quartz, presenting several shades of red and yellow;-Iron-glance, a pure peroxide of iron, in the proportion of iron 69.34 to oxygen 30.66: sp. gr. 50-53; Η=55-65;-Iron-liquor, acetate of iron, used as a mordant by dyers; Iron ore, an oxide of iron; -Ironstone, an ore of iron, of which there are several varieties; - Iron pyrites, a mineral of a brass-yellow colour, approaching to bronze yellow. It is very abundant in nature, and occurs disseminated in rocks, veins, and beds, investing other minerals, and often enclosed in them. It is composed of 2 atoms of sulphur and I of iron. The varieties are Hepatic Pyrites, Arsenical Iron Pyrites, Auriferous Iron Pyrites, White Pyrites, Magnetic Iron Pyrites, Prismatical Iron Pyrites.

I'sagon (Gr.), in mathematics, a figure with equal angles..

I'satine, in chemistry, a compound body obtained from indigo when it is oxidized by means of sulphuric acid and bichromate of potash. It forms hyacinth or orange-red crystals of a brilliant lustre. Isatyde is a yellowish-white powder, obtained when isatine is dissolved in hydrosulphuret of ammonia: formula, C16H6ΝΟ3.

Isa'tis (Gr. isazo to render equal), in botany, a genus of tall, cruciferous herbs, the Woad, all the species of which furnish a blue dye like indigo; type of the order Cuciferæ.

Ischiad'ic (Gr. ischion the hip), in anatomy, relating to the hip, or the parts adjacent. The Ischiadic artery is a branch of the internal iliac, which passes out at the ischiadic foramen, between the puriform and gemelli muscles, in company with the great sciatic nerve. It is distributed within the pelvis to the rectum and the internal obturator, puriform, coccygeal, and levator ani muscles.

Ischialgia (Gr. ischion and algos pain), in pathology, pain about the coxafemoral articulation, or in the course of the ischiatic nerve.

Is'chiocele (Gr. ischion), in pathology, hernia formed by the protrusion of the viscera through the great ischiatic foramen.

The following names have been given to muscles, nerves, &c., connected with the ischium, which are here presented in alphabetical order: -Ischio-clitorianus, the nerves of the clitoris a branch of the pudic; Ischio-clitorideus, the erector clitoridis;-Ischio-coccygeus, the muscle more generally called coccygeus ;Ischio-femoralis, or the Abductor magnus femoris ;-Ischio-femoro

peroneus, the biceps femoris. Ischioperinealis, the transversus perinei muscle;- Ischio-popliti-tibial, the semi-membranosus muscle;-Ischiopratibialis, the semi-tendinous muscle; -Ischio-prostaticus, a name given to the muscular fibres ;-Ischio-trochanteriani, the gemelli muscles. Ischoblen'nia (Gr. ischo to suppress, and blenna mucus), in pathology, suppression of the mucous discharges, to which the following terms have been applied:-Ischoilia, suppression of fæces; constipation; Ischogalactia, suppression of milk;-Ischolochia, suppression of lochial discharge;Ischomenia, suppression of menstrual discharge; -Ischopyosia, suppression of an habitual purulent secretion. Is'chury (Gr.), a stoppage or suppression of urine.

I'serine, in mineralogy, an oxide of

titanium.

I'singlass, a pure form of gelatine, prepared from the entrails of certain fresh-water fishes; a name applied to mica.

Isis, the name of one of the newly-discovered planets, first observed by Pogson in 1856.

Iso, in scientific terms, a Greek prefix, signifying equal; as, Isochromatic, in optics, having the same colours.Isochromatic lines are those coloured rings which appear when a pencil of polarized light is transmitted along the axis of a crystal, as mica or nitre, and is received in the eye after passing through a plate of tourmaline.Isobarometric, in meteorology,applied to the mean difference between the monthly extremes of the barometer.Isodynamic, of equal power, as applied to the earth's surface in which the magnetic forces are equal.-Isogonic, having equal angles, applied to the declinations of the magnetic needle. Isotheral, having the same mean summer temperature. - Isothere, an imaginary line connecting those places on the earth which have the same mean summer temperature. Isomerism (Gr.), identity of elements and proportions, but different properties.

