hanpore in the year 1748, aged 104 years. His eldest son, Ghazy ad Deen, was, at this period, one of the ministers at Delhi; and the second son, Nasir Jung, having obtained possession of the treasure and the army, was too powerful to be dispossessed: he was therefore confirmed by the emperor Ahmed as soubadar of the Deccan. Assassinated in 1750, this prince was succeeded by his nephew Muzuffer Jung, who was put to death the following year, and succeeded by his cousin Salabut Jung, who held the government for ten years. He was then confined by his brother Nizam Aly, who for nearly twenty years was engaged in wars with Hyder Aly, the British, and the Mahrattas; and had it not been for his alliance with the British, in 1800, his kingdom would have been annihilated. Nizam Aly transferred the seat of government from Aurungabad to Hyderabad, and died in 1803, being succeeded by his son Mirza Sekunder Jah; and the family is supported in its authority by a British force of 10,000 men, and by treaties of alliance offensive and defensive. There is also a British ambassador constantly residing at this court.

HYDERABAD, the capital of the above kingdom, is situated on the south bank of the Musa, about six miles from the fortress of Golconda. It is said to have been founded about the year 1586, by Mohammed Kootub Shah, who named it Hyderabad, in compliment to the caliph Aly, one of whose titles was Hyder Allah (the Lion of God). It continued to be the residence of the Kootub Shahy dynasty till 1687, when it was taken by Aurungzebe. The late Nizam Aly was the first of the nizams that made it his residence, and expended considerable sums of money in improving Hyderabad. It is now a fine and flourishing city, of about seven miles in circumference, surrounded by a stone wall, with towers at the angles and gates. It contains two palaces and some handsome mosques; and between it and Golconda are various splendid tombs.

HYDERABAD is also the name of a city, the capital of the province of Sinde, Hindostan. A fortress of this name stands on a rock the foot of which is washed by the Fulalee, a branch of the river Indus. Its shape is an irregular pentagon, defended at the angles by round towers. The fortifications are of such a nature as to be very formidable to the native troops. Inside the fort is a good bazaar and several handsome mosques. It is the residence of the princes, who form the aristocracy by which this province is governed, and contains about 15,000 inhabitants. A considerable trade is carried on, by means of the river, with Moultan Tattah, and other towns at the mouths of the Indus.

HYDNUM, in botany, a genus of the natural order of fungi, cryptogamia class of plants. The fungus is echinated or prickly on the under side. One of the species, viz.

H. imbricatum, is a native of Britain, and is found in woods. It has a convex hat, tiled, standing on a smooth pillar, of a pale flesh color, with white prickles. It is eaten in Italy, and is said to be of a very delicate taste.

HY'DRA, n. s. Lat. hydra. A monster with many heads slain by Hercules: whence any multiplicity of evils is termed a hydra.

Or like the hell-borne hydra, which they faine That great Alcides whilome overthrew, After that he had laboured long in vaine To crop his thousand heads, the which still new Forth budded, and in greater number grew. Spenser. Faerie Queeve.

New rebellions raise

Their hydra heads, and the false North displays Her broken league to imp her serpent wings.

Milton.

More formidable hydra stands within, Whose jaws with iron teeth severely grin. Dryden. Subdue

The hydra of the many-headed hissing crew. Id. HYDRA, in fabulous history, was a serpent in the marsh of Lerna, in Peloponnesus, with many heads, one of which being cut off, another, or two others, immediately succeeded in its place, unless the wound was instantly cauterised. Hercules attacked this monster; and, having caused Iolaus to hew down wood for flaming brands, as he cut off the heads he applied the brands to the wounds, by which means he destroyed the hydra. This bydra is supposed to have been a multitude of serpents which infested the marshes of Lerna, near Mycene, and seemed to multiply as they were destroyed. Hercules, with the assistance of his companions, cleared the country of them, by burning the reeds in which they lodged.

HYDRA, in astronomy, a southern constellation, consisting of a number of stars, imagined to represent a water serpent. See ASTRONOMY.

HYDRA, in zoology, a genus of the order of zoophyta, belonging to the class of vermes. There are several species, known by the general name of polypes. See ANIMALCULE, and Po

LYPUS.

