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ANTIQUE CLOCKS AND WATCHES GlOSSARY
July 26, 2009 | Leave a Comment
GLOSSARY
Act of Parliament Clock: a misnomer applied to a timepiece, usually weight-driven, with seconds pendulum having a large unglazed dial and a small trunk. According to legend, these clocks were first put into inns and post taverns for use of the general public, many of whom had sold their clocks and watches when Pitt introduced his Act in 1797 levying 5s per annum on all clocks and watches. Such distress was caused in the trade that the Act was repealed next year. Actually this design dates from about 1760.
Arbor: the shaft which carries wheels and pinions.
Architectural clock: a clock in which the hood, in long-case, and the top in mantel clocks, is in the style of a classical pediment, with or without supporting columns. Usually a sign of work in the third quarter of the I 7th century, although these pediment tops were revived for a short period early in the igth century.
Arch top, plain: a case, usually in bracket clocks, where the arch rises directly from the sides of the case.
Astrological dials: these are embodied in many early clocks and watches and reflect the important part that astrology played in the everyday life of the people. They show the relation or aspect of the planets to one another at any time. They are usually shown as related to the moon, whose phases are to be seen through an aperture in the dial for this purpose. The distances in degrees are shown by the Trines L (1200), Quartiles ❑ (go’), Sextiles * (6o’), Con-
junction I (o°), and Opposition 0 (18o°).
0 0
Automatic winding: a pocket watch which is wound up by means of a weight actuated by the motion of the body. A patent was taken out in London in 178o by Louis Recordon, but prior claim is made for Abraham Louis Perrelet, of Le Locle.
Balance: an oscillating wheel which, controlled by the balance spring, regulates the rate of going of a watch. It is, in a watch, the counterpart of a pendulum in a clock.
Balance spring: usually known as the hair spring today. It controls the balance.
Balloon: a type of waisted clock popular in the late i 8th and early zgth centuries.
Basket top: a pierced metallic and roughly dome-shaped case top current at the end of the 17th and early in the i8th centuries.
Basket top, double: two pierced metallic basket tops superimposed.
Basket top, wood: where a smooth wooden dome replaces the metallic bracket.
Bell top: the top of a clock case where the lower portion is shaped like the bell of a turret clock with concave sides.
Bell, inverted: as for Bell top, except that the lower portion has a convex outline.
Bezel: the metallic framing of a clock or watch glass.
Bob: the weight at the base of a pendulum rod. The earliest were pear-shaped or nearly spherical. Later the general form was lenticular; in some regulators and special clocks cylindrical.
Bolt and shutter: a form of maintaining power. The shutters cover the winding squares so that the clock cannot be wound without pushing them aside. This action brings into play a small subsidiary force that keeps the clock going during the period of winding.
Bow: the loop at the top of the pendant of a watch.
Bracket clock: many clocks of the 17th and 18th centuries were provided with their own brackets, usually designed to harmonize with the case. Only rarely have original brackets survived. They frequently contain a drawer to hold the winding key. Portable clocks are known as both mantel and bracket clocks.
Bridge: a shaped metallic support having two terminal plates.
Broken arch: an arch terminating on either side with a horizontal projection. There are broken arch dials and cases. If a full semicircle, they are known as deep; if less, and this usually applies to the earliest, as shallow arches.
Buhl: inlay of brass or silver, usually on a base of tortoiseshell. Invented by Andr6 Charles Boulle in the latter half of the 17th century.
Bun feet: small, circular, flat, ‘cheese-like’ feet, sometimes found on early long-case and bracket clocks.
Bushing: the filling up of worn pivot holes and their subsequent opening to size.
Cam: a part so shaped as to turn rotary motion into reciprocal or variable motion.
Cannon pinion: the pinion to which it is usual to fit the minute hand.
Cap (dust): a movable cap, first used early in the 18th century to help keep the movement clean. Only used in watches.
Cartel clock: a mural clock, usually of. somewhat flamboyant design. More often found in France than in England. English are usually of carved wood, whereas the French are usually of cast brass or bronze and gilt.
Cartouche: a decorative panel, sometimes applied, and framing an inscription.
Case, pair: for a century, beginning about the latter part of the 17th century, watches were usually provided with two cases, of which the outer was frequently highly ornate. In some instances a third case was provided to protect the decoration on the second.
Centre seconds: a clock or watch in which the seconds hand is placed on the same arbor as the hour and minute hands.
Champlev6: the cutting away of the dial of a watch, so that the hour numerals, minute ring and inter-horary marks remain raised.
Chapter ring: the applied circle, found in earlier clocks, upon which are engraved the hour numerals. Derives its name from the fact that hours are struck on a bell. Originally a clock served to rouse the sexton, who then struck the hour of the chapter, or religious office, on a bell.
Chiming clock: a clock which sounds at the quarters a chime on four or more bells in addition to striking the hour.
Circular error-. Christiaan Huygens, who invented the
pendulum, discovered that the truly isochronous swing of a pendulum was not the true arc of a circle but on a cycloid. The course of the latter is more U-shaped than the true circle; but fora short distance at the bottom of the swing the two paths coincide. Any lack of time-keeping due to a pendulum swinging beyond this common path is said to be due to circular error.
Clepsydra: a timekeeper motivated by water running either into or out from it. Water clocks are among the earliest forms known; before the discovery of the verge escapement and the weight as a motive power.
