Page images
PDF
EPUB

GOWER-GOWRIE CONSPIRACY.

A difference of opinion as to the objects of government scarcely more real, though attended with far more fatal consequences than that which has divided speculative politicians, has ranged those who have dealt with government as a practical art in two opposite schools. By the one school, its object is said to be order; by the other, liberty; and each of these objects has been supposed to be attainable only to an extent proportioned to that to which the other was sacrificed. A truer insight into the laws of society has led a more enlightened school than either entirely to reverse this latter opinion; and whilst holding the two objects referred to, to be in truth the proximate objects of all government to perceive that they are not only reconcilable, but that each is attainable only in and through the other, and that the perfection with which either is realised in any particular instance will be, not in inverse but in direct proportion to that to which the other is 80. Order, so far from being the opposite of liberty, is thus the principle by which conflicting claims to liberty are reconciled. The principle which is really opposed to liberty is licence, in virtue of which the sphere of the liberty of one individual is endeavoured to be carried into that of another. To the extent to which this takes place, the liberty of both is sacrificed, for the territory in dispute is free to neither of the claimants; whereas order, by preserving the boundary between them, assigns to each the portion which is his due, and prevents the waste of liberty which is necessarily involved in the gratification of licence, and the consequent existence of anarchy. The reasons which have led men to believe that the union between the principles of order and liberty, which it is thus their mutual interest to effect, can, in large states, be effected by means of representative institutions better than by any other political expedient that has yet been devised, will be explained under REPRESENTATIVE GOVERNMENT. See also CONSTITUTION, MONARCHY, DEMOCRACY, LIBERTY EQUALITY and FRATERNITY.

GOWER, JOHN, the date of whose birth is unknown (probably about 1320), is supposed, by his latest biographer, to have belonged to the county of Kent. His history is enveloped in almost total obscurity, but he seems to have been one of the most accomplished gentlemen of his time, and to have been in possession of considerable landed property. He was a personal friend of Chaucer's, who addresses him as 'a moral Gower' in dedicating to him his Troilus and Cressida-an epithet which has indissolubly linked itself to his name. He did not long survive his great contemporary, having died in the autumn of 1408. G. was a voluminous writer, and produced the Speculum Meditantis (a poetical discourse on the duties of married life). It consisted of ten books, written in French verse, but is supposed to have perished; the Vox Clamantis, in Latin (of which there are manuscript copies in the Cottonian and Bodleian libraries); and the Confessio Amantis, by which he is best known, in English. This latter work, extending to the portentous length of 30,000 verses, was first printed by Berthelet in 1573. An excellent edition of the works of G. was published in 1857, under the editorial care of Dr Reinhold Pauli, with a memoir and critical dissertation.

G. is almost uniformly heavy and prosaic. Writing much in French, his English poem is full of NormanFrench words, and in his native tongue he never attained Chaucer's ease and mastery. Apart from literary merit or demerit, his poem is interesting to the scholar and the antiquary, because therein the elements which form our modern English are found side by side, or but indifferently fused together.

GOWRIE, CARSE OF. See PERTHSHIRE and CARSE.

