ostrich, and formerly inhabiting New Zealand.

Dinosau'ria (Gr. deinos and sauros, a terrible lizard), in zoology, a class of gigantic fossil animals of the Saurian or Lizard tribe. Dinothe'rium. (See Deinotherium.) Dicæcia (Gr. a double dweller), a class of plants which have male flowers on one plant, and female flowers on another; it forms the twenty-second class in the Linnæan system.

Dionæ'a (from one of the names of Venus), a genus of very curious plants, commonly known as Venus's Fly-trap, the leaves of which have a peculiar motion, by which insects are entrapped; order Droseraceӕ. Diopside (Gr. diopsis transparent), in mineralogy, a variety of pyroxene. It occurs in pale green prismatic crystals. A specimen from Piedmont contained silica, lime, magnesia, oxides of manganese, and iron. Dioptase (Gr. dioptomai to look through), a mineral of a fine emeraldgreen colour, consisting of oxide of copper, silica, water, and protoxide of iron: sp. gr. 3.2.

Dioptra (Gr.), an instrument for measuring altitudes.

Dioptrics (Gr.), that part of optics which treats of refracted vision, or the different refractions of light in passing through different media.Dioptric, relating to the science of refracted light.

Diora'ma (Gr. seeing through), a mode of painting and scenic exhibition, which is so arranged as to receive shades of light and various hues by means of movable blinds, and thus produce a complete optical illusion.

Di'orite (Gr.), in mineralogy, a variety of greenstone.

Diorrhosis (Gr.), in pathology, the dissolution of the solids of the animal body, and their evacuation by the urinary passages.

Diorthrosis (Gr.), in surgery, the reduction of a fractured or dislocated bone.

Dioscorea'cese, in botany, a nat. order of plants belonging to the class Dictyogens, of which Dioscorea is the type.

Dioxide (Gr. dis double, and oxide), in chemistry, a compound of oxidation; when the second degree of oxidation is formed of single equivalents, and the lowest oxide consists of two equivalents of the + element, one of an oxide, and one of oxygen, the compound is called a dioxide. Diox'ylite (Gr. dis double, oxys sharp, and lithos a stone), a salt of lead,

consisting of the carbonate and sulphate of lead.

Dip, in electricity and magnetism, the angle which the magnetic needle, when freely poised, makes with the plane of the horizon. In geology, the inclination of a stratum or bend

from the horizon.

Dipetalous (Gr.), in botany, having two flower-leaves or petals. Diphtheria, or Diphtheri'tis (Gr. a double membrane), a throat disease, the angina pellicularis, accompanied by the formation of a false membrane.

Diphyllous (Gr. double-leaved), in botany, having two leaves, as a calyx, &c.

Diphyodonts (Gr. dis double, phyo to produce, and odontes teeth), in zoology, animals which produce two sets of teeth in succession.

Dipla, or Diplo, a prefix to numerous scientific words, derived from the Greek word diploos (double); as, diplogenic (producing two substances), diplozoon (doubie-bodied), &c. Dipleidoscope (Gr. viewing a double form), an instrument for observing the transit of the sun over the meridian by day, or of the stars by night, so as to correct a timekeeper.

Dip'loë (Gr. double), in anatomy, the cellular structure which separates the two tables of the skull. In botany, the cellular substance of a leaf.'

Diplomatics (Gr.), the science of deciphering ancient writings, literary and public documents, letters, decrees, charters, and codicils, to ascertain their authenticity, signatures, &c. Diploma, a letter or writing conferring some privileges or degree, as in medicine or law. Diploneu'rans (Gr. double nerves), a vertebrated division of the animal kingdom, so named from their having two nervous systems, the ganglionic and the cerebro-spinal.

Diplopia (Gr. double-sighted), a disease of the eye which causes a person to see an object double. Diplop'tera (Gr. double-winged), in entomology, a division of stinging hymenopterous insects, consisting of Wasps, which have the upper wings doubled up when at rest. Diplozo'on (Gr. double animal), a singular parasitic worm, which has the appearance of two bodies, and infests the gills of the bream. Dipneumo'nians (Gr. double lungs), in entomology, a section of Araneidæ, or Spiders, comprehending those with two pulmonary sacs.

