both crystallized and massive, and consists of silica, alumina, lime, oxide of iron, potash of soda, and water: sp. gr. 2.926.

Prepuce (Fr. from Lat. præputium), the skin which is removed by circumcision; that fold of integument which surrounds and envelops the glans penis.

Presbyopia (Gr. presbys old, and ops the eye), in pathology, a state of the eye observed in advanced age, arising from a flattening of the cornea, and partial loss of the refractive power of the eye.

Pressiros'ter (Lat. pressus, and rostrum a bill), in ornithology, a tribe of wading birds, including those which have a flattened or compressed beak. Pretib'ial (Lat. præ, and tibialis belonging to the legs), in anatomy, situated anteriorly to the tibia. Pricking-up, in architecture, the first coating of plaster in work of three coats.

Primary (Lat. primus first), an epithet of frequent application in art and science. In astronomy, primary planets are those which revolve round the sun as their centre, in distinction from secondary planets or satellites, which revolve round the primaries. In painting, primary colours are those into which a ray of solar light may be decomposed. Newton supposed them to be seven : red, orange, yellow, green, blue, indigo, and violet. - In geology, primary, is a term sometimes applied to those old formations composed of gneiss, mica slate, chlorite slate, and clay slate or other rocks which have undergone great change.

Prime (Lat. primus), in dialling, prime vertical is a vertical circle which is perpendicular to the meridian.-In arithmetic, prime numbers are numbers which have no divisors.

Primitiæ (Lat.), the first-fruits of any production of the earth, which were uniformly consecrated to the Deity by all the nations of antiquity. Prim'itive (Lat.), a term frequently applied to scientific objects. The primitive form of a crystal is one of the regular geometrical solids which a crystal presents on its being split as much as possible in its cleavage. -In painting, the primitive colours are red, yellow, and blue, from the mixtures of which all other colours are obtainable.

Primula'cesæ, in botany, a nat. order of herbaceous plants, of which Primula, or Primrose, is the type. The more common species are the Primrose, P. vulgaris; the Cowslip, P. veris ;

the Oxlip, P. elatior; and the Auricula, P. auricula.

Primum Mobile (Lat. the first mover), that which puts everything in motion; a term frequently used in ancient astronomy.

Prince's Metal, in metallurgy, an alloy of three parts of copper to one of zinc, forming one of the many varieties varieties of brass; called also Prince Rupert's metal.

Principle (Lat. principium beginning), a term sometimes applied to an elementary substance; but sometimes those substances which are the peculiar results of the combination of organized with inorganic matter are called proximate principles. - In science generally, a truth admitted either without proof or as having been already proved.

Priodon'tes (Gr. saw-teeth), in zoology, a division of the Armadillos, consisting of Dasypus gigas, or Great Armadillo, distinguished by having twenty-two to twenty-four small teeth on each side of the jaws. Prion'idæ (Gr.), a family of coleopterous

insects.

Prism (Fr. from Gr. prisma), a geometrical figure or solid, whose two ends are parallel, equal, and straight, and whose sides are parallelograms. -In optics, an instrument or prism of glass whose ends are triangles.Prismatic, relating to or formed as a prism.-Prismatic colours, the seven colours into which a ray of light is decomposed when refracted from a prism.

Pristina, in ichthyology, a sub-family of the Squalidæ, of which the Pristis, or Saw-fish, is the type.

Probe (Lat. probo to prove), a surgical instrument for examining wounds.Probe-scissors, surgical scissors used to open wounds. Proboscis (Gr. pro before, and bosho to feed), a prehensile organ formed by the prolongation of the nose, as the trunk of an elephant.-Proboscidians are a family of pachydermatous Mammals, including those which have the nose prolonged into a prehensile trunk or proboscis, as the Elephant and Mastodon.

Problem (Gr. proballo to throw forward), in geometry, a proposition in which some operation or construction is required, as to divide a line, to raise a perpendicular, &c. It consists of three parts-the proposition, the resolution or solution, and the demonstration.

Procar'dium (Gr. pro, and kardia the orifice of the stomach), in anatomy, the pit of the stomach.

