The New Gresham Encyclopedia Part 17

Pyrocollodion: highly nitrated, soluble gun-cotton. Adopted by the United States.

White Gunpowder: a mixture of pota.s.sium chlorate, pota.s.sium ferrocyanide, and sugar. Very sensitve, and only used in the laboratory.

PROPELLANTS FOR SHOT-GUNS

Amberite: insoluble nitrocotton 18.6 per cent, nitrates 28 per cent, soluble nitrocotton 46 per cent, vaseline 6 per cent.

Du Pont Smokeless Powder: nitroglycerine 10 per cent, ammonium nitrate 67.5 per cent, wood-pulp 8 per cent, salt 15 per cent (for coal-mines).

Soluble nitrocotton 46 per cent, metallic nitrates 2.2 per cent (for shot-guns).

E.C. Powder: insoluble nitrocotton 44 per cent to 48 per cent (Empire Powder), soluble nitrocotton 30 per cent to 34 per cent, metallic nitrates 14 per cent to 9 per cent, vaseline 6 per cent to 7 per cent, camphor 4.6 per cent.

Ideal Powder: made by n.o.bels.

Neonite. Similar to the above compositions, but containing 73 per cent of insoluble nitrocotton, 9 per cent soluble nitrocotton. It is also made for rifled small-arms especially for rim-fire rifles.

New Explosives Company Smokeless Powder. Similar to above.

Rifleite: insoluble nitrocotton 1.7 per cent, soluble nitrocotton 82.5 per cent, nitro-body 4.8 per cent. The nitrocellulose is made from curc.u.ma.

Ruby Powder: a cheap non-solvent powder, 46 per cent insoluble nitrocotton, 4 per cent soluble nitrocotton.

Smokeless Diamond and Stoumarkel Smokeless are similar to above.

PROPELLANTS FOR RIFLED FIRE-ARMS

Amide Powder: ammonium nitrate, pota.s.sium nitrate, charcoal. Has also been used in German artillery.

Ammonpulver: ammonium nitrate and charcoal. Has been used by Austrian artillery, and lately reintroduced by the Germans.

Ballist.i.te: equal parts of nitroglycerine and soluble nitrocotton with some mineral jelly.

Cordite: the princ.i.p.al smokeless powder of the British Empire.

Indurite: gun-cotton and nitrobenzene. Abandoned by U.S. navy.

Neonite: a gelatinized powder. Contains nitrocellulose insoluble and soluble, metallic nitrates, and vaseline.

Noddite: a strip sporting-rifle powder containing nitroglycerine, nitrocellulose, mineral jelly.

Rottweil Smokeless Powder: a gelatined powder containing camphor and diphenylamine.

See also _Grenade_; _Sh.e.l.l_; _Torpedo_; _Fireworks_; _Rockets_.

EXPO'NENT. In algebra a^3 denotes three a's multiplied together; a^n means that n of the letter a are to be multiplied. These numbers or letters placed immediately above and to the right of another number or letter are called exponents, and indicate the power to which the number or letter is raised. Exponents can be fractional or negative, in which case new interpretations can be found. On the a.s.sumption that a^m a^n = a^{m+n} for all values of m and n, a^{1/n} is interpreted as the nth root of a, a^{-n} as the reciprocal of a^n.

EXPONENTIAL THEOREM. If a^x = N, x is said to be the logarithm of N to the base a. There are two bases of logarithms in common use, the base 10 and the Napierian base e. The exponential theorem states that the value of e^x is given by the infinite series 1 + x + x^2/(1.2) + x^3/(1.2.3) + ... + x^n/(1.2.3..n) +, &c. Putting x equal to 1, e = 1 + 1 + 1/(1.2) + 1/(1.2.3) + 1/(1.2.3.4) +, &c. e can be expressed to any number of decimal places by working out the value of the terms on the right-hand side. It is an incommensurable number which to five decimal places is equal to 2.71828.

See _Logarithm_.

EXPORTS. See _Foreign Trade_.