Dipping, in geology, the interruption of

a vein of ore, or of a mineral stratum sloping downwards. The Dippingneedle, in magnetism and navigation, is an instrument which dips or inclines to the earth, and shows the magnetic inclination at the different points of the earth's surface. In the equatorial regions the needle takes a horizontal position; but as we recede from the equator towards either pole, it dipsori clines one end to the earth, the north end as we proceed northward, and the south end as we proceed southward, and the further north or south we proceed, the greater is the dip or inclination.-Craig.

Diprismatic (Gr. doubly prismatic), in mineralogy, having cleavages parallel to the sides of a four-sided vertical prism, and, at the same time, to a horizontal prism.

Dipsaca'ceæ (Gr. thirstiness), in botany, a nat. order of plants, consisting of exogenous shrubs or herbs, of which the Dipsacus, or Teazel, is the genus and type.

Dipso'sis (Gr. thirst), in pathology, a morbid degree of extreme thirst. Dip'tera, or Dip'terans (Gr. doublewinged), in entomology, a class of insects comprising such as have two membranous wings attached to the mesothorax. Dipterous, an epithet applied to insects with two wings. Diptera'ceæ, or Dipterocarpa'ceæ (Gr. double-winged, and karpos fruit), in botany, a nat. order of hypogynous Exogens, consisting of gigantic trees with showy flowers, of which the Dipterocarpus is the type and genus; native of India.

Dipterygians (Gr. two-finned), in ichthyology, a family of fishes furnished with two fins only.

Dipyre (Gr. doubly burnt), a very curious mineral occurring in the Western Pyrenees in slender, indistinctlyformed prisms, of a greyish or reddish-white colour. It consists of silica, alumina, lime, and water: sp.

gr. 2.7.

Direc'trix (Lat.), in geometry, a straight line perpendicular to the axis of a conic section.

Dirigent (Lat.), in geometry, a term applied to the line of motion along which a describent line is carried in the generation of any plane or solid figure.

Di Salto (Ital.), in music, a motion by skips, not by degrees. The degrees and skips of melody are both called by the general term interval, which is the distance between two sounds, or their difference in respect of pitch. Disc, or Disk (Lat. discus), in optics,

the magnitude of a telescope-glass, or width of its aperture. In astronomy, the body and face of the sun or moon, or of a planet, as it appears to us on the earth, or the body and face of the earth, as it would appear to a spectator in the moon. Discoid, or Discoid'al (Gr. resembling a disc or quoit), in botany, a term applied to plants, or the organs of plants, which have two flattened surfaces, with a circular border. In conchology, univalve shells are said to be discoid when their spires are vertically convoluted on the same plane.-In Composite plants, the heads of the flowers are said to be discoid when the florets are all tubular.-Discoidea, in geology, is a genus of fossil Echinodermata, found in the chalk, oolitic, and greensand formations.

Discord, in music, dissonance of sounds; a combination of sounds which are inharmonious, and disagreeable to the

ear.

Discrete (Lat.) In the science of numbers, Discrete proportion is when the ratio of two or more pairs of numbers or quantities is the same, but there is not the same proportion between all the numbers; as, 3:6::8:16, 3 bearing the same proportion to 6 as 8 does to 16; but 3 is not to 6 as 6 to 8. Discu'tient (Lat.), in surgery, an application which disperses a tumour or any coagulated fluid in the body. Disdíapa'son, in music, a compound concord in the quadruple ratio of 4:1 or 8: 2.-Disdiapason diapente is a concord in a sextuple ratio of 1: 6.Disdiapason semidiapente is a compound concord in the proportion of 16: 3.-Disdiapason ditone is a compound consonance in the proportion of 10: 2.-Disdiapason semiditone is a compound concord in the proportion of 24:5.

Disinfectants (Lat.), in chemistry, certain applications which neutralize or destroy miasmatic infections.

Disintegration (Lat. not entire), the act of breaking up or separating integrant parts of a substance, not by chemical action.