Procœlian (Gr.), in anatomy and zoology, noting those vertebræ which have a cavity or cup at the fore part of the body, and a ball at the back part.

Procon'dyli (Lat. pro, and condylus a knuckle), in anatomy, the bones of the fingers next the back of the hand.

Proctag'ra, Proctalgia, Proctitis, and Proctopso'sis (Gr. proktos the anus), in pathology, terms applied to painful affections of the anus.

Proc'tocele (Gr. proktos, and kele hernia), in pathology, inversion and prolapse of the mucous coat of the rectum, from relaxation of the sphincter.

Procyon (Gr. pro, and kyon a dog), in astronomy, a star of the second magnitude in the constellation Canis Minor. It is uncertain whether this star, or Sirius, is properly the Dogstar of the ancients.

Product (Lat. produco to produce), in arithmetic and algebra, the result or quantity produced by multiplying one number by another; as, 24 is the product of 6 and 4, being produced by the multiplication of these numbers. In geometry, the factum of two or more lines.

Proempto'sis (Gr. happening before), in chronology, the lunar equation or addition of a day, necessary to prevent the new moon from happening too soon according to the civil calculation.

Progno'sis (Gr. pro, and ginosko to know), in pathology, that part of medicine by which the progress and termination of diseases are judged. Progres'sion (Lat.), in arithmetic and algebra, series of quantities or numbers advancing or proceeding in the same manner, or according to a certain law. It is either arithmetical, geometrical, or harmonical. An arithmetical progression is one of which the quantities proceed by some common difference, as 2, 4, 6, 8, &c., the common difference being 2. A geometrical progression is one in which the successive terms increase or decrease by a common ratio, as 2, 4, 8, 16, &c., the common ratio or multiplier being 2.-In music, a re

gular succession of chords or movement of parts in harmony. Projectile (Lat. projicio to throw forward), a body projected or put in motion. The science of projectiles is that branch of mechanical philosophy which treats of the motions of bodies impelled from the surface of the earth, and acted on by gravity and the resistance of the air.

Projection (Lat.), a term applied to the projection of the sphere, of which there are three principal points-the stereographic, in which the eye is supposed to be placed on the surface of the sphere; the orthographic, in which the eye is conceived to be at an infinite distance; and the gnomonic, in which the eye is placed in the centre of the sphere. Prolapsus (Lat. prolabor to slide down), in pathology, the falling down or protrusion of a part through the orifice with which it is naturally connected, as of the uterus, rectum, &c. Prolate (Lat. prolatum extended).-In geometry, a prolate spheroid is a solid produced by the revolution of an ellipse about its tranverse diameter; the figure produced by the revolution of an ellipse about its shorter axis is termed an oblate spheroid.

Prolegs, in entomology, the fleshy pediform organs which serve various larvæ instead of legs.

Prolepsis (Gr. pro, and lambano to take), in chronological science, an anachronism when an event is dated before the usual time.-Proleptical, in pathology, is applied to a periodical disease, the paroxysm of which returns at an earlier hour at every repetition.

Promerop'ide (Gr. pro, and merops the bee-eater), in ornithology, a family of tenuirostral birds, of the order Passeres, of which the Hoopoe is the

genus.

Promethean, a small glass tube containing concentrated sulphuric acid, surrounded with an inflammable mixture.

Prom'ontory (Lat.), in geography, a high point of land projecting into the sea beyond the line of coast; a headland.

Promus'eis (Gr.), in entomology, a term applied to the sucking organ of hemipterous insects.

Prona'tion (Lat. pronus bending forward), in anatomy, that motion of the radius by which the palm of the hand is turned downward.

Prona'tor (Lat. pronus), in anatomy, a muscle used in turning the palm of the hand downwards.

Propædeu'tics (Gr. pro, and paideuo to

instruct), the preliminary learning connected with any art or science. Prophylax'is (Gr. pro, and phylaxis a guarding), in pathology, the art of averting a disease.

Prop'olis (Gr. pro, and polis a city), a glutinous substance, with which bees close the holes and crannies of their hives.

