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Hypennolic line, is used, by some authors, for what we call the hyperbola itself. In this sense, the plane surface, terminated by the curve line, is called the hyperbola, or hyperbolic space; and the curve line that terminates it the hyperbolic line. HYPERICUM, in botany, St. John's wort, a genus of the Polydelphia Polyandria class and order. Natural order of Rotaceae. Hyperica, Jussieu. Essential character: calyx five-parted; petals five ; filaments many, connected at the base in five bundles. There are fifty-seven species. These are principally shrubs or under shrubs, with cylindrical, ancipital, or quadrangular stems; leaves frequently with pellucid dots; flowers, sometimes in cymes, frequently in corymbs, with the peduncles often trichotomous and three flowered. HYPHYDRA, in botany, a genus of the Monoecia Gynandria class and order. Essential character: male, calyx one-leafed, three parted; corolla none; stamens six, inserted above the germ; female, calyx and corolla none; style triangular, with three stigmas; capsule one-celled, threevalved ; seed single. There is but one species, viz. H. fluviatilis, a little plant which grows three or four feet under water; it is a native of Guiana. HYPNUM, in botany, a genus of the Cryptogamia Musci class and order. Natural order of Musci or Mosses. Generic character: capsule oblong ; peristoneum double, outer with sixteen broadish teeth, inner membranaceous,equally lanciniated; segments broadish, with capillary ones interposed. Males germaceous, on different plants. Botanists differ greatly as to the number of species; some reckon forty, others fifty, and Dr. Withering enumerates seventy, and to facilitate the investigation of the species, he has thrown them into seven divisions. HYPOCHOERIS, in botany, a genus of the Syngenesia Polygamia Equalis class and order. Natural order of Compositae Semiflosculosae. Cichoraceae, Jussieu. Essential character: calyx subimbricate; down feathered ; receptacle chaffy. There are five species. HYPOTHECATE, in law, to hypothecate a ship, is to pawn the same for necessaries; and a master may hypothecate either ship or goods for relief, when in distress at sea; for he represents the traders as well as owners; and in whose hands soever a ship or goods hypothecated come, they are liable. But it has been recently held in the court of King's

Bench, that if the master pay for the re. pairs himself, and do not hypothecate the ship, he has no lien upon the ship for his debt. HYPOTHENUSE, in geometry, the longest side of a right angled triangle; or it is that side which subtends the right angle. Euclid, lib. i. proposition 47, de. monstrates, that in every rectilinear right angled triangle, the square of the hypothenuse is equal to the squares of both the other sides. This celebrated problem was discovered by Pythagoras, who is said to have sacrificed a heca. tomb to the Muses, in gratitude for the discovery. HYPOTHESIS, in general, denotes something supposed to be true, or faken for granted, in order to prove or illus. trate a point in question. An hypothesis is either probable or improbable, according as it accounts rationally or not for any phenomenon; of the former kind we may reckon the Copernican system and Huygens's hypothesis concerning the ring of Saturn ; and the Ptolemaic system may be esteemed an instance of the latter. HYPOXIS, in botany, a genus of the Hexandria Monogynia class and order. Natural order of Coronariae. Narcissi, Jussieu. Essential character: calyx a two valved glume ; corolla, six-parted, permanent, superior ; capsule narrower at the base. There are fourteen species. HYRAX, in natural history, a genus of Mammalia, of the order Glires. Generic character: front teeth in the upper jaw two, broad and somewhat distant; in the lower jaw four, broad, flat, contiguous, and notched; grinders large, four on each side in both jaws; fore-feet fourtoed, hind feet three-toed ; no tail; no clavicles. What distinguishes this genus from the whole class of Glires, besides, is the circumstance of having four teeth instead of two in the lower jaw, and indeed the teeth in general are differently formed. There are two species. H. capensis, or the Cape hyrax, is about as large as a rabbit, and abounds in the mountainous districts near the Cape of Good Hope, leaping from rock to rock with extreme agility, feeding by day, and retreating at night to the clefts and holes of the mountains. It has no power of burrowing any recess for itself. Its sound is a reiterated squeak. It subsists entirely on vegetable food, and repares a bed for its repose and comfort in its favourite recess. It ruay be easily familiarized, and in a state of domestication is extremely cleanly and alert. H. syriacus, or the bristly hyrax, is to be met with particularly in Ethiopia and Abyssinia, and particularly under the rocks of the Mountains of the Sun. Its full length is about seventeen inches. These animals are called by the natives of these countries Ashkokos. They are gregarious, and, occasionally, seen in companies of several scores, basking before the clefts of the rocks in the open sunshine. They are gentle, weak and fearful, but if handled with roughness will bite with great severity. They are supposed to live on grain, fruits, and roots, and when kept in confinement, they will live upon bread and milk. They feed without any voracity, and even the pangs of hunger could not impel them to attack chickens or smaller birds, which have been thrown to them in that state, in the way of experiment. Their motion is not firm upon their legs, but rather by stealing along, by a few paces at a time, upon their bellies, in the manner of the bat in approaching its prey. For the Hyrax, see Mammalia, Plate XII. fig. 5. HYPTIS, in botany, a genus of the Didynamia Gymnospermia class and order. Natural order of Verticillatae. Labiatae, Jussieu. Essential character : calyx turbinate ; corolla with a very spreading border; lower lip semibifid ; anthers hanging down. There are two species. HYSSOPUS, in botany, hyssop, a genus of the Didynamia Gymnospermia class and order. Natural order of Verticillatae, Jussieu. Essential character: corolla, lower lip with a small middle crenate segment; stamens straight, distant. There are three species. HYSTERICS. See MEDICINE. HYSTRIX, porcupine, in natural history, a genus of quadrupeds of the order Glires. Generic character: two foreteeth in the upper and the under jaw, cut obliquely; eight grinders: body with spines and hair; toes four or five on the

