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A Brief Glossary of Technical Terms (continued)

MAINSPRING

The coiled spring of tempered steel which provides the power source for all watches (except those with battery- or
solar-powered movements) and most clocks.   References to spring-driven clocks in Italian documents of the 15th
century suggest that Italy, rather than Germany, may have been the home of the earliest portable timekeepers.

MAINTAINING POWER

An auxiliary power source to keep a clock or watch running whilst it is being wound.   John Harrison first applied it to
watches;  his system was embodied within the cone of the fusee and was gradually adopted (not necessarily on the most
luxurious or expensive watches) as the 19th century progressed.

MASSEY, Edward

(1772-1852) English watchmaker whose variants of the lever escapement, devised in the second decade of the 19th
century, gained considerable currency until about 1850.   There were five types, all adopting a drum-shaped roller with
the impulse-pin alongside it rather than the usual flat disc with the pin standing on it.   In the Massey I the pin is not
free-standing but is actually cut out of the roller, which therefore forms a pinion with only one leaf.   The Massey III (the
most popular version) has a jewelled pin carried on an outrigger projecting from one end of the roller.

MEAN TIME

A scale of time-measurement in which the units – second, minute, hour etc. – are of the same length throughout the
year.   It is easily forgotten nowadays that this is not true of the sun's time, by which the length of a 24-hour period
shows a variation of up to 30 minutes 46 seconds if measured by a constant-rate timekeeper.   In the 18th century,
‘equation tables’ were published showing the difference between solar time and mean time throughout the year, so that
clocks and sundials could be correlated.

MERLIN, Joseph

(1735-1803) Belgian inventor of (amongst other things) a timekeeper wound by the opening and shutting of a room
door, as well a wheelchair (sometimes called ‘Merlin chair’ after him in the English of 200 years ago).  

MOON HAND

See Breguet hand.

MONTGOMERY DIAL

A dial with each individual minute numbered in arabic figures;  an American fashion of the period 1890-1920.

MONTRE

French for ‘watch’.   Both the French (from the verb montrer, ‘to show’) and the English names seem to contain the idea of
something observed or offered for observation.   This may be connected with the fact that early public clocks seem to
have been designed more for the ear than the eye, since the earliest examples had no dials at all, while 16th-century
dials are remarkably difficult to read;  watches, or the table clocks from which they developed, were therefore the first
primarily visual timekeepers.

MOTION WORK

The gearing, usually consisting of two wheels and a pinion, fitted between the front plate and the dial of a watch to link the
hands to the train and to each other.   The motion wheels are loosely fitted (one being located by the cannon pinion and
the other by a peg on the plate), and if the dial is permanently removed for any reason the motion wheels are almost
predestined to be lost as well.

MOVEMENT

The correct name for the ‘works’ of a watch.   Vast numbers of movements survive without their cases, which have
presumably been removed for melting down;  these often remain in working order and can provide an easy means for the
budget-conscious collector to obtain examples of scarce escapement types or other special areas of interest.

MUDGE, Thomas

(1715-1793) English clock- and watchmaker, pupil of George Graham;  inventor of the lever escapement (in a watch
made for the consort of the future King George III, c. 1757);  early contributor to the development of the chronometer;
allegedly the first to apply jewels to pallets.

MUSIC

The link between music and horology might well form the subject of an extended thesis.   Hans Leo Hassler or Hasler
(1564-1612) of Nuremberg, allegedly the first maker of a chiming watch, was also a distinguished composer who
anticipated Schütz in introducing the Venetian choral style to Germany;  he made a number of  musical automata.
Christiaan Huygens was renowned as a lutenist.   Davies Mell (fl. 1655-75), clockmaker of London, was leader of King
Charles II's violin band.   Charles Clay (d. 1740) made musical watches and clocks for which Handel wrote and
arranged tunes.   John Harrison was an enthusiastic player on the bass viol and developed an idiosyncratic theory on the
musical scales.   And, as a more remote point of contact, Pierre Auguste Caron (1732-1799), watchmaker and
inventor of a form of virgule escapement, is one and the same with Pierre de Beaumarchais, author of the plays Le Barbier
de Séville and Le Mariage de Figaro on which the Rossini and Mozart operas are based.

