a machine constructed in such a manner, and regulated so by the uniform motion of a pendulum (A), as to measure time, and all its subdivisions, with great exactness.

The invention of clocks with wheels is referred to Pacificus, archdeacon of Verona, who lived in the time of Lotharius son of Louis the Debonnaire, on the credit of an epitaph quoted by Ughelli, and borrowed by him from Panvinius. They were at first called nocturnal dials, to distinguish them from sun-dials, which showed the hour by the sun’s shadow. Others ascribe the invention to Boethius, about the year 510. Mr Derham makes clock-work of a much older standing; and ranks Archimedes’s sphere mentioned by Claudian, and that of Pheidonius mentioned by Cicero, among the machines of this kind: not that either their form or use was the same with those of ours, but that they had their motion from some hidden weights or springs, with wheels or pulleys, or some such clockwork principle. But be this as it will, it is certain the art of making clocks, such as are now in use, was either first invented, or at least retrieved, in Germany, about 200 years ago. The water-clocks, or clepsydrae, and sun-dials, have both a much better claim to antiquity. The French annals mention one of the former kind sent by Aaron, king of Persia, to Charlemagne, about the year 807, which seemed to bear some resemblance to the modern clocks: it was of brass, and showed the hours by twelve little balls of the same metal, which fell at the end of each hour, and in falling struck a bell and made it sound. There were also figures of 12 cavaliers, which at the end of each hour came forth at certain apertures or windows in the side of the clock, and shut them again, &c.

The invention of pendulum clocks is owing to the happy industry of the last age: the honour of it is disputed by Huygens and Galileo. The former, who has written a volume on the subject, declares it was first put in practice in the year 1657, and the description thereof printed in 1657. Brecker, de Novo Temporis dimetendi Theoria, anno 1680, contends for Galileo; and relates, though at second-hand, the whole history of the invention; adding, that one Trefler, at that time clock-maker to the father of the Grand Duke of Tuscany, made the first pendulum-clock at Florence, by direction of Galileo Galilei; a pattern of which was brought into Holland. The Academy del Cimento say expressly, that the application of the pendulum to the movement of a clock was first propounded by Galileo, and first put in practice by his son Vincenzo Galilei, in 1649. Be the inventor who he will, it is certain the invention never flourished till it came into Huygen’s hands, who insists on it, that if ever Galileo thought of such a thing, he never brought it to any degree of perfection. The first pendulum-clock made in England was in the year 1662, by Mr Fromantil, a Dutchman.

Among the modern clocks, those of Strasbourg and Lyons are very eminent for the richness of their furniture, and the variety of their motions and figures. In the first, a cock claps his wings, and proclaims the hour; the angel opens a door and salutes the virgin; and the Holy Spirit descends on her, &c. In the second, two horsemen encounter, and beat the hour on each other; a door opens, and there appears on the theatre the Virgin, with Jesus Christ in her arms; the Magi with their retinue, marching in order, and presenting their gifts; two trumpeters sounding all the while to proclaim the procession. These, however, are excelled by two lately made by English artists, and intended as a present from the East India Company to the emperor of China. The clocks we speak of are in the form of chariots, in which are placed, in a fine attitude,

(A) A balance not unlike the fly of a kitchen-jack was formerly used in place of the pendulum. attitude, a lady, leaning her right hand upon a part of the chariot, under which is a clock of curious workmanship, little larger than a thimble, that strikes and repeats, and goes eight days. Upon her finger sits a bird finely modelled, and set with diamonds and rubies, with its wings expanded in a flying posture, and actually flutters for a considerable time on touching a diamond button below it; the body of the bird (which contains part of the wheels that in a manner give life to it) is not the bigness of the 16th part of an inch.

The lady holds in her left hand a gold tube not much thicker than a large pin, on the top of which is a small round box, to which a circular ornament set with diamonds not larger than a sixpence is fixed, which goes round near three hours in a constant regular motion.

Over the lady's head, supported by a small fluted pillar no bigger than a quill, is a double umbrella, under the largest of which a bell is fixed at a considerable distance from the clock, and seems to have no connection with it; but from which a communication is secretly conveyed to a hammer, that regularly strikes the hour, and repeats the same at pleasure, by touching a diamond button fixed to the clock below.

