galleries caught the jest, and joined boisterously that they sailed beneath the houses. Under in the mirth. Garrick, chagrined by the inde- these arches also were ways through which carts corum of the incident, hastened to the Green- loaded with hay could pass with ease. It began room, to meet Mrs. Clive, 'Madam,' said he, in the Forum Romanum; measured 300 paces 'your smiles are always despotic; it was those of in length; and emptied between the temple of Mrs. Clive which called down that burst of mer- Vesta and the Pons Senatorius. There were as riment just now; to-morrow night I hope it will many principal sewers as there were hills. Plibe excited by those of the character she may ny concludes their firmness and strength from intend to personate.' She comprehended his their standing for so many ages the shocks of meaning, and sportively shutting her eyes, she earthquakes, the fall of houses, and the vast loads tapped them with her fan, exclaiming I whip and weights moved over them. the truants that brought me into the scrape; they never again shall so betray their mistress.' Mrs. Clive at length retired to pass the latter part of her life at Little Strawberry Hill, where many persons of rank and eminence courted her society. Her death occurred in 1785. CLIVER, n. s. Teut. & Belg. stein, claver ; stone clover. The plant melilote, more properly written cleaver. It grows wild, the seeds sticking to the clothes of such as pass by them. It is sometimes used in medicine. CLOACE, in antiquity, the common sewers of Rome, to carry off the soil of the city into the Tiber; justly reckoned among the greatest works of the Romans. The first, called Cloaca Maxima, was built by Tarquin I. of huge blocks of stone joined together without any cement, in the manner of the edifices of those early times; consisting of three rows of arches one above another, which at length conjoin and unite together; measuring, in the clear, eighteen palms in height, and as many in width. Under these arches they rowed in boats, which gave occasion to the remark of Plisy that the city was suspended in air, and CLOACINA, the goddess of common sewers. Most heavenly fair, in deed and view, withal. CLOCK S. Goth. klocka; and Sax. CLOCK, n. s. which, by a series of mechanical movements, Wel sikener wos his crowing in his loge, Bacon. The picture of Jerome usually described at his study, is with a clock hanging by. Browne's Vulgar Errours. I told the clocks and watched the wasting light. Dryden. Hudibras. Resolve by sines and tangents straight, So if unprejudiced you scan, CLOCK, in horology, is a machine so regulated, by the uniform action of a pendulum, as to measure time by a series of vibrations in the oscillating body. Under this head, therefore, we propose to treat of the structure and internal mechanism of those machines which owe their property of keeping time to the continued operation of a pendulum, leaving the portable chronometer, or WATCH, to its appropriate place in our alphabetical arrangement. The earliest complete clock, of which there is any certain record, was contrived in the thirteenth century. It was constructed by a Saracen mechanic, who received about £2000 for his ingenuity. This clock is stated to have kept time very accurately, and it was afterwards presented to the emperor Frederic II. by the Sultan of Egypt, under whose direction it was made. Some time after this period, a clock was placed in a Prior. small building, erected for the purpose, in the city of Westminster, the expense of which was defrayed by a fine imposed on one of the judges for malversation in his office. In the fourteenth century an artist, named James Dondi, a Venetian, constructed a clock for the city of Padua, which was long considered as the wonder of that period. Besides indicating the hours, it represented the motion of the sun, moon, and planets, and alз0 pointed out the different festivals of the year. On this account Dondi obtained the surname of Horologio, which became that of his posterity. About the same period William Zelander constructed, for the same city, a clock still more complex, which was repaired in the sixteenth century by Janellus Turrianus, the mechanist of Charles V. About the year 1560 Tycho Brahe was in possession of four clocks, which indicated hours, minutes, and seconds, the largest of which had only three wheels, one of which was three feet in diameter, and had 1200 teeth in it, a proof that clock-work was then in a very imperfect state. Tycho, however, observed, that there was an irregularity in the going of his clocks, which depended upon the changes in the atmosphere; but he does not appear to have known how such effect was produced. In the year 1577 Moestlin had a clock so constructed as to make just 2528 beats in an hour, 146 of which were counted during the sun's passage over a meridian or azimuth line, and determined his diameter to be 34′ 13", so that the science of astronomy began thus early to be promoted by the assistance of clock-work; and, as clocks first promoted the study of astronomy, it will be seen by and bye, that astronomy, in its turn, gave rise to some of the most essential improvements in clock-work; and that, as the arts and sciences became more and more cultivated, improvements in