Cock (Clock): (a). the bracket that supports the pendulum, (b) a bridge with only one terminal plate.
Cock (Watch): the bracket covering and protecting the balance, it also supports the upper end of the balance staff.
Collet: (a) a domed-shaped washer used to render firm the hands of a clock (b) a flange.
Compensation balance: a balance that corrects the influence of heat and cold upon its timekeeping. Usually of bimetallic construction.
Compensation curve: a bimetallic curve in contact with one end of the balance spring. The action of temperature on the curve causes a compensating change in the effective length of the balance spring.
Contrate wheel: a wheel in which the teeth stand perpendicularly to the plane of the wheel. It is used to transmit motion from the arbor of one wheel at right angles to the first.
Count wheel: see Locking plate.
Cromwellian clock: see Lantern clock.
Crown wheel: the escape wheel of the verge escapement. Crutch: that part of the clock mechanism which, fixed to the pallet arbor, transmits the impulse to the independently supported pendulum.
Curb pins: two pins astride the outer end of a balance spring. These are moved by the regulating device, and so alter the effective length of the spring.
Cycloidal cheeks: curves fitted to a pendulum clock to overcome circular error. It was found, however, that the errors they introduced were greater than those they eliminated, hence they were soon abandoned. Only found in the very earliest pendulum clocks.
Cycloidal path: the curve described by a point on the circumference of a circle rolling along a straight line.
Day of the month: a clock with an indication of the date changing daily. Usually the adjustment for the short months has to be made by hand, but some systems provide for this and, in more exceptional cases, for leap year as well. (see Perpetual calendar).
Declination: the angular distance of a star north or south of the celestial equator. In clocks the star is usually the sun, whose declination varies between 231′ north and south of the equator.
Detent: that which detains. The term is applied to the pawl or click that takes into the ratchet wheel.
Dial: the face of a clock or watch on which are marked the hours, minutes and seconds. The division of the circle into 36o equal parts is believed to have originated with the Sumerians about 4000 B.C. Finding that to, the number of the fingers, was not easily divisible, they chose a unit of 6, divisible by 3 and 2. They then adopted a combination of 6 and io up to 6 x io=6o. This formed the basis for another series up to iox6o=600. This again formed a basis, but when they reached 6×600=3,600, they considered that they had reached finality or completeness, which they symbolized as a circle.
Dominical letter: the ist ofianuary is allotted the letter A and the six succeeding letters, B—G, assigned to the six succeeding days. The letter thus falling on the first Sunday of the year is the Dominical letter for that year. In leap years two letters are required, one up to February 29 and the next succeeding letter, if necessary recommencing with A, for the rest of the year. Used in connection with the fixing of Easter Day.
Dutch striking: the repetition of the hour at the half-hour on a different toned bell.
Ecliptic: the apparent orbit of the sun. Total eclipses of the sun or moon are only possible when the moon is in the plane of the ecliptic. The plane of the orbit of the moon is inclined at an angle Of 5° to that of the sun. Where the two intersect is termed the Nodes. They appear on clock dials as R.
Epact: the age of the moon on January I.
Epicycloid: the curve traced by a point on the circumference of a circle as it rolls around another circle. It is a curve used in the cutting of teeth for wheels.
Equation dial: a dial that records both Solar and Mean Time.
Equation kidney: a kidney-shaped cam, invented by Christiaan Huygens in 1695, which made possible the transformation of simple forward rotary motion into a backward or forward motion, varying daily, both in direction and amount, necessary to indicate the daily difference between Solar and Mean Time.
Equation of time: the solar day or time as recorded by a sundial varies each day in length; whereas Mean Time, or time shown by a clock, is exactly twenty-four hours each day. This difference, which varies irregularly daily, is known as the equation of time.
Escape wheel: the wheel that gives impulse to the balance or pendulum.
Escapement: the means by which the motion of a clock or watch is checked and the energy of the motive force, weight or spring, is transmitted to the controller, pendulum or balance.
ANCHOR: invented about 167o by William Clement. It revolutionized timekeeping. With it the pallets are in the same plane as the escape wheel, instead of being at right angles to it, as in the verge escapement. It largely eliminated circular error and also made practical the use of long pendulums swinging more slowly, hence with a lesser cumulative error. It is still used today for most domestic clocks and particularly in long-case clocks with pendulums beating one second. It is also known as the recoil escapement which recoil is seen in the slight shudder at each beat in the seconds hand of long-case clocks so equipped. The vastly improved timekeeping of this escapement made really practical use of clocks for astronomical purposes. Flamsteed, the first astronomer Royal at Greenwich, in 1675, used clocks made by Thomas Tompion, equipped with the anchor escapement. This largely accounted for the far greater accuracy of his observations as compared with his contemporaries. From this invention followed, directly or indirectly, practically all the subsequent improvements in timekeeping in clocks.
CYLINDER: a type for use in watches. A form of this escapement was patented by Tompion, Barlow and Haughton in 1695, but it was never developed. It remained for Tompion’s successor, George Graham, to perfect this escapement about 1725. Graham used it very extensively in his watches, and this greatly helped him to gain the reputation of being the best watchmaker of his day. As with the anchor escapement, the pallets are in the same plane as the escape wheel. This escapement remained the best for watches until supplanted by the duplex and the lever escapements about the end of the 18th century.
