the natives of India, Sabut Jung, or the daring in war. The hero of Arcot had, at Angria's stronghold, and now again under the walls of Calcutta, established his reputation as the first captain of the time. With 600 British soldiers, 800 sepoys, 7 field-pieces and 500 sailors to draw them, he had routed a force of 34,000 men with 40 pieces of heavy cannon, 50 elephants, and a camp that extended upwards of four miles in length. His own account, in a letter to the archbishop of Canterbury, gives a modest but vivid description of the battle, the importance of which has been overshadowed by Plassy. In spite of his double defeat and the treaty which followed it, he madness of the nawab burst forth again. As England and France were once more at war, Clive sent the fleet up the river against Chandernagore, while he besieged it by land. After consenting to the siege, the nawab sought to assist the French, but in vain. The capture of their principal settlement in India, next to Pondicherry, which had fallen in the previous war, gave the combined forces prize to the value of £130,000. The rule of Suraj-ud-Dowlah became as intolerable to his own people as to the English. They formed a confederacy to depose him, at the head of which was Jaffier Ali Khan, his commander-in-chief. Associating with himself Admiral Watson, Governor Drake, and Mr Watts, Clive made a treaty in which it was agreed to give the office of souba, or viceroy of Bengal, Behar, and Orissa, to Jaffier, who was to pay a million sterling to the Company for its losses in Calcutta and the cost of its troops, half a million to the English inhabitants of Calcutta, £200,000 to the native inhabitants, and £70,000 to its Armenian merchants. Up to this point all is clear. Surajud-Dowlah was hopeless as a ruler. His relations alike to his master, the merely titular emperor of Delhi, and to the people left the province open to the strongest. After "the Black Hole," the battle of Calcutta, and the treachery at Chandernagore in spite of the treaty which followed that battle, the East India Company could treat the nawab only as an enemy. Clive, it is true, might have disregarded all native intrigue, marched on Moorshedabad, and at once held the delta of the Ganges in the Company's name. But the time was not ripe for this, and the consequences, with so small a force, might have been fatal. The idea of acting directly as rulers, or save under native charters and names, was not developed by events for half a century. The political morality of the time in Europe, as well as the comparative weakness of the Company in India, led Clive not only to meet the dishonesty of his native associate by equal dishonesty, but to justify his conduct by the declaration, years after, in Parliament, that he would do the same again. It became necessary to employ the richest Bengalee trader, Omichund, as an agent between Jaffier Ali and the English officials. Master of the secret of the confederacy against Suraj-ud-Dowlah, the Bengalee threatened to betray it unless he was guaranteed, in the treaty itself, £300,000. To dupe the villain, who was really paid by both sides, a second, or fictitious treaty, was shown him with a clause to this effect. This Admiral Watson refused to sign; "but," Clive deponed to the House of Commons, "to the best of his remembrance, he gave the gentleman who carried it leave to sign his name upon it; his lordship never made any secret of it; he thinks it warrantable in such a case, and would do it again a hundred times; he had no interested motive in doing it, and did it with a design of disappointing the expectations of a rapacious man." Such is Clive's own defence of the one act which, in a long career of abounding temptations, stains his public life. The whole hot season of 1757 was spent in these negotiations, till the middle of June, when Clive began his march from Chandernagore, the British in boats, and the sepoys along the right bank of the Hooghly. That river, above Calcutta is, during the rainy season, fed by the overflow of the Ganges to the north through three streams, which in the hot months are nearly dry. On the left bank of the Bhagarutti, the most westerly of these, 100 miles above Chandernagore, stands Moorshedabad, the capital of the Mogul viceroys of Bengal, and then so vast that Clive compared it to the Loudon of his day. Some miles farther down is the field of Plassy, then an extensive grove of mango trees, of which enough yet remains, in spite of the changing course of the stream, to enable the visitor to realize the scene. On the 21st June Clive arrived on the bank opposite Plassy, in the midst of that outburst of rain which ushers in the south-west monsoou of India. His whole army amounted to 1100 Europeans and 2100 native troops, with 10 field-pieces. The nawab had drawn