Part 6
The CHRONOGRAPH is undoubtedly the most perfect instrument yet invented for marking the exact time occupied by certain rapid movements or events or performances,--and is therefore well adapted for astronomical and medical observations, for timing machinery, for indicating the speed of a race, and of similar quick events even to the tenth of a second. It consists of an ordinary quick train lever movement on a scale sufficiently large to carry the hands for an 8-inch dial. The peculiar feature of the chronograph is its second hand, which is double, consisting of two distinct hands,--the one lying over the other. The lower of the two is furnished at the tip with a small reservoir having an extremely small orifice below; over this orifice the point of the upper hand is bent so as to fall exactly upon the puncture, and to convey through it, as with a pen, the ink held in the reservoir. The mode of operating with the chronograph at a race has been thus described. 'The chronograph is held firmly in the left hand of the operator, who watches the starters, but need not trouble himself to keep at the same time an eye upon the dial. At the moment of the start he presses the finger or thumb of his right hand gently upon the button of the pendant, and instantly a black dot is deposited on the dial, and--the operator being ready to touch the button at the precise moment of the finish, and thus to complete what we may call the chronogram of the event--the exact length of the race is registered, even to a decimal fraction of a second, and an indisputable record written by the instrument itself in black and white. The chronograph, it should be mentioned is, apart from its chronographic mechanism, an excellent time-keeper, and may be worn as an ordinary watch, being the same size as a gentleman's lever watch.
REPEATING WATCHES are now made so as to require no key. They are constructed with a lever or chronometer escapement, and are known according to their method of repeating,--the ordinary _Repeater_ strikes the hours and quarters,--the _Half-quarter Repeater_ strikes the hours, quarters, and half-quarters,--the _Minute Repeater_ strikes hours, quarters, and minutes. The first tells the time in the dark or to the blind person to within a quarter of an hour, the second tells it within seven minutes and a half, the third tells it to the minute.
The CLOCK WATCH and CLOCK REPEATING WATCH are also made so as to need no key. They strike the hours and quarters while being worn in the pocket, and have not only the two trains of wheels for going and striking as in a clock, but a third train provided for repeating purposes. Both mainsprings are wound up by the same winder by a forward and backward action of the pendant. They are constructed with either Lever, Duplex, or Chronometer Escapements, and some are provided with compensation balances adjusted to act equally at extremes of temperature.
THE INDEPENDENT CENTRE SECONDS WATCH is peculiarly adapted for the use of the medical profession. By means of its two trains it carries, besides the ordinary hands denoting hours, minutes, and seconds, a long seconds hand which can be stopped without stopping the watch. It is made with a stem winder, and therefore requires no key.
THE SPLIT CENTRE SECONDS is not quite so complicated as the last named. It has two centre second hands revolving round the dial, the one directly over the other, as also, in another part of the dial, a small hand revolving five times in a second. Upon pressing a stop-piece one of the long second hands is stopped, and another pressure will stop the other--the space between the two hands will then indicate precisely the time occupied by the event which it is desired to measure. Another push to the stop-piece will make both hands again fly together, and enable the operator it may be to make a new experiment or observation.
+----------------------------------------------------------------------+ | [Illustration: The Perpetual Calendar Keyless Watch.] | +----------------------------------------------------------------------+
THE PERPETUAL CALENDAR KEYLESS WATCH, shows on its dial the year, the month of the year, the day of the month, the day of the week, the phases of the moon, as well as hours, minutes, and seconds. It requires no setting, as the old-fashioned Calendar Watch did at certain intervals, but, by a very ingenious contrivance, the changes from month to month, as for example from February 28th to the 1st of March, or from 30th or 31st of other months to the 1st of the next, are all performed by the watch, which also of itself marks the extra day for Leap Year. When to all the above are added, as is sometimes done, the Minute Repeating Work to repeat the hours, quarters, and minutes, it may be said that the power of complication can no farther go within the limits of the small box which is called a watch case,--for these watches are provided with either Lever, Duplex, or Chronometer Escapements as may be preferred, and with compensation balances adjusted to serve in extremes of temperature. But in the examples set forth in the following illustrations, it will be seen that superadded to all the foregoing are a thermometer, and an index showing the calendar by the old and new style, as indicated by the words Gregorian and Russian,--the former referring to Pope Gregory who decreed the alteration to the new style, and the latter to the fact that the Russians still reckon by the old style.