Proportion (Lat.), in arithmetic, a term applied to the rule by which any three of four numbers so circumstanced being given, the fourth may be found. In mathematics, the equality of ratios; four numbers or quantities being said to be in proportion when the ratio of the first to the second is the same as that of

a

the third to the fourth, as 2, 6, 3, 9, in which the equal ratios of 2 to 6 and 3 to 9 may be expressed, and the proportion is written, 2:6::3:9.-In chemistry, definite proportions are the limited proportions in which elementary substances combine, so as to form compound bodies. Proportional parts is name given in logarithmic and other tables to small tables which are annexed to the differences of the tabular number, and which consist merely in setting down the several tenths of the differences, or the nearest whole numbers to them.Proportional compasses are used in mechanical drawings for diminishing or enlarging. They have two pairs of points movable on a shifting centre, which slides in a groove, and thereby regulates the proportion that the opening at one end bears to that of the other.

Propylæ'um (Lat. from Gr. pro, and pyle a portal), in architecture, the porch of a temple; the vestibule of a house. Prosen'chyma (Gr. a pouring upon), in botany, a cellular tissue, the cellules of which taper to each end, and consequently overlap each other at their extremities. It is the first approach on the part of cellular tissue to the condition of woody fibre.

Prosenneahe'dral (Gr. pros, ennea nine, and hedra a side), in crystallography, having nine faces on two adjacent parts, as a crystal.

Proserpine, in astronomy, one of the recently-discovered planets, first observed by Luther in 1853. Its mean distance from the sun is 253,260,000 miles, and its periodical revolution 4 years and 120 days.

Prostate (Gr. situated before), in anatomy, the prostate gland is a gland situated before the vesiculæ seminales. Prostate concretions, calculi of the prostate gland, consisting of

phosphate of lime, tinged by the secretions of the gland.

Prostyle (Gr.), in architecture, a range of columns before an edifice. Protea'ceæ (from the god Proteus), in botany, a nat. order of exogenous plants, consisting of small trees or shrubs, of which the Protea is the genus.

Protégé (Fr.), one who is protected or patronized by another; a dependant. Pro'teine, the gelatinous semi-transparent substance obtained from albumen, fibrine, or caseine.

Proto- (Gr. protos), a prefix to express priority; as, Protocol or Prototype, the original copy or rough draft of a treaty.

Protoplasm (Gr.), in botany, the soft nitrogenous lining or contents of cells.

Pro'tosalt, in chemistry, a term applied to oxysalts whose base is a protoxide, as protosulphate of lead. Protosulphate, in chemistry, a combination of sulphuric acid with a protoxide.

Protox'ide, in chemistry, a substance combined with oxygen in the first degree; frequently used in chemical nomenclature.

Protozo'a (Gr. protos, and zoon an animal), in zoology, a term applied to the lowest form of animal life, and corresponding with the true Infusoria. Protozo'ic (Gr.), in geology, noting the lowest system of rocks in which the traces of any organic structure have been discovered.

Prunella (Lat.), in pathology, dryness of the throat in fevers. In botany, a medicinal plant.-A preparation of purified nitre.

Prurigo (Lat.), in pathology, an itching of the skin with an eruption of pimples.

Prussiate, in chemistry, a salt formed of prussic acid and a base. Prussic, in chemistry, noting a very poisonous acid, called hydrocyanic, and forming the colouring matter of prussian blue.

Psalterium (Gr. psallo to play on the harp), in anatomy, a part of the brain, consisting of lines impressed upon the under surface of the posterior part of the body of the fornix. Psammite (Gr. psammos sand), in geology, a species of micaceous sandstone.

Psaria'nse, in ornithology, the Blackcaps, a sub-family of Muscicapidæ, or Fly-catchers, of which Psaris, or Black-cap, is the type.

Pselaph'ide, a family of minute coleopterous insects, of which the genus Pselaphus is the type.

Pseudo- (Gr. pseudes), a prefix to numerous words, signifying false or counterfeit.

Pseudoblep'sis (Gr. pseudes, and blepsis sight), in pathology, false vision, or imaginary vision of objects.

Pseudo-bulb, in botany, the solid, aboveground tuber of some of the Orchideæ. Pseudodip'teral (pseudes, dis twice, and pteron a wing), in architecture, applied to temples in which there were eight columns in front, and only one range round the cell.

