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Magic Lantern Clock: Form of NIGHT CLOCK that projects an image of the dial on the wall. Invented in France in the eighteenth century and made in the nineteenth in various styles projecting the image from the front or back of the clock. The idea was revived in the twentieth century when electric clocks were made to project the dial and hands on the ceiling.

Magnet: The idea of using a magnet instead of a BALANCE SPRING was invented as early as 1659 by Adam Kochanski. Special extremely powerful and tiny magnets are used in ELECTRIC arid ELECTRONIC WATCHES, but these are to give IMPULSE by interaction with electro-magnets.

Magnetic Clock: See Tortoise Clock.

Magnetic Escapement: Invented by C. F. Clifford in England in 1948, this ESCAPEMENT has no physical contact between ESCAPE WHEEL and controlling element. Friction is extremely low and the action is silent. Used for German clocks and British TIME SWITCHES. The control element is a short length of spring which vibrates. On the end of this is a small horseshoe magnet. The specially shaped escape wheel teeth pass between the poles of the magnet which release them one by one as the magnet moves up and down.

Magnetic Suspension: A BALANCE WHEEL for modern clocks which carries a small ring magnet under it. This is oppositely magnetized to a fixed ring magnet around the lower PIVOT SO that the balance assembly 'skates' on a magnetic field, considerably reducing friction. Another version uses a magnet a short distance above the steel balance STAFF (axle) to lift it and reduce friction.

Magnetism: Steel parts of watches, especially the HAIRSPRING if of steel, can become magnetized from TV circuits, magnetic kitchen and tool racks, generators, radar equipment, etc., and behave erratically. They can usually be demagnetized without difficulty. 'Anti-magnetic' watches are partly protected by having vital parts NON-MAGNETIC. The best protection is an anti-magnetic screen around the MOVEMENTS of special watches. ELECTRIC WATCHES can be affected and also demagnetized. The DEMAGNETIZER is not strong enough to damage the magnets in them.

Mail Guard's Watch: Special 'watch' carried by the guard on a mail coach, along with his blunderbuss, in the days before railways. Usually in a rectangular brass and wooden case which was locked at the depot. The guard was responsible to the company for seeing that the mail coach kept to its time schedule.

Mainspring: Coiled flat spring for driving a clock or watch, inventor unknown, but may have been a swordmaker/clockmaker of about 1450. The mainspring made the portable clock and the watch possible. Early springs were hammered out of steel or brass. They gave much more power wound than partly wound, which affected timekeeping. Attempts were made to compensate for this by STOPWORK, the STACKFREED, forms of FLY, and particularly the FUSEE. Modern springs are made of tempered carbon steel, stainless steel and various alloys; the unbreakable mainspring (for watches) is an alloy steel containing iron, carbon, nickel, chromium, cobalt, molybdenum, manganese, and beryllium. It is non-magnetic and was introduced in 1947. Some springs are set to a reversed curve like a figure 8 when free. Such alloy springs give more power as they age, not less, like steel springs. Power output of modern mainsprings is fairly even at different tensions, which improves timekeeping performance. Mainsprings break through fatigue, no lubrication, and sudden changes of temperature (see Going Barrel and Setting Up). One form of mainspring for modern clocks running a month at a winding and for cine cameras is coiled round a free-running ARBOR when unstressed. It is wound in the opposite direction round an adjacent arbor. It then runs back onto the first, giving very even power output, but not MAINTAINING POWER, like a GOING BARREL.

Maintaining Power: A clock without a GOING BARREL loses time while it is being wound because there is temporarily no power to drive it. Maintaining work provides this power during winding by an extra weight or spring. A HUYGENS ENDLESS CHAIN in 30-hr. grandfather clocks and AUTOMATIC CLOCK WINDING in tower clocks automatically provides maintaining power. Some of the best weight-driven LONG CASE CLOCKS have BOLT-AND-SHUTTER maintaining power. A similar arrangement for tower clocks is a weighted lever which has to be moved before the winding handle can be turned. Moving it applies power to a clock wheel through a ratchet. For FUSEE clocks and watches, and MARINE CHRONOMETERS, a spring-driven maintaining power invented by John HARRISON in 1735 is employed.

Main Wheel: The driving first wheel in a clock or watch, usually attached to, or part of, the BARREL. In a FUSEE timepiece it is attached to the fusee and often called the 'great wheel'.

Mantel Clock: Clock intended to be placed on a mantelpiece; otherwise similar to a BRACKET CLOCK. The latest are made thin to suit mantels over electric and gas fires.

