the roof; false gables are not uncommon in Italian ecclesiastical archi tecture. In ecclesiastical architecture of the Romanesque and pointed Gothic periods the gables are very important features. In our own country, church gables of the Norman and Early English periods are usually finished with a flat or moulded coping at the sides; and frequently terminated with a cross or finial at the apex. Sometimes in rich Early English and Decorated examples crockets are carried up the coping. Gables of Decorated and Perpendicular date, sometimes have a parapet, either plain, pierced, panelled, or battlemented. In old English secular architecture also, the gable was made a highly decorative feature either constructively or by the addition of ornamental barge-boards. [BARGE-BOARD.] Numerous examples of all the kinds of gables here referred to will be found in Messrs. Brandon's Parish Churches,' and Paley's 'Ornamental Gables.' For examples of some of the many varieties of Elizabethan gables see ELIZABETHAN ARCHITECTURE. In some English houses of the time of Elizabeth and James I., and commonly in old Scottish and continental buildings (especially those of Flanders, Holland, and Germany) the sides of gables are formed like a series of steps: these are known as stepped-gables, in Scotland they are termed corbie-steps. The small gable-like ornaments over niches, on buttresses, &c., in Gothic architecture are called Gablets: see examples under BUTTRESS, col. 472. GADUIN. A brown matter said to be contained in cod liver oil. Its composition is unknown, and its existence as a distinct compound very doubtful. GAEL, GAELIC. Although the language spoken by the Scottish Highlanders is familiarly known among the Lowlanders by the name of the Erse, or, according to the more usual pronunciation, the Ersh,— that is, plainly, the Eirish or Irish,-the people themselves are never called by that name. Among the Highlanders the name Erse is unknown, either as that of the nation or of the language. They call themselves only the Gadhel, also sometimes written and always pronounced Gael; and their language the Gaedheilg, pronounced Gaeilg, or, nearly, Gaelic. The name Gaelic is also in familiar use among the Lowlanders as that of the language. Further, the only name by which the Irish are known to the Scottish Highlanders is Gael; the latter call themselves Gael Albinnich, or the Gael of Albin, and the Irish Gael Erinnich, or the Gael of Erin. The Irish also call themselves the Gadhel, or Gael; and their language the Gaelic. Finally, the Welsh call the Irish Gwyddel, which is evidently the same word with Gadhel, or Gael. This is nearly all that can be stated as matter of fact in regard to the name Gael. The rest is all speculation and conjecture; of that, however, few words have given rise to so much. We shall not here attempt to do more than to indicate and arrange the various points as to which many volumes of philological and historical controversy have been written. It has been generally assumed and admitted that the modern Gael are a portion of the Galli, or Gauls, of antiquity, the people who gave its former name to the country now called France, and who were principally, though by no means exclusively, known to the Greeks and Romans as the inhabitants of that region. This opinion has been adopted upon the grounds of the similarity of the two names,-some historical and traditional testimony to the fact that South Britain was originally peopled from Gaul,--some traces, rather faint and disputable, of identity of institutions and customs,—and, what would be the strongest argument, if it were well made out, the evidences of identity of language conceived to be established by the comparison of the names of places in France, and a few other remains of the old language spoken there, with the modern Gaelic of Scotland and Ireland. The Rev. Archdeacon Williams, in an essay printed in the 'Transactions of the Royal Society of Edinburgh,' vol. xiii., has been the strongest supporter of this theory, and maintains that the Galli Veteres, or Umbrians, of the Romans, the inhabitants of Gallia Cisalpina, were of the Cumic or Cymric races; that their language "formed some portion of the nonHellenic elements of the Latin tongue; that the race was cognate with the Cymri of Wales, and that they were Celts, and not Germans." Supposing the Gael to be the Galli of the Roman writers, and the Galatai (ráarai), or Kellai (KeλTai), of the Greeks, sometimes spoken of by the ancients as a general name for the Gauls, sometimes as the name of only a certain portion of the Gauls, the question arises, whence did the Gaels of Ireland, Scotland, and Wales derive their origin? A tradition exists that Ireland was colonised from Spain, where Celtic tribes certainly existed, and that the Highlands of Scotland were peopled from Ireland. This is not improbable; and Wales might have received the stock from the coast of France. This would account for the variations of the dialects. Diefenbach (Sprachliche Documente zur Geschichte der Kelten ') conjectures Galloway and Northumberland to have received the Celtic element from Ireland, and concludes that the Picts were the sea-rovers of Scandinavia. See also Zeuss's 'Grammatica Celtica e monument vetustistam Hibernicae ling. quam Britannicae Dialecti Cambricae, Cornica, Armoricae, nec non e Gallicae priscae reliquiis construxit,' Leipsic, 1853, as well as J. von Görres, Die drei Grund-Wurzeln des Celtischen Stammes in Gallien und ihre Einwanderung.' Munich, 1845-6. There has been a world of controversy, also, about the origin and meaning of both Gael and Celt (anciently, it is to be remembered, pronounced Kelt); the confusion here again being increased by the difference of opinion as to whether these are different words or only different forms of the same word. The Greek Galatai and Keltai, the Latin Galli, the Gael of the Scotch and Irish, and the Galles of the French for Wales, seem all but variations of the same word. It is hardly necessary to enter into the meanings which the words Gael and Celt bear in the ancient Gaelic language, though they have caused much discussion. It would occupy much more space than we can afford to enumerate even the more important works in