Isomorphism (Gr.), the quality of assuming the same crystalline form, though composed of different elements or proximate principles, yet with the same number of equivalents.

Isoperimetrical (Gr.), in geometry, having equal boundaries, as equal perimeters or circumferences.-Isoperimetry is the science of figures which have equal perimeters or boundaries. Isopoda, or I'sopods (Gr.), in malaco

logy, an order of aquatic Crustaceans, characterized by having uniformly fourteen equal feet, unguiculated, and without any vesicular appendage at their base.

I'sopyre (Gr. isos, and pyros fire), in mineralogy, a silicate of alumina, lime, and peroxide of iron. Isos'celes (Gr.), in geometry, having two legs or sides equal, as a triangle. Isothermal (Gr. isos, and therma heat), having equal heat or temperature.Isothermal lines are imaginary lines which pass through those points on the surface of the earth at which the mean annual temperature is the same. Isothermal zones are spaces on opposite sides of the equator, having the same mean temperature, and bounded by correspondent isothermal lines.

Isthmi'tis (Gr.), inflammation of the fauces.

Isthmus (Gr. isthmos), a neck of land joining a peninsula to the main land. -In anatomy, that which divides the

Jaca Tree, in botany, the name of a Bread-fruit tree, the Artocarpus integrifolia, a native of the East Indies. Jacinth (Lat.), a species of pellucid gem.

Jack, in mechanical science, an implement for raising great weights, of which there are various kinds; as, the Kitchen Jack, in which weight is applied as a power to overcome friction, and a uniform motion obtained by means of a fly-wheel; - Jack-inthe-Box, a large male screw turning in a female one, which forms the upper part of a strong wooden box, shaped like the frustum of a pyramid. It is used by means of levers passing through holes in it. In architecture, iack timbers are a row of timbers, which, being intercepted by other pieces, are shorter than the others.

Jacobs' Membrane (from Dr. Jacobs, the discoverer), in physiology, a serous membrane or layer of the retina in the eye.

cavity of the mouth from that of the pharynx.

Ite, in chemical terms, a termination used to indicate that a saline compound is formed by an acid ending in ous; thus, the sulphurites are formed by sulphurous acids with bases, while the sulphates are formed by sulphuric acid with the same bases. Itis (Gr.), in pathology, a termination affixed to the name of the organ affected, implying a state of inflammation.

Ittť'nerite (after M. von Ittner), a bluish mineral, consisting of silica, alumina, lime, soda, peroxide of iron, and water: sp. gr. 2'38; H=70.

Itt'ria, Ytt'ria, a non-acid compound of the metal ittrium or yttrium with oxygen.

Ix'odes, the name of a genus of parasitical Acari found on the skins of domestic quadrupeds. Ix'olite (Gr. ixos bird-lime, and lithos a stone), a mineral of a greasy lustre, found in bituminous coal.

lour, consisting of sulphur, lead, copper, iron, and antimony: sp.gr. 5.56; Η =2-25.

Janca Tree, Poison-wood, the Amyris foxifera of Wildenow. Japon'ic Acid, an acid obtained from catechine when exposed to the air with caustic alkalies. Jasmina'ceæ (Gr. ia a violet, and osme smell), a nat. order of exogenous plants, consisting of twining shrubs of which the Jasminum, or Jasmine, is the type: often called Jessamine. Jasper, in mineralogy, a siliceous mineral of various colours used in jewellery.

Jau'lignite, a mineral resin obtained from the lignite of juline. Jaundice (Fr. jaune yellow), in pathology, a disease accompanied by a suffusion of bile, giving the eyes and skin a yellow hue, and making things appear yellow to the patient.

Jazel, in mineralogy, a precious stone of an azure colour.

Jeffersonite (in honour of President Jefferson), in mineralogy, a variety of the pyroxene, a dark green foliated variety of augite.