HYDRA, an island between the Archipelago, and the eastern side of the peninsula of the Morea, south of the gulf of Athens and east of that of Napoli, long. 20° 50′ E. lat. 37° 20′ N. It is about twenty-four miles long from north-east to south-west, and ten miles in breadth across the middle, where it is broadest, the extremities tapering almost to a point. If in other parts of Greece, as M. Castellan remarks, we see a people either miserable or diseased. in a rich country and under a balsamic climate, the rocks of Hydra present us with the agreeable spectacle of a vigorous population, which has found the means of creating for itself riches out of a territory naturally confined and barren, and has displayed a spirit of enterprise and speculation almost unique even in Greece. The Schypetars of Albania are found in Hydra as in some other districts of Greece; these colonists, to whom, after the expedition of the Russians into Greece, many refugees from the Peloponnesus united themselves, have improved the ancient race of inhabitants. This appears in the activity which they now discover, and sometimes also by the examples of harshness and cruelty which they afford, and the piracies which they commit.

Happily the greater part of the population of the island prefer enriching themselves by peaceable and honest means, and owe their prosperity solely to their industry. According to M. Pouqueville they have 120 vessels, forty of which are from 400 to 600 tons burden, which used to visit all the ports of the Mediterranean and of the

HYDRASTIS, in botany, a genus of the polygamia order, and polyandria class of plants. There is neither calyx nor nectarium; there are three petals; and the berry is composed of a monospermous acini. HYDRAULICS, n. s. HYDRAULICAL, adj. HYDRAULIC, adj.

Gr. dwp, water, ávλog, a pipe. The science of conveying water through pipes or conduits: hydraulical, hydraulic, from the substantive, relating to the conveyance of water through pipes.

Among the engines in which the air is useful, pumps may be accounted, and other hydraulical engines. Derham.

We have employed a virtuoso to make an hydraulick engine, in which a chymical liquor, resembling blood, is driven through elastick channels. Arbuthnot and Pope.

HYDRAULICS Comprehend the science of the motion of fluids and the construction of all kinds of instruments and machines relating thereto. See HYDROSTATICS.

HYDRIODIC ACID, in chemistry, is, like the muriatic acid, a gaseous substance when in an insulated state. If four parts of iodine be mixed with one of phosphorus, in a small glass retort, applying a gentle heat, and adding a few drops of water from time to time, a gas comes over, which must be received in the mercurial bath. Its specific gravity is 44. It is elastic and invisible, but has a smell somewhat similar to that of muriatic acid. Mercury after some time decomposes it, seizing its iodine, and leaving its hydrogen, equal to one-half the original bulk, at liberty. Chlorine, on the other hand, unites to its hydrogen, and precipitates the iodine. From these experiments, it evidently consists of vapor of iodine and hydrogen, which combine in equal volumes, without change of their primitive bulk. Hydriodic acid is partly decomposed at a red heat, and the decomposition is complete if it be mixed with oxygen. Water is then formed and iodine separated.

We can easily obtain an aqueous hydriodic acid very economically, by passing sulphureted hydrogen gas through a mixture of water and iodine in a Woolfe's bottle. On heating the liquid obtained, the excess of sulphur flies off, and leaves watery hydriodic acid. When exposed to the air, it is speedily decomposed, and iodine is evolved. Concentrated sulphuric and nitric acids also decompose it. When poured into a saline solution of lead, it throws down a fine orange precipitate. With solution of peroxide of mercury, it gives a red precipitate; and, with that of silver, a white precipitate insoluble in ammonia.

The compounds of hydriodic acid with the salifiable bases may be easily formed, either by direct combination, or by acting on the basis in water with iodine. Upon a determinate quantity of iodine, pour solution of potassa or soda, till the liquid ceases to be colored. Evaporate to dryness, and digest the dry salt in alcohol, which will retain the hydriodate. Then distil off the alcohol, and complete the neutralisation of the potassa, by means of a little hydriodic acid separately obtained. Sulphurous and muriatic acids, as well as sulphureted hydrogen, produce

no change on the hydriodates, at the usual temperarute of the air. Chlorine, nitric acid, and concentrated sulphuric, instantly decompose them, and separate the iodine. With solution of silver, they give a white precipitate insoluble in ammonia; with the pernitrate of mercury, a greenish-yellow precipitate; with corrosive sublimate, a precipitate of a fine orange-red, very soluble in an excess of hydriodate; and, with nitrate of lead, a precipitate of an orange-yellow color. They dissolve iodine, and acquire a deep reddish-brown color.