EX POST FACTO, in law, a term designating something as done after and bearing upon something previously done; thus a law is said to be _ex post facto_, or retrospective, when it is enacted to punish an offence committed before the pa.s.sing of the law.

EXPOSURE, the situation of a building, &c., with respect to sun and wind; 'aspect' with regard to the quarter of the heavens. A house facing south-west or south-east will be found much healthier than one facing due north; and as it is also warmer, less fuel will be required for heating purposes.

EXPRESSED OILS, in chemistry, are those which are obtainable from bodies only by pressing, to distinguish them from mineral and essential oils, which last are, for the most part, obtained by distillation.

EXTENSION, (1) in physics and metaphysics, that property of a body in virtue of which it occupies a portion of s.p.a.ce. (2) In logic, _extension_ is the extent of the application of a general term, that is, the objects collectively which are included under it; thus, the word figure is more extensive than triangle, circle, or parallelogram; European more extensive than French, Frenchman, German, &c. Matter and mind are the most extensive terms of which any definite conception can be formed. Extension is contrasted with _comprehension_ or _intension_.--Cf. t.i.tchner, _Text-Book of Psychology_.

EXTINCTEUR (eks-tan-t_eu_r), an apparatus for the extinction of fire, consisting of a metallic case containing water and materials for generating carbonic acid. When required, the materials are brought into contact by pushing a rod which breaks a bottle containing acid, the gas mixes with the water, and the pressure generated is sufficient to project the water charged with the gas to a distance of 40 or 50 feet.

EX'TRACT, a term to denote all that can be dissolved out of a substance by a specified menstruum, such as water, alcohol, ether, &c. In modern pharmacy the term is applied to two kinds of preparation from vegetables.

One is got by digesting the plant in water or other solvent, and evaporating or distilling away the excess of solvent until the extracted matter is sufficiently insp.i.s.sated. The other is got by bruising the plant in a mortar, separating the juice, warming it until the green colouring-matter separates, and filtering it off. The juice is next heated until the alb.u.men coagulates, and again filtered. The juice is now evaporated to a syrup, the green colouring-matter added and well mixed, and the evaporation is thereafter continued until the required concentration is attained. Extracts must be capable of being redissolved, so as to form a solution like that from which they were derived. Extracts are used in cookery, medicine, and the manufacture of perfumery.--_Extract of Meat_ (_extractum carnis_) is a soft, yellowish-brown solid, or very thick syrup, which is employed as a portable soup. It is now manufactured on the large scale by processes proposed by Liebig.

EXTRADI'TION (Lat. _ex_, out, and _tradere_, to hand over), the act by which a person accused of a crime is given up by the Government in whose territories he has taken refuge to the Government of which he is a subject.

Conventions have been entered into by Britain with almost all civilized countries for the apprehension and extradition of persons charged with particular offences, especially those of the most heinous stamp, such as murder, robbery, embezzlement, arson, rape, and piracy. The Extradition Act of 1870 makes special provision that no criminal shall be surrendered for a political offence, and that the criminal shall not be tried for any but the crime for which he was demanded. Other British Extradition Acts are those of 1873, 1895, and 1906. See _International Law_.--Cf. Sir E. Clarke, _The Law of Extradition_.

EXTRAVAGAN'ZA, in music or the drama, a species of composition designed to produce effect by its wild irregularity and incoherence; differing from a burlesque in being an original composition and not a mere travesty.

EXTRAVASA'TION (Lat. _extra_, beyond, and _vas_, vessel), an escape of some fluid, as blood or urine, from the vessel containing it. _Blood extravasation_, in contusions and other accidents, is when blood-vessels are ruptured by the injury, and the blood finds its way into the neighbouring tissues. In some accidents to the urethra and bladder extravasation of urine is a very serious occurrence.

EXTREME UNCTION has been, since an early period, one of the seven sacraments of the Roman Catholic Church. It is performed in cases of mortal disease by anointing in the form of a cross, the eyes, ears, nose, mouth, hands, feet, and reins (in the case of males). It is administered after confession and the eucharist, and is believed to remove the last stains of sin. It can only be administered by a bishop or priest, and is not applied in the case of young children or excommunicated persons.