GOWRIE CONSPIRACY, one of the most singular events in the history of Scotland, took place in August 1600. On the 5th of that month, as King James VI., then residing at Falkland Palace, in Fife, was going out to hunt, Alexander Ruthven, brother of the Earl of Gowrie, whose father had been executed for treason in 1584, came to his majesty, and informed him that, on the previous evening, he had seized a person of a suspicious appearance, and evidently disguised, with a pot full of foreign gold hid under his cloak, and had confined him in his brother's house at Perth. Conceiving him to be an agent of the pope or the king of Spain, the king agreed to examine the man himself, and, without waiting to change his horse, set out for Perth, attended only by the Duke of Lennox, the Earl of Mar, and about 20 others. Soon after his arrival, while his retinue were at dinner, Ruthven conducted the king up a winding staircase and through several apartments, the doors of which he locked behind him, and brought him at last to a small study, where stood a man in armour, with a sword and dagger by his side. Snatching the dagger from the man's girdle, Ruthven held it to the king's breast, and said: 'Who murdered my father? Is not thy conscience burdened by his innocent blood? Thou art now my prisoner, and must be content to follow our will, and to be used as we list. Seek not to escape; utter but a cry, make but a motion to open the window, and this dagger is in thy heart.' The king expostulated with Ruthven, who so far relented that he went to consult his brother, leaving the king in charge of the man in armour. In the meantime, one of Gowrie's servants hastily entered the apartment where the king's retinue were, and announced that the king had just ridden off towards Falkland. All hurried into the street, and the earl, with the utmost eagerness, called for their horses. On Alexander Ruthven's return to the king, he declared that there was now no remedy, but that he must die, and proceeded to bind his hands with a garter. The king grappled with him, and a fierce struggle ensued. Dragging Ruthven towards a window looking into the street, which the man in armour had opened, the king cried aloud for help. His attendants knew his voice, and hastened to his assistance. Lennox and Mar, with the greater number of the royal train, ran up the principal staircase, but found all the doors shut. Sir John Ramsay, of the Dalhousie family, one of the royal pages, ascending by a back stair, entered the study, the door of which was open, and seizing Ruthven, stabbed him twice with his dagger, and thrust him down the stair, where he was killed by Sir Thomas Erskine and Sir Hugh Herries. On the death of his brother, Gowrie rushed into the room, with a drawn sword in each hand, followed by seven retainers, well armed, and was instantly attacked. Pierced through the heart by Sir John Ramsay, he fell dead without uttering a word. The inhabitants of Perth, by whom Gowrie, who was their provost, was much beloved, hearing of his fate, ran to arms, and, surrounding the house, threatened revenge, The king addressed them from a window, and admitted the magistrates, to whom he fully related all the circumstances, on which they dispersed, and he returned to Falkland. Three of the earl's servants were executed at Perth. The man in armour, Andrew Henderson, the earl's steward, was pardoned. All who were examined were totally ignorant of the motives which had prompted the brothers Ruthven to such a deed, and they still remain in some degree of mystery, although recent

GOYA Y LUCIENTES-GRAAL.

discoveries have led to a pretty general belief that the object of the conspirators was to possess themselves of the king's person, to convey by water to Fast Castle, and either to give him up to England, or to administer the government in his name in the interest of that country and of the Presbyterian leaders at home. Most of the documents

relating to the plot are printed.

GOYA Y LUCIENTES, FRANCISCO, the most distinguished painter of the new Spanish school, was born at Fuente de Todos, in Aragon, 31st March 1746, and received his first education in art in the academy at San Luis, Saragossa. On his return from a visit to Rome, the talent and speed with which he executed some paintings for the royal tapestry manufactory gained the approbation of the celebrated Mengs, who superintended that work. His scenes from the common life of the Spanish people excited special admiration ; but all the productions of his easel during this early period, to which belong the altar-piece and the crucifix at the entrance to the choir of the church of San Francisco al Grande in Madrid, are marked by simplicity of composition, charming truthfulness, and a natural and effective chiar-oscuro. In 1780, he was elected member of the academy of San Fernando. From this time, the influence of Velasquez and Rembrandt is observable in his paintings. Among the most celebrated of these is his portrait of Charles IV., for which he was made court-painter. In general, his portraits were executed with great felicity and ease. In 1824, he went to Paris for his health, and continued to reside in France till his death, which took place at Bordeaux, 16th April 1828. Besides his works in oil-colour, G. is celebrated for his essays in frescopainting, etching, lithography, and in almost every department of his art.

GOYA'NNA, a city of Brazil, in the province of Pernambuco, is situated on a river of the same name, 35 miles north-west of Olinda. It has numerous factories and an active trade. Pop. 6000.

GOYA'Z, a city of Brazil, is situated on the river Vermelho, in lat. 16° 21′ S., long. 50° 35' W., nearly in the middle of the empire, being the capital of the central province, which bears its The city contains about 7000 inhabitants; and the province, with an area of 313,000 square miles, has, according to the government returns in 1856, a population of only 180,000, mostly aborigines. The chief productions are cotton, timber,

name.

and cattle.

GOʻZZO (called by the Romans Gaulos), an island in the Mediterranean, belonging to Britain, is about ten miles in length, and about five miles in breadth; has an area of 36 square miles, and a population of 16,000. Its surface is agreeably diversified, and it has many fertile valleys. It appears to have been formerly connected with Malta, from which it is now separated by a channel four miles in width. On this account, and from its natural productions, it is a spot of the highest interest to the naturalist, while the cyclopean walls of the Giant's Tower and Roman monuments of a later period excite the attention of the antiquary. The island abounds in game, and is much frequented by sportsmen. It produces large quantities of grain and cotton, and is celebrated for cattle and for a breed of large asses. From the circumstance of its having two harbours, it is likewise of importance in a commercial and nautical point of view. The chief town is Rabato, situated near the centre of the island. The British governor resides in the Castel del Gozzo.

