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24.) the edge of the paper A C will form a If a line G, instead of going round the spiral line round the cylinder, which will groove of the wheel D, goes round its axle give the thread of the screw. It being I, the power of the machine will be as much evident that the winch must turn the cy: increased as the circumference of the groove linder once round, before the weight of re. exceeds the circumference of the axle : sistance can be moved from one spiral wind. which supposing it to be six times, then one ing to another, as from d to c; therefore, as pound at H will balance six times 48, or much as the circumference of a circle 288 pounds, bong to the line on the axle : described by jhe handle of the winch is and hence the power or advantage of this greater than the interval or distance be- machine will be as 288 to 1. That is to say, tween the spirals, so mnch is the force of the a man, who by bis natural strength could screw. Thus, supposing the distance of the lift an hundred weight, will be able to raise spirals to be half an inch, and the length of 288cwts. by this engine. If a system of the winch twelve inches, the circle describ- pullies were applied to the cord H, the ed by the handle of the winch where the power would be increased to an amazing power acts, will be '76 inches nearly, or degree. When a screw acts in a wheel in about 152 half inches ; and consequently this manner, it is called an endless screw. 152 times as great as the distance between When it is not employed in turning a the spirals ; and therefore a power at the wheel, it consists of two parts: the first is handle, whose intensity is equal to no more called the male, or outside screw, being cut than a single pound, will balance 152 pounds in such a mamer as to have a prominent acting against the screw; and as much ad- part going round the cylinder in a spiral ditional force as is sufficient to overcome manner; which prominent part is called the friction, will raise the 152 ponnds; and the thread of the screw; the other part, the velocity of the power will be to the ve. which is called the female, or inside screw, locity of the weight, as 152 to 1. Hence is a solid body, containing a hollow eyit appears, that the longer the winch is, and linder, whose concave surface is cut in the the nearer the spirals are to one another, so same manner as the convex surface of the much the greater is the force of the screw. inale screw, so that the prominent parts of

A machine for shewing the force or the one may fit the concave parts of the power of the screw may be contrived in the other. A very considerable degree of following manner : let the wheel C have a friction always acts against the power in a screw, (fig. 25.) on its axis, working in the screw; but this is fully compensated by teeth of the wheel D, which suppose to be other advantages ; for on this account the 48 in number. It is plain, that for every screw continues to siistain a weight, even time the wheel C and screw are turned after the power is removed, or ceases to round by the wineh A, the wheel D will be act, and presses upon the body against moved one tooth by the screw; and there. which it is driven. Hence the screw will fore, in 48 revolutions of the winch, the sustain very great weights, insomnch, that wheel D will be turned once round. Then, several screws, properly applied, would if the circumference of a circle, described support a large building, whilst the foundaby the handle of the winch A, be equal to tion was mending, or renewed. the circnmference of a groove round the The screw is of extensive nse in the wheel I), the velocity of the liandie will be printing-press, and in the press for coining 48 times as great as the velocity of any money, and in a great variety of other purgiven point in the groove. Consequently, poses. It has lately been employed in the if a line G goes round the groove, and has a flourmills in America, for pushing the four weight of 48 pounds hung to it, a power which comes from the mill-stones to the end equal to 1 pound at the handle will balance of a long trongh, from which it is conveyed and support the weigist. To prove this by to other parts of the maehinery, in order to experiment, let the circumferences of the undergo the remaining processes. In this grooves of the wlieels C and D be equal to case, the spiral threads are very large in one another; and then if a weight H, of one proportion to the cylinder on which they pound, be suspended by a line going round are fixed. As the lever used with the the groove of the wheel C, it will balance screw moves through a large space when a weight of 48 pounds hanging by the line compared with the velocity of its other exG; and a small addition to the weight H tremity, or of any body which it puts in will cause it to descend, aud so raise up the motion; the screw is of very great use in other weight.

