P

Pagoda Top :
A term occasionally applied to the curved, oriental tops of some 18th century bracket clocks, based on the Europeanised version of the Chinese pagoda roof. The form was an element of rococo Chinoiserie in Chippendale furniture designs.

Pallet :
A catching device that regulates the speed of a clock by releasing one notch of a toothed wheel (ratchet wheel) at each swing of the pendulum or turn of the balance wheel. The unit is usually known as 'pallets complete', abbreviated to 'pallets'.

Pallet Arbor :
Or pallet staff: the axis of the pallets.

Pallet, Entry and Exit :
The entry pallet is the first encountered by an escape-wheel tooth. The exit pallet is that encountered as a tooth leaves engagement with the pallets.

Pallet, Gathering :
In striking work, the arm sometimes called a 'tumbler' which restores the rack to its resting position, gathering one tooth for each blow struck during the striking action.

Pallet Stones :
In better-quality lever escapements the pallets are made from rectangular jewels known as 'stones'. Regulator clocks with dead-beat escapements have the acting faces of the pallets jewelled. These are then referred to as 'jewelled pallets'.

Paperweight Clock, Japanese :
Paperweight or doctor's clocks are small spring-driven timepieces (average length about 4 1/4in.). They resemble pillar clocks, being long and thin with a linear dial that shows the time on a graduated scale. The mechanism is of the pillar-clock variety with the spring and balance in a compartment at one end of the case. The spring is wound by drawing the hand to one end of the dial; as it unwinds the hand passes along the slot showing the time on the adjustable scale. Most such clocks are from the late period, after the 18th century, and have a balance cock in European style.

Papier Mache :
Originally, 'mashed paper', mixed with glue and other materials, which could be moulded. In the early Victorian period there was a vogue for small items of furniture made from layers of tough paper which were glued on to a wood or metal framework and also known as papier mache. Each layer of paper was rubbed down before the next was applied, producing a strong, hard surface. When finished, the object was coated with black lacquer, decorated with painted flowers in gilded panels and sometimes further adorned with inlaid mother-of-pearl. About a dozen different styles of American clock cases of papier mache were made during the period 1850-5. Papier mache was soon imitated by making cases with cast-iron fronts, similarly painted and gilded. These were at first referred to as 'iron mache'.

Parquetry :
A form of marquetry, produced by the same process, in which the pattern, instead of a free arrangement of bird and flower designs or scrolled arabesques, is a geometric layout of different colored veneers. It is a form of decoration more rarely encountered than ordinary marquetry, but it is occasionally found on the long trunk doors of early walnut-veneered longcase clocks.

Parlor Clock :
The carved-case Victorian clock of the mid-to-late 1800s, typically made of walnut, designed to be placed on a shelf or mantel in the parlor.

Pawl :
A click mounted on an oscillating arm used to advance a ratchet wheel. The term is generally used by engineers to denote a click.

Pediment :
An ornamental top on a clock case, frequently curved in shape.

Pedestal Clock :
A clock designed with its own pedestal, to stand in the center of a room or against a wall; also sometimes called 'column' clock or 'term' clock. Certain Renaissance clocks were made in this form, with dials on all four faces, as objects of prestige and curiosity. With the revival of clockmaking in France in the late 17th century, ensembles of large bracket clocks with matching pedestals became extremely popular. Long-pendulum clocks (pendules longue ligne) were never as popular in France as in England, and the pedestal clocks were a reasonable compromise which did not diminish the importance of the clock. Pedestal clocks might be spring-driven but pedestals could also serve to hide weights. Decoration was lavish, frequently in Boulle marquetry. After the middle of the 18th century the relegation of most clocks to the chimneypiece killed the idea of pedestals except in rare cases.

Pedometer :
A device carried on the person, for counting the number of paces walked, and hence determining the distance. Counting was usually carried out by a pawl engaging with a ratchet wheel, the pawl being operated by a lever or weighted sector which rose and fell with the rise and fall of the body in walking. Occasionally an adjustment for length of pace was provided, the ratchet wheel having fine teeth and the number of teeth passed over step by step being pre-set. Otherwise the pedometer was usually set to record one mile for 1,000 double paces. Pedometers were made in the form of watches in the late 18th century, in particular by Ralph Gout and Spencer & Perkins of London.

Pegwood :
The name given to sticks of wood, preferably dogwood, which are used for cleaning out pivot holes. They are usually about six inches long and up to 1/4 in. in diameter. The wood is sharpened to enter a pivot hole and rotated to remove the dirt, a process which is repeated until the wood is clean when removed from the hole. Pegwood is also used for cleaning pinion flutes and other awkward places in clockwork.

Pendule Directoire :
A clock made during the period of the Directory in France (1795 - 1800). The Revolution had caused a break in the clockmaking tradition but, encouraged by the government, it resumed after the re-establishment of stable rule. Gilt-metal cases, especially with decorative figures incorporated, continued to have the greatest popularity, the style becoming heavier and neoclassical elements displaying a worthy correctness of detail. Clocks with Negro figures clearly derived from the debate over slavery, and from confused idealization of the 'noble savage', while clocks showing figures in Roman attire often pointed to the republican ideal. At the same time small astronomical regulators like four-glass clocks and skeleton clocks of similar visual austerity were being developed.

Pendule Empire :
A clock made during the period 1802-14, when Napoleon ruled as emperor of the French. Gilt-bronze cases with figures developed the Directoire themes, but these became subtly influenced by the symbolism of the Empire, as well as by the taste for Egyptian, Roman and Greek antiquities encouraged by the excavations ordered by Napoleon during his Egyptian campaigns. This gilt-metal form of mantel clock, with figures dominating the case, was to remain popular in France in various forms until after c. 1830.