GOZZOLI, BENOZZI, a famous fresco-painter, was born at Florence about the beginning of the

15th c., and studied under Fra Angelico, whose excellence as a painter of sacred subjects he fully equalled, if not surpassed. A glow of rejoicing life seems infused into all G.'s productions. His chief works bearing traces of his master's influence are frescoes in the churches of Orvieto and Rome; his own style being visible in the paintings he executed by command of Pietro de' Medici, in a chapel of the Medici, now Ricardi Palace, at Florence. The great work, however, on which G.'s fame rests, is the immense frescoes executed on the north wall of the famous cemetery, or Campo Santo of Pisa. This wonderful series of paintings, not inaptly termed by Vasari una terribilissima opera (a terrific work '), was undertaken by the artist at the age of sixty, The scenes, and accomplished in sixteen years. which are all scriptural, are 24 in number, and are still in excellent preservation. G. died in 1485.

GRAAF, REGNIER DE, a celebrated Dutch physician, was born at Schoonhove in 1641, and died at Delft in 1673. He studied at the university of Leyden under Dubois (De le Boé), who is better known under his Latinised name of Sylvius; and on the death of the latter, in 1672, would have been unanimously elected to the vacant chair, if his religion (he was a Catholic) had not proved an insuperable obstacle to his appointment. In 1664, when only twenty-three years of age, he published his Disputatio Medica de Natura et Usu Succi Pancreatici, which, although containing several errors-as, for instance, that the pancreatic juice is acid, and that many diseases, and especially intermittent fevers, are due to a morbid condition of this fluid

gained him a great reputation. After a short residence in France, where he took his doctor's degree at Angers in 1665, he returned to Holland, and settled at Delft, where his success in practice gained him much envy. He rendered great service to anatomy in being the inventor of those injections of the blood-vessels which Swammerdam and Ruysch brought to a state of comparative excellence, and which are at the present day the basis of our sound knowledge of most of the tissues of the body. He published several dissertations on the organs of generation in both sexes, which involved him in a prolonged and angry controversy with Swammerdam. According to Haller, his death was occasioned by an attack of jaundice, brought on by the excitement of this controversy, but we do not know Haller's authority for this assertion. All his works were collected in one octavo volume, and published under the title of Opera Omnia in 1677, and they were republished in 1678 and in 1705.

GRAAFF-REINET, the chief town of the division of its own name, is one of the most important and prosperous towns in Cape Colony. Previously to 1857, it numbered 4000 inhabitants. During the ten years immediately preceding, it had risen from an inland village to be a great centre of commerce, having its public library, its agricultural society, its banks, and its newspaper. It owes its advancement partly to its position on the high-road between Port Elizabeth and the northern boundary. It is situated on the Sunday, which enters Algoa Bay, near Port Elizabeth.

GRAAFIAN VESICLES. See OVARY.

GRAAL, GRAL, or GRÉAL (a word derived probably from the old French, perhaps Celtic, gréal, Provençal, grazal, medieval Latin, gradalis), signifies a kind of dish. In the legends and poetry of the middle ages, we find accounts of the Holy GraalSan Gréal -a miraculous chalice, made of a single precious stone, sometimes said to be an emerald, which possessed the power of preserving chastity, prolonging life, and other wonderful properties.

GRABS-GRACCHUS.