subdividing any space into a great number

6f minute parts. Hence it is employed in not been formed in every age and country, the engines for dividing mathematical in- that they have not may be inferred from struments, &c. See OsciLLATION, PEN- the extreme rarity of some particular deDULUM, SUSPENSION, &c.

scriptions ; had collections been universal, MEDAL. This word has generally been surely a much greater number of medals supposed to be derived from Metallum, must have reached us, making due allowfrom which we have the English term me- ance for decay, violence, melting, and losses tal; but it may admit of some doubt whe- during foreign and civil wars. Mr. Pinkerther the derivation is correct, as the word ton inclines to think the world entertained appears to have too comprehensive a sense but little regard for the medals made by to particularize a piece of gold, silver, brass, the numerous small states using the Greek or copper, impressed with figures to convey characters and language, supposing that to posterity some great historical occur. their numbers rendered them of little rence, or to perpetuate the memory of a value ; this idea is extremely probable if person who had rendered the state in wbich extended to the mass of mankind; but as be lived an essential service.

there ever has been individuals of superior We are indebted to the very ancient in- taste and acquirements scattered in every habitants of the world for this method of soil, we might have imagined the aggregate inmortalizing their most important acts of those persons sufficiently great to preand most exalted characters, a method, the serve a larger number than is now to be discovery or invention of whichi, would do found. hoħour to an age enlightened by arts and Many ingenious speculations might be literature, then unknown. Had the same formed as to the origin of medals; it is inclination to preserve those indelible me- not, however, safe or pleasant to wander in mentos prevailed throughout the countries the shades of antiquity without guides, or a which prompted the making of them, we ray of light, we must therefore be conshould Irave possessed a series of valuable tented with the few facts which have been information now for ever interrupted, to gleaned by writers on this subject. From the constant regret of the historiay, who is those it appears, that we are principally incompelled to wander in a maze of conjec. debted to the Romans for the preservation ture, caused by allusious in the works of of the most valuable Greek medals ;-indeed, ancient writers, that were well known to that ambitious people did themselves more the public at the time when they were honour by their successful study of the arts made, but all clue to which is entirely lost. of Greece, than by the conqnests they The satisfaction demonstrated by the learn- achieved in every part of the globe then ed of every nation on the accidental disco- known; with minds elevated beyond the very of an unknown medal, sufficiently paltry consideration of envy, they vot only evinces their importance; if the relief is - collected the medals of that country, but tolerably perfect, or the inscription nearly directed their artists to imitate the beauty or quite legible, every individual becoines of their reliefs, and the gracefulness of their an enthusiast in research, and it has fre- outlines. The encouragement thus afforded quently happened that an important blank by the various governments of Rome, cre. iu chronology, history, or geography, has ated a spirit of emulation amongst the been unexpectedly and satisfactorily filled higher orders of the public, and collections by this means. One very material circum- were formed, to which every subsequent stance contributes fo render ancient medals cabinet has been more or less indebtvaluable, which is their undoubted authen- ed. Whether the medals possessed by ricity; in short, they are the historical acts the curious at that period were methoof kings and states, the durable gazettes of dically arranged, so as to preserve the chroantiquity : they inforin the world that at nology of facts, cannot now be ascertained; such a period a monarch ascended a throne, but we are very certain that numbers of a victory was achieved, the foundations of great value and importance must have been a city were laid, or a temple erected, and irrecoverably lost since the time alluded to, they sometimes introduce to our votice and that the series, in many cases, has been persons, towns, and buildings, which have interrupted by the havock committed at not been mentioned by any of the ancient each conquest of the mistress of the world. writers extant.

