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A Brief Glossary of Technical Terms (continued)


SAFETY PINION

Alternative (mainly U.S.) name for reversing pinion.

SAFETY ROLLER

A second roller, mounted closer to the balance-wheel than the roller which carries the impulse-pin, and with a curved
notch on one side into which the dart fits.

SAVAGE ESCAPEMENT

A variant of the lever escapement with two pins on the roller (for locking) and a third on the lever itself, engaging in a
deeper than usual notch in the roller, for impulse;  invented by George Savage, a Yorkshire watchmaker who
eventually settled in Canada (?-1855).

SELF-WINDING WATCH

Another name for the perpetuelle.

SETTING

A stoppage resulting from a loss of momentum in the balance so that it fails to bridge the gap between one impulse and
the next.   This can be caused by an abrupt movement on the wearer's part;  if this turns the body of the watch in the
same direction as the rotation of the balance, the latter will for a vital instant be motionless in relation to its immediate
surroundings and the dynamics of its operations will be fatally upset.

SET-UP

The initial tension imparted by a maker or repairer to the mainspring, so that it never falls completely slack even when
technically ‘run down’.   This is done by turning the arbor of the barrel.   Until about 1780 set-up was adjusted by means
of a worm between the barrel and the front plate, engaging with a wheel fitted to a squared section of the arbor and turned
by a very small key;  thereafter the usual form was a ratchet-wheel hidden behind the dial (or occasionally, in the early
1800s, mounted visibly on the bottom plate).  The degree of set-up can be critical to a watch's rate.

SIDE LEVER

(or English lever).   The type of lever escapement normal in Britain from about 1815 to 1910;  the lever is positioned
alongside the escape-wheel rather than between the escape-wheel and the balance.

SINGLE SUNK

Of a dial:  having the subsidiary seconds dial recessed, the remainder of the dial itself being flush.   This arrangement
begins to appear in Switzerland in the 1840s and in Britain and America from about 1860.   Swiss dial-makers achieved
it by grinding back the dial surface, British and American by cutting out a hole and soldering a separate panel into place
before applying the enamel.

SKELETON DIAL

A dial in which as much as possible of the material is cut out to reveal the movement behind (the front plate being
similarly cut away).

SPADE HAND

An hour hand with a terminal shaped like a playing-card ‘spade’, but somewhat narrower;  widely used in the period
1790-1900.

SPIRAL BREGUET

Not a maker's name (even a forged one), but merely the French term for an overcoil balance-spring;  often stamped or
engraved on the cuvette of a watch so fitted.

SPRING DETENT

The standard escapement for marine chronometers throughout the 19th century, invented by either Arnold or Earnshaw in
about 1780.   As the balance swings, a cam on the balance-staff comes up against a light flat spring; on the anti-
clockwise arcs this has no effect, but in the other direction the spring is pressed against another stronger one
which carries the pallet for locking.   This releases the lock and the escape-wheel moves, giving impulse through one
of its teeth to a pallet on the balance-staff.

STEADY PIN

A brass peg on the back of a bridge or cock, mating with a hole in the plate and so ensuring that the bridge etc. is
correctly positioned during assembly.

STOP-WORK

(1)   A precaution against overwinding in fusee watches.  The chain, as it approaches the bottom plate, lifts a spring-
loaded arm into the path of a steel cam rigidly fixed to the fusee-cone;  when these two meet, the winding-gear is
immobilised.   (2)   A hack mechanism for stopping the train (and therefore the hands).  

STRAIGHT-LINE LEVER

The 20th-century style of the lever escapement — somewhat confusingly so called, since the lever does not form a
straight line but carries the pallet-arm crossways.   (The name results from the fact that the arbors of the balance, lever
and escape-wheel all line up in a row.)   This form is actually older than the side or English lever which was predominant in
19th-century Britain, a result perhaps of cross-influence from the rack-lever.

SUBSIDIARY SECONDS
DIAL

A small dial for the second-hand, usually at the six o'clock position and (from about 1860) recessed to increase the
clearance between second and minute hands.   Such dials are rare until about 1810, although there is an example by
Tompion dating from the 1680s.

SULLY, Henry

(1680-1728) English clock- and watchmaker working in France, inventor of the oil-sink and early experimenter with the
idea of a precise timekeeper for use in checking a ship's longitude.

SUPPLEMENTARY ARC

The outermost portion of the swing of a balance, before and after its period of interaction with the train.

SWEEP SECOND HAND

A second hand which is centrally mounted so that it sweeps the entire surface of the dial.   The expression is often
wrongly applied to the hand on a subsidiary dial.   Thomas Mudge's first lever watch (1759) seems to be the earliest
example of a centre second hand.

SWITZERLAND

Switzerland, the recognised mistress of the world in the field of watchmaking, came very late to that distinction.
Watchmaking began quite early — Rodolphe Breguet, a direct ancestor of the great Abraham Louis, was already at work
in Neuchâtel in 1594 — but for the next 200 years the Swiss were mainly noted for enamelled cases (a Geneva
speciality), ornate watches for the Chinese and Turkish markets, and inferior forgeries or imitations of English work.   It is
noticeable, however, that several of the greatest names in 18th-century horology were of Swiss origin although they
worked elsewhere:  Breguet and Berthoud in Paris, Josiah Emery (a lever pioneer) in London.   By about 1800 the Swiss
were asserting their identity, still often at the lower end of the market (Japy's volume-production techniques, for
example, or the multitude of automaton or painted-dial watches), but at the same time the two Jaquet-Droz, father and
son, were establishing Swiss craftsmanship at home.   By about 1850 the Swiss had generally adopted the barred layout
and dispensed with the fusee, ideas which were increasingly followed even by those who professed to despise their
originators.   Only in the 20th century, however, did Switzerland finally cast off her reputation for second-class work and
win respect for a combination of quality and consistency, supported by rigorous testing procedures.