Marie Antoinette Watch: Celebrated masterpiece by BREGUET commissioned for the Queen by an officer of the French Royal Guard. It was constructed from 1783 to 1802, by which time the Queen had been executed. The watch incorporated every complication of the time. It was SELF WINDING, with a MINUTE REPEATER, PERPETUAL CALENDAR, INDEPENDENT SECONDS HAND, EQUATION OF TIME DIAL, UP-AND-DOWN DIAL, and a thermometer. The outer gold case was never finished.

Marine Chronometer: Special very accurate timekeeper with a DETENT ESCAPEMENT used for NAVIGATION at sea, surveying, and scientific purposes. Developed by LE ROY, ARNOLD, and EARNSHAW (see also Harrison). The chronometer is usually in a brass case fixed in gimbals in a wooden box some 8 in. square, and runs for two or eight days. It has a COMPENSATION BALANCE with a HELICAL SPRING driven from a MAINSPRING and FUSEE with MAINTAINING POWER. It also has an UP-AND-DOWN DIAL incorporated in its traditional form of dial. See Deck Watch.

Marine Clock: Spring-driven clock with PLATFORM ESCAPEMENT in a cylindrical brass case with a flange at the back for mounting on a bulkhead. For general use. The MARINE CHRONOMETER or DECK WATCH 1S more accurate for NAVIGATION.

Marquetry: Inlaid patterns of holly, boxwood, or ivory in walnut or ebony veneer, usually of LONG CASE CLOCKS. Some were in panels; some all over. Used from about 1675-1720. Superseded largely by burr walnut (see Case, Clock). BOULLE work is also a form of marquetry.

Mary Queen of Scots' Watch: Large SKULL WATCH believed to have been given by the Queen to Mary Seton, one of her Maids of Honour. The forehead of the skull is engraved with a figure of death between a palace and a cottage, and a quotation in Latin meaning 'pale death visits with impartial foot the cottages of the poor and the castles of the rich' (Horace). The skull is held upside down and the jaw lifted to read the silver dial. The hour is struck on a bell. Made by Moyant A Blois (1570-90). The escapement is unfortunately a CONVERSION to lever.

Mass Dial: Ancient sundial to remind churchgoers of times of service. Usually seen today as a little group of radiating lines marking the TIDES, scratched on the south porch of the church. Originally there was a rod sticking out from the centre.

Master: Clock or watchmaker who had served an APPRENTICESHIP and had his MASTERPIECE approved by the Court of the Worshipful Company of Clockmakers.

Master Clock: Clock which controls SLAVE DIALS, a TOWER CLOCK dial, or PROGRAMME CONTROLLER. Invented by Alexander Bain in 1840. Most modern electric master clocks have a SECONDS PENDULUM impulsed by a GRAVITY ARM. Each time it swings to the right, the pendulum turns a 30-toothed wheel one tooth. At each full turn (half minute), a lever on this wheel unlatches a gravity arm which gives an IMPULSE by pressing on an arm fixed to the pendulum. The gravity arm then drops on to an electric contact which operates an electro-magnet to reset the arm and also to provide a brief current to operate SLAVE DIALS.

Masterpiece: The special clock or watch that an APPRENTICE, after a period as a JOURNEYMAN, had to submit for approval (to the Worshipful Company of Clockmakers if he were English) before he could set up on his own. See Clockmakers Company and Nurnberg.

Matted Dial: Centres of brass antique clock dials were often given a rough matt surface by rolling them in all directions with a matting tool-a knurled and hardened, steel roller in a handle. This was done by hand. Today the finish is copied by acid etching.

Mean Time: Mean SOLAR TIME, the time shown by clocks. Days and hours shown by the SUNDIAL actually vary in length. When time was averaged into EQUAL HOURS, this was called 'mean time'.

Mercurial Pendulum: A form Of TEMPERATURE COMPENSATION invented by George GRAHAM in 1721. The BOB of the pendulum is one or two jars of mercury. As the pendulum rod expands downwards in heat, the mercury expands upwards, thus keeping the effective length, or CENTRE OF OSCILLATION, the same. In the RIEFLER CLOCK, the rod of the pendulum is a steel tube almost filled with mercury, which gives better compensation because it is effective over the whole length of the pendulum.

Meridian: The highest position of the Sun in the sky, which indicates noon. Also the highest position of a star. The meridian of a particular place is a circle passing through it and the North and South Poles, i.e. its LONGITUDE.