Hydriodate of ammonia results from the combination of equal volumes of ammoniacal and hydriodic gases; though it is usually prepared by saturating the liquid acid with ammonia. It is nearly as volatile as sal ammoniac; but it is more soluble and more deliquescent. It crystallises in cubes.

Hydriodate of zinc is easily obtained, by putting iodine into water with an excess of zinc, and favoring their action by heat. When dried it becomes an iodide.

HYDROCELE, in medicine, from vdwp, water, and anλŋ, a tumor, would literally signify any swelling or tumor produced by water; bu it is confined by surgeons of the present time to those which possess either the membranes of the scrotum, or the coats of the testicle and its vessels. Of this disease there are only three different kinds, one the anasarcous hydrocele, in which the fluid is lodged in the cellular texture of the scrotum; a second in which it is contained in the tunica vaginalis; and a third in which it it is collected in the spermatic cord.

The anasarcous hydrocele is generally a symptom of dropsy throughout the whole body; but some instances have occurred of a local cause producing a mere local dropsy of the scrotum. Thus, it has been known to happen from swellings in the groin and in the abdomen obstructing the passage of the lymphatics. When this is the case, if tumors producing such obstructions can be extirpated, no other means will afford such effectual relief: but, when they are so deeply seated as to render any attempt for removing them improper, the practice of making punctures in the most depending part of the tumor to drain off the fluid must be employed, with a view to palliate such symptoms as occur.

The hydrocele of the tunica vaginalis, is a preternatural collection of the aqueous fluid, employed by nature for lubricating the surface of the testicle. The symptoms are, a fulness at first observed about the inferior parts of the testicle, and most remarkable when the patient is erect, becoming gradually more tense as the disease advances; the tumor by degrees changing from the globular to the pyramidical form; no degree of pressure making the swelling disappear at any period of the disease. In the early part of the disease, therefore, if it be not combined with hernia, or with a hydrocele of the cord, the spermatic process may be distinctly felt, because the swelling does not extend beyond the scrotum. In its more advanced state, it cannot be distinguished; the weight of the tumor now drags the skin of the neighbouring parts so much as to cause the penis almost to disappear ;

and in this state of the disease the testicle cannot be felt without much difficulty. On a minute examination, a hardness is always to be felt along that part of the scrotum where the testicle is situated; and at this point pressure excites some uneasiness. Fluctuation of fluid may in general be distinguished through the whole course of the disease. In late stages, however, the appearance of a fluid is not very evident.

The transparency of the tumor has been generally supposed to be the principal criterion of this species of the disorder: but this must depend upon the nature of the contents, or thickness of the sac; so that, though the transparency of the tumor is a certain sign of the existence of water, its opacity cannot upon any account be considered as an indication of its absence. Through the whole course of the disease, the tumor is not attended with pain, but some uneasiness is commonly felt in the back by the weight of the swelling of the spermatic cord. This is more particularly the case when a suspensory bandage is not used. In the radical cure of hydrocele, in whatever way it is attempted, some degree of inflammation will take place. The cure of the hydrocele of the tunica was formerly effected by one of three methods; either by caustic, by the seton, or by, incision. Although in most cases any one of these methods will induce a cure, yet that of simple incision is less liable to produce violent inflammation, the danger of which from the proximity of the intestines is too evident to require discussion.

But the surgeons of the present day do not generally make use of any of these systems. The cure is now generally attempted by the injection of some irritating fluid which will cause infiammation throughout the whole extent of the tunica. The preference is usually given to wine, and commonly that is somewhat diluted; but, where no pain is excited by the injection, the liquor should be discharged, and a stronger one used. For where no pain takes place a cure is not to be expected.

The hydrocele of the spermatic cord is either anasarcous or encysted. The anasarcous kind is attended with a colorless tumor in the course of the spermatic cord, soft and inelastic to the touch, and unaccompanied with fluctuation. In an erect position of the body it is of an oblong figure; but, when the body is recumbent, it is flatter. Generally it is no longer than that part of the cord which lies in the groin, though it sometimes extends as far as the testicle, and even stretches the scrotum to an uncommon size; an instance of which is related by Mr. Pott, who from a swelling of this kind discharged eleven pints at once. By pressure a great part of the swelling can always be made to recede into the abdomen; but it instantly returns to its former situation on the pressure being withdrawn.