+----------------------------------------------------------------------+ | [Illustration: Perpetual Calendar.] | +----------------------------------------------------------------------+
THE COMPLICATED PERPETUAL CALENDAR AND INDEPENDENT SECONDS KEYLESS WATCH, is another example of this kind of mechanism, which, without being re-set from time to time for leap year and other changes, keeps a perpetual register of seconds, minutes, hours, days, weeks, months, and years, shows Old and New Styles, the phases of the moon, and variations of heat and cold. It has also two separate trains of wheels and two mainsprings, both of which are wound up by the button at the pendant. It will be seen that the dial has two hour circles with hour and minute hands showing separate time. Below the centre is the sunk seconds dial with two seconds hands, the one over the other, and each working independently, so that the one may be stopped by a push at the button of the pendant and yet the other go on, to be in its turn stopped, so that the operator may use it as a stopwatch. Underneath the hour hands of each circle is the hand showing the month and the day of the week. The two centre hands, with the letters G and R, are pointing to the days of the month, and showing the Gregorian and Russian day. In the small square space just below the centre is the year, and below this and lying over the second hands is another hand pointing to the degrees of temperature to which the watch is exposed; near the top of the dial is a small plate showing the phases of the moon,--the position indicated in this illustration is that of full moon.
The MERIDIAN WATCH shows the time of day in any number of places in any part of the world. It is set to Greenwich time, and marks the difference between this and the time of all the great metropolitan cities in both hemispheres,--as St Petersburg, Constantinople, New York.
The name CHRONOMETER,--derived from the
+----------------------------------------------------------------------+ | [Illustration: The Meridian Watch.] | +----------------------------------------------------------------------+
Greek, and meaning a time-measurer,--is chiefly applied to marine time-pieces and to watches which have been carefully made with chronometer or detached escapements and compensating balances serving to equalize the effects of heat and cold. MARINE CHRONOMETERS are the chief instruments for discovering the longitude at sea, and are therefore subjected to special tests at Greenwich observatory and elsewhere before being sent on board ship. They have dials of three or four inches in diameter, hour, minute, and second hands, besides a hand to indicate the day upon which the instrument was last wound up,--and they are made to go from two to eight days. Being well mounted on gimbals inside of an air and water-tight brass case they do not toss about with the motion of the ship but always preserve their equilibrium. For extra protection they are generally kept enclosed in a mahogany case. Chronometers have for their motive power, like watches and spring-clocks, a mainspring acting on the fusee by the chain,--as the chain winds upon the fusee the force of the spring is so equalized that it is exactly the same whatever the position of the chain. When marine chronometers are sent to the Greenwich observatory they are subjected, under the directions of the Astronomer Royal, to extreme degrees of heat and cold, and up to the year 1835 prizes were awarded to those makers whose instruments best stood these tests; but such prizes are no longer given. It has even been found that chronometers which are most capable of withstanding extremes of temperature are not the most perfect in medium climates, and this discovery brought about new endeavours and a new suggestion known as the Auxiliary or Secondary Compensation.
MARINE TIME-PIECES FOR SHIPS AND YACHTS. These instruments possess the character rather of clocks than of chronometers, inasmuch as they are designed to hang against a bulk-head, and they would not appear unsuitable to house purposes. They are portable and useful clocks, and having a lever escapement with compensated balance, the motion of the vessel does not affect them. Some yacht time-pieces are constructed so as to chime the quarters or tunes, and to strike the ships' bells as well as the hours. They are also sometimes placed in very handsome cases of bronze or ormolu, decorated with special designs to illustrate the name of the ship or yacht to which they belong. Their movements are not as accurately adjusted as those of Marine Chronometers, but they, nevertheless, are made to keep time excellently.
KEYLESS WATCHES.
The keyless mechanism to a watch is one of the great modern improvements in watch work; it does away with the old-fashioned key, with which so many persons have ruined their watches, the watch is wound by turning a knurled knob, placed on the handle or bow (see illustrations, pp. 96-7) instead of by the ordinary means: the hands are set in the same way, with the addition of pressing a small projection on the side of the case. The advantages of these improvements are obvious; the case, which never need be opened in winding, is made air tight and dust tight, thus preserving much longer the fluidity of the oil, and greatly prolonging the intervals between the necessary cleaning of the watch. Besides which, the keyless mechanism being attached to the watch, the key can never be lost or mislaid, or worn out.
