M

Mainspring :
A coiled wire that provides the principal tension or driving power to keep the movement running in a spring-driven clock.

Maintaining Power :
A mechanism to maintain a clock's drive during the operation of winding. The poor accuracy of pre-pendulum clocks meant that there was little need to keep them going during winding. The Christiaan Huygens endless rope or chain provides the simplest maintaining power. A continuous band of rope is run over two pulleys, forming two loops. The driving weight hangs in one loop with a smaller weight or lead ring hanging in the other to tension the system. In a striking clock, one of the top pulleys drives the striking train through a ratchet and click, the other pulley being fixed to the great wheel of the going train. The clock is wound by pulling down the length of rope between the smaller weight and the striking-train pulley. This raises the larger weight without removing its effect from the going train, and one weight drives both trains. The problem with this system is that it is difficult to arrange for the clock to run for longer than 30 hours, whereas in timepieces the top pulley with its rathet is attached to the case or movement, allowing the timepiece to run for up to eight days. In a domestic or turret clock fitted with bolt and shutter maintaining power, the shutter(s) normally covering the winding square(s) can be raised by moving a lever or pulling a cord, which at the same time raises a small weight, coupled with a train wheel by the bolt or a click, to drive the clock during winding.

Maltese Clock :
The Italian altar clock died out in the early 18th century, but the general design was revived in the early 19th century in the island of Malta. The pioneer is believed to have been Kalcidoniju Pisani in the village of Siggiewi; he was followed by others in the same village and in the village of Zebbug. The design differs from its prototype in that the Maltese clock hangs on the wall instead of standing on a table, but the size and shape are similar, though the case has been simplified and the decoration is of painting and gilding, the dial being decorated with flower designs. A small aperture allows the pendulum to be seen. The clocks are weight-driven with the lines carried over a pulley; some have a double pulley with a heavier weight for a longer going period. The escapement is at the bottom of the movement as in the altar clocks. Early examples possessed an hour hand only; late ones had minute hands also. Alarm work is known but striking clocks are rare.

Mandril :
A lathe with a face plate fitted with dogs for gripping work such as flat plates and parts. It is equipped with a spring or pump center with a conical point down the center of the lathe spindle, used to center the work on the mandril. The English mandril is driven by a gut line from a hand wheel or treadle, fitted around a pulley at the back of the lathe head, while Swiss mandrils are hand-driven through gears. The mandril has a slide or toolrest and sometimes a back or tail center which is used to center the work from the front.

Mantel Clock :
A shelf clock.

Marble Clock :
A generic term applied to a type of clock first manufactured in France towards the end of the 19th century. While true marbel has long been used for clock cases, the so-called 'marble' clock has a case made mainly from slate with a high surface polish. These cases are very heavy and provide great stability to pendulum clocks; this, combined with their excellent movements, gives long and satisfactory timekeeping. Ornamentation with true marble may be found in elaborate cases, combined with gilt metal pillars and medallions. One disadvantage of slate is its tendency to chip. It is dangerous to lift marble clocks except by the base, for the case may break apart under its own weight. The surface polish is easily damaged by water and is very difficult to restore. Recently despised, these clocks are now rapidly appreciating in value.

Marine or Lever Clock :
A clock that operates with a hairspring balance and continues to run when transported or set on an uneven surface (unlike pendulum clocks); often used aboard ships.

Marquetry :
A form of decoration made by inlaying wood veneers in various designs. A number of sheets of different colored veneers were pinned together and a pattern was pricked through paper on to the top veneer. The pattern was then cut out with a type of fretsaw known as a 'markatree cutter's donkey'. The various pieces were rearranged like a jigsaw puzzle to give as many designs of contrasting colored woods as there were sheets of veneer. A sheet of paper was then pasted over each arrangement to hold the pieces together and the whole was glued on to the cabinet front, clock case or wherever the marquetry was required. In England there were three types of marquetry: the bird and flower patterns contained in panels of boxwood stringing, all-over flowered patterns, and the all-over patterns of finely worked scrolls and arabesques known as 'seaweed' marquetry.

Mask :
A human or animal face used as a decoration.

Massachusetts Shelf Clock :
A style of clock frequently called half-clock or box-on-box. The upper portion with dial rested on feet on a separate lower section which contained the pendulum. A similar design developed into the case-on-case style. Basically, this was an English bracket case above and a large supporting base to contain the pendulum and weights below. This style became popular during the 1820s; examples display both Sheraton and Hepplewhite influence, many with inlaid lower panels and kidney-shaped dial doors. Decorative glass panels, both gilded and painted, were popular later, often with dished (concave) dials.

