or St. John's Wort, is the genus and type.

Hypermyriora'ma (Gr.), an exhibition consisting of innumerable views. Hyperox'ygenized, supersaturated with

oxygen.

Hypersarco'sis (Gr.), proud flesh. Hypersthene (Gr. hyper, and sthenos strength), Labrador hornblende, a mineral of a greenish-black colour, whose constituents are silica, magnesia, protoxide of iron, lime, and water: sp. gr. 3'3; H=475.

Hypersthe'nia (Gr.), in physiology, excess of vital power. Hypertrophy (Gr.), a morbid enlargement of any part of the body. Hyperzoodyna'mia (Gr. hyper, zoos living, and dynamis power), excessive augmentation of force in the animal

economy.

Hyphomycetes (Gr.) hyphos a crown, and mykos a mushroom), an order of Fungi, in which the spores generally quaternate on distinct sporophores. Hypnotics (Gr.), in the materia medica, a medicine tending to produce sleep. Hypo, a Greek prepositive, frequently used to denote excess.

Hyp'ocaust (Gr. hypo, and kaio to burn), in architecture, a vaulted apartment from which heat is distributed to other rooms by means of earthen tubes. Hypochondria (Gr.), in anatomy, the part of the abdomen, on both sides, that lies under the spurious ribs. Hypochondriac (Gr.), one who is morbidly melancholy.

Hypochondri'asis (Gr.), the hypochondriac affection; melancholy; dis ordered imagination. Hypochondrium (Gr. hypochondrion), the hypochondriac region. Hypodermic (Gr.), introducing medicines under the skin. Hypogastric (Gr.), seated in the lower part of the belly.

Hypogas'trocele (Gr.), a rupture of the lower belly.

Hyp'ogeal, Hypoge'ous (Gr.), in botany, epithets denoting all parts in plants growing under ground.

Hyp'ogene (Gr.), in mineralogy, relating to a class of rocks commonly called primary rocks.

Hypoglottis (Gr. the tongue), in anatomy, a name given to two glands of the tongue. In pathology, an inflammation or ulceration under the tongue, called also Ranula.

Hyponi'trites, in chemistry, a genus of salts, resulting from the combination of hyponitrous acid with salifiable bases; formula N + 3 O, or NO3.

Hyponi'trous Acid, an acid composed of nitrogen and oxygen. Hypophos phite, a compound of hypophosphorous acid and a salifiable base.

Hypophysis (Gr.), a gland and sac in the brain.

Hypo'pium, a deposition of matter in the anterior chamber of the eye. Hyposulphate, a compound of hyposulphuric acid and a base.-Hyposulphite, a compound of hyposulphurous acid with a base.

Hyposul'pho-Ben'zoates, a genus of salts formed by the combination of hyposulpho-benzoic acid with salifiable bases.

Hyposulphuric Acid, a compound of sulphur and oxygen. Hyposulphurous Acid, an acid constistuted of 2 atoms of sulphur, 16 X 2 = 32, and 2 of oxygen, 8 X 2 = 16, its equivalent being 48. Hypoth'enuse (Gr.), in geometry, the longest side of a right-angled triangle, or the line that subtends the right angle.

Hypoxida'ceæ (Gr.), in botany, an order of narcissal Endogens. Hypozo'ic (Gr.), in geology, a term applied to the primary rocks in which no organic remains have been discovered.

Hypsom'etry (Gr.), the art of measuring heights of the earth's surface. Hyri'anæ, in malacology, a sub-family of the Unionidæ, of which the Hyria, a bivalved Mollusc, is the genus. Hys'tatite, a titaniferous iron ore.. Hysteran'thous (Gr.), in botany, applied to those plants the leaves of which expand after the opening of the flowers.

Hysteria (Gr. hystera the womb), a species of neurosis or nervous disease, which generally attacks unmarried women from the age of 15 to 35. Hysterics, fits peculiar to women. Hyster'ocele (Gr.), a rupture of the womb.