_Strict attention to the following simple Directions is necessary for the proper Management of a Watch._
1st.--Wind your watch as nearly as possible at the same time every day--the morning is the best. Care should be taken to avoid sudden jerks.
2nd.--Be careful that your key is in good condition, free from dust and cracks. It should not be kept in the waistcoat pocket, or in any place where it is liable to rust or get filled with dust.
3rd.--Keep the watch while being _wound_ steadily in the hand, so as to avoid all circular motion.
4th.--The watch, when hung up, must have support, and be perfectly at rest; or, when laid horizontally, let it be placed on a soft substance for more general support, otherwise the action of the balance will generate a pendulous motion of the watch, and cause much variation in time.
5th.--The hands of a duplex or chronometer watch should never be set backwards; in other watches this is a matter of no consequence, but to avoid accidents it is much better to set them always forward.
6th.--Should the watch vary by heat or cold, as when worn or not worn in the pocket, the hands may be set to time, but the regulator should not be altered; but when it is found necessary to alter the regulator, it should be done gently, and very little at a time.
7th.--_The glass should never be opened in watches that are set and regulated at the back._
8th.--Keep your watch-pocket free from dust or nap, which generally accumulates in the pocket when much used.
9th.--Be cautious to whom you give your watch for repair; the best watches being frequently irretrievably damaged by inexperienced workmen. Never allow your watch to go longer than two years without being cleaned.
HOUSE CLOCKS.
Between the small wooden Dutch Clock of the value of but a few shillings, and the carefully-made Regulator Clock which costs ten times as many pounds, there is necessarily a wide difference; but both may be considered as within the general designation, 'House Clocks.' The former sometimes go for many years with a fair amount of regularity, and are found to be useful to the humblest classes, whose hours for early morning labour are frequently regulated thereby. The latter are made with such accuracy as to correct the time of other clocks, such as turret and church clocks, which are more exposed to the influence of the weather, and are necessarily made upon a coarser scale. In large mansions there is no handsomer or more necessary appointment for the hall or vestibule than a fine eight-day clock, 'to welcome the coming, speed the parting guest,' and to give the time of day to the entire household.
It would be worth while, did our purpose admit of it, to write a chapter on the longevity of Clocks, by way of showing the comparative cheapness of the solid, well-built piece of mechanism whose every item has been carefully put together of the very best and most durable materials by the most skilled horologers. For generation after generation such a sound, well-made time-piece shall keep accurate time, and put to shame by both its performance and the insignificant expense of keeping it in order, the instruments of, it may be, more showy appearance, but less careful construction. Such a clock descends from father to son until its own age is scarcely to be remembered, and is regarded as one of the family heir-looms,--nay, as more,--almost, we would say, as a friend familiar with all the scenes and experiences which have made up family history. It was of such a clock that Longfellow wrote--
'By day its voice is low and light, But in the silent dead of night, Distinct as a passing footstep's fall, It echoes along the vacant hall, Along the ceiling, along the floor, And seems to say, at each chamber-door, For ever--never, Never, for ever.'
It was such an one that Dickens apostrophized in that wonderfully-genial style which won for him so much love and fame:--'My old cheerful, companionable clock. How can I ever convey to others an idea of the comfort and consolation that this old clock has been for years to me!... What other thing that has not life could cheer me as it does! what other thing that has not life (I will not say how few things that have) has proved the same patient, true, untiring friend! How often have I sat in the long winter evenings feeling society in its cricket voice! how often in the summer twilight, when my thoughts have wandered back to a melancholy past, have its regular whisperings recalled them to the calm and peaceful present! how often, in the dead tranquillity of night, has its bell broken the oppressive silence, and seemed to give me assurance that the old clock was still on guard at my chamber-door!'