This chalice was believed to have been first brought from heaven by angels, and was the one from which Christ drank at the Last Supper. It was preserved by Joseph of Arimathea, and in it were caught the last drops of the blood of Christ as he was taken from the cross. This holy chalice, thus trebly sanctified, was guarded by angels, and then by the Templises, a society of knights, chosen for their chastity and devotion, who watched over it in a temple-like castle on the inaccessible mountain Montsalvage. The legend, as it grew, appears to have combined Arabian, Jewish, and Christian elements, and it became the favourite subject of the poets and romancers of the middle ages. The eight centuries of warfare between the Christians and Moors in Spain, and the foundation of the order of Knight Templars, aided in its development. The stories and poems of Arthur and the Round Table were connected with this legend. About 1170, Chrétien of Troyes, and after him other troubadours, sang of the search for the holy graal by the Knights of the Round Table, in which they met with many extraordinary adventures. Some have supposed that the story of the connection of the miraculous chalice with the Last Supper and the blood of Christ arose from a wrong division of the words san gréal, holy vessel, which were written sang réal, royal blood, blood of the Lord; but although the coincidence is curious, there is no good reason to suppose that a pun could have been the foundation of a superstition which spread over Europe. The legend of the graal was introduced into German poetry in the 13th c. by Wolfram von Eschenbach, who took Guiot's tales of Parcival and Titurel as the foundation of his poem, but filled it with deep allegorical meanings. It is more elaborately treated by the author of Titurel the Younger; and much curious information may be found in a work, On the Description of the Temple of the Holy Graal, by Boisserée (Ueber die Beschreibung des Tempels des Heiligen Graal,' Munich, 1834).

conciliatory spirit were of great service to the state. He married Cornelia, the youngest daughter of P. Scipio Africanus, by whom he had twelve children. Nine of these died in youth; a daughter, Cornelia, married Scipio Africanus the younger. The history of his two sons follows:

1. TIBERIUS SEMPRONIUS GRACCHUS was born about 168 B. C., and was educated with great care by his excellent mother (his father having died while he was yet very young). He first saw military service under his brother-in-law, Scipio Africanus the younger, whom he accompanied to Africa. He was present at the capture of Carthage, and is said to have been the first of the Romans to scale the walls. In 137 B. C., he acted as quæstor to the army of the consul Mancinus in Spain, where the remembrance of his father's good faith and clemency was so fresh after forty years' interval, that the Numantines would treat with no other Roman but the son of their former benefactor. He was thus enabled to save from utter destruction an army of 20,000 Romans, who had been defeated, and were at the mercy of the Numantines. But the peace was considered by the aristocratic party at Rome as disgraceful to the national honour, and was repudiated, Mancinus being stripped naked, and sent back to the Numantines, that the treaty might thus be rendered void. Disgust and disappointment at this result are said by some, though without good reason, to have determined G. to espouse the cause of the people against the nobles; but a much more feasible ground for his conduct is to be found in the oppressed state of the commons at the time. Being elected tribune, he endeavoured to reimpose the Agrarian Law of Licinius Stolo, and after violent opposition on the part of the aristocratic party, who had bribed his colleague M. Octavius Cæcina, he succeeded in passing a bill to that effect. (For a detailed account of the measure, see AGRARIAN LAW.) Tiberius G., his brother Caius, and his fatherenforce its provisions. Meantime, Attalus, king of in-law Ap. Claudius, were appointed triumvirs to Pergamus, died, and bequeathed all his wealth to the Roman people. G. therefore proposed that this should be divided among the poor, to enable them GRA'CCHUS is the name of a Roman family, to procure agricultural implements, and to stock of the gens Sempronia, which contributed several their newly acquired farms. It is said that he also famous citizens to the state. First we have Tiberius intended to extend the franchise, and to receive Sempronius, who was consul in 238 B. C., and Italian allies as Roman citizens. He also diminished conducted some warlike operations in Corsica and the time which citizens were required to serve in Sardinia. Another Tib. Sempronius distinguished the army. But fortune turned against the good himself in the second Punic war, and for his success tribune. He was accused of having violated the in opposing Hannibal, was honoured with the sacred character of the tribuneship by the depoconsulship in 215 B. C., and again in 213 B. C. In sition of Cæcina, and the fickle people in large those days of despondency, he did much to revive numbers deserted their champion and benefactor. the spirit of the senate and people; with the allies, At the next election for the tribuneship, his and 8000 volones, or volunteer slaves (who after- enemies used all their efforts to oust him; and a wards gained their liberty as a reward for their violent scuffle having arisen between the opposing bravery), he withstood the Carthaginians in South factions, G. was slain, along with upwards of 300 Italy, defeated Hanno, and checkmated Hannibal others. His surviving friends were imprisoned, himself; but after many victories, he at length lost exiled, or put to death. his life, either in battle with Mago, or, according to others, by treachery. Hannibal honoured him with a splendid funeral. Passing by some Gracchi of minor note, as the augur of 203 B. C., the tribune of 189 B. C., and others, we come to Tiberius Sempronius, the father of those two reformers and friends of the people whose fame has overshadowed all the others. He was born about 210 B. C., and for many years occupied a foremost position in the state. He was successively tribune, ædile, prætor, consul (twice), and censor, and distinguished himself in several wars. He introduced some important constitutional changes, and was often employed on foreign embassies, in which his judgment and

GRABS, vessels of from 150 to 300 tons, employed on the Malabar coast. They are broad armed ships, with two or three masts, and unsuited for very heavy weather.

