FALSE PENDULUM. Also called a 'mock pendulum'. A small disc on one arm of a balance, visible through a slot or aperture in the dial or balance cock. The motion of the arm with disc attached gives the appearance of a pendulum, the second arm and the rim of the balance not being visible. The type was popular around 1700, particularly in Holland where the balance bridge type continued well into the century. If provided with a glass over the slot and a rim round the bridge, this type affords protection to the balance.

FIGURE PLATE. See REGULATION.

FIVE - MINUTE REPEATER. A repeating watch which gives the hours and a blow for each five minutes past the hour. In some cases the quarters are given in addition. A number were made in the second half of the 18th century and a few a hundred years later, but they are comparatively rare. They first appeared about 1710.

FLAGS. The pallets of the verge escapement are so called.

FLIRT. A lever or other device for causing a sudden movement of mechanism.

FLOATING HOUR DIAL. See WANDERING HOUR.

FLY. A two-bladed fan, acting as an air brake or governor to regulate the speed of striking or repeating.

FLY-BACK HAND. In split-seconds chronographs (q.v.) a centre seconds-hand that can move while remaining superimposed on the first hand, but which can be stopped independently and then made to fly back (or forward) to join the first hand as it moves round the dial.

FOB CHAIN. A short chain (or ribbon with metal attachments) fixed by swivel or bolt ring to the bow of a watch, and hanging outside the pocket.

FOLIOT. The earliest form of escapement controller, and applied to the verge escapement. It was first used in clocks. In a watch it takes the form of a cross bar with weighted ends - giving it a dumb-bell shape - carried at the upper end of the verge. It is found mostly on early German stackfreed watches, though it was being superseded by a plain two-arm ring or balance before 1600. The word probably derives from Old French 'folier', to dance madly.

FORGERIES. Forgeries of famous makers' work were most flagrant in the earlier part of the 18th century and again in the early 19th. In the former period, famous makers such as Tompion, Quare and Graham were the main victims, and in the latter, Breguet. See DUTCH FORGERIES.

FORK. The fork-shaped end of the lever in the lever escapement within which is the notch.

FOURTH WHEEL. The wheel in a watch that drives the escape wheel pinion, to the arbor of which the seconds hand is attached.

FORM WATCH. A watch the case of which is made in the form of a cross, star, skull, flower bud or other bizarre shape. A number were made in the early 17th century and again 200 years later, when musical instruments were the most popular form.

FOUR-COLOURED GOLD. See TINTED GOLD.

FRAME. The movement plates.

FREE - SPRUNG. A balance spring unfettered by curb pins. Used in marine chronometers, pocket chrono-meters and very high grade watches. The rate of a watch so sprung can be adjusted by the timing screws on the balance.

FRICTIONAL REST ESCAPEMENT. An escapement in which the balance is never free from the escapement - e.g. the verge, cylinder and duplex escapements. It is therefore inferior to a detached escapement - e.g. the detent and the lever escapements.

FULL PLATE. A watch calibre in which the top plate (that furthest from the dial), as well as the pillar plate, is a circular plate, with the balance mounted above the top plate. A three-quarter plate movement has a section of the upper (top) plate cut away to allow the balance to be mounted in the same plane as the plate, the balance and the escape wheel having separate cocks. In a half-plate movement, the fourth wheel, escape wheel and balance have separate cocks.

FUSEE. A mainspring-equaliser. A spirally grooved, truncated cone with the great wheel mounted upon it. A length of gut - after about 1670 a chain - connects the fusee to the mainspring barrel, one end being attached to the barrel and the other to the fusee.
The winding key fits over the squared end of the fusee arbor, and the act of winding draws the chain from the barrel on to the fusee, starting at the wide end of the 'cone' and taking it up the spiral groove. As the chain is taken off the barrel, the mainspring is wound. The mainspring when fully wound exerts a greater torque than when it is only partially so. In unwinding, the chain is, of course, drawn off the narrow end of the fusee first, where it is acting with less leverage and this compensates the greater pull of the mainspring. Greater leverage comes into play as the chain is drawn towards the thicker end of the fusee; thus the tapering fusee matches the diminishing strength of the spring. This ensures a relatively constant motive force. The early long, tapering fusees were only moderately effective, but as time went on, and by empirical methods, a form with correct hyperbola curves was evolved.
A stop is fitted to the upper end of the fusee. As the chain coils round the last groove of the fusee, it lifts a lever which comes up against a cam on the fusee and stops the mechanism. The mounting for the fusee stop lever or arm was given decoration after about 1650. The fusee was known - it appears in early manuscripts - in about 1450 - 70. A fusee with maintaining power is known as a 'going fusee'.

FUSEE CHAIN. A steel chain as a substitute for a gut cord was invented in about 1635, but some years elapsed before it was made small enough for watch movements. It is rarely found in watches before 1670, and those on earlier watches are frequently conversions from gut to chain. The grooves in a fusee intended for gut are rounded. It is probable that fusee chains were at first imported for English watches. From the early 19th century Christchurch in Hampshire specialised in fusee chain making. For the first quarter-century the work was done by young women and children in the Christchurch workhouse, but it later developed into a cottage industry.