Pseudo-metal'lic, in mineralogy, affording a lustre only when held to the light, as a mineral.

Pseudoscope (Gr. false view), in optics, a name given to the stereoscope when employed to produce what are called conversions of relief.

Pseudostel'la (Gr. false star), any kind

of meteor or phenomenon appearing in the heavens, and resembling a star. Psilom'elane (Gr. psilos smooth, and melas black), in mineralogy, a massive, botryoidal, dark-coloured ore of manganese.

Psittac'idæ (Gr. psittakos a parrot), in ornithology, an extensive family of scansorial birds.

Psoas, Psoæ (Gr. psoai the loins), in anatomy, the name of a muscle in the loins.

Psophi'ne (Gr.), in ornithology, the Trumpeters.

Psora (Gr.), in pathology, the itch.

Pterodactyle (Gr. winged fingers), in geology, an extinct genus of flying reptiles, of the order of Saurians. Pteropoda (Gr. winged feet), in zoology, a class of Molluscs which live in the open sea, and have a pair of flippers, or wings, by which they pass rapidly through the water. Pterosauria (Gr. winged reptiles), an order of fossil reptiles. Pterygo (Gr. pteryx a wing), in anatomy, a word used in composition, to denote muscles which are connected with the pterygoid processes. Ptisan (Gr.), in pharmacy, a decoction of barley with other ingredients. Ptolema'ic, relating to Ptolemy the astronomer, or his system of the universe, in which the earth is supposed to be the centre.

Ptosis (Gr. a falling), in pathology, a falling of the upper eyelid, with a partial or complete want of power to elevate it.

Ptyal'agogue (Gr. ptyalon spittle, and ago to excite), in pharmacy, any medicine which promotes salivation, or the discharge of saliva.

Pty'aline (Gr. ptyalizo to spit), in chemistry, an organic principle constituting about one-third of the soluble solids of the saliva, and having the power of converting starch into dextrine and into sugar.

Pty'alism (Gr.), in pathology, a flow of saliva; salivation.

the cuticle.

Pso'ries (Gr.), medicine for the itch. Psorophthalmia (Gr. psora the itch, and ophthalmia inflammation of the eye), in pathology, inflammation of the eyelids, with ulceration, &c.

Psyche, one of the newly-discovered planets, first observed by De Gasparis in 1852. Its mean distance from the sun is 278,710,000 miles; and its periodical revolution 4 years 364 days. Psychiatry (Gr. psyche the soul), medical treatment of diseases of the mind.

Psychology (Gr.), a treatise on the soul; mental philosophy.

Psychopathy (Gr. psyche, and pathos suffering), in pathology, mental dis

ease.

Psychrom'eter (Gr. psychros cold, and metron a measure), an instrument for measuring the tension of aqueous vapour contained in the atmosphere. Psychrom'etry (Gr.), the science which treats of the measurement of the moisture in the atmosphere; hygrometry.

Pterocephalinæ, a sub-family of the Raidæ, or Flat-fishes, of which Pterocephalus is the type.

part of the hypogastric region. Pubis (Lat.), in anatomy, the anterior part of one of the bones of the pelvis, corresponding with the genital organs.

Puccoon (Ind.), a red vegetable pigment obtained from a papaveraceous plant, the Sanguinaria Canadensis. Pu'ceron (Fr. from puce a flea), a tribe of small insects, which are found in great numbers on the bark and leaves of plants; the Aphides, or Plant-lice.

Puerperal (Lat.), relating to or happening after childbirth. Pulmonary (Lat. pulmones the lungs), in anatomy, an epithet applied to the various arteries, veins, nerves, and other organs connected with the lungs; and, in pathology, to the morbid affections which are seated in, or directly implicate, the pulmonary

Pulse (Lat. pulsus struck), the pulsation or motion of an artery. In botany, leguminous plants or their seeds, as Peas and Beans.

Pulsim'eter (Lat. pulsus, and Gr. metron a measure), in pathology, an instrument for measuring the quickness or force of the pulse.