The philosopher and the historian will ever Viewing medals in this light, it is a mat. dwell with regret on that long mental ter of some surprise that collections have night which enveloped those bappy regions

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where scievce and the arts had flourished, the largest is that of Cosmo III., and whence their influence had diverged to wards of three thonsand in copper. surrounding nations ; but they must exult

This collection eclipsed every other, in the recollection of the gradual return of though there were many of very great exday, which at length reached its meridian, tent in different parts of the continent; nor and exhibited a grand picture of learning have the learned of England been deficient and the liberal arts. Upon their revival in their exertions to procure those useful the study of medals became an object of evidences of past transactions. Camden, primary importance, and Petrarch appears who first engraved medals for his valuable at the head of those who justly appreciated works, is supposed to have been one of the their value ; sensible of the spirit of emula- tirst collectors; to whom may be added, tion they were calculated to inspire, he Sir Robert Cotton. Henry, Prince of sent the Enperor, Charles IV., several Wales, son of James I., possessed thirty made in honour of great and good men, thousand coins and medals. Archbishop with an invitation to imitate their con- Laud gave five thonsand five hundred coins duct.

to the Bodleian library. The Earl of ArunAlphonso, King of Arragon, acted upon del, celebrated for his taste in selecting the principle recommended by Petrarch, specimens of antiquity, had an excellent and carried a collection he had ordered to collection of medals; and Evelyn enumebe made, constantly with bim, in order that rates the Dukes of Hamilton and Buckhe might remember the qualities which ingham, Sir Thomas Fanshaw, Sir William caused their being struck. Examples like Paston, Sir Thomas Hanmer, Messrs. Shelthose were not without imitation in succeed- don, Selden, and many others, as having ing periods, but the most noble and magni- in their possession cabinets of medals. ficent consequence was the Cabinet of Charles I., a monarch who would have Cosmo de Medici, which was for a long done more to improve the state of the arts time the admiration of Europe. Keysler, in England than all his predecessors, had who saw this collection in 1730, asserts, his reign been happy, collected a vast numthat “ with regard to the number of old ber, which were lost after his dethro necoins, they reckon at present three hundred ment; and his historian, Lord Clarendon, and twelve medallions, among which are endeavoured to rival his royal master in forty-five of silver. The largest copper this interesting pursuit, which appears to medallion is a Julia, the consort of Septi- have been in some degree a favourite one mus Severus. The copper coins of the with Oliver Cromwell. smaller size amount to about eight hundred, Charles II. entertained a similar partiand those of the larger size to one thousand ality for medals, but his successors have eight hundred. The middle sort, by the entirely neglected them, and suffered their French called Moyen Bronze, are two thou- subjects to set them an example which sand two hundred, and this collection is the it is much to be wished they had followed. most valuable and curious, containing a Amongst those were Sir Hans Sloane, the great number of Greek coins. Among the Earls of Pembroke and Winchelsea, and silver pieces are eight hundred consular several others, mentioned by Haym, who ones, and npwards of two thousand others. wrote about 1720. Since the above period Here are six hundred pieces of gold, and our general knowledge of medals has been sixteen medallions of the same metal. I considerably increased, and the skill with was assured by Bianchi, that the largest which the most recent collections were gold medal weighs one hundred and sixteen made, does infinite honour to the penetration Louis d'ors, and represents the Emperor and acumen of our medallists, who are freJohn Palæologus VI., who assisted at the quently enabled to detect fictitions pieces, Council of Florence.

which have been made with sufficient art to The number of medals in gold, silver, impose upon foreigners. Several noblemen and copper, struck in honour of cities and and gentlemen now possess rich cabinets, countries, amonnts to fifteen hundred. The and the British Museum contains a superb gold and copper ones of this assortment collection derived from numerous sources, are the most curious. The whole collec- Medals have from necessity been unition consists of fourteen thousand ancient, formly struck on copper, variously mixed and eight thousand modern medals. Of with other substances, silver, and gold, the the latter there are nine hundred of gold, most ancient of the latter metal are evi. and two thousand of silver, amongst which dently in its native state, neither purified