2. CAIUS SEMPRONIUS GRACCHUS, who was nine years younger than his brother, was possessed of much greater natural powers, and of more comprehensive views. His brother's death, which occurred while he was serving in Spain under Scipio Africanus, deterred him for some years from entering into public life; and the nobles seeing his great abilities, and fearing his influence with the people, endeavoured to keep him as long as possible on foreign service in Sardinia and elsewhere. But at length he unexpectedly returned to Rome, being urged by his brother's shade, as was said, to enter on his great mission. Goaded by the persecution and groundless accusations of his enemies, he stood

GRACE-GRADUAL.

for the tribuneship, and was elected in 123 B. C. After bringing forward some measures to take vengeance on his brother's murderers, he set himself to carry out the agrarian law, which, though not repealed, had by the machinations of the nobles been kept in abeyance. The two great aims of his legislation-viz., to improve the condition of the poor, and to curtail the power of the senate and nobles-were now prosecuted with the utmost vigour, and with unflinching steadiness of purpose. To develop the resources of Italy, and at the same time to employ the poor, he made new roads throughout all parts of the country, repaired old ones, and erected milestones. By his zeal, and by his unwearied industry in personally carrying out his own measures, even to superintending the execution of the public works, and by his affability and kindly good nature, he gained the esteem and approbation of all men with whom he came in contact. With the equites and the poorer classes, he was in special favour. But he at length fell, as his brother had done, by the intrigues of the nobles. One of his colleagues, M. Livius Drusus, was bribed by the opposite faction, and soon succeeded in undermining the influence of Caius by far surpassing him in the liberality of his public measures, and by his benefits to the commons. G. having stood for the tribuneship a third time, was rejected. Ultimately, by a series of moves, the history of which is too long for our space, violence was employed against Caius and his party-a fearful struggle took place in the streets of Rome, in which 3000 men are said to have perished. Many others were imprisoned, and afterwards executed. Caius held aloof from the fight, but was at length compelled to seek safety in flight. He escaped to the grove of the Furies with a single slave, who first slew his master, and then himself. The people saw, when too late, the folly of which they had been guilty in abandoning their best friend in the hour of need, and endeavoured to atone for their crime by erecting statues to the brothers G., by declaring sacred the spots where their blood had been shed, and by offering sacrifices to them as to deities. Caius left a son,

whose after-fate is unknown.

GRACE is an expression frequently used in Scripture and in theological discussion. Its distinctive meaning is the idea of free and unmerited favour. According to Aristotle, this is the proper meaning of charis (Gr. grace), even when applied to man. It is a benefit springing out of the liberality and freeheartedness of the giver, and bestowed without any hope or expectation of reward. Applied to God in the New Testament and in theology, it denotes the free outcoming of his love to man; and when man, on the other hand, is said to be in a state of grace, it implies that he is in the enjoyment of this divine love and favour. St Paul draws a sharp contrast (Rom. xi.) between charis and erga (Gr. works), as mutually excluding one another. And if by grace, then is it no more of works: otherwise grace is no more grace. But if it be of works, then is it no more grace: otherwise work is no more work.'

Theologians have distinguished grace into common or general, and special or particular. Common grace is supposed to denote the love which God has to all His creatures, and the light of nature and of conscience which they all enjoy. Special grace is the love which God has for His elect people, and by which He saves them from their sins. This special or saving grace is sometimes also divided in various ways, and spoken of as electing, justifying, sanctifying grace; also in respect of man, as imputed or inherent grace-the grace, that is to say, of Christ's righteousness imputed or reckoned to the account

of those that believe on Him, and the grace of holy and pious dispositions wrought in the heart by the spirit of God. Grace is also spoken of as efficacious and irresistible, and the relation in which the elect or believing people stand to God is represented as a covenant of grace, in contrast with the primitive relation which Adam bore to his Maker before the fall, which is called a covenant of works.