up 18,000 horse, 50,000 foot, and 53 pieces of heavy ordnance, served by French artillerymen. For once in his career Clive hesitated, and called a council of sixteen officers to decide, as he put it, "whether in our present situation, without assistance, and on our own bottom, it would be prudent to attack the nawab, or whether wo should wait till joined by some country power?" Clive himself headed the nine who voted for delay; Major (afterwards Sir) Eyre Coote, led the seven who counselled immediate attack. But, either because his daring asserted itself, or because, also, of a letter that he received from Jaffier Ali, as has been said, Clive was the first to change his mind and to communicate with Major Eyre Coote. One tradition, followed by Macaulay, represents him as spending an hour in thought under the shade of some treca, while he resolved the issues of what was to prove one of the decisive battles of the world. Another, turned into verse by an Anglo-Indian poet, pictures his resolution as the result of a dream. However that may be, he did well as a soldier to trust to the dash and even rashness that had gained Arcot and triumphed at Calcutta, and as a statesman, since retreat, or even delay, would have put back the civilization of India for years. When, after the heavy rain, the sun rose brightly on the 22d, the 3200 men and the six guns crossed the river and took possession of the grove and its tanks of water, while Clive established his headquarters in a hunting lodge. On the 23d the engagement took place and lasted the whole day. Except the 40 Frenchmen and the guns which they worked, the enemy did little to reply to the British cannonade which, with the 39th Regiment, scattered the host, inflicting on it a loss of 500 men. Clive restrained the ardour of Major Kirkpatrick, for he trusted to Jaffier Ali's abstinence, if not desertion to his ranks, and knew the importance of sparing his own small force. He lost hardly a white soldier; in all 22 sepoys were killed and 50 wounded. His own account, written a month after the battle to the secret committee of the court of directors, is not less unaffected than that in which he had announced the defeat of the nawab at Calcutta. Suraj-ud-Dowlah fled from the field on a camel, secured what wealth he could, and came to an untimely end. Clive entered Moorshedabad, and established Jaffier Ali in the position which his descendants have ever since enjoyed, as pensioners, but have not unfrequently abused. When taken through the treasury, amid a million and a half sterling's worth of rupees, gold and silver plate, jewels, and rich goods, and besought to ask what he would, Clive was content with £160,000, while half a million was distributed among the army and navy, both in addition to gifts of £24,000 to each member of the Company's committee, and besides the public compensation stipulated for in the treaty. It was to this occasion that he referred in his defence before the House of Commons, when he declared that he marvelled at his moderation. Ile sought rather to increase the shares of the filcet and the troops at his own expense, as he had done at Gheriah, and did more than once afterwards, with prize of war. What he did take from the grateful nawab for himself was less than the circumstances justified from an Oriental point of view, was far less than was pressed upon him, not only by Jaffier Ali, but by the hundreds of the native nobles whose gifts Clive steadily refused, and was openly acknowledged from the first. He followed a usage fully recognized by the Company, although the fruitful source of future evils which he himself was again sent out to correct. The Company itself acquired a revenue of £100,000 a year, and a contribution towards its losses and military expenditure of a million and a half sterling. Such was Jaffier Ali's gratitude to Clive that he afterwards presented him with the quit-rent of the Company's lands in and around Calcutta, amounting to an annuity of £27,000 for life, and left him by will the sum of £70,000, which Clive devoted to the army. While busy with the civil administration, the conqueror of Plassy continued to follow up his military success. He sent Major Coote in pursuit of the French almost as far as Benares. He despatched Colonel Forde to Vizagapatam and the northern districts of Madras, where that officer gained the battle of Condore, pronounced by Broome " one of the most brilliant actions on military record." He came into direct contact, for the first time, with the Great Mogul himself, an event which resulted in the most important consequences during the third period of his career. Shah Aalum, when Shahzada, or heir-apparent, quarrelled with his father Aalum Geer II., the emperor, and united with the viceroys of Oudh and Allahabad for the conquest of