of CHOLERA INFANTUM.

DIAS, A. GONÇALVEZ, a Brazilian poet, born in Caxias, Aug. 10, 1823. He was educated in Portugal, and returning to his native country, published at Rio de Janeiro in 1846 a volume of poems entitled Primeiros cantos, which was followed by his drama of Leonor de Mendonça (1847), Segundos cantos (1848), and Ultimos cantos (1850). In 1848 he was chosen professor of national history in the college of Don Pedro II.; in 1850 he was sent on a scientific mission to the provinces bordering on the Amazon; on his return he was employed in the office of the minister of foreign affairs, and in 1855 was charged with a scientific mission to Europe. His poetry is exceedingly popular in Brazil.

DIAS, BARTHOLOMEO, a Portuguese navigator, born in the latter part of the 15th century, lost in a storm at sea, May 29, 1500, while on his way from Brazil to India. In 1486 he sailed on an expedition to explore the W. coast of Africa, and without knowing it was carried around the southern point of the continent and landed at the mouth of Great Fish river, where he discovered that he was on the E. coast. The stormy cape he called Cabo Tormentoso, a name which the king of Portugal changed into Cape of Good Hope. Dias subsequently sailed on another African expedition under Vasco da Gama, and he commanded one of the vessels in the fleet with which Cabral discovered Brazil. It was on this expedition that he perished.

DIAS, HENRIQUE, a Brazilian general, born at Pernambuco at the beginning, died in the latter part of the 17th century. He was a freed negro, who by his superior attainments rose in 1639 to

the supreme command of the colored soldiery of the Brazilian army. He took a conspicuous part in the protracted warfare which finally led to the overthrow of Dutch supremacy in Brazil. DIASTASE (Gr. diorηu, to separate). When the grain of wheat, oats, or barley begins to germinate, there is formed at the base of the sprout a peculiar nitrogenous compound, very soluble in water, called diastase, the exact composition of which has never been determined. It is also found in the germ of the potato. It seems to be gluten in an altered form. By the action of this substance and of acetic acid, which also now first appears in the seed, the mucilaginous substance called dextrine, formed from the starch of the grain, is converted into starch sugar. This by fermentation passes into alcohol. It is therefore an essential element for the process of brewing. It may be obtained by digesting bruised barley malt with a little cold water, then expressing it through cloth. The liquor is then treated with sufficient alcohol to destroy its viscidity and cause the albumen to separate. This is removed by filtration. An additional quantity of alcohol then throws down the diastase in an impure state. It is redissolved in water and again precipitated with alcohol. When separated and dried, it is a white, tasteless, solid substance, without action upon gum or sugar, but capable at a temperature of 160° of converting starch suspended in water into dextrine, and this into grape sugar. One part of dextrine, it is found, is sufficient to cause 2,000 parts of starch to undergo this change.

DIATHERMANCY AND ATHERMANCY. The various dispositions of light entering the substance of different bodies are familiar. Some bodies, extinguishing the light, are termed opaque; others, through which it passes without sensible diminution, transparent, or diaphanous; but in most media both diaphaneity and extinction occur, in degree. Results entirely similar are now found to hold in the case of heat. All may observe that the sunbeams after passing through the air or through window glass are still very sensibly warm, while the glass and the air may remain at the same time in a great degree unwarmed. By a double convex lens of ice, the heat of the solar beam has been brought to a focus, and gunpowder and other combustibles fired, while the ice itself remained quite unaffected by the heat passing through it. A pane of glass held before a fire, however, stops the transmission of the heat striking it, and becomes warmed. From these facts, we conclude that from sources of heat there proceed outward on all sides rays of heat, just as from luminous bodies we have light rays; moreover, that there are media, as the air, which transmit heat rays freely, while others arrest (or, as it is often with doubtful propriety phrased, absorb) these rays; still a third class of bodies both transmitting and arresting portions of them. Bodies of the first of these classes are termed diathermanous; those of the second, athermanous; those of the VOL. VI.-29

third are imperfectly diathermanous. These subjects were first investigated in 1811-'12, by M. Prevost of Geneva, and M. de la Roche in France, but our knowledge of them is mainly due to M. Melloni, who began in 1832 a series of remarkable investigations, which won for him from M. de la Rive the title of "the Newton of heat." These researches, determining as they did the transmission of an invisible agent, heat, and often in degrees far too feeble to be detected by the nicest sensibility of the hand or by the ordinary means, would have been impossible but for the invention, by Nobili and Melloni, of a new thermoscopic apparatus, consisting of a thermo-electric pile connected with a highly sensitive galvanometer; the delicacy of the arrangement being such that if, in a room at ordinary temperatures, the human hand were presented in a line with the apparatus and at the distance of several feet, the heat radiating from the hand would cause the needle to be sensibly deflected. Some of the results discovered with the aid of this apparatus will be briefly stated. A plate or crystal of rock salt, even if an inch in thickness, was found, after diminishing the incident heat 7.7 per cent. by reflection, to transmit the entire remainder; this body, only, arrested within its substance no sensible portion of the heat rays. Hence, rock salt has been styled the true glass for heat; and its permeability by heat exceeds even that of glass by light. Smoked, or coated with soot, so as to be quite opaque, this body still allowed many of the heat rays to pass through it; and the same was true of smoked quartz and black glass. But citric acid, alum water, and limpid candy, although quite transparent, almost totally arrested the heat of the sun, of a flame or other source of intense heat, while they cut off entirely the rays from bodies raised to about red heat, and of all temperatures below. Bodies are not, therefore, diathermanous in proportion as they are transparent. But the amount of transmission of heat rays is found to depend on at least 4 particulars: 1, the nature of the source of heat; 2, the intensity of heat of the source; 3, the nature of the medium; and 4, its thickness. Solar heat has the greatest penetrating power; that of bodies in an incandescent state passes through the same medium in greater quantity than that of bodies at a dark heat; while of the heat of naked flame rock salt transmits 92.3 per cent., Iceland spar passes 39, white topaz 33, and alum 9 per cent.; and up to a certain thickness in every case, the amount transmitted diminishes with increase of thickness of the medium. Beyond a certain increase of the number or thickness of the plates, however, the diminution of heat ceases. The heat rays that can get through the first half inch or inch of glass, for example, will then go on undiminished through a much greater distance; so that it seems that certain heat rays are sifted out by each medium, as being incapable of moving through it with freedom; the others