Hysteropto'sis (Gr.), a falling down of the womb; prolapsus uteri. Hysterorrhea (Gr.), a discharge of blood or mucus from the womb. Hysteroscope (Gr.), an instrument whereby a view of the os uteri in the living subject may be obtained. Hysterotomy (Gr.), dissection of the womb.

Hystric'idæ (Gr. hys a pig, and thrix a bristle), in zoology, a family of mammiferous animals, of which the genus Hystrix, or Porcupine, is the type.

Iatro-(Gr.iatros a physician), in medical science, a prefix to compound words, signifying a connection with physicians or medicine. Iatrophic acid, the acrid principle of croton oil.Iatrolept, one who cures by anointing.

Ic, in chemistry, a termination affixed to those acids which contain in combination the highest known quantity of the acidifying principle.

Ice (Sax.), water or other liquid solidified by cold; water becoming solid at 32o Fahrenheit. -Icebergs are vast bodies of ice, among the most remarkable of which are those of Spitzbergen. Some of these icebergs are the creation of ages, and receive annually additional bulk by the falling of snow and of rain, which often instantly freezes, and more than repairs the loss occasioned by the influence of the sun. Icefloe is an aggregated mass of floating ice, frequent in the northern seas, and very dangerous to navigation.

Iceland Spar, in mineralogy, a pure variety of calcareous spar or carbonate of lime, remarkable for its clearness, and the beautiful double refraction which it exhibits.

Ice Spar, a mineral of a whitish-grey colour, consisting of silica, alumina, potash, lime, peroxide of iron, and water: sp. gr. 4°32; H = 3. Ichneu'mones, a tribe of parasitical hymenopterous insects. Ich'nites (Gr. ichnos a footprint), in geology, fossil footprints of animals. -Ichnolite is a stone retaining the impression of fossil footmarks. Ichnography (Gr.), in perspective, the view of anything cut off by a plane parallel to the horizon. In architecture, a transverse or horizontal section of a building, exhibiting the plot of the whole edifice, and of the several apartments in any story.Among painters the word is used to describe images or ancient statues of marble and copper, of busts and semibusts, of paintings in fresco, or mosaic works.

Ichnology (Gr.), the science of fossil footprints.

Ichor (Gr.), a thin and sanious fluid, which escapes from wounds or sores, and irritates or inflames the parts over which it flows.

Ichthyocol'la (Gr. ichthys a fish, and kollos glue), the scientific name of isinglass, a very pure form of gelatine, prepared from certain parts of the

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entrails of several fish. Good isinglass is free from smell or taste, and perfectly soluble in boiling water. Ichthyodor'ulites (Gr. ichthys, doru a spear, and lithos a stone), in geology and ichthyology, a name for the fossil spines of fishes.

Ichthyolite (Gr. a fish stone), a stone containing the petrifaction of a fish or any of its parts. Ichthyology (Gr.), the science or knowledge of fishes; that department of natural history which treats of the structure, habits, and classification of fishes. Ichthyotomy, the anatomy

of fishes.

Ichthyophthalmite (Gr. ichthys, and ophthalmos the eye), a mineral of pearly lustre; the fish-eye stone. Ichthyopteryg'ia(Gr.ichthys, and pteryx a fin), an order of fossil reptiles with limbs like fins, formed for swimming. Ichthyosaurus (Gr. ichthys, and sauros a lizard), in palæontology, an extinct marine animal, the Fish-lizard. Ichthyo'sis (Gr.), in pathology, a roughness and thickening of the skin, portions of which become scaly, and occasionally corneous, with a tendency

to excrescences.

I'cica Resin, in botany, the name of those useful resinous exudations of S. America, where the Icica trees occur, and furnish the valuable resins, carana, elemi, and tacamahaca.

Icterus (Gr.), in pathology, the jaundice. Icteric, affected with jaundice. Iconography (Gr. eikon an image, and grapho to write), in the fine arts, a description of statues and similar monuments of ancient art.

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Icosahedron (Gr.), in geometry, regular solid, consisting of twenty triangular pyramids, whose vertices meet in the centre of a sphere, which is supposed to surround it, and therefore have their height and bases equal.

Icosan'dria (Gr.), the twelfth Linnæan class, comprising such plants as have twenty or more stamens inserted in the calyx.