Bengal. He advanced as far as Patna, which he besieged with 40,000 men. Jaffier Ali, in terror, sent his son to its relief, and implored the aid of Clive. Major Caillaud defeated the prince's army at the battle of Sirpore, and dispersed it. Finally, at this period, Clive repelled the aggression of the Dutch, and avenged the massacre of Amboyna, on that occasion when he wrote his famous letter, "Dear Forde, fight them immediately; I will send you the order of council to-morrow." Meanwhile he never ceased to improve the organization and drill of the sepoy army, after a European model, and enlisted into it many Mahometans of fine physique from Upper India. He re fortified Calcutta. In 1760, after four years of labour so incessant and results so glorious, his health gave way and he returned to England. "It appeared," wrote a contemporary on the spot, "as if the soul was departing from the government of Bengal." He had been formally made governor of Bengal by the court of directors at a time when his nominal superiors in Madras sought to recall him to their help there. But he had discerned the importance of the province even during his first visit to its rich delta, mighty rivers, and teeming population. It should be noticed, also, that he had the kingly gift of selecting the ablest subordinates, for even thus early he had discovered the ability of young Warren Hastings, destined to be his great successor, and, a year after Plassy, made him "resident" at the nawab's court. In 1760, at thirty-five years of age, Clive returned to England with a fortune of at least £300,000 and the quitrent of £27,000 a year, after caring for the comfort of his parents and sisters, and giving Major Lawrence, his old commanding officer, who had early encouraged his military genius, £500 a year. The money had been honourably and publicly acquired, with the approval of the Company. The amount might have been four times what it was, had Clive been either greedy after wealth or ungenerous to the colleagues and the troops whom he led to victory. In the five years of his conquests and administration in Bengal, the young man had crowded together a succession of exploits which led Lord Macaulay, in what that historian termed his "flashy essay on the subject, to compare him to Napoleon Bonaparte. But there was this difference in Clive's favour, due not more to the circumstances of the time than to the object of his policy-he gave peace, security, prosperity, and such liberty as the case allowed of to a people now reckoned at 240 millions, who had for centuries been the prey of oppression, while Napoleon warred only for personal ambition, and the absolutism he established has left not a wreck behind. During the three years that Clive remained in England he sought a political position, chiefly that he might influence the course of events in India, which he had left full of promise. He had been well received at court, had been made Baron Clive of Plassy, in the peerage of Ireland, had bought estates, and had got not only himself but his friends returned to the House of Commons after the fashion of the time. Then it was that he set himself to reform the home system of the East India Company, and commenced a bitter warfare with Mr Sulivan, chairman of the court of directors, whom finally he defeated. In this he was aided by the news of reverses in Bengal. Vansittart, his successor, having no great influence over Jaffier Ali Khan, had put Kossim Ali Khan, the son-in-law, in his place in consideration of certain payments to the English officials. After a brief tenure Kossim Ali had fled, had ordered Summers, or Sumroo, a Swiss mercenary of his, to butcher the garrison of 150 English at Patna, and had disappeared under the protection of his brother viceroy of Oudh. The whole Company's service, civil and military, had become demoralized by such gifts, and by the monopoly of the inland as well as export trade, to such an extent that the natives were pauperized, and the Company was plundered of the revenues which Clive had acquired for them. The court of proprietors, accordingly, who elected the directors, forced them, in spite of Sulivan, to hurry out Lord Clive to Bengal with the double powers of governor and com. mander-in-chief. What he had done for Madras, what he had accomplished for Bengal proper, and what he had effected in reforming the Company itself, he was now to complete in less than two years, in this the third period of his career, by putting his country politically in the place of the emperor of Delhi, and preventing for ever the possibility of the corruption to which the English in India had been driven by an evil system. On the 3d May 1765, he landed at Calcutta to learn that Jaffier Ali Khan had died, leaving him personally £70,000, and had been succeeded by his son, though