DFADDEAT: invented by George Graham about 1715. Graham was the leading astronomical instrument-maker of his day, and from his close connection with astronomers was, doubtless, aware of their demand for still greater accuracy than could be attained with the anchor escapement. The deadbeat escapement is an improvement on the anchor in that it eliminates the recoil, and remains steady at the end of each beat. It held the field for the most accurate escape for astronomical work for nearly two hundred years. It is still used today in high-grade clocks, both long-case and mantel.
DUPLEX: invention uncertain. Usually attributed to Pierre LeRoy, Paris, about 1750. The escape wheel has two sets of teeth, one long and pointed, the other short and triangular and rising from the plane of the escape wheel. The long teeth escape through a small notch in the balance staff, which also carries a long arm by which the impulse is given through the short triangular teeth.
LEVER: first invented about 1758 by Thomas Mudge and incorporated in a watch given by King George III to Queen Charlotte. Mudge only made one or two other examples and does not seem to have realized the importance of his invention, which lies in the fact that the balance is free from interference for the greater part of its swing, thus leaving it free to perform its true function as controller. From the commencement of the second quarter of the I 9th century the lever escapement, in one of its many forms, became the standard escapement for watches, and still is so today. Before that date, despite the appearance of the cylinder, duplex and lever escapements, the standard watch escapement was the verge.
PIN-PALLET: invented by Amant, Paris, about 1740. A type in which the pins stand out from the side of the escape wheel. Not much found in English clocks.
RECOIL: see Anchor escapement.
TIC-TAG: a modified form of the anchor escapement found in some early clocks. The ‘anchor’ only embraces two or three teeth of the escape wheel.
VERGE: this was the original escapement for mechanical clocks. Date of invention unknown, possibly 13th century.
The writer considers the inventor of this escapement one of the greatest men in horology, for he had nothing prior to guide him. Although it is an escapement in its worst form, in that it never leaves the pendulum or balance free for an instant, nevertheless it was in its day as revolutionary an invention as was, later, the anchor escapement. It held the field unchallenged for about four hundred years; even thereafter it remained in use for clocks and watches, along with better types, for another one hundred and fifty years. It was used in bracket clocks as long as there were only one or two in a house, and they were carried from room to room, since it does not need any very careful levelling.
Foliot: the earliest form of controller in a mechanical clock. Always found with a verge escapement. The balance wheel and, especially later, the pendulum so improved timekeeping that it is very rare to find a clock with its original foliot. Its origin is unknown, but presumably attributable to the inventor of the verge escapement. Consists of a horizontal rod fixed to a pivoted bar carrying the verge pallets. Regulation was by moving the weights carried at each end. The word may be derived from the French esprit foller, a goblin associated with Puck and represented by its to and fro motion.
Form watch: a watch made in some form that departs from the standard of the period, e.g. book, cruciform, skull, dog, etc. These are found in the 17th century, Later, at the end of the i8th century, there are lyres, mandolines, baskets of flowers, fruit, etc.
Fly: a rapidly revolving vane, the final component of the striking train, which acts as a governor for the rate of striking. Invention unknown, but presumably concurrent with the Locking plate.
Frets: pierced metallic decorative pieces, originally used to hide the balance in lantern clocks. Later, either in wood or metal, inserted into clocks cases to facilitate the elimination of sound.
-shaned and spirally-grooved pulley Fusee: a con;-11 I
which, utilizing the principle of the lever, equalizes the pull of the main-spring of a clock or watch on the train. This has generally been attributed to Jacob the Czech, of Prague, based on the earliest known survival in a clock by him, owned by the Society of Antiquaries of London, dated 1525• Leonardo da Vinci had many sketches of the fusee in his note-books of about 1490. The writer’s researches have shown that there may be a possible connection between the two men through Bona, Queen of Poland, for whom the clock was made. Bona was a Sforza of Milan, at whose court Leonardo was during her girlhood. It is now thought that Jacob only put into practice Leonardo’s idea. This invention has not been bettered, and is still in use today in high-grade spring-driven clocks. Catgut was originally used to connect the fusee with the main-spring barrel, but from the end of the 17th century a chain is usually employed.
Gathering Pallet: a pin or finger that revolves when the clock is striking and gathers up, at each revolution, a tooth of the striking rack.
Golden numbers: see Metonic cycle.
Gong: a piece of hardened, tempered wire wound in a volute, on which the hours are struck, instead of a bell. First used in the last quarter of the 18th century.
Grandfather clock: properly known as a long-case clock. Came into existence directly after the invention of the anchor escapement, 1670. The narrow arc of swinging of this escapement made possible the enclosing of the weights and pendulum in a narrow trunk. When the term ‘grandfather’ clock first came into use is uncertain, but Barham uses the term in his Ingoldsby Legends, which date from about 1835-
Grandmother clock: a small long-case clock, not exceeding 6 feet 6 inches in height.
Grand sonnerie: a system of striking whereby the hour and the quarter are struck at each quarter. The earliest
known example is the movement with the silent escapement made by Tompion about 1676-80. This system of striking was rendered possible by the invention by Edward Barlow, in 1676, of the rack and snail method of striking.