which these various controverted points have been discussed in our own and other languages. We shall only mention The Highlanders of Scotland, their Origin, History, and Antiquities,' by W. F. Skene, 2 vols., 8vo, London, 1837, being an essay to which a prize had been awarded by the Highland Society of London. Mr. Skene's views and reasonings are of considerable ingenuity; but whatever may be thought of the part of it which relates to the origin of the Gael, the work is an important contribution to early Scottish history. The essay by the Rev. Archdeacon Williams, 'On One Source of the Non-Hellenic Portion of the Latin Language,' printed in vol. xiii. of the Transactions of the Royal Society of Edinburgh,' read in March, 1836, has much ingenious argument and learning in support of the theory we have already mentioned. GAGE or GAUGE, any apparatus for measuring the state of a phenomenon. But the term is usually restricted to some particular instruments, such as the gage of the air-pump, which points out the degree of exhaustion in the receiver; the steam-gage, for measuring the pressure of steam; and the gas-gage for that of gas; also the wind-gage [ANEMOMETER], the tide-gage, &c., all of which are mentioned in connection with their several subjects. There are also various gages used in certain trades and manufactures, such as the rod-iron gage, the nailrod gage, the button maker's gage; others are used in watch-work; there are also the gun-maker's gage, and gages for measuring wires and sheet metals. These generally consist of thick plates of steel of several sizes and forms, around and near the edges of which holes are drilled, with a notch leading from the edge into each hole. There is no system in the gages in common use, so that much confusion arises in attempting to reduce the measure to a common standard. Thus, the Birmingham gage for iron-wire, sheet-iron, and steel, differs from that used for sheet-brass, gold, silver, &c., and both these differ from the Lancashire gage for round steel wire. To render the confusion worse, gages nominally of the same value are made by different manufacturers without sufficiently agreeing as to the unity of measure. To avoid these inconveniences, our best tool makers have long advocated the adoption of a uniform scale. Mr. Holtzapffel, in the appendix to the second volume of his Mechanical Manipulation, proposes to employ only the decimal divisions of the inch, and thos under their true appellations only. The division of the inch into a hundred parts would be sufficiently minute; and the measures 1, 2, 5 10, 50, &c. hundreds would be sufficiently impressive on the mind It does not follow that the entire hundred notches should be used; a in the greater thicknesses of wire and sheet metal the gradations from one size to another are not so minute as in those of the thinner kind. In the measurement of precious metal, where a hundredth of an inch might be too much, either there might be half-degrees or numbers, or a finer scale might be adopted below one-tenth of an inch. Holtzapffe enumerates the following advantages as likely to result from the use of such a decimal scale for denoting the thickness of wires, sheets, plates &c. :-It would introduce a system which would be easily and equally known to all whom it might concern, and who would all interpret it ir the same sense. It would facilitate the employing of verbal and written instructions, by lessening the chances of mistake or misinter pretation. It would render very easy the proportioning of various magnitudes so as to form a series. It would enable quantities to be written down more easily and accurately than at present. It would facilitate the comparison of one size with another; seeing that in vulgar fractions each has a specific relation to the unit, whereas in decimal fractions all have a general relation in common. It would bring all foreign measures within more easy reach of our knowledge It would allow the exact weight in every superficial foot of sheet metals and other substances to be readily arrived at, by taking the specific gravity as the other element in the calculation. Lastly it would furnish constant multipliers for determining, from the specific gravities of substances, the exact thicknesses of plates or sheets of the same which shall precisely weigh one ounce or one pound, troy or avoirdupois. The graduation into hundredths being effected, the nomenclatures would follow easily; let a wire one-tenth of an inch in diameter, or a plate or sheet one-tenth of an inch thick, be called No. 10, and so on for other dimensions: there will then be swept away a large amount of confusion which now besets our factories and workshops. Nearly related to this subject is Mr. Whitworth's exquisite contrivance for gaging or measuring minute quantities. In the Proceedings of the Institution of Mechanical Engineers, for 1859, an account of this remarkable machine is given; showing it to be the most accurate measuring apparatus yet devised. Newton's colures of thin plates, interpreted by formula of later introduction, show that a millionth of an inch is an appreciable quantity in relation to the breadth of waves of light; but Mr. Whitworth is the first who has felt justified in dealing with such extremely minute quantities as being measurable by strictly mechanical means. He can measure the relative lengths of two small pieces of steel, of which one exceeds the other by not more thar one millionth of an inch. Nay, he feels confident of being able to test even one-half of this minute quantity. If we touch a piece of cold metal for an instant with the fingers, it expands by the increase of heat and the amount of this expansion we can measure. If the bar be a yard long, the touch even by a finger-nail is sufficient to produce an elongation which his machine can determine. The mechanism by which the astonishing result is produced mainly consists of exquisitely cut screws with graduated nuts or heads. At present, this is rather a scientific than a manufacturing agent; but Mr. Whitworth has succeeded in bringing into use new gages for wire-drawers and the manufacturers of sheet metal, in which the thousandth of an inch is an admitted and practicable element. Gages