not before the Government had been further demoralized by taking £100,000 as a gift from the new nawab; while Kossim Ali had induced not only the viceroy of Oudh, but the emperor of Delhi himself, to invade Behar. After the first mutiny in the Bengal army, which was suppressed by blowing the sepoy ringleader from the guns, Major Munro, "the Napier of those times," scattered the united armies on the hard-fought field of Puxar. The emperor, Shah Aalum, detached himself from the league, while the Oudh viceroy threw himself on the mercy of the English. Clive had now an opportunity of repeating in Hindustan, or Upper India, what he had accomplished for the good of Bengal. He might have secured what are now called the North-Western Provinces and Oudh, and have rendered unnecessary the campaigns of Wellesley and Lake. But he had other work in the consolidation of rich Bengal itself, making it a base from which the mighty fabric of British India could afterwards steadily and proportionally grow. Hence he returned to the Oudh viceroy all his territory save the provinces of Allahabad and Corah, which he made over to the weak emperor. But from that emperor he secured the most important document in the whole of | He lacked a sufficient number of British artillerymen, and would not commit the mistake of his successors, who trained natives to work the guns, which were turned against us with such effect in 1857. It is sufficient to say that Government has returned to his policy, for not a nativo gunner is now to be found save in a few unhealthy and isolated frontier posts. Clive's final return to England, a poorer man thau he went out, in spite of still more tremendous temptations, was the signal for an outburst of his personal enemies, exceeded only by that which the malice of Sir Philip Francis after wards excited against Warren Hastings. Every civilian, whose illicit gains he had cut off, every officer whose conspiracy he had foiled, every proprietor or director, liko Sulivan, whose selfish schemes he had thwarted, now sought their opportunity. He had, with consistent generosity, at once made over the legacy of £70,000 from the grateful Jaffier Ali, as the capital of what has since been known as "the Clive Fund," for the support of invalided European soldiers, as well as officers, and their widows, and the Company had allowed 8 per cent. on the sum for an object which it was otherwise bound to meet. Burgoyne, of Saratoga memory, did his best to induce the House of Commons, in which Lord Clive was now member for Shrewsbury, to impeach the man who gave his country an empire, and the people of that empire peace and justice, and that, as we have seen, without blot on the gift, save in the. matter of Omichund. The result, after the brilliant and honourable defences of his career which will be found in Almon's Debates for 1773, was a compromise that saved England this time from the dishonour which, when Warren Hastings had to run the gauntlet, put it in the same category with France in the treatment of its public benefactors abroad. On a division the House, by 155 to 95, carried the motion that Lord Clive "did obtain and possess himself" of £234,000 during his first administration of Bengal; but, refusing to express an opinion on the fact, it passed unanimously the second motion, at five in the morning, "that Robert, Lord Clive, did at the same time render great and meritorious services to his country." The one moral question, the one stain of all that brilliant and tempted life-the Omichund treaty—was not touched. our Indian history up to that time, which appears in the records as "firmaund from the King Shah Aalum, granting the dewany of Bengal, Behar, and Orissa to the Company, 1765." The date was the 12th August, the place Benares, the throne an English dining-table covered with embroidered cloth and surmounted by a chair in Clive's tent. It is all pictured by a Mahometan contemporary, who indignantly exclaims that so great a "transaction was done and finished in less time than would have been taken up in the sale of a jackass." By this deed the Company became the real sovereign rulers of thirty millions of people, yielding a revenue of four millions sterling. All this had been ac complished by Clive in the few brief years since he had avenged "the Black Hole" of Calcutta. This would be a small matter, or might even be a cause of reproach, were it not that the Company's, now the Queen's, undisputed Sovereignty proved, after a sore period of transition, the salvation of these millions. The lieutenant-governorship of Bengal, with some additions since Clive's time, now contains sixty millions of people, and yields an annual revenue of twelve millions sterling, of which eight goes every year to assist in the good government of the rest of India. But