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fore feet. There are five species. H. cristata, or the common porcupine, is about two feet in length, exclusively of the tail. It is found in Africa and India, and is seen not unfrequently in the warmer climates of Europe, particularly in Italy and Sicily. It is covered on the upper part of its body with variegated spines, or quills, which are long and sharp, and which, when irritated, it erects with particular intenseness, and a rustling and alarming noise, giving the idea of formidable hostility. It was supposed by the ancients to possess the power of darting these with unerring, and sometimes fatal, aim against its $o: but it is ascertained to employ them merely to repel an assailant. Its principal food consists of the bark of trees, roots, and fruit, and is almost universally collected by it in the night. In the day it lies retired, and sleeping in a subterraneous habitation, which it is said to construct with particular ingenuity, dividing it into several apartments. It produces two at a birth, and if taken young is tamed with considerable facility. Its flesh is eaten, not only in Africa but in Italy, and is thought extremely luscious, on which account it can be taken by few in any large joy. See Mammalia, Plate XII.

H. prehensilis, or the Brazilian porcupine. This is about a foot long, and its tail about a foot and a half, by which it clings to the branches of trees, and facilitates its object of attack or escape. It is covered with strong, short, and extremely sharp spines, on most of those parts of its body particularly exposed to assault. It is found in the warm climates of America, and particularly in Brazil, where it inhabits the woods, and subsists not only upon fruits and vegetables, like the former species, but also on small birds. Its sounds resemble the grunting of a pig. It secludes itself during the day in the hollows of trees, or under their roots, and by night engages in its excursions *. repasts. See Mammalia, Plate XII.

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or i, the ninth letter, and third vowel 3 of the alphabet, is pronounced by throwing the breath suddently against the palate, as it comes out of the larynx, with a small hollowing of the tongue, and nearly the same opening of the lips as in pronouncing a or e. Its sound varies; in some words it is long, as high, mind, &c.: in others short, as bid, hid, sin, &c.; in others again it is pronounced like y, as in collier, onion, &c.; and in a few it sounds like ee, as in machine, magazine, &c. No English word ends in i, e being either added to it, or else the i turned into v. But besides the vowel, there is the jod consonant; which, because of its different ronunciation, has likewise a different orm, thus, J j. In English it has the soft sound of g, nor is it used but when go soft is required before vowels where g is usually hard : thus we say, jack, jet join, &c. instead of gack, get, goin, &c. which would be contrary to the genius of the English language. * I, used as a numeral, signifies no more than one, and stands for so many units as it is repeated times: thus I, one ; II, two ; III, three, &c. and when put before a higher numeral it subtracts itself, as IV, four; IX, nine. &c.; but when set after it, so many are added to the higher numeral as there are I's added : thus VI, is 5-H 1, or six; VII, 5+2, or seven ; VIII, 5-H3, or eight. The ancient Romans likewise used IO for 500, CIO for 1,000, IOO for 5,000, CCIOO for 10,000, IOOO for 50,000, and CCCI000 for 100,000. Farther than this, as Pliny observes, they did not go in their notation ; but, when necessary, repeated the last number, as CCCI000, CCCIOOO for 200,000; CCC1000,CCCIOOO,OCCI000 for 300,000; and so on. JACK, in mechanics, an instrument of common use for raising heavy timber, or very great weights of any kind. The common kitchen jack is a compound engine, where the weight is the power applied to overcome the friction of the parts, and the weight with which the spit is charged ; and a steady and uniform motion is obtained by means of the fly. Jack, in naval affairs, a sort of flag, or colour, displayed from a staff erected on the outer end of a ship's bowsprit. In