are now made, having decimal numbers on one side from No. 18 to No. 300, measuring from 018 to 300 of an inch. It will be for the manufacturers to decide how many thousandths of an inch there shall be in any particular sheet or wire; but this point once determined, Mr. Whitworth's gage will enable them to measure it. He observes, "I consider that for the shop the use of standard gages is better than any measuring machine, on account of the difficulty of using a sufficiently delicate instrument in regular shop-work, and the greater liability there would be to alteration in the standard both of diameter and length." GALATIANS, ST. PAUL'S EPISTLE TO THE, one of the canonical books of the New Testament. Its authenticity has never been doubted: it was frequently cited by the apostolical and succeeding fathers (Lardner's Credibility of the Gosp. History,' vol. ii.), and was admitted by Marcion to a place among the apostolical writings. The date of this epistle is much disputed, some critics supposing it to have been written as early as A.D. 48, and others as late as 58. Two journeys of St. Paul to Galatia are mentioned in the Acts; one in A.D. 50 (Acts xvi. 6); and the other in 55 (Acts xviii. 23). It must have been written shortly after one of these visits, since St. Paul complains (i. 6) "that they were so soon removed from him that called them into the gospel of Christ unto another gospel." Michaelis, 'Introduction,' vol. iv., contends that it was written soon after the first visit, which took place probably about A.D. 49 or 50. But in chap. iv. 13, St. Paul himself says, "Ye know how through infirmity of the flesh I preached the gospel unto you at the first (TO TрÓTEроv)," which proves that the apostle had visited them twice; and thus we may conclude that it was written after the second visit, or about A.D. 56 or 57, an opinion coincided in by the great majority of critical authorities. It is stated at the conclusion to have been written from Rome, but this is probably incorrect, though Michaelis and others support it. It appears that shortly after St. Paul had left Galatia, some Judaising teachers had effected a great change in the churches of that country by teaching the Gentile converts that it was necessary for them to observe the ceremonial law, and submit to the rite of circumcision. They alleged that the other apostles taught this doctrine, and that St. Paul alone differed from them. They argued that the Galatians ought not to rely upon the authority of St. Paul, since he was not an apostle. These individuals were so successful that some of the Galatians appeared to have submitted to circumcision. To counteract these errors St. Paul wrote this epistle, in which he maintains that the authority of the other apostles could not be quoted as superior to his own, since he had received his apostleship from Christ himself, and had on this very subject "withstood Peter to the face, because he was to be blamed." (i. ii.) After thus vindicating his apostolical dignity, he argues in the remaining part of the epistle that the law had only been intended as a preparation for Christianity, as a schoolmaster to bring men unto Christ, that they might be justified by faith," and that those who considered the observance of the Jewish law as necessary for salvation deprived themselves of the blessings of the Gospel. He concludes by exhorting them not to use the liberty which the Gospel gave them " for an occasion to the flesh, but by love to serve one another." On the undesigned coincidences with the 'Acts,' see Paley's 'Hora Paulina.' The number of commentaries on this Epistle have been very numerous, in Latin, German, French, and English. One by Luther is still highly esteemed. GALAXY. [MILKY WAY.] GALENA. LEAD, Sulphide of.] GALILEE, in ecclesiastical architecture. In medieval churches a portion of the western end of the church was frequently parted off from the rest and appropriated to strangers or those not numbered among the faithful. This was termed the Galilee, in allusion, as is supposed, to the scriptural "Galilee of the Gentiles." Sometimes in cathedrals it was an entrance porch, as at Ely and Lincoln; sometimes, as at Durham, a large chapel at the west end of the nave: see the plan of Durham Cathedral under CHURCH. It is said that this Galilee was built for the use of females, who were prohibited passing beyond the north porch in Durham Cathedral. In some parish churches a portion of the western end of the nave was marked off by a step or line of division, and called the Galilee. GALIPEA. (Materia Medica.) The genuine Angostura or cusparia bark is obtained from a species of this genus, but whether from the G. cusparia, as stated by Humboldt, or from a distinct species, G. officinalis, as asserted by Dr. Hancock, is not determined. Angostura bark is obtained both from the stem and branches; the specimens from the stem are flat, from 2 to 3 lines thick, while those from the branches are often quilled, and from to 1 line thick. The pieces are sometimes from 6 to 15 inches, but more frequently only from 2 to 6 inches long, and from to 2 inches broad. Some specimens have the surface covered with a thick, fungus-like, whitish-yellow or clay-coloured crust, which may be more or less easily scraped off, and beneath which is a yellowish-red smooth bark, often exhibiting small cracks. Other specimens have this covering much thinner and closely adhering to the bark. The internal surface is generally smooth, of a tawny or reddish-yellow colour. The bark is easily broken, and the recent fracture is of a brownishred colour, smooth, with a resiny shining surface. The shining appearance is best seen when a transverse section is made with a sharp knife. The smell is disagreeable: the taste pleasantly bitter, warm, aromatic, and causing a flow of saliva. The powder has the colour of rhubarb. The infusion is of an orange-yellow colour; the decoction a clear light brown. Brandes thought that he had discovered an alkaloid, which he proposed to call Angosturin, but it has not been detected by subsequent chemists. This bark contains neither gallic acid nor tannin. According to the analysis of Fischer it consists ofVolatile oil (of an acrid nature) 0.3 Bitter hard resin 1.7 So