or combined with copper, though there are sidered their denarius as of the same value some which are supposed to be of gold and with the drachma. The didrachm of silver silver. Philip of Macedon caused the gold was double the amount of tbe drachma; used for coining in his dominions to be the tridrachm was three drachmas, and made of the utmost parity, and in this par. the tetradrachm, the largest of Greek silver ticular he was imitated by Alexander the coins, except the tetradrachm of the Egi, Great, and others nearly his contemporaries. nean standard, is equivalent to five shillings The Romans profiting by the experience of our money. of ages, and perceiving that the purity of The silver drachma was divided into the metal improved the beauty of the im- several denominations, as the tetrobolion pression, determined to use it in as perfect worth a modern sixpence; the hemidrachm, a state as possible; the silver coins of that or triobolion, the diobolion, the obulus, the people were less pure, and became at length hemiobolion, the tetartobolion, and the greatly debased.

dichalcos; the latter was worth about a farThe pure brass medals, and the red, or thing and a halt. Very few of those minute copper, called by the ancients Cyprian silver coins have reached us, and others are brass, were generally covered by platina. mentioned by Greek writers, which were The best mixture was electrum, composed still less, and are consequently entirely de. of one fifth of silver, and the remainder of cayed, or have been overlooked or nege gold : in some instances this was a natural lected for the larger species. combination, in others artificial. Pinker. It may be proper in poticing these coins, ton says, the earliest Lydian coins, and to mention the figures impressed on some those of particular states of Asia Minor, are of them, for instance, Pallas and Proserof this description, as are those of the pine on the tetradrachm, and the troizene; Kings of the Bosphorns Cimmerius, dur. the cistophori had the mystic chest of Bacing the imperial ages of Rome. The Egyp- chus, with a serpent rising out of it; but tian coins, made when that country was the Athenian coins were the most numer. under the dominion of Rome, were at first ous, though the execution of them was of good silver, but degenerated afterwards ; indifferent. The first copper coins extant indeed lead, and even tin, have been used are Syracnsan; those of Greece are the for the purposes of money.

chalcos, originally of very inconsiderable The sbapeless coins of very great apti- value. It does not appear that gold was quity were mere fragments of metal, the used for this purpose in Greece before the value of which was regulated entirely by reign of Philip of Macedon, and Athens weight, and this method extended to the was destitute of this description of money comparatively worthless substance, brass, at the commencement of the Peloponnesian The silver coins of Greece, first known as war; Sicily had set the example in this rebearing marks, are those with a tortoise on spect, the government of which island had one side, and indented on the other; it is issued gold coins four hundred and ninety, extremely doubtful when these coins were one years before Christ. The Xpuros, or made, but they are supposed to have been Philippus was a didrachm, the common from the celebrated mint of Ægina, where, form of gold coins of very remote times, according to some writers, the tirst coinage and was equal in value to one pound sterof money took place by command of Phi- ling. The Philippus was divided into four don, King of the Argives. Herodotus as- parts, and there were still smaller coins of serts, that the Lydians invented the art of this precious metal. The Arxpuoos of Aleximpressing figures on their coins, whether ander and Lysimachus was of greater value correctly or not, cannot now be decided. than the Philippus, and is said to have been Phidon is said to have lived about eight worth forty shillings of our money. Some hundred and tifty years before the Chris- of the Egyptian monarchs quadrupled the tian æra, and the tortoise is known to be Xpucos, consequently their coins equalled the badge of the Peloponnesus.