At the feet of the lady is a gold dog; before which from the point of the chariot are two birds fixed on spiral springs; the wings and feathers of which are set with stones of various colours, and appear as if flying away with the chariot, which, from another secret motion, is contrived to run in a straight, circular, or any other direction; a boy that lays hold of the chariot, behind, seems also to push it forward. Above the umbrella are flowers and ornaments of precious stones; and it terminates with a flying dragon set in the same manner. The whole is of gold, most curiously executed, and embellished with rubies and pearls.

Of the general Mechanism of CLOCKS, and how they measure Time. The first figure of Plate CXLVI. is a profile of a clock: P is a weight that is suspended by a rope that winds about the cylinder or barrel C, which is fixed upon the axis a a; the pivots b b go into holes made in the plates TS, TS, in which they turn freely. These plates are made of brass or iron, and are connected by means of four pillars ZZ; and the whole together is called the frame.

The weight P, if not restrained, would necessarily turn the barrel C with an uniformly accelerated motion, in the same manner as if the weight was falling freely from a height. But the barrel is furnished with a ratchet-wheel KK, the right side of whose teeth strikes against the click, which is fixed with a screw to the wheel DD, as represented in fig. 2, so that the action of the weight is communicated to the wheel DD, the teeth of which act upon the teeth of the small wheel d which turns upon the pivots c c. The communication or action of one wheel with another is called the pitching; a small wheel like d is called a pinion, and its teeth are leaves of the pinion. Several things are requisite to form a good pitching, the advantages of which are obvious in all machinery where teeth and pinions are employed. The teeth and pinion leaves should be of a proper shape, and perfectly equal among themselves; the size also of the pinion should be of a just proportion to the wheel acting into it; and its place must be at a certain distance from the wheel, beyond or within which it will make a bad pitching.

Vol. VI. Part I.

The wheel E.E is fixed upon the axis of the pinion d; and the motion communicated to the wheel DD by the weight is transmitted to the pinion d, consequently to the wheel E.E, as likewise to the pinion e and wheel FF, which moves the pinion f, upon the axis of which the crown or balance wheel GH is fixed. The pivots of the pinion f play in holes of the plates LM, which are fixed horizontally to the plates TS. In a word, the motion begun by the weight is transmitted from the wheel GH to the palettes IK, and, by means of the fork UX rivetted on the palettes, communicates motion to the pendulum AB, which is suspended upon the hook A. The pendulum AB describes, round the point A, an arc of a circle alternately going and returning. If then the pendulum be once put in motion by a push of the hand, the weight of the pendulum at B will make it return upon itself, and it will continue to go alternately backward and forward, till the resistance of the air upon the pendulum, and the friction at the point of suspension at A, destroy the originally impressed force. But as, at every vibration of the pendulum, the teeth of the balance-wheel GH, act so upon the palettes IK (the pivots upon the axis of these palettes play in two holes of the potence s t), that after one tooth H has communicated motion to the palette K, that tooth escapes; then the opposite tooth G acts upon the palette I, and escapes in the same manner; and thus each tooth of the wheel escapes the palettes IK, after having communicated their motion to the palettes in such a manner that the pendulum, instead of being stopt, continues to move.

The wheel EE revolves in an hour; the pivot c of the wheel passes through the plate, and is continued to r; upon the pivot is a wheel NN with a long socket fastened in the centre; upon the extremity of this socket r the minute-hand is fixed. The wheel NN acts upon the wheel O; the pinion of which p acts upon the wheel gg, fixed upon a socket which turns along with the wheel N. This wheel gg makes its revolution in 12 hours, upon the socket of which the hour-hand is fixed.

From the above description it is easy to see, 1. That the weight p turns all the wheels, and at the same time continues the motion of the pendulum. 2. That the quickness of the motion of the wheel is determined by that of the pendulum. 3. That the wheels point out the parts of time divided by the uniform motion of the pendulum.

When the cord from which the weight is suspended is entirely run down from off the barrel, it is wound up again by means of a key, which goes on the square end of the arbor at Q by turning it in a contrary direction from that in which the weight descends. For this purpose, the inclined side of the teeth of the wheel R (fig. 2.) removes the click C, so that the ratchet-wheel R turns while the wheel D is at rest; but as soon as the cord is wound up, the click falls in between the teeth of the wheel D, and the right side of the teeth again act upon the end of the click, which obliges the wheel D to turn along with the barrel; and the spring A keeps the click between the teeth of the ratchet-wheel R.