minute an account of this substance would not be necessary, were not the true Angostura bark liable to be confounded with the false, which possesses such poisonous properties that very fatal consequences have resulted from the substitution of the one for the other. bark which comes from the East Indies, is the bark of the Strychnos It has been ascertained beyond any doubt, that the false Angostura nux vomica. But even in Calcutta this false bark is confounded with rohuna, the harmless bark of Soymida febrifuga. [SOYMIDA.] False Angostura bark was first observed in 1804 by Dr. Rambuch, of Hamburg, by poisonous effects following the use of a decoction of the Austrian government ordered all the Angostura bark in the the bark; and similar consequences having been observed at Vienna, empire, genuine as well as false, to be burnt, and interdicted its future importation. The Russian and Würtemburg authorities made known the denger, and published the marks of distinction, which are sufficiently characterised, and to prevent accidents, may be here enumerated. SPURIOUS. Pieces of greater breadth than length; thickness never less than a line, often two lines. Epidermis generally clear (but sometimes undergoing a peculiar transformation), and seldom having any, or not more than two lichens (Opegrapha Pelletieri, and Pyrcnu'a nitida). A species of chiodecton has been supposed to be found on it, but this appearance arises from an alteration of the epidermis. The crust has the general properties of the bark, and assumes a deep green by the action of nitric acid. It contains a resinous colouring principle, Strychnochromin. Crust not easily removed. Inner surface brown, or even black, not separable into layers. Texture compact, heavy, not easily broken, fracture even, but not shining or resinous, exhibiting two layers. Very difficult to cut. Scarcely softens in water. No smell. Taste in the highest degree dis gustingly bitter; very durable, and not at all aromatic or astringent. Spurious Angostura bark, in the dose of eight grains, killed a dog in two hours; ten grains killed a young dog in a few minutes. A very small glassful of an infusion endangered the life of an adult, while a dose of the decoction destroyed a child with acute suffering. Ether and laudanum seem to act as antidotes. Oil of turpentine may be GALLSTONE. [CHOLESTERIN.] GALLEON (galoion in French, galen in Spanish) was the name given to very large ships, with three or four decks, of which many were employed in the Spanish Armada in 1588. Subsequently the name became restricted to the large vessels which the court of Spain used to send at fixed periods to the coasts of Mexico and Peru, to receive on board the gold and silver bullion extracted from the mines, and bring it to Spain. Commodore Anson intercepted, and captured after a short engagement, one of these galleons on its way from Acapulco to Manilla. GALLERY of Mine is the passage leading from the shaft or entrance of the mine to the place where the powder is deposited. MILITARY.] GALLERYTHRONIC ACID. [TANNIO ACID.] [MINE, GALLEY (galère in French, galera in Italian and Spanish), a largesized vessel propelled by oars and sails, which was much in use in the Mediterranean until the end of the 18th century. It carried two masts with lateen sails, was long and narrow, and drew but little water; it was therefore calculated for coast navigation, and for making the shore in shallow water; and by means of its oars it had a great advantage, in the dead calms so frequent in the Mediterranean, over sailing vessels, an advantage in which it has been effectually superseded by the introduction of the steam-boat. Even long before that invention the use of galleys as a naval force had been given up by France, their construction rendering them unfit for long navigation, and for encountering the waves of the ocean. The Knights of Malta, Naples, the Pope, and other Italian states, were the last to continue the use of galleys for the purpose of coping with the Barbary privateers, whose vessels, although of a similar description, were generally smaller and unable to resist the large and well-disciplined galleys of the Christian powers. The largest galleys were 166 feet long and about 32 wide, with 52 oars. The rowers, who were generally convicts or Turkish prisoners, with chains to their feet, sat on benches on the deck. The ship carried a 24-pounder and two 8-pounders. (See a description and plate of a large-sized galley in the Dictionnaire de Marine,' article Galère in the 'Encyclopédie Méthodique.') The galleys appear to have been an imitation of the ancient triremes, and they retained the ancient names for several parts of the rigging, such as 66 antenna," &c. The felucca is a kind of small galley. [FELUCCA.] The Venetians had a sort of large galley, with a very lofty poop, called "Galeazza.” GALLIARD (Gagliarda, Ital.), a lively dance in three-crotchet time, which had its origin in Rome, but has fallen into disuse. GALLIC ACID. (3HO,C,,H,O,+2Aq.) The well-known astringent property of various parts of plants is due to the presence of tannic or gallic acids. Gallic acid occurs in far less abundance than tannic acid. It may be extracted directly, by precipitating tannic acid from an aqueous infusion of a bark, root, &c., by means of solution of gelatine, and then evaporating the filtered liquid, which contains the gallic acid, to dryness. The residue, digested in alcohol, treated with animal charcoal and the solution allowed to evaporate spontaneously, yields the gallic acid in a crystalline state. Gallic acid is, however, usually prepared by a kind of fermentation from the tannic acid in nut-galls. [GALLS, in NAT. HIST. DIV.] Powdered galls, well moistened with water, are exposed in a warm place to the action of the air for two or three months. Mould rapidly forms on the surface of the mass, and must be occasionally removed; oxygen is absorbed and carbonic acid evolved. On subsequently boiling the whole in a considerable quantity of water, gallic acid is dissolved out, and is deposited in crystals on the cooling of the liquor. When obtained quite pure, by recrystallisation from alcohol, and ARTS AND SCI. DIV. VOL. IV. Yellowish green colour. Carbonate of Potass. Dark