TACT, Montre à

A Breguet invention providing a simple and inexpensive means of telling the time from a watch by touch alone.   The wide
bezel carries an additional chapter-ring with a projecting knob at each hour.   An extra hand, fitted outside the crystal,
revolves over this ring;  it is pushed round manually, not driven by the train, but when it reaches a position directly over
the main hour hand it comes up against a stop.    It can therefore be used in conjunction with the chapter-ring to tell the
time to within ten minutes or so.

THIRD WHEEL

The train wheel between the centre wheel and the fourth wheel.   In a full-plate watch it is usually recessed into the front plate.

THIRTY-TOOTH
ESCAPE WHEEL

A fashion of the years 1805-1825.   The fourth wheel is omitted and the escape-wheel, which takes its place and
carries the second-hand, has thirty teeth rather than the usual fifteen, so that the hand makes a complete circle in fifteen
seconds.   A watch with this arrangement (usually a rack-lever) can be recognised at once because the seconds dial is
numbered only 5-10-15.

THREE-QUARTER PLATE

A style of watch that has a back-plate almost complete but cut away at one side to make room for the balance-wheel,
which is mounted level with the plate instead of protruding beyond it.   This style was introduced by British makers in
about 1820 as a concession to the growing demand for slimmer movements.   For much of the 19th century it was often
chosen for movements of better than average quality and precision.

TIMING SCREW

One of a number of small screws, often of gold, inserted horizontally in the rim of a compensated balance.   Adjusting
these selectively can alter the poise of the balance and may help to correct position errors;  adjusting them uniformly
modifies the circumference of the wheel and therefore alters its speed of oscillation, affecting the rate of the watch.
Such screws are occasionally found in uncompensated balances.

TIPSY KEY

An alternative name for the Breguet key, which incorporated a ratchet so that if turned the wrong way it revolved
harmlessly instead of damaging the movement.

TOBIAS

An influential family of English watchmakers who specialised in pretentious but well-made products for the rising
middle classes.   Morris Tobias worked in Wapping, near the London Docks, from 1794 onwards;  Michael Isaac
operated in Liverpool until 1829 and was one of the principal exponents of the rack-lever.   From about 1850 the name
was often applied to Swiss movements, recognisable by their barred layout and engraved cuvettes and by the (probably
deliberate) mis-spelling of the name as M. J. TOBIAS.

TOMPION, Thomas

(1639-1731)   English clock- and watchmaker, who more than anyone else established the supremacy of English
watchmaking in the 18th century;   associate of Robert Hooke and maker of the earliest English balance-spring watches;
pioneer of the repeater (with Quare) and of the seconds hand.   In the literature of his day his name appears as a byword
for outstanding quality in timekeepers, like ‘Breguet’ in the 1800s or ‘Rolex’ today.

TOP PLATE

Alternative name for front plate.

TOURBILLON

An invention of Breguet's for minimising positional errors.   The balance-wheel and escape-wheel are mounted on a
revolving platform geared to the third wheel so that it makes a complete turn every sixty seconds;  thus any imbalance
in the weight-distribution of these parts, which might otherwise affect the rate of the watch in some orientations, can
make itself felt only for a few seconds each minute before being cancelled out by the change in alignment.   Later
chronometer-makers found that it was unnecessary to resort to so very short a cycle;  the karrusel, a later development
of the same idea, is allowed 52.5 minutes to rotate.

TRACK

The circle of divisions on a dial marking the minutes or seconds, usually consisting of radial strokes between a pair of
circular lines;  on many late 19th-century Swiss watches the latter are only guides, drawn as faintly as possible.   Dots
instead of strokes, with the circles omitted, are sometimes found between about 1760 and 1800.

TRAIN

(1)   The sequence of wheels and pinions that transmits the drive from the barrel (or fusee cone) to the controller.   It
normally consists of the great wheel, centre wheel, third wheel, fourth wheel and escape-wheel;  each of these carries a
pinion to receive the drive from the preceding component.

(2)   When the word train is qualified by a number, as ‘14,400 train’, it indicates the number of beats made by the
escapement in one revolution of the great wheel, or one hour.   14,400 (four per second) is the usual figure for a large
19th-century English full-plate watch;  in later Swiss and American watches the figure is 18,000 (five per second).  

TRIPPING

A malfunction of escapements which deliver the impulse in only one direction, such as the duplex and spring detent.
Occasionally the escape-wheel will judder against the controller and deliver impulse twice in one cycle, resulting in a
double-length drop.

TURKISH MARKET

From the early 18th century onward, the upper classes in the Ottoman empire developed a liking for European watches,
a demand which at first was principally met by London makers;  later on (from about 1800) the Swiss gained possession
of the field, still however marking many of their products with pirated English names, a practice which lasted throughout
the nineteenth century.   Turkish watches are easily recognised by their chapter-rings; the numerals consist mostly of
narrow triangles set point downwards, and the figure 5 is represented by a circle.  The watches are often very ornate,
with decorated cases and dials and triple or even quadruple cases.  Most disconcertingly for the modern collector, they
retain a largely 18th-century appearance to the very end, deep in calibre and with floridly-shaped bows and
highly-domed crystals; one must look at the movement, which is often a commonplace Swiss ébauche of barred type, to
know these watches for what they are.


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