We shall now explain how time is measured by the motion of the pendulum; and how the wheel E, upon the axis of which the minute-hand is fixed, makes but one precise revolution in an hour. The vibrations of a pendulum are performed in a shorter or longer time in proportion to the length of the pendulum itself. A pendulum of 3 feet 8½ French lines in length, makes 3600 vibrations in an hour; i.e., each vibration is performed in a second of time, and for that reason it is called a second pendulum. But a pendulum of 9 inches 2½ French lines makes 7200 vibrations in an hour, or two vibrations in a second of time, and is called a half-second pendulum. Hence, in constructing a wheel whose revolution must be performed in a given time, the time of the vibrations of the pendulum which regulates its motion must be considered. Supposing, then, that the pendulum A makes 7200 vibrations in an hour, let us consider how the wheel E shall take up an hour in making one revolution. This entirely depends on the number of teeth in the wheels and pinions. If the balance-wheel consists of 30 teeth, it will turn once in the time that the pendulum makes 60 vibrations; for at every turn of the wheel, the same tooth acts once on the pallet I, and once on the pallet K, which occasions two separate vibrations in the pendulum; and the wheel having 30 teeth, it occasions twice 30, or 60 vibrations. Consequently, this wheel must perform 120 revolutions in an hour; because 60 vibrations, which it occasions at every revolution, are contained 120 times in 7200, the number of vibrations performed by the pendulum in an hour. Now, in order to determine the number of teeth for the wheels EF, and the pinions ef, it must be remarked, that one revolution of the wheel E must turn the pinion e as many times as the number of teeth in the pinions is contained in the number of teeth in the wheel. Thus, if the wheel E contains 72 teeth, and the pinion e 6, the pinion will make 12 revolutions in the time that the wheel makes 1; for each tooth of the wheel drives forward a tooth of the pinion, and when the 6 teeth of the pinion are moved, a complete revolution is performed; but the wheel E has by that time only advanced 6 teeth, and has still 66 to advance before its revolution be completed, which will occasion 11 more revolutions of the pinion. For the same reason, the wheel F having 60 teeth, and the pinion f 6, the pinion will make 10 revolutions while the wheel performs one. Now, the wheel F being turned by the pinion e, makes 12 revolutions for one of the wheel E; and the pinion f makes 10 revolutions for one of the wheel F; consequently, the pinion f performs 10 times 12 or 120 revolutions in the time the wheel E performs one. But the wheel G, which is turned by the pinion f, occasions 60 vibrations in the pendulum each time it turns round; consequently the wheel G occasions 60 times 120 or 7200 vibrations of the pendulum while the wheel E performs one revolution; but 7200 is the number of vibrations made by the pendulum in an hour, and consequently the wheel E performs but one revolution in an hour; and so of the rest.

From this reasoning, it is easy to discover how a clock may be made to go for any length of time without being wound up: 1. By increasing the number of teeth in the wheels; 2. By diminishing the number of teeth in the pinions; 3. By increasing the length of the cord that suspends the weight; 4. By increasing the length of the pendulum; and, 5. By adding to the number of wheels and pinions. But in proportion as the time is augmented, if the weight continues the same, the force which it communicates to the last wheel GH will be diminished.

It only remains to take notice of the number of teeth in the wheels which turn the hour and minute-hands.

The wheel E performs one revolution in an hour; the wheel NN, which is turned by the axis of the wheel E, must likewise make only one revolution in the same time; and the minute-hand is fixed to the socket of this wheel. The wheel N has 30 teeth, and acts upon the wheel O, which has likewise 30 teeth, and the same diameter; consequently the wheel O takes one hour to a revolution: now the wheel O carries the pinion p, which has 6 teeth, and which acts upon the wheel q of 72 teeth; consequently the pinion p makes 12 revolutions while the wheel qq makes one, and of course the wheel qq takes 12 hours to one revolution; and upon the socket of this wheel the hour hand is fixed. All that has been said here concerning the revolutions of the wheels, &c., is equally applicable to watches as to clocks.