Pulvil'lus (Lat.), in entomology, a membrane capable of being inflated, which covers the feet of insects, and by which they can create a vacuum, and thus suspend themselves or walk against gravity.

Pumice (Lat. pumex), a porous substance ejected from volcanoes. Pumice-stone, a slag or cinder of some fossil.

Pump (Fr.), an engine or machine by which water is drawn up from wells. -The forcing pump, a pump which is capable of driving a stream of water above the pump-barrel by means of compressed air. Chain-pump, a pump used in ships-of-war.

Pupip'ara (Lat. pupa, and pario to bring forth), in entomology, a family of dipterous insects distinguished by the larvæ issuing from the mother in the form of a soft white egg, the skin of which hardens and becomes a firm shell, from which, in time, the perfect insect emerges.

Purbeck, in geology, a fresh-water deposit, consisting of marl and limestone.-Purbeck beds constitute the lowest members of the Wealden group, lying below the Hastings sands, and immediately above the Portland beds. The Purbeck limestone abounds in organic remains. Purlin, in architecture, a horizontal piece of timber lying on the main rafters.

Purple Wood, in botany, the wood of the Copaifera pubiflora of Guiana. Purples, in pathology, spots of a livid

red colour; a purple fever.

Purpura (Lat. purple), in heraldry, one of the tinctures used in blazonry, represented in engraving by diagonal lines from the sinister to the dexter side of the escutcheon.-In pathology, the scorbutus, or scurvy; an eruption of small, distinct, purple specks and patches, attended with languor, general debility, and pain in the limbs. The varieties are-P.simplex, petechial scurvy; P. hæmorrhagica, land scurvy; P. urticans, nettle-rash scurvy; P. senilis, scurvy of old age; P. contagiosa, contagious scurvy. Pursuivant (Fr.), in heraldry, a kind of probationer in the Heralds' College. Pus (Lat.), in pathology, a peculiar fluid yielded from the blood in consequence of inflammation

Pustule (Lat.), in pathology, a cuticular elevation with an inflamed purulent base.

Puzzola'na (from Puzzuoli, whence it was brought), a substance formed of volcanic ashes more or less compacted together, and valuable for the foundation of lighthouses and other marine erections.

Pyæ'mia (Gr. pyos pus, and haima blood), in pathology, a dangerous disease, consisting of a peculiar alteration of the blood, and the formation of numerous abscesses in various parts of the body.

Pycnite (Gr. pyknos thick), a prismatic mineral, a variety of topaz, the constituents of which are alumina, silica, and fluoric acid: sp. gr. 3.57. Pyc'nodonts (Gr. thick-toothed), in geology, an extinct family of fishes which prevailed extensively during the middle period of geological history. Pycnogon'idæ (Gr. pyknos, and gonon race), a family of Entomostraca, consisting of spider-looking creatures, with eight very long unguiculated legs, of which the Pycnogonon is the type and genus. Pycnostyle (Gr. thick-columned), in architecture, an arrangement of columns, in which the intercolumniations are equal to one diameter and a half.

Pycnoti'næ, in ornithology, a subfamily of dentirostral birds, of the order Passeres.

Pylo'rus (Gr.), in anatomy, the lower orifice of the stomach, through which the food passes into the intestines. Pyophthalmia (Gr. pyon pus, and ophthalmia inflammation of the eye), purulent ophthalmia.

Pyorrhœ'a (Gr. pyon, and rheo to flow), a continued purulent discharge, especially from the genital organs, lungs, and other parts.

Pyr-, or Pyro- (Gr.), a prefix to numerous scientific words, denoting fire, or the idea of fever or heat. Thus, in chemistry, the products which are obtained by subjecting certain organic acids to heat are termed pyroacids, as pyro-citric, pyro-gallic, pyro-kinic, pyro-maric, pyro-meconic, and pyro-sorbic acids. Pyral'lolite (Gr. pyr, allos another, and lithos a stone), a mineral which changes its colour by heat.

Pyramid (Gr.), a solid figure standing on a polygonal square or triangular base, and terminating in a point at the top. In anatomy, an osseous eminence in the tympanum, enclosing the stapedius muscle. In surgery, the pivot or centre-pin attached to the crown of the trephine.