Gregorian calendar: the old Church calendar assumed a solar year of exactly 356J days and that ig solar years contained exactly 235 lunation. Neither of these is quite accurate. By 1582 the cumulative error amounted to io days. Pope Gregory XIII introduced the Gregorian calendar - or New Style - which brought the vernal equinox back to March 21 instead of March 11. This change was not adopted in England till 1752, by which time the error was 11 days. In that year September 2 was followed by September 14. The ignorant populace rioted, saying, ‘Give us back our eleven days!’. This change accounted for the financial year ending on April 5 instead of March 25 in 1753, and it has so remained ever since.
Hood: the upper removable portion of a long-case. In all, except very early cases, it draws forward.
Hood, rising: the earliest form, before the door was introduced in the front, in which the hood slides up on grooves in the back-board and is held in place by a catch, thus allowing access to the dial. As clocks increased in height, the rising hood became impracticable, and the draw forward type with door was introduced.
Hoop wheel: a wheel, forming part of the striking train of a clock, to which is affixed a narrow band, having a slot and projecting at right angles to the plane of the wheel. This serves as a regulator between each blow of the hammer.
Hour circle: see Chapter ring.
Hours, Babylonian: The Babylonians are believed to have divided the day into equal hours of sixty minutes, each of sixty seconds. For the origin of the sixty see Dial.
Hours, canonical: time signals were given in ancient Rome at three-hourly intervals, starting at 6 a.m. They were mane, tertia, sextes, nona and vespera and were later adopted by the Christian Church. In time other offices were added to the Church day, and the times of these offices or chapters advanced, until nona fell at noon. The original function of a clock was to let off an alarm every hour to warn the sexton to ring the bell for the office.
Hours, Italian: the Italians reckoned the time as twenty-four equal hours a day, starting from sunset. In some early Continental clocks dials were marked I to XII twice over and had a movable ring marked 1-24 in Arabic numerals, enabling the clock to be set daily at sunset for the Italian hour.
Hours, Nuremberg: in South Germany, until the early part of the 17th century, time was recorded as so many hours of daylight and so many of darkness. These varied from sixteen hours of daylight and eight of darkness in midsummer to the converse in mid-winter. Public tables told when an hour should be transferred from one section to the other. In the town of Rothenburg this system of time recording was retained up to the early 19th century.
Indiction: a period of fifteen years arising from Roman taxation laws. Used in ecclesiastical calculations. Dials marked 1-15, with a hand revolving once in fifteen years are sometimes found on astronomical clocks.
Involute curve: the curve described by a point on a taut line unwound from a cylinder.
Involute gear teeth: wheels having teeth cut on the principle of the involute curve.
Isochronous: performing the same motion in equal time, i.e. when the balance of a watch or the pendulum of a clock performs each vibration in the same time irrespective of the arc of vibration or swing.
Jewels: when the bearings of pivots are formed of jewels to reduce wear and friction. jewels were first introduced by Facio de Duillier in 1704; he was a Swiss settled in London.Rubies and sapphires are usually used. Jewels are sometimes found as pallets in very high-grade regulators.
Julian calendar: a system of time reckoning introduced by Julius Caesar to reconcile the civil and tropical years. It assumed a year of exactly 3651 days and 235 lunations to equal exactly ig solar years. These figures were not quite accurate; the accumulated error led to the introduction of the Gregorian calendar.
Lancet clock: design of late 18th and early 19th centuries, in which a bracket clock has a pointed ‘gothic’ top.
Lantern clock: a typically English design evolved in the early part of the 17th century, and persisting, especially in the provinces, until well into the 18th century. Erroneously called a Cromwellian clock. Much copied today. All original lantern clocks are weight-driven and, with the rarest exceptions, never exceed a thirty-hour going period.
Lantern clock, Wing: a type, popular for about a quarter of a century, at the end of the 17th century, where the pendulum was placed between the going and striking trains, and took the form of an anchor, the flukes of which appeared each side of the main framework, and were protected by wings.
Lantern pinion: an early type in which the leaves are formed by wires affixed between two circular end plates.
Latched plates: the retaining plates of the movement where the distance pillars are secured at one end by swivelled catches instead of by pins passing through the head of the pillar.
Leaf, Pinion: the longitudinal teeth of a pinion are known as leaves.
Lenticle: the glass let into the door of a long-case clock to allow the motion of the pendulum bob to be seen.
Locking plate: a plate with notches set at increasing intervals around its circumference, which allows the striking train to sound the correct number of blows before the locking arm falls into a notch and stops the train. Invention unknown, probably i3th century, concurrently with the
verge escapement.
Long-case: the correct horological term for a grandfather or grandmother clock.
Lunar Dial: a dial which shows the lunar periods.
Lunar work: that part of the train which actuates the lunar dial.
Lunation: a period of 29 days 12 hours and 45 minutes, being the time taken by the moon to make a complete revolution round the earth and occupy the same position relative to the sun. Except in very special astronomical clocks, the period is usually taken as 291 days.
Maintaining power: a device used in weight clocks and in clocks and watches fitted with a fusee, whereby a subsidiary force is brought into play to keep the clock going while it is being wound. In early clocks the winding squares were often covered by shutters, which, when pulled aside, brought into operation the maintaining power, thus ensuring its use.
Mantel clock: alternative name fora bracket clock.