Meridian Line: The line of longitude zero passing through GREENWICH OBSERVATORY from which GREENWICH MEAN TIME is measured. It is marked in the forecourt by a white line so that visitors can stand with one foot in the eastern and the other in the western hemisphere.

Metropolitan Museum Collection: Fine collection of timekeepers in New York, which includes the PIERPONT MORGAN COLLECTION Of watches.

Microsecond: A millionth of a second, symbol us.

Middle Temperature Error: A BI-METALLIC BALANCE arid HAIRSPRING 1S only truly accurate at two temperatures. In between these, the timepiece gains. This middle temperature error was reduced by AUXILIARY COMPENSATION (used particularly on MARINE CHRONOMETERS) and almost eliminated by the GUILLAUME BALANCE. Modern materials have eliminated it. See Compensation Balance.

Millisecond: Thousandth of a SECOND, contracted to 'ms'.

Miniature Rotor: A very small winding ROTOR, less than half the diameter of the SELF-WINDING WATCH, which enables the watch to be made thin.

Miniature Watch: See Smallest Watch.

Minute: Sixtieth part of an hour. The Babylonians divided the path of the Sun into 360 steps representing days of the year, which gave us our 360 in a circle. Since angles of 60 were easily constructed and the smallest division of 60 by repeated halving is 15, 360 was divided into 24 angles of 15. As the Earth turns 360 in a day, the day was thus divided into 24 hours. The association of 60 with time may therefore account for the division of the hour into 60 minutes. (But see definition of Second.)

Minute Hand: Hand indicating minutes, incorporated as early as the sixteenth century on ASTRONOMICAL CLOCKS, but not in general use for clocks until after the practical PENDULUM was invented in 1657 and for watches until about 1700, after the BALANCE SPRING was invented.

Minute Repeater: A REPEATER WATCH or CLOCK that will sound the last hour, quarter, and minute on bells or gongs, at will. Such clocks were made from the early eighteenth century and watches from the nineteenth. The last hour is sounded first in the deeper of two tones, the last quarter is sounded by one, two, or three TING TANGS on the two gongs, then the number of minutes in the higher tone. The earliest known is by Benedict Felder.

Mock Pendulum: Some pendulum BRACKET CLOCKS have a curved slot near the top of the dial in which a disc (the mock pendulum) fixed to the PALLETS swings to and fro, to show the clock is going. Also called a 'false bob'. See Pendulum Watch.

Momento Mori: Reminder of death. Another name for SKULL WATCH or clock.

Monastery Clock: Very early ALARM used in Monasteries to give warning to a monk of when to ring the prayer bell. Most still existing are of iron in GOTHIC style, but the earliest of them made in Italy in the fourteenth or fifteenth century is of brass with a 24-hour revolving dial and fixed hand, and a wheel type of BALANCE. It is only 9 3/4 in. high and is in a private collection in Italy. See Canonical Hours.

Monumental Clock: One built like a monument.

Moon Dial: Aperture behind which a dial is moved to show an engraved or painted moon face gradually wax and wane. Common on clocks from about 1750. The moon was then the only 'street lighting'. For most clocks, the lunar month is 29 1/2 days (actually it is 29 days 12 hr. 44 min. 3 sec.). Two moon faces are shown, one black (new moon) and one white (full moon). Later clocks have two full moons, displayed one after the other, on a larger disc turned in 59 days in the BREAK ARCH. The age of the moon is often shown on the edge of the disc through a small aperture in the dial. Another form of moon dial is a globe painted half black and half white or silver which is revolved in a close-fitting hole in the dial by gearing during a lunation; sometimes called a 'Halifax Moon.'

Moon's Effect on Rate: In 1927-28, A. L. Loomis compared three FREE PENDULUM clocks with a QUARTZ CLOCK by means of a spark CHRONOGRAPH he invented. His results showed that during a lunar month the attraction of the moon on the pendulums caused them to vary by 2/10,000 of a second.

Morbier Clock: French clock of unusual design, the early MOVEMENTS having bars instead of PLATES, and a straight instead of curved RACK to operate the striking. Usually LONG CASE or LANTERN style with a very wide and decorative LONG PENDULUM. Also called 'Comptoise clock'. Made in Morbier from about 1750 to this century. The style has changed.

Motion Work: Twelve to one gearing driving the hour hand from the minute hand.

Movement: The 'works' of a timepiece.

Moving Arm Watch: Watch in which a human figure (AUTOMATON) on the dial indicates the time by moving its arms. The arm on the left points to the hour on a curved scale marked 12, 1, 2, 3 ... 12; the other shows the minutes on a scale marked 0-60. Made in France in the nineteenth century. Also called 'bras mobile' or 'bras en l'air' watch.