NORTON, Eardley

(fl. 1760-1794)  Fashionable London maker patronised by King George III and Catherine of Russia;   probably the
victim of more piracies than any other watchmaker in history, Breguet not excepted.   These are generally Swiss and
some of them attempt to follow English design conventions such as the single-footed cock, but they betray themselves
by their roughly-painted dials, coquerets and winding holes in the dial.   On Norton's death his business was taken over
by a partnership including one Tolkien, earliest recorded ancestor of J. R. R. Tolkien.

OIGNON

(French:  ‘onion’)   A French watch of the late 1600s whose very deep calibre gave it a bulbous shape, the source of the
name.   There is generally only one hand;  the arbor of this is hollow and the winding-square projects through it in the
centre of the dial.

OIL SINK

A saucer-shaped indentation surrounding the hole where a pivot comes through the plate.   This serves to retain oil and
prevent it from spreading uselessly over the surface of the plate.   Oil-sinks were invented in about 1720 by Henry
Sully, an Englishman working in Paris.

ORMSKIRK

Town in Lancashire, north-west England, a few miles from Liverpool, where there was a substantial colony of
watchmakers in the early 19th century – an English equivalent of Le Locle or Chaux-de-Fonds in Switzerland.   The
place was particularly noted for a variant of Pierre Debaufre's escapement.

OVERCOIL

A method of improving the isochronous characteristics of a hairspring by bending its outermost coil inwards and upwards
so that it ends and is anchored well within the circumference of the spring.   Breguet invented it and it is often called after
him;  see spiral Breguet.

PAIR CASE

The usual style of case on British watches from about 1680 to 1820 (also used in Europe, but less exclusively).   The
movement is housed in a very plain case which incorporates the crystal and pendant and (in Britain) is pierced at the
back by the winding-hole;  this is fitted into a completely separate outer case with openings for the crystal and pendant,
sometimes decorated with enamel, repoussé work or (later) engine-turning.   The outer case has to be removed for
winding.   The pair-case gradually gave way to the consular case but was still fitted at times until about 1890, the Scots
being its last champions.

PALLET

A tongue or cam mounted on the balance-staff, or (in certain escapements like the lever escapement and some types of
detent) on a component interacting with it, and designed to engage with the escape-wheel for the purpose of either
receiving impulse or performing the locking function.   There are usually two pallets, one for each operation;  they may
interchange their functions (lever, verge) or each may be specifically designed to do one or the other (spring detent).

PARACHUTE

An arrangement for insulating the fragile balance-staff against lateral shocks by mounting each of its pivots in a springy
steel arm; invented by Breguet.   Click here for an example.

PASSING-SPRING

A flat spring which allows a rotating and an oscillating component (e.g. escape-wheel and balance) to pass each other
with virtually no resistance in one direction but which obstructs the wheel on the return swing of the balance.   This is
applied in the spring detent escapement, where the effect is achieved by making the passing-spring (which carries the
locking pallet) very weak but mounting a stronger spring alongside it, so that the balance encounters the passing-spring
alone when turning one way but meets both on its return, pushing the stronger spring with its locking-pallet into the path
of the escape-wheel teeth.

PENDANT

The shaft which protrudes from one side of a watch-case, ending in a cross-piece on which the bow is hinged.

PENDULUM WATCH

This expression is often found in advertisements and other descriptions of the late 17th century – too often to be
explained simply as a reference to the false pendulum.   I suspect that, because the pendulum and the balance-spring
served the same purpose, appeared at much the same time and were perhaps invented or at least applied by the same
man (Huygens), the name was transferred from the former to the latter.


PERPETUELLE

A watch that is wound automatically and continuously by the motions of a weight that swings round under the influence
of gravity as the wearer's movements put the watch into different positions.   The principle was known in the eighteenth
century.


PERRON ESCAPEMENT

A variety of lever escapement in which the pallets are replaced on the lever by pins and the escape-wheel teeth are
shaped like wedges with the broad end outwards;  invented by Perron of Geneva in 1798, applied by G. F. Roskopf
in his inexpensive ‘People's Watches’ from 1867 onwards, and still found in some cheap 20th-century watches.


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