Master Clock :
All time distribution systems must have an accurate controlling clock. Carl August Steinheil, who first applied electricity to time distribution, used the term 'central' clock; Alexander Bain later referred to the 'parent' clock, where in England the term 'master' clock would be used for the central clock which supplies accurately controlled current pulses to the circuit of controlled or impulse dial clocks. The first master clock capable of combining both functions was devised by Steinheil in 1839, Bain's following a little later. It was not until 1895 when Frank Hope-Jones and George Bennet Bowell invented the synchronome clock, or remontoire, that electric master clocks became absolutely reliable, their clock sending out current pulses at half-minute intervals. Many other makers devised similar clocks later, but the synchronome was the most successful. Modern master clocks are of the quartz-crystal type and have electronic circuits generating the current pulses to drive the impulse dials.

Matting :
The granular finish given to the center of a brass clock dial, or a type of finish for clock parts. The effect is produced by punching the matted center dial all over with a single or multipointed punch, or by rolling the dial between rollers, one of which has fine spikes. A matted effect can also be obtained by etching with acid.

Mean Time :
When all hours and days are of equal time. The average over a whole year of a solar day is termed a 'mean solar day', and a timekeeper divides this as accurately as possible into hours, minutes and seconds of exactly equal length.

Medallion :
An applied cirular, oval, or square decorative turning used on a clock case.

Mercury Pendulum :
In American clocks, a silvery-looking, usually cylindrical pendulum designed to simulate French examples, which actually contained mercury.

Milling :
A method for giving specific shape to metal parts with revolving cutting tools, mostly known as milling cutters. It is faster than other methods of shaping. Although milling cutters may be used in a lathe, they are more often employed in a milling machine. These machines are of two types, those with vertical spindles and those with horizontal ones. Milling cutters are made to produce clock wheels or pinions, and they cut or 'gash' one tooth space at a time in the wheel or pinion blank. When cutting a wheel with a milling cutter, the milling machine can be arranged so that the revolving cutter moves through the stationary blank; alternatively, the blank can be mounted in an attachment which moves it in the path of the revolving cutter. Hobbing is a quicker and more accurate way of cutting gears; hobs are cutters in the form of a worm, the cutting edges being formed by flutes across the worm thread. The work and the hob are revolved together, the two often being suitably geared by the hobbing machine.

Mirror Clock :
Also known as looking-glass clock. A term used almost exclusively in connection with New Hampshire wall clocks cased in frames with split columns on all four sides, usually with corner blocks mounted with brass rosettes, and containing a looking-glass front and decorated dial glass. The period of their popularity was 1825-38. They were eight-day, both strikers and timepieces, all weight-operated.

Mission-Style Clock :
A clock with a plain, straight-lined case made of oak, popular from about 1900 to 1925.

Mock Pendulum :
A small secondary pendulum bob attached to the real pendulum arbor, which appears in a segmental aperture on the dials of some 18th-century verge bracket clocks. It showed that the clock was going and enabled it to be started or stopped without opening the door; it also gave the clock a lively appearance. Mock or false pendulum bobs are usually small, about 1/2 in. in diameter.

Molding :
A continuous decorative edging.

Monastery Clock :
Monasteries in the Middle Ages, required to hold services at certain hours of the day and night, originally used water clocks to indicate the time. Later, simple verge escapement mechanical clocks with alarm work were made, and although these are now rare illustrations of them have been preserved in tarsia panels from Italy, one of which is in the Victoria and Albert Museum, London. This shows the clock in a cupboard with a square hole cut below it for the weight cords to descend, and casts light on an item in the records of Battle Abbey, Sussex, in 1512, 'For repairing the clock in the Cubiculo of the Sacristy XXd'.

Monastic Alarm Clocks, Italian :
In the late 15th and early 16th centuries, the art of pictorial marquetry or inlay work was widespread in Italy as a decoration for studies, other rooms and monastic choir stalls; a fair number of these marquetry pictures show clocks, almost always of the type known as monastic alarm clocks. The simple structural framework is kept at a distance from the wall against which it is standing. The train has three wheels, of which the main one has four crossings and carries the winding drum, there being two cords, one for winding and the other for the weight. The escape wheel has a lantern pinion, and the arrangement for striking the alarm consists of a simple winding drum which, when released, vibrates a vertical verge-type arbor to shake a platform which holds a bell. The clock dial is of the rotating, 24-hour type with Roman figures, and has a series of holes in its edge in which a pin is placed to free the alarm as required. The foliot is S-shaped and has two small weights to regulate the period of oscillation. Later marquetry pictures show clocks which are not unlike this. The structure is of iron or brass and always very simple; occasionally, wood is used in parts of the structure. The train has two or three wheels, and the dial always rotates through 24 hours; the time controller is of the foliot or balance type. Few clocks of this kind have survived. Two in private collections in Italy are comparatively well known. The first, completely in brass, is in the High Gothic style with three wheels, a circular balance and a catherine-wheel alarm. It also has a mechanism, now almost entirely missing, with which it could strike a single blow at regular intervals, presumably every hour. It can be dated about the middle of the 15th century. The second, of iron and brass, is late 15th century, and has an alarm of the oscillating type and a foliot regulator.