The Hall clock is often a plain, simple, undecorated instrument, where all others are perhaps somewhat ornamented. Bracket clocks for the staircase or landings, Mantelpiece clocks for the drawing and dining rooms, for the study, the boudoir, and the best bed rooms, have each their separate shape and character specially designed, and are to be found in simple black-stained wood or real ebony, in marble of different colours, in bronze, in buhl, and in ormolu, with or without enamel ornaments, and with or without miniature figures at base, sides, and top. Until lately most of our ornamental mantelpiece clocks were imported from the continent, although French workmanship is generally inferior to our own, but preference was shown by the public to the former on account of the greater attention given by the French to external decorations and variety of pattern. I am endeavouring to provide that for the future this branch of clockmaking shall not be abandoned entirely to our continental neighbours, whose exports of this kind to our country yearly are very considerable. Henceforth by means of new designs specially made for me and by me, and of a sufficiently skilled staff of artistic workmen, selected for the purpose of working under my superintendence, on my own premises, I shall be able to compete on equal, nay, as to mechanism, on superior, terms with the best specimens of decorated clocks from foreign _atéliers_. There is no reason why the admitted superiority of English mechanism should not be coupled with the best designs for decorated clock-cases; there is every reason why handsome clocks should be made which will keep time well, and add not only by their beauty but their usefulness to the enjoyment of domestic life. If the proverb, 'handsome is that handsome does,' applies to clocks, English workmanship should soon obtain pre-eminence, for it is well known that the principle upon which French clocks are generally made renders them less durable time-pieces.
The most ancient clocks differed in many respects from those now in use. Clocks of the earlier period had, as we have said, instead of the pendulum now in use, a _balance_, vibrating on the top of the clock, as the regulating medium. The escapement was of the verge construction, a sketch of which will be seen below, which represents a clock of a most ancient character.
+----------------------------------------------------------------------+ | [Illustration: Old Balance-Clock.] | +----------------------------------------------------------------------+
Without entering into any very minute detail of the manner in which motion in a clock is successively communicated from one toothed wheel (G or R) or pinion (_e_ or _g_) to another, which, indeed, would only tend to perplex the mind of the general reader, it will be sufficient to state the following. S is a square piece of steel fixed to and forming part of the pinion P. In winding the clock the key is placed upon this square, and being turned round continuously in one direction, the pinion P turns with it. This communicates its motion to the wheel R, which is fixed to the cylinder B, and which in its revolution coils or winds up the cord to which is attached the weight A. While this takes place the wheel G is held in check by another wheel, called the 'ratchet,' and a click (neither of which is seen in the sketch), but when the operation of the winding is completed, and the weight A begins to descend, the cylinder B, together with the wheel G, turn on their common pivots V, V, and the motion is thus communicated from wheel to pinion until it reaches the escapement-wheel I. The teeth of this wheel, in its revolution, act alternately on the pallets _i_, _h_, which project from and form part of the spindle or verge K, M, and thus produce a vibratory or backward and forward motion of the balance L, L.
Were it not for this detention, the duration of which is much increased by the swing of the balance, the weight A would descend with gradually accelerated speed, till, in a few moments, the cord would be entirely unwound from the cylinder, and the clock be at rest.
+----------------------------------------------------------------------+ | [Illustration: Clock Spring.] | +----------------------------------------------------------------------+
The SPRING CLOCK as ordinarily made is thus constructed. The frame consists of two oblong plates of brass pinned together by short pillars, and pierced with holes, in which run the arbors of the various wheels. Next, the mainspring, the moving or motive power of the clock, which is a riband of steel, highly tempered, and enclosed in a cylinder or barrel. In the middle of this barrel is the spring or barrel arbor, to which the spring is hooked at one end, the other end being fixed to the circumference of the barrel. Outside the frame or plate, and at the end of the arbor, is the ratchet, a wheel with saw-like teeth. This is acted upon by a click, which, falling into the ratchet teeth, prevents the recoil of the mainspring, so that the spring has no means of uncoiling itself, except by the moving of the train of wheels. This click is screwed to the outside of the oblong plate. The power of the mainspring is transmitted to the train of wheels by means of a chain or gut, one end of which is fastened to the outer edge of the barrel, and the other end to the fusee, which is of conical shape, securely fastened to the arbor or axis of the main wheel; on this same arbor is the square, on which the key is put for winding. When this square is turned in winding, the fusee draws the chain or gut from off the outer edge of the barrel, and coils up the spring within it. The spring when fully wound, and consequently at its greatest power, acts by means of the chain or gut on the small end of the fusee, which in turning drives the train of wheels. As the spring becomes gradually uncoiled, and the power exerted less, the leverage is increased in the same proportion by the increased width of the fusee on which it acts.