Moving Eye Clock: Animated figures with clocks include many with rolling eyes, the eyeballs being connected to the PENDULUM or BALANCE. Negroes, dogs, owls, and lions are examples.

Mozart: This Austrian composer wrote some works in the eighteenth century for playing on musical clocks for Count Josef Deyn who had a collection. In The Magic Flute, he imitated mechanical music on bells.

Mudge, Thomas (1715-94): Made the greatest invention of all, the LEVER ESCAPEMENT, in QUEEN CHARLOTTE'S WATCH, 1759. He thought it capable of extremely good performance, but too complicated to be commercially successful. It was perfected 23 years later by Josiah Emery, who made three. Billions are in use today. Mudge also invented a REMONTOIRE and DETACHED ESCAPEMENT in a clock made for the Swiss astronomer Huber (who was once a pupil of the Astronomer Royal, Bradley) in 1755. Came from Exeter, was apprenticed to GRAHAM, in London, and became perhaps the finest craftsman of all. Left Fleet Street in 1771 to go to Plymouth and devote himself to perfecting MARINE CHRONOMETERS.

Musical Alarm: An ALARM that plays a tune on a small MUSICAL BOX instead of ringing a bell. Produced in large numbers by the Swiss and Germans from 1897 to 1914 and still made.

Musical Box: Clockwork mechanism playing music on bells or cymbals, or on the steel comb which may have been invented by Antide JANVIER in 1775. Louis Favre of Geneva probably made the first musical box in 1770. Musical movements were fitted into snuff -boxes, jewel cases, even watch and door keys. Best makers of larger musical boxes were Nicole Freres from 18151903. Most played six or eight tunes. Small musical movements are turned out by factories in Switzerland today in large quantities for musical cigarette boxes and other novelties.

Musical Clock: Both TURRET CLOCKS and domestic clocks have been made to play tunes at the hour, one of the earliest of the latter by N. Vallin, 1598 (in the BRITISH MUSEUM COLLECTION), having 13 bells. Later ones had steel combs played by a revolving barrel with pins in it. Famous eighteenth-century makers were Robert Philip, Markwick Markham, David Evans, Wm. Carpenter, and Christopher PINCHBECK. Carillons of turret clocks are played by large revolving barrels operating the bell hammers. See Organ Clock.

Musical Watch: Watch playing a tune at the hour and usually at will also, by moving a slide. Invented about 1725 in Switzerland and most popular after 1800. The earliest had separate steel teeth, like the blades of a fan, plucked to give the notes by pins in a rotary disc. A metal comb and BARREL with pins superseded this. Some were REPEATERS, repeating the tune. See Musical Box.

Musk Ball Watch: Earliest form of watch still in existence. Those made by Peter HENELEIN were of this type. The case is a metal sphere about 4 in. in diameter. Like a scent 'bottle' of the period and, like it also, hung by chain or cord round the neck. The spring-driven MOVEMENT is inside the hinged case and the dial is a smaller diameter disc (like a base, for standing) at the bottom with one hand and no glass. Of the six such spherical watches known still to survive, the earliest is German and dated 1525-50. There is a German one of c. 1550 with CLOCK WATCH movement in the ASHMOLEAN MUSEUM; and a French one of 1551 by Jacques de la Garde in the NATIONAL MARITIME MUSEUM. The DRUM WATCH may have been invented about the same time or soon after. See Nurnberg Egg.

Mystery Clock: Clock which appears to work without any power or wheels. A domestic type has the hand 'floating' in double glass dial. Actually one of the circular glasses holds and rotates the hand, being driven from a MOVEMENT in the base. More mysterious are two large hands, freely attached to nothing but a sheet of glass, which work on their own. Each contains a watch movement in its counterpoise which alters the centre of gravity as it runs and causes the large hand to take up new positions. This idea was invented by John Schmidt, London, in 1808, who made clocks with an open CHAPTER RING and a single counterpoised hand, supported from the tail of a dolphin, and revolving without any apparent clockwork. Another mystery clock, invented by A. R. Guilmet, of Paris, in 1872, has a statuette on top of the case. In one hand, this figure holds a PENDULUM which swings without apparent connexion to the clock. Actually the statuette is given an almost imperceptible twist in alternate directions. IMPULSING is in principle similar to that in the RIEFLER CLOCK, through the SUSPENSION SPRING, 15 years later. There are examples in the VICTORIA AND ALBERT MUSEUM and ILBERT COLLECTIONS.

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