Idæ, or Ides, a Greek termination, employed in natural history to denote a certain order or class of animals to which the termination ida or ides is affixed.

Ide, in chemistry, a termination for certain compounds which are not acid; as oxides, chlorides, &c. Ide'alism, in metaphysical science, the theory or system which makes everything consist in ideas, and denies the

existence of material bodies. Ideology is a treatise on ideas, or the science of mind.

Idiolec'tric (Gr. idios peculiar), having the property of manifesting electricity on friction.

Idiopathy (Gr.), in pathology, a primary disease, not consequent on other morbid affections.

Idiosyncrasy (Gr. a peculiar mingling), in physiology, a peculiarity of temperament or constitution, which predisposes persons to the attacks of certain disorders from which others are exempt.

Id'ocrase (Gr. seeing a mixture), a nineral of various shades of brown and green, with a vitreous lustre, consisting of silica, alumina, protoxide of iron, lime, and magnesia: sp. gr. 3'34; H = 6.

Id'rialine, a mineral substance, composed of 18 parts of carbon and I of hydrogen.

Ignis Fat'uus (Lat. a deceptive fire), a luminous meteor seen in summer nights in marshy places; Jack-alantern; Will-with-the-wisp. The general opinion is, that this light is produced by the decomposition of animal or vegetable matter, or by the evolution of gases which spontaneously inflame in the atmosphere. Iguan'ide, a family of Saurian reptiles, of which Iguana is the type and

genus.

Iguan'odon (Gr.), in geology, an extinct Saurian reptile of enormous size. The remains of one discovered in Tilgate Forest measured 70 feet from the snout to the tip of the tail; the head was 4 feet in length; the tail, 13 feet; height of the body, 9 feet; its circumference, 14 feet; length of the thigh and leg, 8 feet 2 inches. (Dr. Mantel). The Wealden formation, which contains the remains of these more than gigantic tenants of a former world, is overlaid by the chalk rocks of England, and is a fresh-water deposit.

Il'ia (Lat.), in anatomy, the small intestines; that part of the abdomen which contains the intestines. Iliac, relating to the lower bowels, or ilia. -In pathology, the iliac passion is a spasmodic and dangerous colic.Iliacus internus is a thick, broad, and radiated muscle, which is situated in the pelvis, upon the inner surface of the ilium, which is the last portion of the small intestine, so named from its convolutions.Ilium os, the haunch bone.

Illecebra'ceæ (Lat. illicio to allure), in botany, a nat. order of exogenous herbaceous plants (the Knotworts),

of which the Illecebrum, a pretty flowering plant, is the type.

Il'menite, in mineralogy, a variety of iron ore, of a dark brown colour, consisting of titanic acid, peroxide of iron, protoxide of iron, protoxide of manganese, and magnesia: sp. gr. 476; H=575.

Immersion (Lat.), in astronomy, the disappearance of any celestial object behind another, or its shadow. Thus, in the eclipse of one of Jupiter's satellites, the immersion takes place when the satellite disappears behind the body of the planet, or enters into the planet's shadow; and in an occultation of a planet or fixed star by the moon, the immersion is the disappearance of the star or planet behind the body of the moon, and its reappearance is called its emersion.

Impact (Lat.), in mechanical science, the action of one body upon another, to put the latter, if at rest, in motion. or if in motion, to increase, retard, or alter its direction. The point against which the impelling body acts is called the point of impact. Impasta'tion, in sculpture, the mixture of different matters bound together by means of cements, capable of resisting the action of fire or air. Imperato'rine, in chemistry, a peculiar acrid substance extracted by ether from the root of Imperatoria ostruthium. It forms long transparent crystals.

Imperial (Lat.), in architecture, an epithet sometimes applied to the Moorish or Saracenic dome, particularly when it tapers towards the top, and is more than ordinarily spread out below. -Imperial Medals were such medals or coins which were struck after the conclusion of the Roman republican era, and until the fall of the Eastern empire.-At the present time Imperial is the name of a gold coin of different dates and values, current in Russia for ten roubles, or nearly £1 135.