Jamaci'na, a vegetable alkaline principle obtained from the Cabbagebark tree, Geoffroya Famaicensis. Jame'sonite (from Professor Jamieson), a crystallized mineral of a steel co

part of the small intestines, reaching from the duodenum to the ilium. Jessant, in heraldry, an epithet applied to a lion or other beast when erected over two or more colours.

Jet (Fr. jayet), in mineralogy, a very beautiful fossil, of a fine deep black colour; a variety of coal of a very compact texture, susceptible of a high polish; used for the manufacture of trinkets.-Jet-lustre is a Bohemian black-lead for polishing grates. In military tactics, jet is the movement of any body pushed forward by main force.

Jettee, Jetty (Fr.), in architecture, a border round the stilts under a pier; in bridges, a projection in building; a mole projecting into the sea. Jewel (Fr. joyau), an ornament of dress; a precious stone.

Jews' Frank'incense, a resin obtained from the plant Styrax officinale. Jigging, in mining, the process of sorting ore by passing it through a wirebottomed sieve.

Joggles, in architecture and masonry, joints of hard stones or other masses so indented that the adjacent stones fit into the indentations.

Johan'nite, in mineralogy, a sulphate of the protoxide of uranium, of a grassgreen colour: sp. gr. 3°19; H=2.5. Join'ery, in mechanical science, the art of fitting and joining pieces of timber in the construction of utensils or parts of a building, so as to form one entire piece.

Jointer, in architecture and bricklayıng, a crooked piece of iron forming two curves of contrary flexure by its edges on each side, and used for drawing, by the aid of the jointing-rule, the coursing and vertical points of the work. Jointing-rule is a straightedge used by bricklayers for regulating the direction and course of the jointer in the horizontal and vertical joints of brickwork.

Jugate (Lat. juga a yoke), in botany, a term applied to the leaflet pairs in compound leaves.

Ju'gular (Lat. jugulum the throat), pertaining to the throat or neck.Jugular veins are the veins which bring the blood from the head down the sides of the neck. By their union with the subclavian vein, they form

the superior vena cava, which terminates in the superior part of the right auricle of the heart.-Jugulars, in ichthyology, comprehend that class of fishes which are distinguished by having ventral fins anterior to the pectorals.

Jujubes, in the materia medica, a fruit of the pulpy kind, produced on a tree which Linnæus considers as a species of Rhamrus.

Julep (Arab.), in medicine, a mucilaginous mixture.

Julus, in botany, a catkin; an inflorescence of the Willow, Hazel, &c. Junca'ceæ (Lat. juncus a rush), in botany, a nat. order of endogenous herbaceous plants, of which Juncus, the Rush, is the type. Juncagin'eæ, in botany, an order of alismal Endogens (Arrow - grass), consisting of aquatic plants. Jungermannia'ceae (from Jungermann, a German botanist), in botany, a nat. order of Acrogens, consisting of creeping moss-like plants, of which Jungermannia is the genus and type. Jun'kerite, a crystallized mineral of a yellow-grey colour, consisting of protoxide of iron, carbonic acid, silica, and manganese: sp. gr. 38; H=3.81.

Jupiter, in astronomy, the largest planet of the solar system, which is attended by four satellites. Its equatorial diameter is 1,086 times that of the earth, or upwards of 86,000 miles. Its mean distance from the sun is 490,000,000 miles. It revolves on its axis in 9 hours 55 min. 49 sec. Juras'sic, in geology, a term applied to the oolitic system, and so called from its occurrence in the Jura mountains of Switzerland.

Jure'ma Bark, an astringent bark obtained from the Acacia jurema of

Brazil.

Juwan'za, in botany, the name of the Camel's Thorn (Alhagi Maurorum), which furnishes the manna of the desert, and is used for making screens, &c.

instrument which gives forth sweetsounding vibrations.

Kak'oxene (Gr. kakos bad, and oxys sharp), a mineral with red or brown radiated crystals.

Kaleidoscope (Gr. a beautiful view), an optical instrument or toy, which exhibits a great variety of beautiful colours and symmetrical forms. Kali (Arab.), a plant, the ashes of which are used in making glass; hence the word alkali.