four pounds. The drachma, or eighth part of an ounce, The Romans estimated their money by was the leading denomination of the Gre. weight, as the Greeks bad done before, cian money, and their coins were generally but they differed from that people in adopt. named from their weights, though some- ing silver for their coins, as they used coptimes the case was reversed; the silver per, not in preference, but from necessity. drachma was equivalent on a medium to The Roman pound was twelve ounces, connine pence sterling, and the Romans cou. sisting of four hundred and fifty-eight grains, though the money.ounce appears to it weighed three ounces previons to the have been four hundred and twenty troy diminution of its value. The sextans, or grains, or five thousand and forty to the sixth part, were not sufficiently numerous, pound; this was the standard of copper. and other divisions were made to answer After silver was introduced, the ounce con- the public convenience, such as the uncia, sisted of seven denarii, and gold was esti. or twelfth part of the pound, the semi-unmated by the scruple, the third part of a cia, and the sextula, or sixth part of an denarius, and the preceding weights. The ounce; besides these there was the decus. sestertius, or half the third, a division of the sus, valued at ten ases, or one denarius; number ten equally improper, and subse. the vicessus, the value of two denarii; and quently umisual, was chosen by the Romans the centussis was the largest coin of this as the principle estimate of their money. metal, which was worth ten denarii, or one Servins Tullus introduced the practice of hundred ases, and may be said to be equiimpressing figures on their copper or aes, valent to six shillings and three-pence ster. which were those of pecus, or small cattle, ling. from which circumstance the word pecunia The ancient denarius seems to have de. was derived. This manner of distinguishing rived its name from the fact of its contain: the coin was afterwards changed, and Janus ing denos-æris or ases, or ten ases, though on one side, and the prow of a galley on the the weight varied; during the time of the other, became the marks of the aes; this, Commonwealth it was the seventh part of with the triens, the quadrans, and sextans, an ounce. In that ot Claudius the weight impressed with the form of a vessel, were was precisely an attic-drachm; the former for a very long period the only medium; equalled eight-pence of our money, and the but five years before the first Punic war, latter seven-pence, without entering into circumstances had enabled the Romans to fractions in either case. Bigatus and quaduse silver, which they coined into denarii, rigatns were terms applied to the denarius, bearing the head of the genius of Rome, alluding to the bigæ or chariot with two with a helmet on one side, and on the other horses impressed upon it, and the quadrigæ chariots drawn by two or four horses. The or chariot with four horses. Clodius intro. coin called victoriati received the figures of duced the victoriatus mentioned before, Victory and of Rome; and the sestertii which was equal in value to the half of a generally had the protectress of the city, denarius; it also bore the name of quinawith Castor and Pollux.

rius, from its containing the value of five The Emperors usually ordered their own ases. The celebrated sestertius, so called busts to be placed on their coins, except from sesquitertius, as consisting of two ases Augustus, who had Capricorn. Sixty-two and a half, was half the victoriatas, and a years elapsed between the introduction of fourth part of the denarius ; exclusive of silver and that of gold, which occurred in the above jame it was frequently called the consulship of M. Livius Salinator. The nummus and sestertius nummus, the value as, derived from æs, brass, originally con. of which, in modern money, was extremely sisted of one poupd weight, but the diffi. small, being little more than one penny. culties experienced during the first Punic The obulus, or the sixth part of the dena. war, compelled the public to reduce the rius, was nearly of the same amount. The value of the as, and to convert one into six libella, the tenth of the deparius, equalled ases. The success of Hannibal in the se. the as, or the supposed pound of copper or cond contest, under the above term, pro- brass. The semi-libella explains itself, and duced still greater distress in the state, and the teruncius, or fortieth part of the depaanother reduction in their value took place, rius, was worth three ounces of the metal when the as became but ong ounce in just mentioned. weight; this was again reduced, by a law of The most remarkable Roman coins of Papyrius, to half an ounce, in which state gold were the aurei denarii, which were it afterwards remained. The as, supposed thus termed probably from their resem. by Kennet to be equal in value to a far. blance in size, or the similarity of the fithing and a half sterling, was the tenth gures they bore on their surtaces to the depart of the denarius, and the semi-æs, or narii. Those coined under the Common. semissis, was the half; the triens, as the wealth weighed two silver denarii, and word implies, was the third part of the as, were worth seventeen shillings, one penny, and the quadrens the fourth, which was and something more than a farthing stersometimes called triuncis and teruncias, as ling; the aureas, made after the change in

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