EXU'MA, GREAT and LITTLE, two of the Bahama Islands. The former is 30 miles long and 3 miles wide, and has a good harbour. Pop. 3465.

EYALET ([=i]'a-let), a former administrative division of the Turkish Empire, subdivided into sanjaks or provinces, and kazas or districts. It was ruled by a pasha, and gave place to the vilayet on the reorganization of the empire in 1871.

EYCK ([=i]k), Hubert and Jan van, brothers, famous painters of the old Flemish school, born at Maaseyck, Hubert in 1366, Jan probably about 1385.

They lived first at Bruges, whence the younger brother is called John of Bruges, and afterwards at Ghent, to which they removed about 1420. Here they executed the celebrated _Adoration of the Lamb_ for the Cathedral of Ghent; a painting which, in its different parts, contains above three hundred figures, and is a masterpiece. It was in two horizontal divisions, comprising ten panels, of which only the two central ones remain at Ghent, the others being at Berlin. Hubert did not live to see it completed. He died at Ghent (1426), as did also his sister Margaret, who was likewise a painter (1431). Jan finished the work in 1432, and returned to Bruges, where he remained till his death, which took place in 1441, and executed several excellent pieces. His reputation became very great even during his lifetime, by his share in the introduction of oil-painting; the original invention of which has been incorrectly ascribed to him by many. Jan van Eyck also introduced improvements in linear and aerial perspective, and in painting upon gla.s.s. Three portraits by Jan van Eyck, _The Scholar_, _The Man with a Turban_, and _Giovanni Arnolfini and his Wife_, are in the National Gallery, London; the _Madonna of the Chancellor Rollin_ is in the Louvre.--Cf. W. H. J. Weale, _John and Hubert van Eyck_.