red colouring, with slight precipitate. Greenish colouring, with dirty yellow precipitate. the usual treatment with animal charcoal, gallic acid is obtained in long, silky, nearly colourless needles or prisms of astringent taste, but no odour. They are soluble in one hundred times their weight of cold water, but in three parts of boiling water. Alcohol dissolves them readily, ether only sparingly. A heat of from 410° to 420° Fahr. causes the decomposition of gallic acid into pyrogallic acid which sublimes in brilliant white crystals, and carbonic acid, which is evolved as gas. The sudden application of too high a temperature (above 480°) to gallic acid causes the evolution of water as well as carbonic acid and metagallic acid or gallulmic acid remains. Ebullition with strong solution of potash converts gallic acid into tannomelanic acid. Gently heating with sulphuric acid converts it into rufigallic acid, while nitric acid rapidly oxidises gallic acid to oxalic acid. Gallates are formed by the union of gallic acid with bases. In this way three classes of salts result:— In the solid state the gallates are tolerably stable, in solution they rapidly absorb oxygen if exposed to the air and are decomposed. The characteristic reaction for the detection of gallic acid is the production of a deep bluish-black solution on the addition of a mixture of protoand per-salts of iron. GALLIOT, a strong-built flat-bottomed vessel of a peculiar construction, used as a bomb-ship to fire against forts or batteries on the coast. The largest are of the burden of 400 or 500 tons, and above 100 feet in length. See account and plate of the same in the 'Dictionnaire de Marine,' in the 'Encyclopédie Méthodique,' art. "Galiotte." Galliot is also a kind of small galley or large felucca, used chiefly in the Mediterranean, especially by the Barbary corsairs. [GALLEY.] The Dutch, Swedes, and other northern nations have a sort of merchant-ship which they call Galliot, heavy and clumsily built, but strong of timber, rounded both fore and aft, and of the burden of from 200 to 300 tons. GALLITANNIC ACID. [TANNIC ACID.] GALLON, an old English measure of capacity. The Latin of the middle ages is galo, galona, jalo, lagena, &c. Dr. Bernard thinks the latter is the original. Ducange cites an old assize of David of Scotland, in which it is said the lagena should contain 12 lbs. of water, namely, 4 of sea water, 4 of still water, and 4 of running water. But that various gallons were used is evident from statutes of Henry III. and later kings, in which it is enacted that ale, wine, and corn shall be measured by the same gallon, containing eight troy pounds of dry wheat from the middle of the ear. These statutes produced no effect, and distinct gallons for wine, ale, and beer, and corn and dry goods, continued in use until the Act of 5 Geo. IV., c. 74, which came into operation May 1, 1825. By statutes of 1689 and 1697, the wine gallon was declared to contain 231 cubic inches. But in 1688, by an experiment, at which Flamsteed, Halley, and others (among whom was Ward, author of the 'Young Mathematicians' Guide,' who relates the circumstance) were present, it was very distinctly proved that the sealed gallon at Guildhall (which was the usual standard) contained only 224 cubic inches. "However," says Ward, "for several reasons it was at that time thought convenient to continue the former supposed content of 231 cubic inches." The fact was, that the Guildhall gallon was an incorrect copy of the old Exchequer standard, placed in a more accessible locality. Previously to this, Dr. Bernard had stated his full conviction, from the measurements of predecessors whom he cites, that the said gallon contained 223-549 cubic inches; the agreement of these two experiments leaves no doubt as to their accuracy. By the Act of the 5th of Queen Anne, the wine gallon of 231 inches was made the standard; and a gallon was accordingly constructed for the Exchequer, 8 which the committee of the House of Commons, in 1758, found to contain 231 cubic inches. The account of the experiment in 1688 was preserved, and is cited by the committee. The ale gallon was measured in 1700 or thereabouts, and found to contain 282 cubic inches. Ward imagines that this gallon was meant to bear the same relation to a pound avoirdupois which the wine gallon did to a pound troy; and 231 is to 282, very nearly as 5760 to 7000, the latter being the proportions of the two pounds. But if the wine gallon were only 224 cubic inches, then the ale gallon should have been 272; or, as we shall see, the corn gallon much more nearly coincides with the hypothesis. The corn gallon was thought, in the middle of the last century, to contain exactly 2724 cubic inches. Dr. Bernard, on the same authorities, states it to have been determined at 266 cubic inches; and the statute of 1697, which declares that a round corn-bushel must be 8 inches deep and 18 inches wide, had in fact fixed the gallon at 268% cubic inches. The imperial gallon, as settled by the Act of Geo. IV., is to contain 10 lbs. avoirdupois of distilled water, of which it is declared that 252-458 grains fill a cubic inch consequently, the imperial gallon contains 277 274 cubic inches; being very nearly a mean between the old ale and (previously to 1697) corn gallon. According to the parliamentary standards, then, we have Old wine gallon, 231 cubic inches. GALLULMIC ACID. [GALLIO ACID.] GALVANIC BATTERY. An apparatus for generating current electricity. The simplest combination which can be formed for this purpose, is that of a plate of zinc and a plate of copper placed, generally, in vertical positions and parallel to one another in a vessel containing a diluted acid, the upper edges of the metals being connected by a copper wire. In this state a current of positive electricity passes from the zinc, through the acid, to the copper, and from the latter, along the wire to the zinc: at the same time a current of negative electricity passes from the zinc, along the wire, to the copper, and from thence, through the acid, to the zinc. It is evident that the quantity of fluid furnished by a combination of this kind will be proportional to the superficies on which the acid can act; and an apparatus