Clive, though thus moderate and even generous to an extent which called forth the astonishment of the natives, had all a statesman's foresight. On the same date, he obtained not only an imperial charter for the Company's possessions in the Carnatic also, thus completing the work he began at Arcot, but a third firmaun for the highest of all the lieutenancies or soubaships of the empire, that of the Deccan itself. The fact has only recently been discovered, by distinct allusion to it in a letter from the secret committee of the court of directors to the Madras Government, dated 27th April 1768. Still so disproportionate seemed the British force, not only to the number and strength of the princes and people of India, but to the claims and ambition of French, Dutch, and Danish rivals, that Clive's last advice to the directors, as he finally left India in 1777, was this, given in a remark able state paper but little known: "We are sensible that, since the acquisition of the dewany, the power formerly belonging to the soubah of those provinces is totally, in fact, vested in the East India Company. Nothing remains to him but the name and shadow of authority. This name, Only one who can personally understand what Clive's however, this shadow, it is indispensably necessary we power and services were will rightly realize the effect on should seem to venerate." On a wider arena, even that of him, though in the prime of life, of the discussions through the Great Mogul himself, the shadow was kept up till it which he had been dragged. We have referred to Warren obliterated itself in the massacre of English people in the Hastings's impeachment, but there is a more recent parallel. Delhi palace in 1857; and the Queen was proclaimed, first, | The marquis of Dalhousie did almost as much to complete direct ruler on the 1st November 1858, and then empress the territorial area and civilized administration of British of India on the 1st January 1377 India in his eight years' term of office as Lord Clive to found the empire in a similar period. As Clive's accusers sought a new weapon in the great famine of 1770, for which he was in no sense responsible, so there were critics who accused Dalhousie of having caused that mutiny which, in truth, he would have prevented had the British Government listened to his counsel not to reduce the small English army in the country. Clive tells us his own feelings in a passage of first importance when we seek to form an opinion on the fatal act by which he ended his life. In the greatest of his speeches, in reply to Lord North, he said," My situation, sir, has not been an easy one for these twelve months past, and though my conscience could never accuse me, yet I felt for my friends who were involved in the same censure as myself. I have been examined by the select committee more like a sheep-stealer than a member of this House." Fully accepting that statement, and believing him to have been purer than his accusers in spite of temptations unknown to them, we see in Clive's and the result merely of physical suffering, of chronic disease which opium failed to abate, while the worry and chagrin Having thus founded the empire of British India, Clive's painful duty was to create a pure and strong administration, such as alone would justify its possession by foreigners. The civil service was de-orientalized by raising the miserable salaries which had tempted its members to be corrupt, by forbidding the acceptance of gifts from natives, and by exacting covenants under which participation in the inland trade was stopped. Not less important were his military reforms. With his usual tact and nerve he put down a mutiny of the English officers, who chose to resent the veto against receiving presents and the reduction of batta at a time when two Mahratta armies were marching on Bengal. His reorganization of the army, on the lines of that which he had begun after Plassy, and which was neglected during his second visit to England, has since attracted the admiration of the ablest Indian officers. He divided the whole into three brigades, so as to make each a complete force, in itself equal to any single native army that could be brought against it. His one fault was that of his age and his position, with so small a number of men. caused by his enemies gave it full scope. This great man, TH the eyes. Reserved to the many, he was beloved by his own family and friends. His encouragement of scientific undertakings like Major Rennell's surveys, and of philological researches like Mr Gladwin's, was marked by the two honorary distinctions of F.R.S. and LL.D. The best authorities for his life, which has yet to be worthily written, are-article "Clive," in the second or Kippis's edition of the Biographia Britannica, from materials supplied by his brother, the