Matting: a system of rendering dull the surface of the brass dial plate. The art is now lost. Usually confined to the centre of the chapter ring. In some early pendulum clocks the dials are matted all over.
Metonic cycle: the Greek astronomer Meton discovered that the days of the month on which full moon accur constitute a cycle of 19 years. This was considered so wonderful that the Greeks had it carved on stone in letters of gold. Clocks are to be found with a dial marked i-ig, the hand revolving in ig years.
Minute wheel: the wheel which is driven by the cannon pinion and of which the pinion drives the hour wheel, to which the hour hand is attached.
Micrometer adjustment: a graduated wheel fixed to the pendulum suspension to give accurate adjustment for regulation. Early use of this was made by both Wm. Clement and A. Fromanteel, but who had prior claim is uncertain. Later replaced by a subsidiary dial on the clock face, the hand of which actuated a rack and pinion or a cam connected with the pendulum suspension.
Mock pendulum: a swinging bob attached to the escape arbor, which shows through a slot in the dial plate. Only used in clocks with the verge escapement. Sometimes called a false bob.
Month clock: a clock that goes fora period of one month with one winding. The usual period is 32 days.
Moon dial: see Lunar dial.
Moon work: see Lunar work.
Movement: the ‘works’ of a clock or watch.
Mural clock: a clock made to hang on the wall.
Musical clock or watch: one that plays a tune at each hour or other predetermined time, as opposed to a chiming clock.
Night clock: a clock that shows the time by night, usually by means of a light shining through a pierced dial. Nodes: see Ecliptic.
Nuremberg egg: a misnomer applied to early South German watches. Arose from the misreading and mistranslation of `Uhrlein’ into ‘Eierlein’ (little clocks into little eggs) These early watches were usually drum shaped.
Orrery: see Planetarium.
Pallet: that part of the escapement through which the escape wheel gives impulse to the balance or pendulum.
Parquetry: a type of veneer in which the applied woods are worked into a pattern with straight-sided components—e.g. squares, diamonds, rectangles, etc.
Pendant: the small neck of metal connecting the watchcase to the bow.
Pendulums
BOB: the earliest form invented by Christiaan Huygens in
1657 and used with the verge escapement. In England the
pendulum rod was usually fixed to the end of the escape pallet arbor, but on the Continent suspension was generally from a silk cord, the pendulum being actuated by a crutch. Regulation was by means of a fine thread cut on the lower end of the pendulum rod. The hole in the bob had a softwood core which ‘took up’ the threads on the rod.
DOUBLE BOB ‘. a spring-suspended type, appearing towards the latter part of the 18th century in which the rod carries two lenticular-shaped bobs.
HALF SECONDS: Length 9.8-in. beats twice a second. This is the longest pendulum normally found on verge escapement clocks.
SECONDS: this pendulum, 39.14 in- long, and those of longer length (see under) were made practical by the invention of the anchor escapement. The vastly improved timekeeping resulting from the adoption of the seconds pendulum and the anchor escapement in the early 1670s caused it to be called the Royal pendulum. It is the standard pendulum today for long-case clocks.
ONE AND A QUARTER SECONDS: 5 ft. z in. When the im-
proved performance of the seconds pendulum and anchor escapement were realized, attempts were made to increase this by using longer pendulums. Wm. Clement first made clocks with 11 seconds pendulums. The seconds dial Of a clock originally so made should have four divisions between each 5-second interval on the seconds dial. Sometimes clocks have their escapement sand pendulums altered from 1 second to 1I seconds in order to enhance their value. These will generally have their old seconds dials with five divisions. The base of a I i-seconds clock should have a door to allow access to the bob.
Two SECONDS: 13 ft. of in. When making the first two clocks for Greenwich Observatory, in 1676, Thomas Tompion introduced 2-seconds pendulums and year move-ments, in an attempt to secure the greatest accuracy. These are thought to be the first clocks so designed in England. When the clocks were removed from Greenwich they were converted to movements with I -second pendulums. 2-second pendulums are now only found in some turret clocks.
COMPENSATION: a pendulum which provides for the compensation of the effects of heat and cold.
CONICAL: a pendulum that rotates in a circle, the point of suspension being the apex of the cone. Robert Hooke experimented with conical pendulums in 1666. Huygens also made experiments, but it is seldom found in practice.
ELLICOTT: invented in 1752, utilizing the principle of the difference in the expansion between steel and brass. The heavy bob is carried on two angular hinged supports. As the length of the pendulum rod changes with temperature the vertical arms of the support are raised or depressed, giving a complementary movement to the horizontal arms carrying the heavy bob. Very expensive to make and not materially better than the gridiron, hence not extensively used.
GRIDIRON: invented about 1725 by John Harrison, a carpenter born in Soulby in Yorks, 1693. Sometimes attributed jointly with his brother James. Harrison discovered that brass and steel have an expansion ratio of 3 :2. This property is utilized in this pendulum, with its alternate rods of brass and steel. One side only is required, the other rods being put in for balance and symmetry. Still used today in high-grade clocks.
MERCURY: invented in 1726 by George Graham, who had previously experimented with brass and steel without conclusive results. The bob of the pendulum consists of a jar containing mercury. As the temperature changes the length of the pendulum rod, the level of the mercury in the jar alters in the inverse sense, thus keeping constant the
Still
centre of oscillation of the pendulum. in use today in
high-grade clocks.