designated a battery, which may be said to consist of two plates only, one of zinc and the other of copper, was executed many years ago for the London Institution. Each plate was 50 feet long and 2 feet wide, and the two were coiled together upon a cylinder of wood, so as to leave everywhere an interval between the two metals: in that interval rope-bands of horse-hair were passed round with the coils so as to keep the metals asunder. The dilute acid was contained in a cylindrical vessel; and when the battery had to be used, the coils of metal were lowered by machinery into the vessel. C One of the earliest forms of apparatus was the pile of Volta, in which were combined together a considerable number of small plates of zinc and copper, alternately, with the acid between them. Under GALVANISM are explanations of the electrical action that takes place, and we here merely describe the construction of the pile. A circular plate of zinc, 2, usually about 14 inch diameter and inch thick, is laid upon and generally soldered to a thin plate of copper c, of equal diameter; and any convenient number of these are placed above one another, with the copper side undermost in all between every two compound plates is a circular piece of paper p, or cloth moistened with diluted sulphuric acid; and the whole column or pile is made to preserve a vertical position by being formed within three pillars of glass or baked wood, which are connected together by having their extremities inserted in boards, of which the lower one serves as a base for the column. The paper or cloth should be rather less in diameter than the plates of metal; and no moisture should be allowed to escape over the edges of the plates. : In this state the lowest plate of zinc attracts the positive electricity from the copper below it, and this continually receives a supply from the earth through the table, or the base of the pile; the quantity thus attracted is conveyed to the copper plate immediately above, through the moistened cloth, the latter serving as a conductor: again, the zinc in the second plate attracts electricity from the copper below it, and, at the same time, receives that which is transmitted to the latter from the zinc in the lowest plate. Thus the quantity of positive electricity in the zinc of the second plate becomes nearly twice as great as that which is in the lowest plate; and the process continuing, the quantity in the zinc of each plate above may be conceived to be such a multiple of that which is in the lowest plate as is expressed by the number of the compound plate from the bottom of the pile. There is consequently obtained a current of positive electricity passing upwards from the zinc, through the acid, to the copper; and if a copper wire be made to pass from the top of the uppermost zinc plate to the copper in the lowest plate, the same current will return downwards, so that a circulation of the fluid will continue till the energy of the pile is exhausted. At the same time there is a current of negative electricity passing down the pile from the copper, through the acid, to the zinc, and returning upwards along the wire. If a second pile be formed, the plates in it may be placed in a reverse order, the copper side above and the zinc side below if a third pile be formed, the order may be the same as in the first pile; if a fourth, the same as in the second; and so on: then, in uniting them together, a metal wire passes from the copper at the bottom of the first pile to the zinc at the bottom of the second; another wire passes from the copper at the top of the second to the zinc at the top of the third, and so on. When a wire connects the opposite ends of one pile, or of a system of piles, the circuit is said to be complete: it is said to be broken if there are two separate wires, one proceeding from the copper at bottom, and the other from the zinc at the top. If an animal body were in connection with the farther extremities of the wires it would complete the circuit, and experience shocks. The opposite extremities of the pile, or of the wires which are in contact with them, are called the poles of the battery. As the current of positive electricity seems to issue from the zinc at the top of the pile, that extremity is called the positive pole of the battery; at the same time the negative electricity seems to issue from the copper at the bottom, and therefore the terminating copper plate is called the negative pole. These designations are reversed when a single pair of plates separated by an acid is mentioned. In that case, since the positive electricity passes from the zinc plate, through the acid, to the copper-plate, and the wire passes through the air from the edge of the copper to that of the zinc plate; it is evident that the positive electricity will flow from the copper, and therefore the copper is the positive pole of the combination; the negative electricity flowing at the same time along the wire, from the zinc, the latter is the negative pole. The terms positive and negative poles, as applied to the extremities of the battery, have been objected to on the ground that before connecting the two terminal wires no electricity is evolved, and when the connection is formed the electricity moves in a circuit, no portion of which is apparently more positive or more negative than another portion. Hence Faraday proposed, instead of pole, the word electrode, which signifies a way for the negative pole cathode, signifying the descending way or downwards; and for the positive pole anode, which signifies ascending way or upwards. In forming these terms he supposed the battery to be placed on the ground with its copper or + end to the east, and the wire connecting the ends of the battery to be bent into an arc, similar to the course of the sun; in such case the electric current would flow up from the east end of the battery, and descend into it at the west end. The fluid decomposed by a current passing through it was termed an electrolite: the elements liberated by the decomposition were termed ions; those which appeared at the cathode were named cations, and those set free at the anode anions; thus in the decomposition of sulphate of copper the metal is the cation, and