Kangaroo', in zoology, a marsupial quadruped of Australia, having short fore legs, and long hind legs, on which it leaps.

Ka'olin (Chinese), in mineralogy, a fine species of porcelain clay, composed of silica and alumina from decomposed felspar. There is a large tract of this substance found at St. Austel, in Cornwall.

Karpholite (Gr. a shrivelled stone), in mineralogy, a hydrated silicate of alumina and manganese, in stellated crystals, consisting of silica, alumina, oxide of manganese, oxide of iron, lime, fluoric acid, and water: sp. gr. 2.93.

Karphosid'erite (Gr. shrivelled steel), a hydrated phosphate of iron. Kathetom'eter (Gr. kathelos perpendicular), an instrument for measuring perpendicular heights.

Keesh, in metallurgy, the flakes of the carburet of iron. Kelænone'sian (Gr. kelainos black, and nesos an island), in ethnology, an epithet applied to the dark-coloured inhabitants of the Pacific Islands.

Kelp, the alkaline calcined ashes of the weed used in the manufacture of glass and soap, but barilla is the article now chiefly employed.

Kepler's Laws, in astronomy, the laws of planetary motion laid down by Kepler, by which are established the important principles that the planets each describe ellipses, of which the sun is the centre; and that squares of lines of the revolutions of the planets are as the cubes of their mean distances from the sun.

Kerasine (Gr. keras a horn), a mineral of a yellowish colour, the primary crystal of which is a rectangular four-sided prism. Its constituents are oxide of lead, muriatic acid, and carbonic acid: sp. gr. 6; Η = 3.0. Kerate (Gr.), in mineralogy, a substance of a corneous nature. Kerates are not metallic, but it is a name applied to an order of earthy minerals: sp.gr. 5.5-6.5.

Kerati'asis (Gr. keras), in pathology, a horn-like excrescence developed on the forehead or temple.

Keratonyx'is (Gr. keras, and nyxis a puncture), in surgery, the operation of couching, performed by introducing a needle through the cornea of the eye, and depressing or breaking the opaque lens.

Keratophite (Gr. keras, and phyton a plant), a name given to a horny Zoophyte.

Kermes (Arab.), a small insect, used as a scarlet dye. Kermes mineral, a reddish mineral.

Kerosene, a liquid hydrocarbonate, obtained from a kind of bituminous shale in New Brunswick.

Keuper (Germ.), in geology, the upper portion of the new red sandstone formation.

Key (Sax. cag), a term applied to different branches of science. In music, the particular diatonic scale in which a composition begins and ends, and which more or less prevails in a given piece of music.-Key-board consists of the series of tenors in a keyed instrument, the keys being coloured black and white. In hydrography, a ledge or lay of sunken rocks, applied more particularly to certain_rocks, called the keys, in the West Indies. -Key-stone is a term applied to the middle voussoir in the arch of a bridge, or the arch-stone over the centre of the arch.

Kil'lenite, a mineral of a greenish and brownish yellow, so named from occurring in granite veins at Killeny, near Dublin; it consists of silica, alumina, potash, oxide of iron, and

water: sp. gr. 2.69; Η = 4.0.

Kilogram, a French weight, equal to 2 lbs. 3 ozs. 5 drs. Kil'olitre, a French measure of 1,000 litres, or 264 gallons.

Kilomètre, a French itinerary measure of a thousand mètres, or about five furlongs.

Kim'meridge Clay, in mineralogy, a greyish yellow and blue clay of the oolite formation.

Kinetics (Gr. kineo to move), that part of mechanical science which treats of motion without reference to the forces producing it.

King-post, in architecture, the middle post of an assemblage of trussed fram-ing for supporting or suspending the beam at the middle and lower end of the struts.

King's Yellow, the name given to orpiment, or the yellow sulphuret of arsenic, when used as a pigment. Kingwood, in commerce, one of the most beautiful of the hard woods imported from Brazil.

Kínic Acid, a vegetable acid discovered in cinchona bark, and sometimes called cinchonic acid; it reddens litmus. Its compounds are kinates of quina and cinchona, lime, potash, soda, &c. Kinoyle is a sublimate obtained in yellow needles when a kinate is distilled.