the British navy, the jack is a small union flag; but in merchant ships the union is bordered with red. JAck smoke. See SMoke jack. Jack in the boar, a large wooden male screw, turning in a female one, which forms the upper part of a strong wooden box, shaped like a frustum of a pyramid. It is used by means of levers passing through holes in it, as a press in packing, and for other purposes. Jack block, a block occasionally attached to the top-gallant tie, and through which the top-gallant top-rope is reeved, to sway up or to strike the yard. JACKALL, in zoology, an animal of the dog kind, with a slender snout. See CAN is. JACKET cork. See Conkjacket. JACOB's staff;sometimes called a crossstaff, a mathematical instrument to take altitudes at sea, consisting of a brass cir. cle divided into four equal parts by two lines cutting each other in the centre; at each extremity of either line is fixed a sight perpendicularly over the lines, with holes below each slit for the better discovery of distant objects. The cross is of course mounted on a stand for use. JACOBUS, an ancient gold coin, worth 25s. See Col N. JACQUINIA, in botany, so named in honour of Nic. Jos. de Jacquin, professor of botany at Vienna, a genus of the Pentandria Monogynia class and order. -Na. tural order of Dumosae. Sapotae, Jussieu. Essential character: corolla ten-cleft; sta. mens inserted into the receptacle; berry one-seeded. There are four species, natives of the West Indies and South America. JACTITATION of marriage, in law, is when one of the party boasts, or gives out, that he or she is married to the other, whereby a common reputation of their matrimony may ensue. On this ground the party injured may, libel the other in the spiritual court; and unless the defendant undertake, and make out a proof of the actual marriage, he or she is enjoined perpetual silence on that head. JADE. See NEPHRIt E. JALAP is the root of the convolvolus jalappa. It derives its name from Xalapa, a town of Mexico, in the environs of which it grows plentifully. It is also found among the sands of Vera Cruz. This plant resembles in appearance the convolvolus of our hedges. Its stem is climbing, angular, and covered with a slight down. Its leaves alternately disposed are rather large, sometimes entire and cordiform, sometimes divided into several lobes, more or less distinct. The flower is campaniform, whithish on the outside, and of a dark purple within. Its root, which is the only part in use, is tuberose, large, lengthened out into the form of a French turnip, white on the inside, and full of a milky juice. The weight of the roots is from twelve to twenty pounds. They are cut into slices, in order to dry them. They then acquire a brown colour, and a resinous appearance. Their taste is rather acrid, and excites a nausea. Jalap to the amount of 50,000l. sterling is consumed in Europe annually. IAMBICS, certain songs, or satires, which are supposed to have given birth to the ancient comedy. The word is applied also to a particular kind of Latin verse, of which the simple foot consists of a short and long syllable. Ruddiman makes two kinds of iambic, viz. dimeter and trimeter; the former containing four feet, and the latter six. JANSENISTS, in church history, a sect of the Roman Catholics in France, who follow the opinions of Jansenius, bishop of Ypres, and docter of divinity of the Universities of Louvain and Douay, in relation to grace and predestination. In the year 1640, the two universities just mentioned, and particularly Father Molina and Father Leonard Celsus, thought fit to condemn the opinions of the Jesuits on grace and free-will. This having set the controversy on foot, Jansenius opposed to the doctrine of the Jesuits the sentiments of St. Augustine, and wrote a treatise on grace, which he entitled Augustinus. This treatise was attacked by the Jesuits, who accused Jansenius of maintaining dangerous and heretical opinions; and afterwards, in 1642, obtained of Pope Urban VIII. a formal condemnation of the treatise wrote by Jansenius : when the partisans of Jansenius gave out that this bull was spurious, and composed by a person entirely devoted to the Jesuits. After the death of Urban VIII. the affair of Jansenism began to be more warmly controverted, and gave birth to an infinite number of polemical writings concerning grace; an what occasioned some mirth, was the titles which each party gave to their writings: one writer published “The Torch of St. Augustin,” another found