ROYAL: see Seconds pendulum.
SIMPLE: a theoretical conception consisting of a weight or mass suspended by a weightless thread.
WOOD: a pendulum rod made Of well-seasoned, straight-grained and varnished wood is little affected by temperature or humidity. It is sometimes used in high-grade clocks and
regulators.
Perpetual calendar: a calendar which corrects itself for the short months, and more exceptionally for leap year. Usually consists of a slotted wheel revolving once a year (or four years) with slots of varying length which control the movement of a lever, allowing it to pass one or more teeth of the calendar wheel at a time.
Pillars: the distance pieces separating the back and front (or top and bottom) plates of a clock or watch. Their style is a guide to the date of the piece.
Pin drum: the spiked drum of a musical or chiming clock, the spikes of which actuate the hammers as the drum revolves.
Pinion: a small-toothed wheel, in which the ratio of the axial length to diameter is greater than in a wheel. The teeth of pinions are called leaves. In clock and watch movements wheels and pinions alternate in the train.
Pivot: the reduced end of an arbor, round which it revolves.
Planetarium: a representation of the chief celestial bodies, sun, moon, earth and planets, which, when put into action, usually by turning a handle (although some are driven by clocks), shows the relative motion of these bodies. More usually called`Orreries’, after Richard Boyle, 4th Earl of Orrery, in the mistaken beleif that the first of these was made for him. The first was made by Tompion and Graham for Prince Eugene in about 1705-
Plates, Back and front and top and bottom: plates between which are pivoted the trains of a clock or watch. Early back plates in clocks were quite plain, except for the signature; later they began to be decorated, and the decor-ation became more and more ornate, reaching a peak in the first quarter of the 18th century. From this point it declined until the last decade of this century saw the return of the plain back plate. These back plates are a useful guide to the date of a clock.
Plinth: properly speaking, the base of a clock, but more usually applied to its skirting.
Positional error: the variations in the rate of going of a watch due to change of position; pendant up, pendant down, dial up, dial down, etc.
Potance: the bracket supporting the lower pivot of the crown wheel arbor in a verge escapement.
Pulse watch: see Stop watch.
Pump across: in ting-tang quarter-striking clocks the quarters are struck on different-toned bells. Usually there are two hammers, one for each bell and the striking action is ‘pumped across’ from one hammer to the other.
Quarter clock: a clock striking at the quarters as well as at the hour.
Quoins: representations of the corner stones of a building. In almost all cases it will be found that the long cases so decorated originate in Lancashire, late 18th century.
Rack and snail striking: a system invented in 1676 by Edward Barlow which, except for turret clocks, has practically superseded the locking plate in this country. This type of striking made repeating clocks possible.
Rate: the regular amount by which a clock gains or loses in a stated period of time, usually per day.
Rating nut: the nut placed below the bob of the pendulum and used to regulate it. In some early 19th century clocks the rating nut appears above the bob, in these cases movement of the rating nut is inverse.
Regulator: a high-grade long-case clock with compensation pendulum and possibly other refinements, such as roller bearings and jewelling. The hour is frequently read off a disc revolving behind the dial proper, and showing
through an aperture.
Repeater: a clock or watch on which the hours, and generally also the quarters, and in rare cases the five minutes and even the minute, can be made to strike at will by the pulling of a cord, the pressing of a knob, etc. Repeating clocks were common until the end of the first quarter of the 19th century, when matches were introduced.
Repeating work: the motion work necessary to make a clock or watch repeat.
Ringing: the practice at the turn of the 17th and 18th centuries of surrounding the winding square holes, and sometimes the seconds hand arbor, with concentric decoration.
Rise and fall: the subsidiary dial of a clock for pendulum regulation purposes.
Roman strike: a system devised by Joseph Knibb in the latter part of the r 7th century to reduce the power needed, in spring-driven clocks especially, to drive the striking train. The hours are struck on two different-toned bells, one striking up to III and the other once for V, and twice for X. In clocks so made the IIII is usually marked IV. Sometimes found also in long- case clocks.
Sand glass: an early form of measuring time by the period required for a given quantity of fine sand to pass from one bulb of the glass to the other, through a fine neck. Usually found in sets of four, the glasses recording the four quarters of the hour. In genuine early examples the two bowls are separate and joined by an applied band.
Seconds dial: the subsidiary dial on a clock on which the seconds are marked.
Sedan clock: a large-dialled watch some 4 to 6 inches in diameter, with bow for hanging in a conveyance. Usually has a small watch type of movement behind the much larger dial.
Self-winding watch: see Automatic winding.
Shagreen: a product made from shark skin.
Sheepshead: a lantern clock in which the chapter ring extends appreciably beyond the rectangular frame of the front dial plate.
Skeleton dial: one in which the metal is cut away from the applied chapter ring, leaving only the numerals, minutes and interhorary marks.
Spandrels: decorative corner-pieces found on clock dials for about one hundred years from 1675-80. Their design is a guide to the date of the clock.
Spoon: a hinged hook on the inner side of the top of the front of a long-case clock, so that when the door is closed the lower ’spoon handled’ part of the hook is pressed back and the upper hooked part pressed forward to keep the hood locked until the trunk door be opened again. Only found in early long-case clocks with rising hoods.