Bengal Army; Aitchison's Treaties, second edition, 1876; Archdeacon Clive, by Henry Beaufoy, M.P.; Broome's History of Orme's History; and Malcolm's Life. (G. SM.) CLOCKS THE origin of clock work is involved in great obscurity. | 1292 one is mentioned in Canterbury Cathedral as costing Notwithstanding the statements by many writers that £30. And another at St Albans, by R. Wallingford the clocks, horologia, were in use so early as the 9th century, abbot in 1326, is said to have been such as there was not and that they were then invented by an archdeacon of in all Europe, showing various astronomical phenomena. Verona, named Pacificus, there appears to be no clear A description of one in Dover Castle with the date 1348 on evidence that they were machines at all resembling it was published by the late Admiral Smyth, P.R.A.S., those which have been in use for the last five or six in 1851, and the clock itself was exhibited going, in the centuries. But it may be inferred from various allusions Scientific Exhibition of 1876. In the early editions of to horologia, and to their striking spontaneously, in the this Encyclopædia there was a picture of a very similar 12th century, that genuine clocks existed then, though one, made by De Vick for the French king Charles V. there is no surviving description of any one until the 13th about the same time, much like our common clocks of the century, when it appears that a horologium was sent by the last century, except that it had a vibrating balance, but sultan of Egypt in 1232 to the Emperor Frederick II. "It no spring, instead of a pendulum, for pendulums were not resembled a celestial globe, in which the sun, moon, and invented till three centuries after that. planets moved, being impelled by weights and wheels, so that they pointed out the hour, day, and night with certainty." A clock was put up in a former clock tower at Westminster with some great bells in 1288, out of a fine imposed on a corrupt chief-justice, and the motto Discite The general construction of the going part of all clocks, except large or turret clocks, which we shall treat separ ately, is substantially the same, and fig. 1 is a section of any ordinary house clock. B is the barrel with the rope coiled round it, generally 16 times for the 8 days; the barrel is fixed to its arbor K, which is prolonged into the winding square coming up to the face or dial of the clock; the dial is here shown as fixed either by small screws x, or by a socket and pin z, to the prolonged pillars p, p, which (4 or 5 in number) connect the plates or frame of the clock together, though the dial is commonly, but for no good reason, set on to the front plate by another set of pillars of its own. The great wheel G rides on the arbor, and is connected with the barrel by the ratchet R, the action of which is shown more fully in fig 14: The intermediate wheel r in this drawing is for a purpose which will be described hereafter, and for the present it may be considered as omitted, and the click of the ratchet R as fixed to the great wheel. The great wheel drives the pinion c which is called the centre pinion, on the arbor of the centre wheel C, which goes through to the dial, and carries the long, or minute-hand; this wheel always turns in an hour, and the great wheel generally in 12 hours, by having 12 times as many teeth as the centre pinion. The centre wheel drives the "second wheel" D by its pinion d, and that again drives the scape-wheel E by its pinion e. If the pinions d and e have each 8 teeth or leaves (as the teeth of pinions are usually called), C will have 64 teeth and D 60, in a clock of which the scape-wheel turns in a minute, so that the seconds haud may be set on its arbor prolonged to the dial. A represents the pallets of the escapement, which will be described presently, and their arbor a goes through a large hole in the back plate near F, and its back pivot turns in a cock OFQ screwed on to the back plate. From the pallet arbor at F descends the crutch Ff, ending in the fork f, which embraces the pendulum P, so that as the pendulum vibrates, the crutch and the pallets necessarily vibrate with it. The pendulum is hung by a thin spring S from the cock Q, so that the bending point of the spring may be just opposite the end of the pallet arbor, and the edge of the spring as close to the end of that arbor as possible-a point too frequently neglected. cap and nearly equal circular ares of the same pendulum, varies neatly as the arc itself. If a, the arc, is increased by a small amuonut du, the pendulum will lose 10800ada seconds a day, which is rather more than 1 second, if a is 2° (from zero) and da is 10', since the numerical value of 2° is 035. If the increase of arc is considerable, it will not do to reckon thus by differentials, but we must