the acid the anion. Daniell employed the word platinode for the negative, and zincode for the positive pole; while Graham introduced the terms zincous and chlorous poles, to represent the+and. Much of this nomenclature appears to us to be as uncouth as it is unnecessary: it was introduced at a time when the introduction of the constant battery by Daniell, and the splendid discoveries by Farnday, had somewhat unsettled the scientific mind on the subject of voltaic electricity. The new terms, with a few exceptions, have scarcely obtained a footing; which is not surprising, seeing that the old expressions positive and negative poles, and electro-positive, and electro-negative bodies, are far more simple and quite as accurate as the terms by which it is proposed to supersede them. As the arrangement of the pile was inconvenient for experimental purposes, and, moreover, did not give much power, and the power that it did give was soon exhausted, an arrangement was introduced called the trough battery, of which there were many forms. The first consisted of the pile, with the plates on edge, cemented into grooves made in three sides of a wooden trough, spaces being left between every two compound plates for pouring in dilute acid, which took the place of the paper or cloth. In another form, the trough was made of glazed earthenware, by nine or more parallel partitions of the same material, which permitted no communication between one cell and another. As many pairs of plates, zinc and copper, of equal superficies, as there were partitions, were provided; the two plates of each pair were soldered or fastened together at their upper extremities, so that they might be parallel to one another; and all were united together by a rod of wood, so that they could at once be placed into or removed from the cells. The bridges or connections between the zinc and copper plates stood directly over the partitions, so that there was a copper and a zinc plate in each separate cell, except at one extremity of each trough, in which, till two troughs were connected together, the cell had only a zinc plate. When one trough was to be connected with another, in order to increase the battery, a slip of copper, as at a, soldered at the top of a zinc plate, was bent and made to enter the cell B, containing only a zinc plate at one end of the preceding trough. In order to form the complete circuit, one extremity of a wire was series of troughs, where it was placed in contact with the copper slip, as a the positive current then flowed along the wire from the extremity first mentioned to the other. The above form was contrived by Mr. Children; but Dr. Wollaston proposed, as an improvement upon it, to have in each cell a zinc plate between two plates of copper; for thus both surfaces of each zinc plate would become efficient in producing the electric current, and the power of the battery would be increased by one half. The battery at the Royal Institution was of Mr. Children's kind; it contained 2000 pairs of plates, each 8 inches long and 4 inches deep, and with it Sir Humphry Davy made his principal discoveries. The battery invented by Professor Daniell consists of any number of cylindrical vessels of copper, open at the top, about 16 inches high and 3 inches in diameter, and containing a saturated solution of sulphate of copper; the exterior surface of each may be painted, but the interior, which alone is efficient in producing electricity, is made bright. On the top of the cylinder is placed a hemisphere a of wood, through which, in the direction of the axis of the cylinder, is a perforation above an inch in diameter; and to its base is attached a short tube b of copper, less in diameter than the cylinder, and carrying near its upper extremity an annular plate e of copper, in which are pierced several small holes. When the wooden cover is 2 placed on the cylinder its base rests on the top of the latter; and the part of the cylinder between the short tube and the annular plate is filled with crystals or pieces of sulphate of copper, which, gradually dissolving, preserve the strength of the solution in the lower part of the cylinder. ༤ To the interior of the short tube was affixed, in the original arrangement, one end of a piece of ox gullet d, about the same length as the copper cylinder, and having its lower extremity tied so that the whole formed a membranous bag; this is to contain diluted sulphuric acid (eight parts water to one of acid). A rod of zinc z, about the same length as the cylinder, an inch in diameter, and terminating at the upper extremity with a brass ball, is passed through the perforation in the wood, down the interior of the membrane, so that its shoulder rests on the top of the wood; the surface of the zinc being previously covered with an amalgam of mercury. Instead of a membrane, a bag of paper or canvas, or a vessel of porous earthenware, may be more conveniently used. If now, a connection, by means of a wire or metallic rod, were made between the ball at the top of the zine rod and the top of a stem e which rises from one side of the copper cylinder, the zinc will be corroded by the sulphuric acid, and the electric fluid will pass to the copper through the acid, the membrane, and the solution in the cylinder. [GALVANISM.] The battery invented by Mr. Grove consists of several porous vessels containing strong nitric acid, and, in each, a rod or plate of platinum; each of these vessels is placed between two plates of zinc within a trough in which is diluted sulphuric or muriatic acid. The rod of platinum holds the place of the plate of copper in Children's battery, and constitutes the negative pole of each combination; the zinc plate being the positive pole. By mixing sulphuric acid with the nitric acid in the porous cells, a more uniform current is obtained. This battery is expensive, and must be placed under a chimney or a hood to carry off the nitrous fumes. For the sake of economy Bunsen uses, instead of the platinum, cylinders of carbon prepared by heating a mixture of powdered coke and caking coal, or powdered coke moistened with a strong solution of sugar. The carbon answers very well while fresh, but it soon deteriorates by absorbing the nitric acid. Poggendorf