Impeti'go (Lat.), in pathology, a cutaneous eruption, consisting of clustering pustules of a yellow colour and very itchy, and terminating in a scaly crust, intersected with cracks. In'aline, a vegetable product, resembling starch, obtained from the roots of Inula hellenium by boiling them in water.

In'cidence (Lat. falling on). In dynamics and optics, the angle of incidence is the angle made by a ray of light falling on an object with a line drawn perpendicularly to the surface struck.

Incinera'tion (Lat.), in pharmacy, the process by which a vegetable or animal substance is reduced to ashes for pharmaceutical use.

Inclina'tion (Lat.), in mathematics, the tendency or inclination of two planes or two lines towards each other, so as to form an angle. Inclination of the axis of the earth is the angle which it makes with the plane of the ecliptic, or the angle between the planes of the equator and ecliptic, which is 23° 28'.-Inclination of meridians, in dialling, is the angle that the hour line on the globe, which is perpendicular with the dial-plate, makes with the meridian.-Inclination of a planet, an arc or angle comprehended between the ecliptic and the plane of a planet in its orbit. Inclined Plane, in mechanical science, a sloping plane, or a plane that forms an oblique angle with the horizon. Inclinometer (Lat. inclino to bend, and Gr. metron a measure), an apparatus for determining the vertical element of the magnetic force. Inclu'sa (Lat.), a family of testaceous Mollusca.

Incommen'surable (Lat.), not to be reduced to any common measure.-In geometry, a term applied to homogeneous magnitudes which have no common measure.-Incommensurable numbers are such as have no common divisor that will divide them both equally. Incras'sate (Lat. crassus thick), in pharmacy, to make fluids thicker by = evaporating the thinner parts, and making fluids thicker by the mixture of other substances less fluid.

In'crement (Lat.), in mathematics, a small but finite increase of a variable quantity.

Incrusta'tion (Lat.), in chemistry, the disposition of stone-like molecules on the surface of bodies exposed to the action of waters impregnated with calcareous salts. In anatomy, the development of osseous plates in the organic tissues, from age or chronic inflammation. In architecture and sculpture, a work fixed with cement or cramp-irons into notches made to receive it.

Incuba'tion (Lat.), in pathology, the period intervening between the development of a disease and the impression of the causes by which it has been produced. In zoology, the action commonly exercised by birds of sitting on their eggs, in order to develop the contained embryo. Incumbent (Lat.), in entomology, a term applied to the wings of insects, when the one lies over the other.-

Indehis'cent (Lat. not gaping), in botany, applied to fruits which do not split open, as the apple. Indented (Lat. in, and dentes teeth). In fortification, indented line is a serrated line forming several angles, so that one side defends another. Indeterminate (Lat.). In algebra, indeterminate analysis is a branch which has for its object the investigation of problems that admit of an infinite number of different solutions.-Indeterminate coefficient is a method of analysis of very extensive application in the higher mathematics. Index, pl. In'dexes, and in mathematics In'dices (Lat. an indicator), in music, a character or director at the end of a stave to direct to the first note of the next stave. In arithmetic and algebra it is used as an exponent.In optics it expresses the constant ratio which exists between the sines of the angles of incidence and refraction. Index of a globe is a little style fitted on to the north pole, and turning round with it, pointing to certain divisions in the hour circle. In'dian Corn, in botany, the valuable produce of the plant Zea mays, called Maize by the South Americans. There are many varieties, one of which, the Zea curagua, or Valparaiso Cross-corn, is held in a sort of religious veneration. Indian Cress is the common name of the plants of the genus Tropæolum. Indian ink, called also China ink, is an ink manufactured in China, and imported into this country in square cakes. It is used as a water-colour, and in linear drawings. Indian red, a variety of ochre-a fine purple earth, of compact texture, and great specific gravity.

In'dianite, a greyish shining mineral found in the Indian Carnatic, in masses of a foliated structure.

Indicator (Lat.), applied to the muscle which extends the forefinger. In'dicolite (indigo, and Gr. lithos a stone), an indigo-coloured mineral, a variety of tourmaline or schorl, found in Sweden.