take the difference of time for the day as 5400 (a,2-a), which will be just great importance to obtain cycloidal vibrations of clock pendulums, 8 seconds if a=2° and a=3°. For many years it was thought of and it was done by making the suspension string or spring vibrate between cycloidal checks, as they were called. But it was in time discovered that all this is a delusion,-first, because there is and can be no such thing in reality as a simple pendulum, and cycloidal cheeks will only make a simple pendulum vibrate isochronously; secondly, because a very slight error in the form of the heeks (as Huyghens himself discovered) would do more harm than the circular error uncorrected, even for an are of 10°, which is much larger than the common pendulum arc; thirdly, because there was always some friction or adhesion between the cheeks and the string; and fourthly (a reason which applies equally to all the isochronous contrivances since invented), because a common clock escupement itself generally tends to produce an error exactly opposite to the circular error, or to make the pendulum vibrate quicker the farther purpose of helping to counteract the error due to the escapement, it swings; and therefore the circular error is actually useful for the and the clock goes better than it would with a simple pendulum, describing the most perfect cycloid. At the same time, the thin spring by which pendulums are always suspended, except in somie causes the pendulum to deviate a little from circular and to approxi French clocks where a silk string is used (a very inferior plan), mate to cycloidal motion, because the bend does not take place at one point, but is spread over some length of the spring. We may now go to the front (or left hand) of the clock, and describe the dial or "motion-work." The minute hand fits on to a squared end of a brass socket, which is fixed to the wheel M, and fits close, but not tight, on the prolonged arbor of the centre wheel. Behind this wheel is a bent spring which is (or ought to be) set on the same arbor with a square hole (not a round one as it sometimes is) in the middle, so that it must turn with the arbor; the wheel is pressed up against this spring, and kept there, by a and a small pin through the end of the arbor. The consequence is, that there is friction enough between the spring and the wheel to carry the hand round, but not enough to resist a moderate push with the finger for the purpose of altering the time indicated. This wheel M, which is sometimes called the minute-wheel, but is better called the hour-wheel as it turns in an hour, drives another wheel N, of the same number of teeth, which has a pinion attached to it; and that pinion drives the twelve-hour wheel H, which is also attached to a large socket or pipe carrying the hour hand, and riding on the former socket, or rather (in order to relieve the centre arbor of that extra weight) on an intermediate socket fixed to the bridge L, which is screwed to the front plate over the hour-wheel M. The weight W, which drives the train and gives the impulse to the pendu lum through the escapement, is generally hung by a catgut line passing through a pulley attached to the weight, the other end of the cord being tied to some convenient place in the clock frame or seat-board, to which it is fixed by screws through the lower pillars. It has usually been the practice to make the case of house clocks and astronomical clocks not less than 6 feet high; but that is a very unnecessary waste of space and materials; for by either diminishing the size of the barrel, or the number of its turns, by increasing the size of the great wheel by one-half,, or hanging the weights by a treble instead of a double line, a case just long enough for the pendulum will also be long enough for the fall of the weights in 7 or 8 days. Of course the weights have to be increased in the same ratio, and indeed rather more, to overcome the increased friction. but that is of no consequence. PENDULUM. The claim to the invention of the pendulum, like, the claim o most inventious, is disputed; and we have no intention of trying to settle it. It was, like many other discoveries and inventions, probably made by various persons independently, and almost simul. taneously, when the state of science had become ripe for it. The discovery of that peculiarly valuable property of the pendulum called isochronism, or the disposition to vibrate different arcs in very nearly the same time (provided the arcs are none of them large), is commonly attributed to Galileo, in the well-known story of his being struck with the isochronism of a chandelier hung by a long chain from the roof of the church at Florence. And Galileo's son appears as a rival of Avicenna, Huyghens, Dr Hooke, and a London clockmaker named Harris, for the