All these theological distinctions have arisen in the course of extended argument and discussion on divine truth. They are not to be found at least in their more technical sense-in the New Testament. The charis of St Paul is not a logical distinction, but a spiritual fact. It is the loving aspect of God towards the sinner-towards all sinners, whereby all who confess their sins have free access into His favour, and receive the adoption of sons.' The technical distinctions of theology, however, are not without their value when rightly apprehended and interpreted. They mark the course of past controversy-they give precision to theological thought and when not allowed to deface the simpler proportions of divine truth, they may teach needful and important lessons.

GRACE, DAYS OF. See BILL.

Hesiod and most

GRACES, the goddesses of grace, favour, and gentleness, the sources of all grace and beauty, appear in Homer in indefinite numbers as the attendants of Cytherea (Venus), whom it is their office to bathe and anoint. other poets mention three G.-Aglaia, Thalia, and Euphrosyne, the daughters of Zeus and Eurynome. Their worship is said to have been first introduced into Greece at Orchomenos, in Bootia, by Eteocles.

The Lacedemonians and Athenians

originally recognised only two Graces, called, by the former, Phanna and Kleta; by the latter, Hegemone and Auxo. In the early ages, the G. were represented in elegant drapery; at a later period, slightly draped, or entirely nude. appear holding each other by the hand, or locked in each other's embrace.

They

GRACIO'SA, one of the Azores Islands (q. v.), and the seventh of that group in population and importance.

GRA'DIENT. A tortoise walking is said, in Heraldry, to be gradient.

GRADIENT, a term used chiefly in connection with railways, to signify a departure of the line from a perfect level.

[ocr errors]

GRA'DUAL, in the Liturgy of the Roman and other Western churches, means that portion of the mass which intervenes between the epistle and gospel, and consists of a few verses of the Holy Scriptures, generally taken from the Psalms. It was originally called the Responsum,' or 'Cantus Responsorius;' but, probably for the sake of distinguishing it from other portions of the service called by the same name, its present appellation has been substituted. The name 'gradual' is derived from the place at which this response was chanted, and which was either the ambo, or chanting pulpit, which is approached by steps' (gradus) or the steps' themselves, whether of the ambo or of the altar. Originally, as we find from St Augustine, the gradual response consisted of an entire psalm, and in the mass of the first Sunday of Lent the entire of the 91st (90th in the Vulgate) psalm is chanted. In the Ambrosian Liturgy, the gradual is partly from the Old and partly from the New Testament. The gradual, in the Roman liturgy, is always followed by the alleluia,' except in penitential time, when a slow and mournful chant, called the 'Tract,' is substituted.

[ocr errors]

GRADUAL PSALMS GRADUATION.

GRADUAL PSALMS, or 'PSALMS OF THE STEPS,' or 'SONGS OF DEGREES,' a name given both by the Hebrews and in the Christian servicebooks to the fifteen psalms, 120-134 (119-133 in the Vulgate). The origin of this name is uncertain. The rabbins trace it to a fabulous incident connected with the building of the second temple; others explain it as an allusion to the fifteen steps by which (Ezekiel xl. 22—26) the temple was reached; others, again, regard these psalms as containing a prophetic allusion to the return from captivity, which, in the language of the Jews, was 'a going up,' the 134th psalm being the full outburst of exultation at the accomplishment of that great object of hope and longing. These psalms, in the Romish Church, form part of the office of each Wednesday during the Lent.

GRADUALE, the name given to the music of the above described portion of the Roman Liturgy It is performed during mass after the epistle is read. It is said to have been used from the earliest times to allow the officiating priest time, during its performance, to take his place on the steps of the reading-desk, or on the steps of the gospel side of the altar. The music is according to the character of the words, and may be either an aria, duet, or chorus. The composition must not be long, as the priest has little ceremony to go through during its performance. The best specimens of the graduale are Haydn's Insance et Vana Curae; Salve Regina; or Mozart's Misericordias Domini; Sancta Maria; De Profundis, &c.