Indic'tion (Lat.), in chronology, a cycle of fifteen years, instituted by Constantine the Great.

Indigofera (Ind. indigo, and Lat. fero to bear), a genus of leguminous plants, the flowers of which are purple, blue, or white, and disposed

Indivisibles, in geometry, are the elementary parts or principles into which a body or figure may be resolved; elements infinitely small.

Induction (Lat.), in electricity, that condition of an electrified substance which, when opposed to another, causes the latter to acquire, under certain circumstances, an opposite electric state upon the surface opposed to the inducing body, and is rendered electro-polar.

Inductom'eter (Lat. and Gr.), an instrument for measuring the force of electrical induction.

Indu'plicate (Lat.), in botany, having the margins bent abruptly inward. Indu'siæ (Lat. a covering), in zoology, a case or covering of certain larvæ.Indusial, composed of indusiæ.Indusial limestone, a name given to a certain limestone from its containing the indusiæ, or cases, of the larvæ of Phryganea.

Indu'sium (Lat.), in entomology, the case or covering of certain larvæ.In botany, the membrane which encloses the thecæ in ferns.

Inen'chyma (Gr.), in botany, a term applied to those tissues which consist of cells with spinal fibres.

Iner'tia (Lat. inert), in obstetrics, inertion or failure of the uterine constrictions at the time they are necessary for expelling the fœtus. In physics, the quality by virtue of which matter is incapable of spontaneous change. Inescutcheon, in heraldry, a species of ordinary, being an escutcheon placed upon the fess point, and containing the third part when charged, and the fifth when otherwise.

In'fantry (Fr.), in military science, the foot-soldiers of an army. Infantry exercise applies to the use of the firelock, and practice of the manœuvres for regiments of foot, according to military regulations established by authority.

Infection (Lat.), in pathology, the propagation of disease through the medium of the air, distinguished from contagion, which results from absolute contact with a diseased person, or with the substances which have been contaminated by him.

Inferobranchia'ta (Gr. branchia gills), an order of gasteropod Mollusca, which have their branchiæ not placed on the back, but in two long series of laminæ situated on the two sides of the body.

Infiltra'tion (Lat.), in pathology, an infusion of fluid into the areolæ of a structure, and especially of the cellular tissue.

Inflammation (Lat.), in pathology, a redness and swelling on any part of the animal body, caused by excessive action of the blood, and usually attended with painful and febrile symptoms.

Inflection (Lat. a bending), in optics, the effect produced by the edges of an opaque body on the light passing in contact with them, by which the rays are bent out of their course. Influen'za (Ital.), in pathology, a febrile epidemic catarrh, prevalent at certain seasons.

Infra (Lat. within or beneath), a prepositive particle, often prefixed to scientific terms; as, Infra-costal, beneath the ribs;-Infra-maxillary, beneath the jaw;-Infra-orbital, beneath the orbit; -Infra-spinous, beneath the spinal process. Infundibu'liform (Lat. funnel-shaped) in botany, applied to a monopetalous corolla, with an inversely conical border springing from a tube. Infundibulum (Lat. infundo to pour in), in anatomy, a small cavity of the cochlea, at the termination of the modiolus. - Infundibula are the membranous tubes which embrace the mammillæ of the kidneys. Infuso'ria (Lat.), in entomology, microscopic insects, or minute animalcules found in water as well as in moist atmosphere and other situations, and constituting the last and lowest link in the animal kingdom. The great entomologist Ehrenberg has ascertained that the Infusoria, which have hitherto been considered as scarcely organized, have an internal structure resembling that of the higher animals, viz., muscles, intestines, eyes, nerves, and organs of reproduction. Their powers of reproduction are so great, that, from one individual, a million were produced in ten days; on the eleventh, twelve millions; and on the twelfth day, sixteen millions. Ehrenberg has described and figured more than five hundred species, and has found them in fog, rain, and snow. Inges'ta (Lat.), in pathology, a term applied to different kinds of nutriment taken into the system.

Inglu'vies (Lat. a crop), in ornithology,