honour of having first applied the pendulum to regulate the motion of a clock train, all in the early art of the 17th century. Be this as it may, there seems little doubt that Huyghens was the first who mathematically investi. gated, and therefore really knew, the true nature of those properties of the pendulum which may now be found explained in any mathematical book on mechanics. He discovered that if a simple pendulum (i.e., a weight or bob consisting of a single point, and hung by a rod or string of no weight) can be made to describe, not a circle, but a cycloid of which the string would be the radius of curvature at the lowest point, all its vibrations, however large, will be performed in the same time. For a little distance near the bottom, the circle very nearly coincides with the cycloid; and hence it is that, for small arcs, a pendulum vibrating as usual in a circle is nearly enough isochronous for the purposes of horology; more especially when contrivances are introduced either to compensate for the variations of the arc, or, better still, to destroy them altogether, by making the force on the pendulum so constant that its arc may never sensibly vary. The difference between the time of any small arc of the circle and any arc of the cycloid varies nearly as the square of the circular are; and again, the difference between the times of any two small The accurate performance of a clock depends so essentially on the pendulum, that we shall go somewhat into detail respecting it. First then, the time of vibration depends entirely on the length of the pendulum, the effect of the spring being too small for considera. tion until we come to differences of a higher order. But the time does not vary as the length, but only as the square root of the length; i.e., a pendulum to vibrate two seconds must be four times as long as a seconds pendulum. The relation between the time of vibration and the length of a pendulum is expressed thus :where is the time in seconds, the well-known symbol for 3.14159, the ratio of the circumference of a circle to its diameter, the length of the pendulum, and g the force of gravity at the latitude where it is intended to vibrate. This letter g, in the latitude of London, is the symbol for 32 2 feet, that being the velocity (or number of feet per second) at which a body is found by experiment to be moving at the end of the first second of its fall, being necessarily equal to twice the actual number of feet it has fallen in that second. Consequently, the length of a pendulum to beat seconds in London is 39'14 inches. But the same pendulum carried to the equator, where the force of gravity is less, would lose 2 minutes a day. The seconds we are here speaking of are the seconds of a common clock indicating mean solar time. But as clocks are also required for sidereal time, it may be as well to mention the proportions between a mean and a sidereal pendulum. A sidereal day is the interval between two successive transits over the meridian of a place by that imaginary point in the heavens called T, the first point of Aries, at the intersection of the equator and the ecliptic; and there is one more sidereal day than there are solar days in a year, since the earth has to turn more than once round in space before the sun can come a second time to the meridian, on account of the earth's own motion in its orbit during the day. A sidereal day or hour is shorter than a mean solar one in the ratio of 99727, and consequently a sidereal pendulum must be shorter than a mean time pendulum in the square of that ratio, or in the latitude of London the sidereal seconds pen. dulum is 38.87 inches. As we have mentioned what is 0 or 24 o'clock by sidereal time, we may as well add, that the mean day is also reckoned in astronomy by 24 hours, and not from midnight as in civil reckoning, but from the following noon; thus, what we call 11 A.M. May 1 in common life is 23 . April 30 with astronomers. It must be remembered that the pendulums whose lengths we have been speaking of are simple pendulums; and as that is a thing which can only exist in theory, the reader may ask how the length of a real pendulum to vibrate in any required time is ascertained. In every pendulum, that is to say, in every body hung so as to be capable of vibrating freely, there is a certain point, always some. where below the centre of gravity, which possesses these remarkable properties that if the pendulum were turned upside down, and set vibrating about this point, it would vibrate in the same time as before, and moreover, that the distance of this point from the point of suspensica is exactly the length of that imaginary simple pendulum which would vibrate in the same time. This point is therefore called the centre of oscillation. The rules for finding it by saleula |