The ingenious Dr Franklin contrived a clock to show the hours, minutes, and seconds, with only three wheels and two pinions in the whole movement. The dial-plate (fig. 3.) has the hours engraved upon it in Fig. 3. spiral spaces along two diameters of a circle containing four times 60 minutes. The index A goes round in four hours, and counts the minutes from any hour by which it has passed to the next following hour. The time, therefore, in the position of the index shown in the figure is either 32½ minutes past XII, III., or VIII.; and so in every other quarter of the circle it points to a number of minutes after the hours which the index last left in its motion. The small hand B, in the arch at top, goes round once in a minute, and shows the seconds. The wheel-work of this clock may be seen in fig. 4. A is the first or great wheel, containing 160 teeth, and going round in four hours with the index A in fig. 3. let down by a hole on its axis. This wheel turns a pinion B of 10 leaves, which therefore goes round in a quarter of an hour. On the axis of this pinion is the wheel C of 120 teeth; which goes round in the same time, and turns a pinion D of eight leaves round in a minute, with the second hand B of fig. 3. fixed on its axis, and also the common wheel E of 30 teeth for moving a pendulum (by pallets) that vibrates seconds, as in a common clock. This clock is wound up by a line going over a pulley on the axis of the great wheel, like a common thirty hour clock. Many of these admirably simple machines have been constructed, which measure time exceedingly well. It is subject, however, to the inconvenience of requiring frequent winding by drawing up the weight, and likewise to some uncertainty as to the particular hour thrown by the index A. Mr Ferguson has proposed to remedy these inconveniences by the following construction. In the dial-plate of his clock (fig. 5.) there is an opening, a b c d, below the centre, through which appears part of a flat plate, on which the 12 hours, with their divisions into quarters, are engraved. This plate turns round in 12 hours; and the index A points out the true hour, &c. B is the minute-hand, which goes round the large circle of 60 minutes whilst the plate \(a b c d\) shifts its place one hour under the fixed index \(A\). There is another opening, \(e f g\), through which the seconds are seen on a flat moveable ring at the extremity of a fleur-de-lis engraved on the dial-plate. \(A\) in fig. 6. is the great wheel of this clock, containing 120 teeth, and turning round in 12 hours. The axis of this wheel bears the plate of hours, which may be moved by a pin passing through small holes drilled in the plate, without affecting the wheel-work. The great wheel \(A\) turns a pinion \(B\) of ten leaves round in an hour, and carries the minute hand \(B\) on its axis round the dial-plate in the same time. On this axis is a wheel \(C\) of 120 teeth, turning round a pinion \(D\) of six leaves in three minutes; on the axis of which there is a wheel \(E\) of 90 teeth, that keeps a pendulum in motion, vibrating seconds by palettes, as in a common clock, when the pendulum-wheel has only 30 teeth, and goes round in a minute. In order to show the seconds by this clock, a thin plate must be divided into three times sixty, or 180 equal parts, and numbered 10, 20, 30, 40, 50, 60, three times successively; and fixed on the same axis with the wheel of 90 teeth, so as to turn round near the back of the dial-plate; and these divisions will show the seconds through the opening \(e f g h\), fig. 5. This clock will go a week without winding, and always show the precise hour; but this clock, as Mr Ferguson candidly acknowledges, has two disadvantages of which Dr Franklin's clock is free. When the minute-hand \(B\) is adjusted, the hour-plate must also be set right by means of a pin; and the smallness of the teeth in the pendulum-wheel will cause the pendulum-ball to describe but small arcs in its vibrations; and therefore the momentum of the ball will be less, and the times of the vibrations will be more affected by any unequal impulse of the pendulum-wheel on the palettes. Besides, the weight of the flat ring on which the seconds are engraved will load the pivots of the axis of the pendulum-wheel with a great deal of friction, which ought by all possible means to be avoided. To remedy this inconvenience, the second plate might be omitted.

A clock similar to Dr Franklin's was made in Lincolnshire about the end of the 17th century or beginning of the 18th; and is said to be in London in the possession of a grandson of the person who made it.