EYE, the organ of vision, is an instrument presenting some a.n.a.logy to a photographic camera. It is provided with a lens for focussing images upon a sensitive membrane called the _retina_. The walls of the globe of the eye are formed princ.i.p.ally of two fibrous membranes: one white and opaque--the _sclerotic_ (Gr. _skl[=e]ros_, hard)--which envelops two-thirds of the globe posteriorly; and the other transparent, and resembling a h.o.r.n.y plate, whence its name, _cornea_ (Lat. _corneus_, h.o.r.n.y). The sclerotic is a tough fibrous coat, and is the part to which the phrase 'white of the eye' is applied. In the front of the globe the sclerotic is abruptly transformed into the transparent portion (the cornea), which is circular, and which forms a window through which one can see into the interior. A membrane, the _conjunctiva_, so named because it unites the eye to the lid, spreads over the anterior portion of the globe, and then folds back on itself and lines the internal surface of the eyelids. On the internal surface of the sclerotic is a vascular membrane called the _choroid_. This is essentially the blood-vessel coat of the eyeball. About the place where the sclerotic pa.s.ses into the cornea the choroid becomes continuous with the _iris_, a round curtain, the structure seen through the cornea, differently coloured in different individuals. In its centre is a round hole, the _pupil_, which appears as if it were a black spot. The _iris_ forms a diaphragm suspended in the s.p.a.ce behind the cornea which is filled with clear fluid, the _aqueous humour_. The _iris_ consists of a framework of connective tissue, and its posterior surface is lined by cells containing pigment which gives the colour to the eye. In its substance are bundles of involuntary muscular fibres, arranged in a ring round the margin of the pupil. In a bright light the circular fibres contract and the pupil is made smaller; but in the dark these fibres relax and allow the pupil to dilate more or less widely, thus allowing more luminous rays to enter the eye. Just behind the pupil is the _crystalline lens_, resembling a small, very strongly magnifying gla.s.s, convex on each side, though more so behind. Minute bands of muscle in the choroid can alter the convexity of the lens, and thus adapt its focus to the position of objects at different distances. The large s.p.a.ce in the globe of the eye that intervenes between the retina lining its inner surface and the lens in front is occupied by a transparent jelly-like ma.s.s called the _vitreous body_. The internal surface of the choroid, or rather the pigmentary layer which covers it, is lined by the retina or nervous tunic upon which the images of the objects that we see are focussed. The retina is a very complex mechanism consisting of certain elements which are stimulated by light, and others that transmit the effects of such stimulation as a nervous current to the optic nerve which carries it to the brain. It is composed of cones and cylinders or _rods_, joined together like the stakes of a palisade, perpendicular to the plane of the membrane, and forming by their free extremities a mosaic, each microscopic division of which is about 0.0008 of a line in diameter according to Helmholtz, and represents a section of a rod. These rods and cones are believed to be the agents by whose aid the waves of light become transformed into the stimulus of a sensation. The ocular globe is put in motion in the orbit by six muscles, grouped two by two, which raise or lower the eye, turn it inward or outward, or on its antero-posterior axis. In these movements the centre of the globe is immovable, and the eye moves round its transverse and vertical diameters. These three orders of movements are independent of each other, and may be made singly or in combination, in such a manner as to direct the pupil towards all points of the circ.u.mference of the orbit. Each eye is furnished with two eyelids, moved by muscles, which shield it from too much light and keep it from being injured. They are fringed with short, fine hairs called eyelashes; and along the edge of the lids is a row of glands similar to the sebaceous glands of the skin. The eyebrows, ridges of thickened integument and muscle, situated on the upper circ.u.mference of the orbit and covered with short hairs, also regulate to some extent the admission of light by muscular contraction. In reptiles, some fishes (sharks, &c.), in birds, and in some mammals a third eyelid or nict.i.tating membrane is present, and can be drawn over the surface of the eye so as to clear it of foreign matters, and also to modify the light. The lachrymal apparatus is composed of, firstly, the _lachrymal gland_, which lies in a depression of the orbital arch; secondly, the _lachrymal ca.n.a.ls_, by which the tears are poured out upon the conjunctiva a little above the border of the upper lid; thirdly, the _lachrymal ducts_, which are destined to receive the tears after they have bathed the eye, and of which the orifices or _lachrymal points_ are seen near the internal ends of the lids; fourthly, the _lachrymal sac_, in which the lachrymal ducts terminate, that empties the tears into the _nasal ca.n.a.l_. The tears, by running over the surface of the conjunctiva, render it supple and facilitate the movements of the globe and eyelids by lessening the friction. The influence of moral or physical causes increases their secretion, and when the lachrymal ducts do not suffice to carry them off they run over the lids.

[Ill.u.s.tration: Section of the Human Eye]

_Vision._--The retina renders the eye sensible of light, and we may therefore consider it as the essential organ of vision. The function of the other portions is to focus the luminous rays on the surface of the retina, a condition necessary for distinct vision and the clear perception of objects. The visual impressions are transmitted from the retina to the brain by means of the optic nerve. The two optic nerves converge from the eyes toward the centre of the base of the brain, where there is a partial interlacement of their fibres in such a manner that a portion of the right nerve goes to the left side of the brain, and a part of the left nerve to the right side; this is called the _chiasma_ or _commissure_ of the optic nerves. The princ.i.p.al advantage of having two eyes is in the estimation of distance and the perception of relief. In order to see a point as single by two eyes we must make its two images fall on corresponding points of the retinas; and this implies a greater or less convergence of the optic axes according as the object is nearer or more remote. To accommodate the eye to different distances the lens is capable of altering itself with great precision and rapidity. When we look at a near object, the anterior surface of the lens bulges forward, becoming more convex the nearer the object; the more distant the object the more the lens is flattened. When the transparency of the cornea, the crystalline lens, or any of the contents of the globe of the eye is destroyed, either partially or entirely, then will partial or total blindness follow, since no image can be formed upon the retina; but although all the media and the cornea be perfectly transparent, and retain their proper forms, which likewise is necessary to distinct vision, yet injury or inactivity of the optic nerve, or injury of the parts of the brain with which it is connected, may produce disturbance of vision or total blindness. Defective vision may also arise from the crystalline lens being so convex as to form an image before the rays reach the retina (a defect known as short sight or myopia), in which case distinct vision will be procured by interposing a concave lens between the eye and the object of such a curvature as shall cause the rays that pa.s.s through the crystalline lens to meet on the retina; or the lens may be too flat, a defect which is corrected by convex lenses. In old age, and in fact in most people after about forty-five years of age, the elasticity of the lens becomes reduced, and convex lenses become necessary to make it possible to focus near objects. This condition is known as _presbyopia_. In the lower organisms the organs of sight appear as mere pigment spots. In higher forms, simple lenses or refracting bodies occur. Insects, crustaceans, &c., have large ma.s.ses of simple eyes or ocelli aggregated together to form compound eyes--the separate facets or lenses being optically distinct, and sometimes numbering many thousands. In the cephalopods well-developed eyes presenting a distant a.n.a.logy in structure to those of the highest animals are found; and in all vertebrate animals the organ of vision corresponds generally to what has been described, though they vary much in structure and adaptation to the surroundings of the animal.--Cf. J. Herbert Parsons, _Diseases of the Eye_.