Monstrance Clock :
A monstrance is a vessel used in the Roman Catholic Church to display the consecrated bread; clocks are known made in a shape similar to that of this receptacle. The movement is placed in a drum supported by a stand and is of the type usually found as a horizontal table clock. Astronomical work is normally provided and the quality of these clocks altogether is high. The period of manufacture was from the mid 16th to the mid 17th century, and Augsberg was probably the origin of the type.

Month Clock :
The late 17th and 18th centuries witnessed many innovations for improving methods of timekeeping. It was but a short step to convert the principle of an eight-day clock into one going for a month, three months, or even a year. All that was required was the addition of a fifth wheel to the existing train of four wheels. While this extended the going duration, the extra wheel reduced the power to the escapement because of the higher gearing, and accordingly a heavier weight had to be used to drive it. The addition of the fifth wheel also meant that instead of turning the winding key in a clockwise direction as for an eight-day clock, the key of a month clock was turned anticlockwise. This was so that the second hand, on the escape-wheel arbor, would rotate clockwise.

Moon Dial :
The dial at the top of a clock that shows the phases of the moon.

Morez Clock :
Another term for Comtoise Clock. Morez is a small village in the Morbier district of the Franche-Comté region of France, near the Swiss border, and both Morez and Morbier are descriptive terms for clocks produced in the region between c. 1750 and 1900. During the 19th century Morbier and Morez seem to have been the center for the production of the decorative stamped-iron pendulums used with certain forms of cased Comtoise clocks.

Motion Work :
The train of wheels in a clock giving the usual 12 to 1 reduction between the minute and hour hands.

Motor :
The term used in the United States for the mainspring and barrel. It also applies to the driving unit of electric clocks.

Movement :
The "works" of a clock. The whole mechanism of a clock, excluding the dial and case.

Musical Alarm :
An alarm that plays a tune on a small musical box. It was popular from the late 1890s to about 1915.

Musical Clock :
A clock which plays a tune at the hours or at certain specific hours, (e.g. 3, 6, 9 and 12 o'clock). The name is also sometimes given to clocks with musical chimes only. The musical movements of clocks fall into three categories, in all of which the tune is played by a revolving barrel, occasionally a wheel, set with metal pins. In the first type pins activate hammers to play a carillon on bells, in the second the pins play a tune directly on a steel comb, and in the third (organ clocks) pins or metal bridges control the supply of air from bellows to pipes. Musical-box movements and organ clocks were both popular in the 18th century when certain composers of note wrote tunes for such toys. In the 19th century the trade in automata and musical boxes, including those incorporated in clocks, passed almost wholly to the Swiss.

Musical Work :
The parts of a clock which play a tune, by means of a pin barrel, on bells, organ pipes or reeds; similar in action to a music box.

Mystery Clock :
A clock in which the mechanism is not immediately apparent or explicable. The idea originated very early, probably in Germany or France, but most mystery clocks date from the 19th century when the French particularly were keen on such devices. In the later 17th century Grollier de Serviére produced the amusing 'tortoise clock', a horizontal table clock on which the center of the dial within the chapter ring was dished and filled with water. On this floated a small turtle which crept round the edge of the chapter ring pointing to the hours. The secret of the movement of the tortoise lay in a magnetic hour hand fixed under the chapter ring, which attracted to it the turtle body which was primed with a small amount of soft iron. Versions of this principle with, for example, a mouse inching along a flat arch marked with the hours, have been described. Later horological enigmas took several forms, one of the most popular having hands which appear to revolve of their own accord. The dial, in fact, is three layers of glass, the center one, to which the hand is attached, having a toothed edge which is rotated by a movement concealed in the base. The commonest form of mystery clock, produced cheaply in great numbers from c. 1880, is in the form of a figure with outstretched arm holding a timepiece; an elephant holding a timepiece in his trunk was also popular. The clock movement and dial form an upper weight on a rod with a pendulum bob at the lower end. This compound pendulum is supported just above its center of gravity so that it swings slowly from side to side. The pendulum movement releases the escapement, which causes a small weight to move in the opposite direction to that of the pendulum, thus keeping it swinging.