A clock, showing the apparent diurnal motions of the sun and moon, the age and phases of the moon, with the time of her coming to the meridian, and the times of high and low water, by having only two wheels and a pinion added to the common movement, was contrived by Mr Ferguson, and described in his Select Exercises. The dial-plate of this clock (fig. 7.) contains all the twenty-four hours, of the day and night. \(S\) is the sun, which serves as an hour index by going round the dial-plate in twenty-four hours; and \(M\) is the moon, which goes round in twenty-four hours fifty minutes and a half, the time of her going round in the heavens from one meridian to the same meridian again. The sun is fixed to a circular plate (see fig. 8.) and carried round by the motion of that plate on which the twenty-four hours are engraven; and within them is a circle divided into twenty-nine and a half equal parts for the days of the moon's age, reckoning from new moon to new moon; and each day stands directly under the time, in the twenty-four hour circle, of the moon's coming to the meridian; the XII under the sun standing for noon, and the opposite XII for midnight. The moon \(M\) is fixed to another circular plate (fig. 6.) of the same diameter with that which carries the sun, part of which may be seen through the opening, over which the small wires \(r\) and \(b\) pass in the moon-plate. The wire \(a\) shows the moon's age and time of her coming to the meridian, and \(b\) shows the time of high-water for that day in the sun-plate. The distance of these wires answers to the difference of time between the moon's coming to the meridian and high-water at the place for which the clock is made. At London their difference is two hours and a half. Above the moon-plate there is a fixed plate \(N\), supported by a wire \(A\), joined to it at one end, and fixed at right angles into the dial plate at the midnight XII. This plate may represent the earth, and the dot \(L\) London, or the place to which the clock is adapted. Around this plate there is an elliptic shade on the moon-plate, the highest points of which are marked high-water, and the lowest low-water. As this plate turns round below the plate \(N\), these points come successively even with \(L\), and stand over it at the times when it is high or low water at the given place; which times are pointed by the sun \(S\) on the dial-plate; and the plate \(H\) above XII at noon rises or falls with the tide. As the sun \(S\) goes round the dial-plate in twenty-four hours, and the moon \(M\) in twenty-four hours fifty minutes and a half, it is plain that the moon makes only twenty-eight revolutions and a half, whilst the sun makes twenty-nine and a half; so that it will be twenty-nine days and a half from conjunction to conjunction. And thus the wire \(a\) shifts over one day of the moon's age on the sun-plate in twenty-four hours. The phases of the moon for every day of her age may be seen through a round hole \(m\) in the moon-plate: thus at conjunction or new-moon, the whole space seen through \(m\) is black; at opposition or full moon this space is white; at either quadrature half black and half white; and at every position the white part resembles the visible part of the moon for every day of her age. The black-shaded space \(N f F l\) (fig. 8.) on the sun-plate serves for these appearances. Fig. 8. \(N\) represents the new moon, \(F\) the full moon, and \(f\) her first quarter, and \(l\) her last quarter, &c. The wheel-work and tide-work of this clock are represented in fig. 9. \(A\) and \(B\) are two wheels of equal diameters; \(A\) has fifty-seven teeth, with a hollow axis that passes through the dial of the clock, and carries the sun-plate with the sun \(S\). \(B\) has fifty-nine teeth, with a solid spindle for its axis, which turns within the hollow axis of \(A\), and carries the moon-plate with the moon \(M\); both wheels are turned round by a pinion \(C\) of nineteen leaves, and this pinion is turned round by the common clock-work in eight hours; and as nineteen is the third part of fifty-seven, the wheel \(A\) will go round in twenty-four hours; and the wheel \(B\) in twenty-four hours fifty minutes and a half; fifty-seven being to twenty-four as fifty-nine to twenty-four hours fifty minutes and a half very nearly. On the back of the wheel \(B\) is fixed an elliptical ring \(D\), which, in its revolution, raises and lets down a lever \(E F\), whose centre of motion is on a pin at \(F\); and this, by the up- right bar G, raises and lets down the tide-plate H twice in the time of the moon's revolving from the meridian to the meridian again; this plate moves between four rollers R, R, R, R. A clock of this kind was adapted by Mr Ferguson to the movement of an old watch: the great wheel of a watch goes round in four hours; on the axis of this he fixed a wheel of twenty teeth, to turn a wheel of forty teeth on the axis of the pinion C; by which means that pinion was turned round in eight hours, the wheel A in twenty-four, and the wheel B in twenty-four hours fifty minutes and a half.