clockwork kept pace with them, and employed the talents of the most ingenious men of each succeeding age. As the construction of every modern horological machine must depend, mainly, on a judicious combination of wheel-work, it may be desirable to examine, first, the principle of a common wheel and pinion, and then to show its application to the movement of a clock. In the wheel and axis A, B, fig. 1. plate I. of HoROLOGY, two cords of similar length are made to support weights, attached to their lower extremity; the weights being placed in equipoise, although the one is twice as heavy as the other. This apparently paradoxical effect is produced, by giving a mechanical advantage to the cord B, which is twice as far from the centre, or fulcrum, as the one that supports the larger weight: the velocity of the two weights are effected also in an equal ratio. So that if the wheel be made to revolve upon its axis, the weight marked 1 will descend two feet, while the opposite side will only be raised one foot. Here then the gain in power is compensated for by a loss of time, and vice versâ; and upon this circumstance depends the advantageous use of a wheel and pinion. In fig. 2, the pinion D. is supported by a separate axis, round which it is made to revolve; and the wheel B B, being three times as large as the pinion, the latter will make three revolutions to one of the former, or about one revolution for the portion of a circle shown in the diagram. If we consider the weight C as the maintaining power, it will be evident, that, for every revolution made by its axis, there will be three revolutions of the next wheel in succession. If we combine a series of wheels and pinions, a still greater increase in speed will result. This is shown at fig. 3; and it will be seen that there are four revolutions of the pinion c for one of the wheel that drives it; and as the wheel dis attached to the same axis, the pinion e will make sixteen revolutions to one of the prime mover. A reference to this simple mode of increasing velocity in wheel-work, will readily explain why a clock, which makes but twelve revolutions at the barrel, is enabled to beat half and quarter seconds, and even to go as many days as there are turns at the prime mover. Having determined upon the kind of clock to be made, the first thing to be done, and that in which the clock-maker is generally deficient, is, to calculate the movement, or proper number of teeth in the wheels, and of leaves in the pinions of the going part of the mechanism. Dr. Derham, in his Artificial Clock-maker, has treated this subject at considerable length; and has laid down rules which have tended more to puzzle than to assist the workman in the choice of his numbers. He proposes to take at random, a certain number of vibrations per hour for a pendulum of an assumed length, to represent his train, and then to find the factors or numbers, which, used as multipliers, shall give the regular product, or nearly so; after which each factor is represented by a ratio of two optional numbers, to constitute a wheel and its pinion. We will not here follow the Doctor through his processes, but merely observe, that, by calculating his whole movement at one operation from an assumed number of vibrations, he has introduced a variety of such trains into portable clocks and watches, as make a vibration of the short pendulum, and an oscillation of the balance, no exact fraction of a second; in short, he has begun at the wrong end of the business; has first fixed on the length of his pendulum, in inches, without considering exactly the number of vibrations it would make, and then calculated a train that would so nearly suit it, that the adjustment for time, by the bob, would compensate the defect of the numbers; the consequence has been, that the exact value of a vibration in a portable clock, and of an oscillation in an ordinary watch, has hitherto been disregarded in the construction. On the ccntrary, we recommend to the clock-maker, first to fix upon his number of vibrations per second, and then to calculate the true length of his pendulum, and exact value of his train, agreeably to the number of vibrations per second that he previously determined. The most simple way of calculating the numbers proper for the movement of any clock, intended to show seconds, is, by dividing it into three portions, and then by calculating the wheels and pinions for each separate portion, by a separate calculation, beginning at the bottom of the train; thus, we first fix upon the pinion of the hour arbor to be, suppose eight, which is a good, practical number; and as our piece is to go eight days, we will make the fusee to revolve in twelve hours, which construction will require the great wheel on its arbor to be 812, or 96, because the pinion of 8 revolves with the minute-hand on its projecting pivot, in one hour; hence if we divide 192, the number of hours in eight days, by 12, the time of one revolution of the great wheel, the quotient 16 will be the number of effective spiral grooves necessary to be cut on the circumference of the fusee, in order that the piece may go just eight days. This portion of the movement is not, however, called a part of the train, but only determines, as has been said, the