When the tumor is connected with general anasarca of the system, it can only be cured with the rest of the disease; but, when the swelling is local, the remedy is also to be locally applied. An incision is to be made of such a size as may be sufficient for discharging the whole of the water; in the performance of which, attention is necessary to guard against hurting the sper

matic vessels. The contents of the tumor being discharged, the sore is to be treated like any other simple wound.

Encysted hydrocele of the spermatic cori sometimes begins in the upper, but generally i the lower part of the spermatic cord. On its first appearance it is so small as to give little or no trouble; hence it is seldom particularly attended to till it has acquired a considerable size. By degrees it extends as far as the abdominal muscles, and sometimes reaches to the bottom of the scrotum; and, to a person unacquainted with the appearance of the disorder, may be mistaken for a hydrocele of the tunica vaginalis. But here the tumor is always above the testicle, which is distinctly felt below; whereas, in the advanced stages of hydrocele in the vaginal coat the testicle cannot be distinctly felt. In the encysted hydrocele of the cord, the figure and size of the penis is little altered; whereas, in cases of common hydrocele, the penis frequently disappears almost entirely. In adults, the cyst, in every variety of incysted hydrocele, becomes so firm as not to be affected by external applications; so that, when the tumor becomes large, it is necessary to use means for producing either a palliative or radical cnre, in the same manner as is done for a hydrocele in the tunica vaginalis. See SURGERY and MEDICINE.

HYDROCEPHALUS, in medicine, (from vowp water, and kepaλn the head), is as the name imports a dropsy of the head, and is commonly called water on the brain. It is a disease almost peculiar to children, being seldom observed in persons above the age of twelve or fourteen, and it seems to be most prevalent in scrofulous families. With respect to the proximate cause of hydrocephalus very opposite opinions are entertained by different medical writers. It appears generally to begin with slight inflammation, but whether as a cause or only as a symptom is a matter of dispute. The disease appears to be constitutional. Patients usually complain first of a pain in some part below the head, commonly about the nape of the neck and shoulders; often in the legs; and sometimes, but rarely, in the arms. The pain is not uniformly acute, nor always fixed to one place; and sometimes does not affect the limbs. Some have violent sickness and head-aches alternately. From being perfectly well and sportive, some are in a few hours seized with those pains in the limbs, or with sickness, or head-ach, in a slight degree; whilst others are observed to droop a few days before they complain of any local indisposition. In this manner they continue three, four, or five days. They then complain of an acute deepseated pain in the head, extending across the forehead from temple to temple; of which, and a sickness, they alternately complain in short and affecting exclamations; dosing a little in the intervals, breathing irregularly, and sighing much while awake. Sometimes their sighs, for a few minutes, are incessant. As the disease advances, the pulse becomes slower and irregular, till within a day or two of the fatal termination, when it becomes exceedingly quick; the breath ing being deep, irregular, and laborious. After the first access, which is often attended with

feverish heats, the heat of the body is for the most part temperate, till at last it keeps pace with the increasing quickness of the pulse. The head and præcordia are always hot from the first attack. The sleeps are short and disturbed, sometimes interrupted by watchfulness and startings. In the first stage there is a peculiar sensibility of the eyes, and intolerance of light. But in the progress of the disease a very opposite state occurs. The pupil is remarkably dilated, and cannot be made to contract by the action even of strong light. Various methods of cure have been attempted, but the disease almost always terminates fatally. See MEDICINE.

HYDROCYANIC ACID. See PRUSSIC

ACID.

HYDROCHARIS, the little water lily, a genus of the enneandria order, and diœcia class of plants: natural order first, palmæ. Male spatha diphyllous: CAL. trifid: COR. tripetalous; the three inferior filaments styliferous. Female CAL. trifid: COR. tripetalous; the styles six: CAPS. Six celled and polyspermous inferior. There is only one species, a native of Britain, growing in slow streams and wet ditches. It has kidney-shaped leaves, thick, smooth, and of a brownish-green color, with white blossoms. There is a variety with double flowers of a very

sweet smell.