Disoxida'tion, in chemistry, the process of freeing from oxygen by disengaging it from a substance.

Disper mous (Gr.), in botany, containing only two seeds. Dispersion (Lat. a scattering), in optics, the separation of the coloured rays of light in passing through a prism, varying according to the refracting power of the material of which the prism is composed. Disruption (Lat. a rending asunder), in geology, a displacement of the crust of the earth; earthquakes, volcanoes, or other disturbing causes. Dissection (Lat.), in anatomy, the operation of cutting off the constituent parts of an animal body, for the purpose of critical examination as to the structure and use of its parts.

Dissep'iment (Lat. dis, and sepes a hedge), in botany, a partition in an ovary or fruit.

Dissolution (Lat.), in pathology, Dissolution of the blood is a state of the blood which does not allow it to coagulate when cooling after leaving the body, as in cases of malignant febrile diseases.

Dissolvent (Lat.), in pathology, a solvent, or any medicine capable of dissolving concretions or calculi of the body.

Distance, in military science, a term of frequent occurrence; thus, it often denotes the relative space left between men standing under arms in rank, or the interval which appears between those ranks, &c. -The Distance of divisions is the number of paces, of thirty inches each, comprised in the front of any division or body. In fortification, Distance of the bastion is a term applied to the exterior polygon.

Distem'per, in painting, a method of tempering paint with oil, or mixing colours with something besides oil and water.

Distichi'asis (Gr. dis, and stichos a row), in pathology, a double row of eyelashes, by the innermost of which the eyeball is irritated and inflamed. Dis'tichous (Gr. double row), in botany, having flowers arranged in two opposite rows.

Distillate (Lat. distillo to distil), in chemistry, a fluid distilled and found in the receiver of a distilling apparatus.

Distilla'tion (Lat.), in chemistry, a process by which heat is applied to certain substances in covered vessels of a particular form in order to separate their more volatile constituents into vapour; and for condensing them immediately by cold into the liquid state in a distinct vessel, called a refrigerator.

Distortion (Lat. twisting out of shape), in optics, the change in the form of an image depending on the form of the lens.

Distribution (Lat.), in architecture, the disposing of the several parts of a building according to the rules of art and science. In natural philosophy, Distribution of electricity is a term applied to the densities of the electrical fluid in different bodies

placed so as to act electrically upon one another, or in different parts of the same body.

Disulphuret, in chemistry, a sulphuret, containing two equivalents of the sulphur to one of the base. Ditetrahedral (Gr.), in crystallography, having the form of a tetrahedral prism with dihedral summits.

Ditone (Gr. dis, and tonos tone), in music, an interval comprehending two tones; the proportion of the sounds that form the ditone is 4: 5, and that of the semiditone 5: 6. Ditrichotomous (Gr.), in botany, having the stems of a plant continually dividing into double or treble ramifications; sometimes applied to a panicle of flowers. Ditrig'lyph (Gr. twice treble division), in the Doric order of architecture, an arrangement of intercolumniations by which two triglyphs are obtained in the frieze between the triglyphs that stand over the columns.

Diu'resis (Gr. dia, and ouron urine), in pathology, an increased flow of urine. -Diuretic, increasing the secretion of urine.

Diur'ni (Lat. diurnus daily), in natural history, a term variously applied: in entomology, to a family of lepidopterous insects, from their flying chiefly during the day; and in ornithology, to a section of the Accipitres, or birds of prey.

Divarica'tion (Lat. to straddle apart), in botany and physiology, a branching at an obtuse angle; a forking; a crossing or intersection of fibres at different angles.

Diver'gence (Lat.), in natural history, the condition of two lines or organs emanating and branching from a common point or centre. In optics, Divergent rays are those which, going from a point of the visible object, are dispersed, and continually depart one from another in proportion as they are removed from the object..

Divertimento, in music, a short, pleasant composition, vocal or instrumental, written in a light and familiar style. Dr. Busby.