uses sheet or cast iron, which is not acted on by strong nitric acid. In Smee's battery the negative or conducting plate is of silver, on which finely divided platinum has been deposited, this roughness of surface facilitating the escape of the hydrogen; each side of the silver plate is exposed to a plate of amalgamated zinc of the same size, which acts as the positive plate, and is excited by dilute sulphuric acid. Grove's gas battery possesses a theoretical, rather than a practical interest. It is stated, under GALVANISM, that the amount of force set in motion in a voltaic arrangement depends on the difference between the affinity of the two metals for the active principle, or radicle of the acid. The liquid which excites the chemical action is decomposed, its elements are separated, and they either combine with the metallic plate, or accumulate on its surface. By these means the voltaic action is opposed and enfeebled, in consequence of the tendency of the com ponent parts of the fluid to re-unite; for example,'when dilute sulphuric acid is used, it is important to get rid of the hydrogen which adheres to the platinum, and produces a counter-current, which may be made evident by connecting a platinum plate, opposed to a zinc plate with a galvanometer wire, when, on attaching to the other end of the galvanometer wire another platinum plate, free from hydrogen bubbles, and plunging both into dilute acid, the needle will be powerfully deflected. In the gas battery a plate covered with oxygen, is opposed to a plate covered with hydrogen. A cell of this battery consists of two tubes; through the upper end of each is soldered a platinum wire attached to a platinum plate extending to the bottom of the tube. The hydrogen tube has twice the capacity of the oxygen, and the tubes are supported in a vessel containing dilute sulphuric acid. At the beginning of the experiment the tubes are filled with the dilute acid, and are charged with gas, by being connected with a voltaic battery. When the tubes are in this way charged, they are separated from the battery, and the mercury cups at the top of the tubes being connected with a galvanometer there is a strong deflection of the needle, and by connecting 8 or 10 cells in such a way that the oxygen of one cell may be connected with the hydrogen of the next cell, sparks between charcoal points and various chemical decompositions may be obtained. The gases gradually diminish in bulk, but the current is maintained so long as they remain uncombined. For the formation of a voltaic circuit, it is usually stated that two dissimilar metals, and a fluid acting upon one of them, are required. We have seen in the case of the gas battery a variation from this rule, which may be still farther departed from in various ways. For example:-if a single metal be plunged one end into a liquid capable of acting on it, while the other end is dipped into a different liquid communicating freely with the first liquid, but having little or no action on the metal, a current will be established. If, for example, we place in the bend of a U tube a piece of tow, and in one limb pour in a solution of chloride of copper, and in the other limb one of common salt, and connect the two open ends of the tube by means of a strip of copper dipping therein, crystals of copper will be formed upon the end of the strip immersed in the metallic solution, while the end of the strip immersed in the salt and water will be corroded, and chloride of copper be formed. By using various liquids in the two limbs, Becquerel has obtained many of the metals in beautiful crystalline forms. It has also been shown that similar actions are going on within the earth's crust; for by connecting, by means of wires attached to a galvanometer, the surfaces of two contiguous lodes of ore, the existence of feeble but continuous currents was detected. The battery used at first by Professor Wheatstone for his electrical telegraph was formed nearly on the same principle as that of Mr. Daniell. A small outer vessel contained a solution of sulphate of copper, together with the plate of copper which formed the negative pole; within this, a small porous cell contained diluted sulphuric acid, and at the bottom was an amalgam of zinc and mercury, which constituted the positive pole. Various other forms of battery, and also an electro-magnetic apparatus, have been employed for working the telegraph. [TELEGRAPH.] A notice of galvanic apparatus would not be complete without referring to Deluc's dry pile, which consists of circular disks of paper, one surface of which is coated with leaf gold or silver, and the other surface with zinc foil. Some thousands of these disks are arranged in a glass tube, with all the zinc surfaces in one direction, and the silvered or gilt surfaces in the other direction. If these disks be pressed together, and a wire attached to each end, the leaves of the gold-leaf electroscope may be made to diverge by touching the cap of the instrument with one end of the pile, and connecting the other end with the earth. If the two ends of the pile be made to terminate in metal disks placed about an inch or so from each other, and be well insulated, an insulated slip of gold-leaf suspended midway between them will oscillate backwards and forwards for months, and even years. A dry pile consisting of 20,000 disks gave sparks, and charged a Leyden battery so as to produce shocks. The term dry pile is, however, a misnomer, since the action depends on the moisture contained in paper when exposed to the air if the paper be artificially dried the pile ceases to act. Zamboni substituted finely-powered peroxide of manganese for the gold or silver leaf, with good effect. The pile terminated in metal plates, which compressed the paper disks by means of ligatures of silk, and the pile was insulated by giving it a coating of sulphur. In all voltaic actions power is transferred by means of a polar influence propagated through the solid as well as the liquid particles of the circuit. As a consequence of polarisation we get electric tension, the effects of which may be shown by a numerous series of alternations of zinc and copper (Mr. Gassiot's battery consisted of 3520 pairs), each |