Stackfreed: an early South German device of unknown origin to be found in very early watches, whereby a roller attached to a strong spring bears against a shaped snail or cam, the radius of which decreases. The friction on the pivots of the snail and roller decreases as the spring is allowed to approach the centre of revolution of the snail; as the main spring is unwound and loses power the braking action of the roller decreases, tending to keep constant the force exerted by the spring on the watch movement. The principle of the lever underlies this as in the fusee. Both methods are found in the early 16th century, but the fusee ultimately supplanted the stackfreed everywhere.
Stop watch: one in which the seconds hand can be stopped or restarted at will without stopping the whole movement. In the earliest stop watches, c. 168o-go, the stop stopped the whole movement. They were used by doctors and were called ‘pulse watches’.
Strike-silent: any mechanism that stops at will the striking or chiming of a clock. The early forms had a pin showing through the dial, attached to a lever, and had the dial marked ‘N’ and ‘S’ (Not and Strike). Later a subsidiary dial appeared for this purpose.
Sunray clocks: a type developed in the late 17th century at the time of the cult of the ‘Roi Solcil, Louis XIV. A central circular dial with carved wooden sun’s rays emanating therefrom. Much copied today. Original clocks have the rays of hand-carved wood.
Suspension: refers to the method of supporting the pendulum of a clock, spring, silk, knife-edge.
Table clocks: a clock with a horizontal dial, designed to be placed on a table and viewed from above.
Tidal dial: a dial that indicates daily the time of high tide at any given port. Not found on Continental clocks. The earliest English dials were made for London, and show high tide at new and full moon at 3 o’clock. Since the 24-hour cycle is completed each lunation, by having two circles, one fixed and marked 1-291 (the days of the lunation) and the other movable, marked 1-12 twice over; if the time of high tide at any port at new moon be known, by placing that hour under 291, the daily times of high tide for that port will be shown.
Time, Mean: time calculated on an average basis of a day of 24 hours exactly. A year contains 3651 mean days.
Time, Sidereal: time as calculated by the successive passage of a selected star across the meridian. A sidereal day is 23 hours 56 minutes 4 seconds of mean time. There are 366 sidereal days in a mean year of 365J days.
Time, Solar: time as calculated by the successive passages of the sun across the meridian, as shown on a sundial. This varies daily. See Equation of time.
Ting-tang: the sounding of the quarters on two different toned bells.
Tourbillion: a watch in which the escapement is mounted on a revolving carriage, which carries it round.
Invented by A. L. Breguet in 18o i to avoid positional error.
Train: a series of wheel and pinions geared together, forming the mechanism of a clock or watch. They are going, striking, chiming, musical, astronomical trains, etc.
Tropics: the interval in the celestial sphere between the parallels of latitude demarking the maximum declination of the sun north and south of the ecliptic. The Tropic of Cancer in the north and the Tropic of Capricorn in the south.
Trunk: that part of a long-case clock between the hood and the base.
Turret clock: a clock for use in a church tower or other building.
Up and down: a subsidiary dial in highest-grade watches to indicate the extent to which the spring is run down.
Warning: the partial unlocking of the striking train, which precedes the full release at the precise moment of striking.
Warning-piece: that which arrests the warning-wheel between the warning and the time to strike.
Warning-wheel: a wheel in the striking train which carries a pin and which is arrested and then released by the warning-piece.
Watch bow: the loop at the end of the pendant.
Water clock: a contrivance used in Egyptian, Greek and Roman times for measuring time by the regular flow of a stream of water changing the level in a container, on the surface of which floated a means of indication on a fixed scale. Water clocks in the 17th and 18th centuries were drums with internal pierced sloping divisions, causing the water to pass slowly from one to the other, making the drum revolve and its axis roll down a graduated framework. Very few genuine examples exist.
Wheel, Centre: the wheel to which the cannon pinion is attached.
Wheel, Count: see Locking plate.
Wheel, Great: that which is attached to the going barrel, fusee or, in weight-driven clocks, the gut barrel.
Year clock: a clock designed to go for one year with one
winding.
Year, Sidereal: the period of one complete revolution of the earth round the sun.
Year, Tropical: the interval between two successive returns of the sun to the same tropic, or equinox.
Yorkshire clock: a broad and ill-proportioned long-case clock made for some years towards the end of the 18th century and early 19th.
Zodiac: a belt of the heavens outside which the sun, the moon and the planets do not pass. Divided into twelve signs, each Of 3o degrees, termed in astrology Celestial Houses: Aries (The Ram), Taurus (The Bull), Gemini (The Twins), Cancer (The Crab), Lco (The Lion), Virgo (The Virgin), Libra (The Balance), Scorpio (The Scorpion), Sagittarius (The Archer), Capricornus (The Goat), Aquarius (The Water Carrier) and Pisces (The Fishes).
Jul
26
ANTIQUE CLOCKS AND WATCHES
July 26, 2009 | Leave a Comment
CLOCKS AND WATCHES
WHEN clocks as we know them today, i.e. a series of wheels and pinions geared together with a weight as a motive force, first came into use is a matter of conjecture. The only early records are monastic manuscripts, and these use the term ‘horologium’ indiscriminately, whether referring to a sundial, a water clock, or a mechanical clock.