“Snuffers for St. Augustin's Torch,” and Father Vernon formed “A Gag for the Jansenists,” &c. In the year 1650, sixtyeight bishops of France subscribed a letter to pope Innocent X, to obtain an inquiry into, and condemnation of, the five following propositions, extracted from Jansenius's Augustinus: 1. Some of God's commandments are impossible to be observed by the righteous, even though they endeavour with all their power to accomplish them. 2. In the state of corrupted nature, we are incapable of resisting inward grace. 3. Merit and demerit, in a state of corrupted nature, does not depend on a liberty which excludes necessity, but on a liberty which excludes constraint. 4. The semipelagians admitted the necessity of an inward preventing grace for the performance of each particular act, even for the beginning of faith, but they were heretics in maintaining that this grace was of such a nature that the will of man was able either to resist or obey it. 5. It is semipelagianism to say, that Jesus Christ died, or shed his blood, for all mankind, in general. JARGON. See ZIncox. JASIONE, in botany, a genus of the Syngenesia Monogynia class and order. Natural order of Campanaceae. Essential character: calyx, common, ten-leaved ; corolla five-petalled, regular; capsule inferior, two-celled. There are four species, natives of the West Indies. JASMINUM, in botany, English jasmine-tree, a genus of the Diandria Monogynia class and order. Natural order of Sepiariae. Essential character: corolla salver-shaped ; berry dicoccous; seeds arillated; antherae within the tube. There are seventeen species. JASPER, in mineralogy, a species of the clay genus, divided by Werner into six sub-species, viz. the Egyptian, the striped, the porcelain, the common, the agate, and the opal jasper. The Egyptian jasper exhibits two or more colours in concentric zones or bands, more or less regular, with interspersed spots or dendritic figures. It is brittle, and the specific gravity is about 2.6. It occurs in rolled pieces, which are mostly spherical. Before the blow-pipe it is infusible without addition. It is found in Egypt and the adjoining desarts, and, on account of its beautiful colour and great hardness, it is used for similar ornamental and useful purposes as the agate The colours of the striped jasper are grey, green, yellow, and red ; these are often found together, and arranged in

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It occurs in beds in pseudo-volcanic hills, and it is supposed that it is slaty clay, converted into a kind of porcelain by the action of fire. It is found in great plenty in Bohemia. The common jasper is found generally in veins that occur in primitive rocks in many parts of Europe. It is susceptible of a high polish, and is in considerable request for ornamental purposes. Opal jasper is found in nests, in porphyry, near Tokay, in Hungary, in the neighbourhood of Constantinople, and in some Siberian mountains. It is supposed to be the connecting link between jasper and opal, and is distinguishable by the liveliness of its colours, its superior lustre, and constant conchoidal fracture. JATROPHA, in botany, a genus of the Monoecia Monadelphia class and order. Natural order of Tricocco. Euphorbia, Jussieu. Essential character: male, calyx none ; corolla one-petalled, funnelorm ; stamina ten, alternately longer and shorter: female, calyx none, corolla fivepetalled, spreading ; styles three, bifid ; capsule three-celled ; seed one. There are fourteen species, of which we shall give a short account of the J. elastica, elastic gum-tree; it is a native of Guiana, of Quito, and Brazil, particularly in Para, where it is called masaradub. The Indians, by an incision in the bark, extract a viscid white substance, like that which issues from the fig-tree ; they receive it into earthen moulds, to makerings, brace. lets, girdles, syringes, hats, boots, flambeaux, figures of animals, &c. the abbe

Rouchon says that the inhabitants of Madagascar also made flambeaux of it, which burn without wicks, and afford them a . good light when they go out to fish in the night time; that surgery has derived some benefit from it, as it serves to make excellent bandages; and that in a state of solution it is very proper for coating over silk, to render it impervious to air or water. It has the extensibility of leather, with a very considerable elasticity. Spirit of wine makes no impression on this substance, but it dissolves in ether and linseed oil, or in nut oil digested gently in a sand bath : there are also other fat and oily substances which affect it very sensibly. The Chinese have been long acquainted with the art of dissolving it, and of giving it various colours. JAUN DICE. See MEDI cir. E. JAY, in ornithology, the variegated corvus, with the covering feathers of the wings blue, variegated with black and white. See Corvus. * IBERIS, in botany, candy-tuft, a genus of the Tetradynamia Siliculosa class and order. Natural order of Siliquosz, or Cruciformes. Cruciferae, Jussieu. Essential character: corolla irregular, with the outer petals larger : silicle emarginate, many-seeded. There are fourteen species. IBFX, in zoology, an animal of the goat kind, with extremely long nodose horns, which bend backwards, and are of a blackish colour, and annulated on the surface. The body is of a dark dusky colour, and is less in proportion to the height than that of the common goat: it has a great resemblance to the deer kind; the legs are also perfectly like those of the deer, straight, elegant, and slender. It is frequent in many parts of Europe, and, notwithstanding its vast horns, runs, and leaps with surprising force and agility. See CAPRA. ICE, water in the solid state. When water is exposed to a diminished temperature, it assumes the solid state, by shooting into crystals, which cross each other in angles of 60 degrees. During this process of solidification, the temperature remains constant, being 32 degrees of the scale of Fahrenheit. See CAlon1c ; also FREEz1|NG. During congelation most of the gasi. form fluids, which may have been contained in the waser, are separated in the elastic form, and exhibit bubbles in the ice, unless the congelation may have been gradually effected from the bottom, or one of the sides; in which case the bub

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