Diving Bell, in hydrostatical science, an apparatus consisting of a bottomless chest of cast-iron, into which men are placed, and supplied with air by means of an air-pump through a flexible tube, the air in the apparatus preventing the water from ascending into it, as in the case of an inverted tumbler immersed in water. Doc'imacy (Gr. dokimasia), in materia medica, a process for determining the purity of medicines. In medical jurisprudence, it is a term applied to a series of tests to which the lungs of a new-born child are subjected, for the purpose of determining whether it has respired after birth or not. In metallurgy and chemistry, the art of testing and assaying the purity of metallic bodies.

Docimology (Gr.), a treatise on the art of assaying or examining metallic bodies, &c. (See Docimacy.)

Do'deca (Gr.), a prefix to compound words, signifying twelve.

Dodecagon (Gr. twelve-angled), in geometry and mathematics, a figure of twelve angles or sides. The area of a dodecagon is three times the square of the radius of a circle inscribed in it, or 11'1961524 of the square on the

side.

Dodecagyn'ia (Gr.), the Linnæan name for any order of plants in which the number of pistils is twelve.

Dodecahedral (Gr. twelve-sided), in geometry, consisting of twelve equal sides. In mineralogy, Dodecahedral corundum is one of the names of the mineral spinel, the colours of which are blue, brown, black, green, and white. It consists of alumina, silica, magnesia, oxide of iron, and lime. Dodecahedral garnet is a species of the garnet, of which there are ten sub-species. Dodecahedral mercury is a mixture of mercury and silver which occurs in quicksilver mines with cinnabar.

Dodecahedron (Gr. twelve-sided), in crystallography, a figure with twelve sides, either triangular, quadrangular, or pentagonal.

Dodecan'dria (Gr. dodeka, and andres males), a class of plants in the Linnæan system having twelve stamens. -Dodecandrian is an epithet applied to plants that have twelve to nineteen stamens. - Dodecapetalous, having twelve petals.

Dodec'astyle (Gr.), in architecture, a building that has twelve columns in front.

Dolab'riform (Lat. dolabra an axe, and forma), in botany, an epithet applied to certain fleshy leaves which are straight at the front, taper at the base, and compressed, dilated, rounded, and thinned away at the upper back end, so as to appear axe-shaped. -In zoology, shaped like a hatchet, as the foot of certain bivalves.

Dol'erite, in mineralogy, a variety of trap rock, consisting of augite and Labrador spar.

Dollar (Swed. Dan. and Germ. daler, or thaler), in the science of numismatology, a silver coin of different States, of the average value of 4s. 2d. The dollar is coined in various States,

but the general type of the whole is the Spanish dollar, which is minted at the rate of 8 to the Castilian mark (3550 troy grains) of silver. The dollar is still minted at the rate of 8 to the mark in all the SpanishAmerican republics except the Columbian. That of the United States is of nearly the same value, 4s. 2 d., containing 3714 grains of pure silver. -Cycl. of Commerce.

Dolly, in mining, a perforated board placed over a tub containing the ore to be washed.

Dolomite, in mineralogy, a variety of magnesian limestone which occurs in mountain masses, sometimes slaty and translucent on the edges. It constitutes a portion of the Apennines. Compact dolomite is snow-white and very hard. It consists of carbonate of lime and carbonate of magnesia. -Dolomitic marble is a variety of dolomite of a white colour, occurring in small granular concretions. Dol'orite, in mineralogy, a variety of trap rock.

Doric (from Doris, in ancient Greece), in architecture, the Doric order is the second of the five orders, being that between the Tuscan and the Ionic. Temples of this order were usually dedicated to Juno, Minerva, Mars, and Hercules. Its proportions are: the height of the column, including the capital and base, sixteen modules, which, divided into eight parts, give two for the architrave, three for the frieze, and three for the cornice. Doris (Gr.), in astronomy, the name of a planet or asteroid, first noticed by Goldschmidt in 1857. Dorsal (Lat. dorsum a back), in natural history, an epithet of frequent occurrence, applying to the back, and often used as a prefix to scientific compounds.