Kir'wanite, a dark, olive-green mineral, found in cavities of basalt on the north-east coast of Ireland. Its constituents are silica, protoxide of iron, lime, alumina, and water: sp. gr. 2'94; Η = 2.

Klinkstone, in geology, a basaltic stone, of the fletz trap formation.

Klinom'eter (Gr.), in geology, an instrument for measuring the inclination of stratified rocks, &c.

Kneb'elite, a greyish, opaque mineral of glistening lustre, consisting of silica, protoxide of iron, and protoxide of manganese.

Knee (Germ. kne), in anatomy, the articulation of the leg bones and thigh.-Knee-pan is a little round bone on the fore part of the knee joint, attached by a strong ligament to the upper end of the tibia.-In architecture, a piece of timber bent artificially, on which another piece is received to relieve any given weight, or resist any particular

strain.

Lab'danum, a resin which exudes from the plant Cistus Creticus. Label, in Gothic architecture, a term applied to the drip-stone, or projecting moulding over windows, doorways, &c.

La'biate, La'biated (Lat. labium a lip), in botany, applied to certains, plant so named from the order Labiatæ, in which the divisions of the corollas resemble lips; the Mint, Rosemary, and Thyme are familiar examples. La'bium (Lat. a lip), in entomology, the lower lip of insects. In conchology, the inner lip of the shell.

Laboratory (Fr.), a place fitted up for chemical investigations and experiments; a chemist's lecture-room.In military affairs, a place where fireworks are prepared for actual service and experiment.

Lab'radorite, Labrador spar; a beautiful variety of opalescent felspar from Labrador, consisting of silica and alumina, lime, soda, and oxide of iron: sp. gr. 2'7; Н = 60.

Lab'ride (Lat. labrum a lip), in ichthyology, a genus of acanthopterygious fishes, covered with large scales, of which Labrus is the genus.

Labri'ne (Lat.), a sub-family of the

zeolite or prehnite, of a green colour, from the Pyrenees. Kre'osote. (See Creasote.) Krokid'olite (Gr. krokis woof, and lithos), an opaque mineral of a bluish colour, consisting of silica, protoxide of iron, protoxide of manganese, magnesia, lime, soda, and water: sp. gr. 3°2; H=4.

Kryolite, in mineralogy, a hydrated fluate of alumina and soda. Krys'taline, the name of a salifiable base. Kungoo, a red powder produced by steeping turmeric root in an alkali. Kunkur, a variety of nodular limestone found in India.

Kupferschief'er (Germ. copper slate), in geology, the copper slate of Thuringia, a low member of the magnesia limestone series.

Kyanite, a bluish mineral, found both massive and in regular crystals. Kyanize (from Mr. Kyan, the inventor), to preserve timber from the dry-rot, by the use of a solution of corrosive sublimate (perchloride of mercury). The timber is immersed in the solution, by which process the primary element of fermentation is neutral. ized, and the fibre of the wood ren. dered indestructible.

Chætodonidæ, of which Labrus is one of the genera.

Laburnum (Lat.), in ), in botany, the common name of the Cytisus alpinus and C. laburnum.

Labyrinth (Gr.), in anatomy, the internal part of the ear.-In metallurgy, a series of troughs attached to a stamping-mill, through which a current of water passes. - Labyrinth fret, in architecture, is a fret with many turnings in the form of a labyrinth.

Labyrin'thodon (Gr. labyrinth, and odontes teeth), an extinct genus of reptiles, supposed to have been one of the Batrachian order, found in the new red sandstone formation.

Lac, a resinous substance considered as a gum, but inflammable, and not soluble in water. The commercial varieties are stick-lac, seed-lac, and shell-lac, the last being the purest. The great consumption of lac is in the manufacture of dye-stuffs, sealing-wax, and of certain varnishes and lacquers.-Lac-dye and lac-lake, the name given to two preparations of lac imported into this country in small cubic cakes.-Laccic acid is a yellow and crystallizable acid ob