advantages of our common clock were thus, in some measure, obtained.

The French historians describe a clock sent to Charlemagne in the year 807, by the famous Eastern Caliph, Haroun al Raschid, which was evidently furnished with some kind of wheelwork, although the moving power appears to have been produced by the fall of water. This clock was a rather wonderful affair, and excited a great deal of attention at the French court. In the dial of it were twelve small doors forming the divisions for the hours, each door opened at the hour marked by the index, and let out small brass balls, which, falling on a bell, struck the hours-a great novelty at that time. The doors continued open until the hour of twelve, when twelve figures representing knights on horseback came out and paraded round the dial plate.

Wheelwork was known and skilfully applied by Archimedes; but no description of any piece of mechanism resembling our clocks is found among the ancient Greeks. The term horologe, by which clocks only came to be denoted in process of time, was formerly applied indiscriminately to dials and clocks, so that nothing decisive, as to the era of invention, can be inferred from its use; nor is it possible to point out any individual who can with propriety be called the inventor of clocks. The first author who has introduced the term as applicable to a clock that struck the hours appears to be Dante, who was born in 1265, and died in 1321. In Italy, however, it would appear that striking clocks moved by weights were known in the latter part of the twelfth century. Our own country was in possession of these improved time-meters at rather a later period. In the 16th of Edward I., or 1288, a fine imposed on the Chief-Justice of the King'sBench was applied to the purpose of furnishing a clock for the clock-house near Westminster Hall, which clock was to be heard by the courts of law. This clock was considered of such

consequence in the reign of Henry VI. (which commenced in 1422) that the king gave the keeping of it, with the appurtenances, to William Warby, dean of St. Stephen's, together with sixpence per day, to be received at the Exchequer. The clock at St. Mary's, at Oxford, was also furnished, in 1523, out of fines imposed on the students of the university. Mention is made in Rymer's "Fœdera" of protection being given by Edward III. to three Dutch horologers who were invited from Delft into England, in the year 1368; and we find in Chaucer, who was born in 1328, and died in 1400, the following lines: "Full sickerer was his crowing in his loge,

As is a clock, or any abbey orloge."

In the year 1334 Giacomo Dondi erected at Padua his celebrated clock, which, besides the hour of the day, showed the course of the sun in the ecliptic, and the places of the planets. The celebrity which this clock acquired, tended greatly to advance this particular branch of mechanical art, and the author was dignified with the surname of Horologius.

About the middle of the fourteenth century, the famous Strasburg clock appears to have been erected in the cathedral church of that city. It was a most complicated piece of mechanism, the plate exhibiting a celestial globe, with the motions of the sun, moon, earth, and planets, and the various phases of the moon, together with a perpetual almanac on which the day of the month was pointed out by a statue; the first quarter of the hour was struck by a child with an apple, the second by a youth with an arrow, the third by a man with the tip of his staff, and the last quarter by an old man with his crutch. The hour itself was struck on a bell by a figure representing an angel, who opened a door and saluted the Virgin Mary; near to the first angel stood a second, who held an hour-glass, which he turned as soon as the hour had finished striking. In addition to these was the figure of a golden cock, which, on the arrival of every successive hour, flapped its

wings, stretched forth its neck, and crowed twice.

Two

hundred years after, this celebrated clock was almost entirely

renewed, when great al

terations in the original mechanism were made. At present we believe it has fallen quite into disuse. A clock with a similar complicated machinery, though differing considerably in its external performances, was erected somewhere about the year 1385 in the cathedral of Lyons. The next important clock of which we have any description was regulated by a balance; it was the work of Henry de Wyck, a German mechanician of considerable ingenuity, and was placed in the tower

of a palace of the Emperor Charles V. about the year 1364. This clock of De Wyck, and indeed all those made with a balance for the regulator, without any regulating spring, must have been very imperfect machines, yet our present clocks and watches are but improvements upon this rude beginning. At what period portable clocks were first made, is uncertain; there is, however, a story told of a gentlemen of the court of Louis XI. of France, which shows that the reduction of the time-piece to a portable compass had taken place towards the end of the fifteenth century. It appears that the courtier

in question, after having lost a large amount of money at play, stole a clock belonging to the king, and hid it in his sleeve. The clock nevertheless continued its movements, and after a time gave notice of its place of concealment by striking the hour; this immediately discovered the theft, and the king, capricious in his kindness as well as in his cruelties, not only forgave the offender but actually made him a present of the clock. In the year 1544 the corporation of master clock-makers at Paris obtained from Francis I. a statute in their favour, forbidding any one who was not an admitted master to make clocks, watches, or alarms, large or small. Before portable clocks could be made, the substitution of the main-spring for a weight, as the moving power, must have taken place; and this may be considered a second era in horology, from which may be dated the application of the fusee; for these inventions completely altered the form and principles of horological machines.

The application of a pendulum to the clock, marked another era in their construction. Galileo and Huygens contended for the priority of applying the pendulum to clocks; but the honour really belongs to a London artist named Richard Harris, who invented and made a long-pendulum clock in 1641, seventeen years before the date at which Galileo describes himself to have made, or directed the making of one.

In 1617, Barlow, a London clock-maker, invented the repeating mechanism by which the hour last struck may be known by pulling a string; but a much more important addition to the improvements in clocks speedily followed, namely, the invention of the anchor escapement, which, like most others that have stood the test of time, belongs to the English. This was the work of Clement, a London clock-maker, in 1680.

It would be a matter of some difficulty to determine what artist first reduced the portable spring-clock to the dimensions of a watch to be worn in the pocket. The small clocks prior to the time of Huygens and Hooke were very imperfect

machines; they did not even profess to subdivide the hours into minutes and seconds until the invention of the balancespring, which is to the balance what gravity is to the pendulum, and its introduction has contributed as much to the improvement of watches as did that of the pendulum to clocks. The honour of this invention was warmly contested by the lastnamed individuals previous to 1658; but, so far as priority of publication is concerned, the honour is due to Hooke.

Towards the end of the last century a clock was constructed by a Genevan mechanic named Droz, capable of performing a variety of surprising movements, which were effected by the figures of a negro, a shepherd, and a dog. When the clock struck, the shepherd played six tunes on his flute, and the dog approached and fawned upon him. This clock was exhibited to the King of Spain, who was highly delighted with the ingenuity of the artist. The king, at the request of Droz, took an apple from the shepherd's basket, when the dog started up and barked so loud that the king's dog, which was in the same room, began to bark also. We are moreover informed, that the negro, on being asked what hour it was, answered the question in French, so that he could be understood by those present.

A common watch has for its moving power a main-spring, the variable force of which is equalized, or rendered uniform, by the introduction of the fusee-a very beautiful contrivance, which is, nevertheless, nothing more than a variable lever, upon which the main-spring acts through the medium of the chain. As the chain winds upon it, the distance from the centre of motion of the fusee to the semi-diameter of the chain which is in contact with it varies, in the proportion, that the distance of the centre of motion of the fusee to the semi-diameter of the chain, at that point where it leaves the fusee for the barrel, multiplied by the force of the main-spring acting on the chain at that time, shall be what mathematicians term a constant quantity—that is, it shall be the same whatever point of the fusee may be taken.