Dorsibran'chiates (Lat. back-gills), in ichthyology, an order of the Annelids, in which the branchiæ are equally distributed along the whole of the body. Dorsocervical Region (Lat. dorsum, and cervix the neck), in anatomy, the region at the back part of the head. Dosology (Gr. dosis that which is given, and logos a discourse), a discourse or treatise on the proper administration of doses of medicine. Dossil (old Fr.), in surgery, a nodule or lump of lint to be laid on a sore. Double, a term of frequent use in connection with art and science.-In music, Double octave is an interval composed of fifteen notes in diatonic progression;-Double-bass is a large musical instrument of the viol kind. -In navigation and seamanship, Double-banked is having two opposite oars managed by rowers on the same bench, or having two men to the same oar.

Doublet (Fr.), in optics, a magnifying glass, consisting of a combination of two plane convex lenses. - In lapidary work, a counterfeit stone, composed of two pieces of crystal, and sometimes glass, softened together with their proper colours between them, that they may have the same appearance to the eye as if the whole substance of the crystal had been tinged with these colours. -Craig.

Douche (Fr.), in therapeutics, the name given to a shock of a column of fluid on the body, of a nature, temperature, and volume determined by the circumstances of the case.

concave

Doucine (Fr.), in architecture, a moulding, convex below and above, which serves as a cymatium to a cornice.

Dover's Powder, in pharmacy, a compound of ipecacuanha, opium, and sulphate of potash; an excellent sedative and sudorific..

Dovetail Joint, in anatomy, the serrated articulation or suture of the bones of the skull, &c.

Draco (Gr. and Lat. a dragon), in zoology, a genus of saurian reptiles (the Dragons), which are distinguished by a development of the gular skin, or expansive membranes on the sides of the body. In entomology, the name of an insect found in India and Africa, and distinguished from the Lizard tribe merely by having a broad lateral membrane, strengthened by radii or bony processes. It lives among trees, and is able, by means of the membrane, to spring from tree to tree. In meteorology, Draco volans is a term applied to a meteor in cold marshy countries, consisting of phosphuretted or carburetted hydrogen, which, in certain excitements and combinations, becomes lumi

called the Guinea-worm) in the muscular parts of the legs and arms. Dragan'tin, the name of a mucilage obtained from gum tragacanth. Dragon (Gr.), in zoology, a genus of Saurian reptiles, characterized by two wing-like projections of the skin. -In architecture, a term applied to a horizontal piece of timber on which the angle rafters of a roof pitch. Dragon Fly, the common name of the neuropterous insects belonging to the genus Agrion or Libellula. Dragon's Blood, the indurated drops from the cut wood of the tree Pterocarpus draco.

Dragon's Head and Tail, in astronomy, the nodes of the planets, or the two points in which the orbits of the planets intersect the ecliptic. Drain Traps, in the arts, certain contrivances for preventing the escape of foul air from drains, but admitting the water into them.

Drastic (Gr. effective), in pharmacy, an epithet applied to medicines which are powerful and rapid in their operations and effects.

Draught Com'passes, in engineering and the arts, compasses with movable points, used for drawing the finer lines in mechanical plans, &c. Dredging Machine, in excavation, an engine used for taking up mud or gravel from the bottom of rivers or docks.

Dressing, among type-founders, a process by which they dress the casting of letters for the use of printers by scraping and bearding, &c. In agriculture, manure spread over land.In joinery, Dressings is a term applied to the architraves, and to all sorts of mouldings beyond the naked walls or ceilings.

Drift (Dan. and Sax. drifan), in geology, a term applied to the diluvian formation of the earth's crust.-In mining, a passage cut out under the earth between shaft and shaft, or turn and turn. In architecture, the horizontal force or tendency which an arch exerts to overset the piers.In navigation, the angle which the line of a ship's motion makes with the nearest meridian when she drives with her side to the wind and waves, and is not governed by the helm. Dropsy (Gr. hydor water, and opsis appearance), an unnatural appearance of water in any part of the body.

Dropwort, in botany, a British flowering herb of the order Spiræaceæ, sometimes called Queen of tho Meadow.

Drosera'cese (Gr. droseros dewy), in bo