GRADUATION, the art of dividing mathematical, astronomical, and other instruments. The simplest problem in graduation is the dividing of a straight line, such as an ordinary scale or rule. This is commonly done by copying from a standard scale, for which purpose a dividing square and a suitable knife for cutting the divisions are used. The dividing square is a hard steel straight-edge, with a shoulder at right angles like a carpenter's square. This is made to slide along the standard scale, and halt at each required division, when a corresponding one is cut upon the rule, &c., by using the steel straight-edge as a guide to the knife. The original graduation of a straight line into equal divisions, as in making a first standard scale, &c., is performed either on the principle of bisection or stepping. In bisecting, the points of a beam-compass (see COMPASS) are adjusted to nearly half the length of the line to be divided; one point is then placed at one end of the line, and a faint arc struck towards the middle: this is repeated at the other end; the small distance between these arcs is then carefully bisected with the aid of a fine pointer and magnifier, which gives an accurate half of the line. The half thus obtained is again bisected in like manner, and these quarters bisected again, and so on until the required subdivision is attained. Stepping is performed with delicately pointed spring-dividers, which are set at once as nearly as possible to the opening of the small division required; then the points are made to step on, leaving at each step a very fine dot; and when it is found that the last dot either falls short of or overpasses the end of the line, the opening is adjusted accordingly, until perfect accuracy is obtained. Thus, if a line were divided into a thousand parts, and each division were th too long or too short, the error would amount to a whole division at the end of a thousand steps. The method of bisection is practically the most accurate, and has been adopted by Graham, Bird, Ramsden, Troughton, and other eminent artists in original graduation. Curved lines are divided on this

It

principle. The chord of an arc of 60 is equal to the radius; therefore, the opening of the compasses required for striking the circle gives this are at once to start with. An arc 90°, or a quadrant, is obtained by bisecting 60°, and adding the half. By continual bisection of 60°, the finer graduations are produced. The amount of care, patience, skill, and delicacy of touch required in the original graduation of important astronomical instruments, is such, that not above one or two men in a generation have been found competent to the task, and these have become almost as famous as the astronomers who have successfully used the instruments. would be out of place here to point out in detail the minute precautions and methods of correction that are adopted in this most delicate manipulation; but, as an example, we may mention the fact, that Graham, when dividing the mural quadrant for the from a scale made for the purpose; but before laying Greenwich Observatory, measured his larger chords these down on the quadrant, he left the scale, beamcompasses, and quadrant to stand for a whole night, in order to acquire exactly the same temperature, and that neglect of this precaution would have of such extreme accuracy will be understood when involved a notable amount of error. The necessity divisions. When, for example, the mariner deterwe consider the application that is made of these mines his latitude by taking the meridian altitude of the sun, the graduated arc of the limb of the the curved surface of the globe, and the error is sextant or quadrant he uses represents, practically, magnified just to the same extent as the radius of the earth exceeds that of the divided arc of the instrument. Supposing this are to be part of a circle of 60 inches' circumference, each degree will occupy 4th of an inch. An error of th of an inch in the division would thus mislead the mariner to an extent of more than four statute miles as regards his position on the waters. But such a ship's quadrant is but a coarse and rude instrument compared with astronomical instruments for measuring celestial angular distances by means of a divided arc; in these, an error of a thousandth part of an inch would be regarded as one of serious magnitude.

The methods of original graduation above described are not practically adopted except for the largest and most important astronomical or geodesical instruments. Ordinary instruments are graduated by dividing plates or engines which copy and adapt a set of already existing divisions. The dividing plate which is used for common purposes, such as dividing compass rings, &c., is a divided circle with a steel straight-edge, made movable on the axis or arbor of the plate in such a manner that its edge during every part of its revolution shall fall in the exact line from centre to circumference. The ring, protractor, or other instrument to be divided, is clamped upon the plate with its centre exactly coinciding with that of the plate, and the straight-edge is moved round, and made to halt at the required divisions on the circumference of the dividingplate, and by using the steel straight-edge as a guide, corresponding divisions are marked off upon the concentric arc of the instrument to be divided. The dividing-engine is a very complex machine, requiring the greatest accuracy and care in its construction; so much so, that the possession of a good one affords the means of obtaining a very good income, with a moderate amount of labour in using it. Such was the case with the instrument of Mr Parsons of London, who for many years divided a large proportion of the best theodolites, sextants, &c., that were made in this country. Among the most celebrated dividing-engines may

« PreviousContinue »