time that the clock shall continue to go, after each winding up of the maintaining power; and it is easy to conceive, that, if a fusee or a barrel, with twenty-four turns of the catgut or chain, were placed on the hour arbor, the clock would go a natural day without the large wheel, and, also, that if an intermediate wheel and pinion were placed on the arbor between the hour arbor and the great wheel, the time of going might be prolonged to ten, twelve, or even twenty times eight days, but then the maintaining power must be proportionably increased, which circumstance renders such a construction by no means desirable in a regulator, particularly as the auxiliary spring, now in use, will keep the piece in motion during the act of winding up. The remaining portion of the movement is properly called the train, including those wheels and pinions only which are used for counting the vibrations made in an hour; the train is most easily ascertained by two calculations, one for the two wheels and two pinions which multiply the minutes into seconds, and the other for that wheel and pinion, or those wheels and pinions, which subdivide the seconds into vibrations; the former of these two portions of the train, like the first portion of the movement, or portion for the period of continuance, is the same for all clocks, let the time of vibration be what it may: a circumstance not usually considered. The ratios of velocity to be gained by the pinion on the arbor of the seconds' hand, compared with the wheel on the arbor of the minutes' hand, is required to be 60: 1; which effect might be produced by one wheel of 300 teeth and a pinion of five leaves, as is done in some of the ornamental French pieces; but the size of the wheel is cumbersome, therefore a pair of wheels, with a pair of pinions, che constituting a ratio or vulgar fraction equal in value to 8, and the other equal to 7, making 8 x 7160, or any other two numbers making a similar product will produce the same effect with fewer teeth; for, if the pinions be each 8, the wheels, in this case, will be respectively 64 and 60, the compound ratio, & ×, being equal to the simple; and by the same process, if pinions of 10 had been chosen, the wheels would have been 8 x 1080, and 10 x 775, which numbers would, indeed, have less friction than the preceding ones by reason of their teeth acting at less depth, the diameters of the wheels remaining the same, and would, moreover, be capable of acting more behind than before the line joining the centres of the wheel and pinion; in like manner pinions of 6 would require wheels of 48 and 45, and pinions of 12, wheels of 96 and 90. The last portion of the movement, or second portion of the train, for a half-seconds' pen.lulum, will require only one wheel of sixty teeth on the seconds' arbor, properly shaped for the escapement; for, as one tooth in the dead-beat and common anchor escapements escapes con. pletely at two vibrations of the pendulum, sixty teeth will escape, that is a whole revolution of the seconds' hand will be made, in 120 vibrations; if, however, the pendulum had been required to vibrate seconds, the wheel in question, usually called the swing wheel in opposition to the crown wheel which requires another escapement, would have demanded only thirty teeth for that purpose; and, if three vibrations had been fixed upon, the number to correspond must have been ninety, otherwise there must have been a wheel and pinion of the value of three, like or, an addition to the usual swing wheel of thirty, or, which is the same thing, a wheel and pinion of the value of six, like or, must have been introduced between the seconds' arbor and a pallet, or a swing wheel of 15. Thus all the variety in the calculation of trains, where se conds are indicated, is confined as we have intimated to the last portion of the movement, and the calculation itself so simple, that the mere altering of the numbers of the pallet-wheel will convert a clock with a seconds' pendulum into one with half-seconds, and vice versa. The calculation of numbers suitable for an eight-days' clock, with a half-seconds' pendulum, being thus readily obtained by three simple operations, which may be had by mere inspection of the three tables which we shall presently subjoin, the whole may be represented, and its value estimated again, by a compound fraction, 8 8 8 1 thus: viz. of X of of twelve 96 64 60 60 × 2 hours, or, which is the same thing in effect, thus 8 8 8 X X X 1 512 1 44236800 64800 of twelve hours, or 86400 vibrations in twelve hours, which is the time of a revolution of the fusee, and great wheel, 96, on its arbor, and therefore or 7200 vibrations, each of " 12 half a second in duration, in one hour, constitute the value of this train. 96 64 60 60 × 2 86400 This mode of notation gives the value better than any other, perhaps, that has been adopted; but the position of the wheels and pinions will be better understood from the ordinary mechanical method of writing them down thus :Great wheel 96 : Pin 8-64 hour wheel Indeed it is difficult to write down the movement by any one notation that shall express, at the same time, both the value and position of the wheel-work, on which account we recommend the workman to write down his numbers by both |