EYE ([=a]), a munic.i.p.al borough, England, county Suffolk, 19 miles north of Ipswich. Up till 1885 it sent a member to Parliament, and it still gives its name to a parliamentary division of East Suffolk. Pop. 1781.

EYEBRIGHT (_Euphrasia officin[=a]lis_), a small plant belonging to the nat.

ord. Scrophulariaceae, which is common in Britain and most parts of Europe, in North Asia, &c. It is an annual, half-parasitic on gra.s.s-roots, from 3 to 8 inches high, often much branched. The whole plant has a bitter taste.

Under the name of _euphrasy_ it formerly enjoyed a great reputation in diseases of the eyes.

EYEMOUTH, a fishing-town of Berwickshire, Scotland, at the mouth of the Eye, an important place in the thirteenth century. Pop. 2477.

EYE-PIECE, in a telescope, microscope, or other optical instrument, the lens, or combination of lenses to which the eye is applied. As the use of a single lens limits the field of view, eye-pieces are generally formed from two lenses or lens systems, called the eye-lens and the field-lens, placed at a distance apart. The Ramsden or positive eye-piece consists of two lenses of equal focal length placed at a distance apart equal to two-thirds of the focal length of either lens. The object looked at requires to be a short distance in front of the field-lens. In the Huyghens or negative eye-piece the focal lengths of the field- and eye-lenses are in the ratio 3 to 1, and the distance between the lenses is twice the focal length of the eye-lens. As a result the image formed by, say, the objective of a telescope is in focus when between the two lenses.

EYLAU ([=i]'lou), a small town, about 28 miles distant from Konigsberg, in Prussia, famous for a b.l.o.o.d.y battle fought between Napoleon and the allied Russians and Prussians, on the 7th and 8th of Feb., 1807. Both sides claimed the victory. The loss of the Allies was about 20,000 men, while that of the French must have been considerably greater.

EYRE ([=a]r), Edward John, Australian explorer and colonial governor, born in Yorkshire 1815, died in 1901. He went to Australia in 1833, in 1839 discovered Lake Torrens, and in 1840 explored its eastern sh.o.r.es and the adjacent Flinders Range. He then commenced his perilous journey along the sh.o.r.es of the Great Australian Bight, and reached King George's Sound, in Western Australia, a distance of 1200 miles, with a single native boy, having left Adelaide more than a year before. In 1845 he published _Discoveries in Central Australia_. After filling several governorships, he was appointed Governor of Jamaica in 1862. In 1865 he was confronted with a negro rebellion, which he crushed with some severity, and was recalled. On his return to England John Stuart Mill and other so-called humanitarians took measures to try him for murder, but failed. Tennyson and Carlyle were among his most strenuous defenders.