To this article we shall subjoin a brief account of two curious contrivances. The first, for giving motion to the parts of a clock by making it to descend along an inclined plane, is the invention of Mr Maurice Wheeler; the clock itself was formerly seen in Don Saltero's coffee-house at Chelsea. DE, fig. 10, is the inclined plane on which the clock ABC descends; this consists externally of a hoop about an inch broad, and two sides or plates standing out beyond the hoop about one-eighth of an inch all round, with indented edges, that the clock may not slide, but turn round whilst it moves down. One of these plates is inscribed with the twenty-four hours, which pass successively under the index LP, fig. 11, which is always in a position perpendicular to the horizon, and shows the hour on the top of the machine; for this reason the lower part of the index, or HL, is heaviest, that it may preponderate the other HP, and always keep it pendulous, with its point to the vertical hour, as the movement goes on. Instead of this index, an image may be fixed for ornament on the axis g, which with an erected finger performs the office of an index. In order to describe the internal part or mechanism of this clock, let LETQ be the external circumference of the hoop, and f the same plate, on which is placed the train of wheel work 1, 2, 3, 4, which is much the same as in other clocks, and is governed by a balance and regulator as in them. But there is no need of a spring and fusee in this clock: their effects being otherwise answered as we shall see. In this machine the great wheel of r is placed in the centre, or upon the axis of the movement, and the other wheels and parts towards one side, which would therefore prove a bias to the body of the clock, and cause it to move, even on a horizontal plane, for some short distance: this makes it necessary to fix a thin plate of lead at C, on the opposite part of the hoop, to restore the equilibrium of the movement. This being done, the machine will abide at rest in any position on the horizontal plane HH; but if that plane be changed into the inclined plane DE, it will touch it in the point D; but it cannot rest there, because the centre of gravity at M acting in the direction MI, and the point T having nothing to support it, must continually descend, and carry the body down the plane. But now if any weight P be fixed on the other side of the machine, such as shall remove the centre of gravity from M to the point V in the line LD which passes through the point D, it will then rest upon the inclined plane, as in the case of the rolling cylinder. If this weight P be supposed not fixed, but suspended at the end of an arm, or vectis, which arm or lever is at the same time fastened to a central wheel r, moving on the axis M of the machine, which wheel by its teeth shall communicate with the train of wheels, &c., on the other side, and the power of the weight be just equal to the friction or resistance of the train, it will remain motionless as it did before when it was fixed; and consequently the clock also will be at rest on the inclined plane. But supposing the power of the weight P to be superior to the resistance of the train, it will then put it into motion, and of course the clock likewise; which will then commence a motion down the plane; while the weight P, its vectis PM, and the wheel r, all constantly retain the same position which they have at first when the clock begins to move. Hence it is easy to understand, that the weight P may have such an intrinsic gravity as shall cause it to act upon the train with any required force, so as to produce a motion in the machine of any required velocity; such, for instance, as shall carry it once round in twenty-four hours: then, if the diameters of the plates ABC be four inches, it will describe the length of their circumference, viz. 1256 inches, in one natural day; and therefore, if the plane be of sufficient breadth, such a clock may go several days, and would furnish a perpetual motion, if the plane were infinitely extended. Let SD be drawn through M perpendicular to the inclined plane in the point D; also let LD be perpendicular to the horizontal line HH, passing through D; then is the angle HDE = LDS = DMT; whence it follows that the greater the angle of the plane's elevation is, the greater will be the arch DT; and consequently the further will the common centre of gravity be removed from M; therefore the power of P will be augmented, and of course the motion of the whole machine accelerated. Thus it appears, that by duly adjusting the intrinsic weight of P, at first to produce a motion showing the mean time as near as possible, the time may be afterwards corrected, or the clock made to go faster or slower by raising or depressing the plane, by means of the screw at S. The angle to which the plane is first raised is about ten degrees. The marquis of Worcester is also said to have contrived a watch that moved on a declivity. See farther Phil. Transf. Abr. vol. i. p. 468, &c. or No 167.

The other contrivance is that of M. de Gennes for making a clock ascend on an inclined plane. To this end let ABC (fig. 12.) be the machine on the inclined plane EDE, and let it be kept at rest upon it, or in equilibrium by the weight P at the end of the level PM. The circular area CP is one end of a spring barrel in the middle of the movement, in which is included a spring as in a common watch. To this end of the barrel the arm or lever PM is fixed upon the centre M; and thus, when the clock is wound up, the spring moves the barrel, and therefore the lever and weight P in the situation PM. In doing this, the centre of gravity is constantly removed farther from the centre of the machine, and therefore it must determine the clock to move upwards, which it will continue to do as long as the spring is unbending itself; and thus the weight and its lever PM will preserve the situation they first have, and to do the office of a chain and fusee. Phil. Transf. No 140. or Abridg. vol. i. p. 467.

By stat. 9 and 10 W. III. cap. 28. § 2. no person shall export, or endeavour to export out of this kingdom. dom, any outward or inward box-case or dial-plate, of gold, silver, brass, or other metal, for clock or watch, without the movement in or with every such box, &c., made up fit for use, with the maker's name engraven thereon; nor shall any person make up any clock or watch without putting his name and place of abode or freedom, and no other name or place, on every clock or watch; on penalty of forfeiting every such box, case, and dial-plate, clock and watch, not made up and engraven as aforesaid; and 20l. one moiety to the king, the other to those that shall sue for the same.