HYDROCOTYLE, water navelwort, a genus of the digynia order, and pentandria class of plants; natural order forty-fifth, umbellata. The umbel is simple; the involucrum tetraphyllous; the petals entire; the seeds are half round and compressed. There are several species, none of which are ever cultivated in gardens. One of them, a native of Britain, growing in marshy grounds, is supposed by some farmers to occasion the rot in sheep. The leaves have central leaf-stalks, with about five flowers in a rundle; the petals are of a reddish white.

HYDROGEN GAS, in chemistry (from vdwp, water and yɛvvaw to produce), is the lightest species of ponderable matter hitherto discovered. The following is the best method of obtaining it :-Into a phial furnished with a bent tube fitted to its cork, or into a retort, put some pieces of pure redistilled zinc, or harpsichord iron wire, and pour on them sulphuric acid diluted with five times its bulk of water. An effervescence will ensue, occasioned by the decomposition of the water, and disengagement of hydrogen, which may be collected in the pneumatic apparatus. For very accurate researches, it must be received in jars over mercury, and exposed to the joint action of dry muriate of lime, and a low temperature. It derived its name from the property it possseses of forming water when mixed with oxygen, and exposed to the electric shock. If a bottle, containing the effervescing mixture of iron and dilute sulphuric acid, be shut with a cork, having a straight tube of narrow bore fixed upright in it, then the hydrogen will issue in a jet, which, being kindled, forms the philosophical candle of Dr. Priestley. If a long glass tube be held over the flame, moisture will speedily bedew its sides, and harmonic tones will soon begin to sound. Mr. Faraday, in an ingenious paper inserted in the tenth number of

the Journal of Science, states, that carbonic oxide produces, by the action of its flame, similar sounds, and that therefore the effect is not due to the affections of aqueous vapor, as had formerly been supposed. He shows, that the sound is nothing more than the report of a continued explosion, agreeably to Sir H. Davy's theory of the constitution of flame. Vapor of ether, made to burn from a small aperture, produces the same sonorous effect as the jet of hydrogen, of coal gas, or olefiant gas, on glass and other tubes. Globes from seven to two inches in diameter, with short necks, give very low tones; bottles, Florence flasks, and phials, always succeeded; air jars, from four inches diameter to a very small size, may be used. Some angular tubes were constructed of long narrow slips of glass and wood, placing three or four together, so as to form a triangular or square tube, tying them round with pack-thread. These, held over the hydrogen jet, gave distinct tones.

Professor Dobereiner has discovered that, by throwing a jet of hydrogen gas on a small pellet of spongy platinum, the platinum instantly be comes red hot and the jet of hydrogen inflamed. Mr. Gordon of Oxford Street has formed a lamp on this principle, which is actually a new apparatus for procuring instantaneous fire. See our articles CHEMISTRY in which the nature properties and combination of hydrogen are fully treated of, and Gas in which its application to lighting of roads, shops, &c., is detailed. One of the principal objections to its use as a light is the strong disagreeable smell. But if hydrogen gas, obtained by the solution of iron in sulphuric acid, be made to pass into pure alcohol, it almost entirely loses its smell. Water added to the alcohol renders it milky; and, on resting some hours, a volatile oil separates, which is the cause of the well-known smell of hydrogen gas. This gas is obtained perfectly free of smell, by putting into pure water an amalgam of potassium; but, if there be added to the water an acid or sal-ammoniac to accelerate the development of the gas, the latter will have the smell, which is observed during the solution of zinc in weak sulphuric acid. Ann. de Chim. et de Phys., October 1824.

HYDROGRAPHER, n. s. 7
HYDROGRAPHY, N. S.

Fr. hydroSgraphe; Greek, υδωρ and γραφω. One who draws maps of the sea. Description of the watery parts of the globe.

It may be drawn from the writings of our hydrographers. Boyle. HYDROGRAPHY is the art of measuring and describing the sea, rivers, canals, lakes, &c. With regard to the sea, it gives an account of its tides, counter-tides, soundings, bays, gulfs, creeks, &c.; also the rocks, shelves, sands, shalows, promontories, harbours; the distance and bearing of one port from another; with every thing that is remarkable, whether out at sea or on the coast.

HYDROLEA, in botany, a genus of the digynia order, pentandria class of plants: CAL. pentaphyllous: COR. rotaceous; the filaments at the base cordate: CAPS. bilocular and bivalved.