There are certain rough guides. Dante describes the motion of a clock in his Paradiso of 1321, and we have definite written evidence of a very elaborate astronomical clock being in existence in Strasburg about 1350. Around 136o DONDI DEL OROLOGIO (the title given him in recognition of his masterly production) constructed a clock in a seven-sided frame, with a complicated astronomical dial above each of the seven sides. If by the middle of the 14th century there were men capable of making very complicated astronomical clocks, we can assume that the earliest and simplest mechanical clock, with weight and foliot was evolved at least one hundred years earlier. At all events, the unknown inventor or inventors of the verge escapement with foliot and the locking plate striking arrangement, with its fan, or air brake, were geniuses; they had nothing prior to guide them.
Towards the end of the 15th century in Italy, and early in the 16th in South Germany, the coiled spring as a motive force was being brought into use. Heretofore it has been the custom to ascribe to PETER HENLEIN, of Nuremberg, the invention of the portable timekeeper driven by a coiled spring, but certainly LEONARDO DA VINci’s notebooks show this device, with the fusee to equalize its power, some thirty years earlier, although it is doubtful whether he applied it to timekeeping. The South German method of equalization of power was the stackfreed, and since this is much less efficient and was later universally replaced by the fusee, it seems likely that the two systems were developed independently and more or less concurrently; both localities were the cradles of early clockmaking.
The next development was the balance wheel to replace the foliot; the method of regulation thus changing from the alteration of the weights on the foliot bar to the adjustment of the amount of the driving weight. This change, however, did not materially improve timekeeping.
After this came the momentous discovery of the pendulum by CHRISTIAAN HuY(;ENS in 1657. Galileo had earlier perceived the principle of the pendulum, but there is no evidence to show that he developed it other than as an accurate recorder of oscillations to be counted by an observer. Huygens’s work can be described as independent, and certainly he was the first to apply the pendulum to clocks.
The vastly improved timekeeping of pendulum clocks, even with the verge escapement, over foliot and balance was due to the fact that the pendulum was the controller of the driving force, whereas formerly the driving force controlled the clock. Most clocks were converted to this new method of timekeeping, and it is very rare today to find a clock with its original foliot or balance.
Only thirteen years later came the revolutionary invention of the anchor escapement by WILLIAM CLEMENT. This largely abolished circular error and made timekeeping sufficiently accurate for use in astronomical observations; hence the superiority of the observations of the first English Astronomer Royal, John Flamsteed, over those of his contemporaries.
In 1675 Christiaan Huygens introduced the spiral balance spring for watches. This did for the watch what the pendulum had done for clocks in the matter of improved timekeeping. ROBERT HOOKE claimed priority and there are grounds for his support, but he did not make any public claim until after Huygens had published his invention, when he charged him with plagiarism. The truth is that both men probably worked independently.
Now comes the great age of English horology. THOMAS T o m P 10 N is justly famed as the chief contributor to England’s supremacy in clock-making at this time. Tompion’s main contribution to clockmaking was his genius in designing complicated movements and the meticulous finish to all his work. Later GEORGE GRAHAM and JOHN HARRISON made further improvements to timekeeping, as opposed to clockmaking, which kept England in the lead for the whole of the 18th century.
George Graham’s deadbeat escapement, about 1715, held the field for astronomical observations for over two hundred years. Graham’s mercury pendulum is still in use today, as is John Harrison’s gridiron pendulum. Graham’s cylinder escapement for watches, about 1725, put his work in the lead for eighty years or so, until the lever escapement, invented about 1759 by THOMAS MUDGE, became more generally adopted in the early part of the 19th century.
John Harrison’s name is always associated with the winning of the prize OfC20,000 for the solution of the problem of ‘the Longitude’, i.e. making a timepiece sufficiently accurate to enable mariners to ascertain their longitude when at sea. Harrison’s efforts, starting with long-case clocks made entirely of wood (he was a carpenter by trade), progressing through the three trial machines that took the form of clocks of unique design, and ending with his finally successful piece, in the form of a large watch, can properly be included in this brief survey. But Harrison’s work was too complicated and expensive for general use, and it remained for JOHN ARNOLD and THOMAS EARNSHAW to introduce the simplified types of chronometers that are the basis of those made today.
Between the last quarter of the 18th and the first quarter of the 19th centuries, the limit of the period we are con-sidering, there were no British inventions of fundamental or
revolutionary importance.
Up to the beginning of the 18th century astrology played an important part in day-to-day life, and clocks embodying the relative aspects of the planets are not infrequent. Clocks indicating the day of the month and those showing the phases of the moon are common. From time to time, but more rarely, we find dials to tell the time of high tide, at first for London, where the Thames was the main highway, and later for marine ports.
In the latter part of the 17th century and in the early 18th, when clocks were only to be found in the spacious rooms of large mansions, we find various systems of complicated striking, which indicate the hour at more frequent intervals than one hour. Until clocks became sufficiently cheap, handles were attached so that they could be carried from room to room. In those made towards the end of the 18th century the handles were ornamental, in keeping with the decoration of furniture at the time. Movement of bracket clocks from room to room accounts for the retention of the verge escapement in this type for a hundred years or so after the invention of the much superior anchor escapement – the verge does not require the accurate levelling called for by the anchor.
Again, we find repeating clocks in use until about the time of the invention of matches; the repeating watch, being carried on the person, indoors and outdoors, was favoured until a later period.