Pendule Longue Ligne :
The French term for longcase clocks. They were never as popular in France as in England, but some magnificent examples were made, the cases often by distinguished ébénistes. Pendules longue ligne were cased in wood long after smaller clocks had abandoned wood in favor of gilt bronze, marble or porcelain. The earliest varieties, c. 1670, take the form of a religieuse above a shaped body. Gradually the suggestion of separation between hook and trunk died out and by the 1740s they had developed into the full rococo form of the clock by Jean Charost, cased by Jean Pierre Latz. From the mid 18th century the longcase form was used for régulateurs by such makers as Ferdinand Berthoud and Pierre Le Roy, the form and decoration of the cases becoming more severe but no less handsome, to match the dignity of their movements with gridiron pendulums, specialist escapements and other refinements. Comtoise clocks and Normande clocks were provincial versions of the pendule longue ligne.

Pendule Louis XIII :
The reign of Louis XIII (1610-43) spanned the last period of Renaissance clockmaking in France before the mid 17th-century fashion for watches apparently caused the almost complete cessation of clockmaking (a largely unexplained phenomenon). Survivals from this period are rare but tend to be of very high quality, like the clock made for the brother of Louis XIII. The style was international; cases were of gilded metal for the small square, cylindrical or octagonal table clocks, and for the larger versions with horizontal dials. Surfaces were elaborately engraved, the subjects often taken from engravings of allegories or myths.

Pendule Louis XIV :
The early part of Louis XIV's reign (1643-1715) was a bad time for clockmaking, though watches were fashionable. The development of the pendulum caused renewed interest in clocks, leading to the introduction of the religieuse. Early influences on both the science and art of clock-making came from Holland, but the French soon outstripped their masters in both fields. Louis XIV was lavish in his patronage of all the arts and under his influence the decoration of the religieuse developed and other styles grew up. Designers like Daniel Marot and André-Charles Boulle produced sketches for clock cases, while members of the Martinot family produced equally fine clocks. Forms became somewhat stereotyped; the tête de poupeé form and the arch-topped, scroll-footed clock, now seen as typical of the period, succeeded the religieuse and continued into the Regency. Pedestal clocks were popular, both clock and pedestal heavy with ebonized mouldings and gilt-bronze mounts.

Pendule Louis XV :
Louis XV's long reign (1723-74) was a period of great development and diversification in clock casework. At the beginning of the period clocks still retained some of the prestige value of the preceding century. As the century progressed clocks were produced in far greater numbers, and their casing records their assimilation into decorative schemes. Pedestal clocks and pendules longue ligne had their place, but increasingly clocks were relegated to the wall, standing on brackets or, as cartel clocks, being hung directly on panelling, or even on an overmantel mirror. The classic Louis XV clock, if such a thing can exist amid such diversity, was the wooden-cased, waisted clock standing on its own bracket, the dial perhaps of thirteen pieces, the case veneered with horn or tortoiseshell, or colored with vernis Martin, and set with gilt-bronze mounts. This was to be the last use of wood for casing small clocks in the 18th century. Gilt bronze came into favor once more, particularly for cartel clocks, which incorporated all the extravagances of the new rococo style - ragged shells, asymmetric scrolling, animals and fanciful Chinese figures. About the middle of the century clocks found their way to the chimneypiece. Highly decorative clocks were produced, some of the most fanciful with the clock in the branches of a gilt-bronze tree amid porcelain flowers or birds from Vincennes or Germany. Garnitures de cheminée came into favor, the form of the clock echoed by flanking vases or candelabra, together forming a major element in the decoration of a room. Clock movements, apart from the horologically more sophisticated régulateur movements, began to be standardized in drum form. Early gilt-metal dials with enamel hour cartouches were superceded in turn by the large thirteen-piece dials, and with the advent of smaller movements by one-piece enamel dials. Gilt-metal hands were cast and pierced with very delicate patterns.

Pendule Louis XVI :
Louis XVI's reported interest in horology is often cited to explain the horological sophistication attained during his reign (1774-92). It may explain the encouragement given to precision timepieces, but it was the atmosphere of luxury which furthered the development of exquisite casework. The two traditions sometimes met, as in the pendules régulateurs made by men such as Ferdinand Berthoud. For small clocks gilt bronze continued predominant. The use of porcelain developed, for plaques and for whole cases, and marble was used above all. Cartel clocks, of gilt metal only, were produced with fashionable neoclassical motifs - rams' heads, urns and swags of flowers - superceding the rococo motifs of Louis XV. But mantel clocks were more fashionable. Vase clocks and lyre clocks traded on the popularity of neoclassicism, and clocks set with mythical or allegorical gilt-bronze figures were common. Pendules montgolfiéres paid light-hearted tribute to the ballooning craze, incorporating the balloon outline in a most elegant case form. Marble was used in conjunction with gilt bronze on clock bases or in portico clocks, which were popular at the end of the reign.

Pendule D'officier :
A gilt-metal or brass travelling clock made in France, Germany or Switzerland from c. 1780 until c. 1820. Of several types, they preceded the classic pendules de voyage of the later 19th century, and often had complicated repeating work as well as alarms. Their popularity during the Napoleonic wars probably earned them their name, and many of the cases were decorated in high relief with laurel wreaths or trophies of arms. Leather cases were originally supplied with these clocks.

Pendule Portative :
A small clock, usually fitted with a handle, designed to be moved from place to place in the house, like an English bracket clock. Pendule portative is in no way synonymous with pendule de voyage. The clock made by Robert Robin, which is believed to have belonged to Marie Antoinette may be considered a pendule portative, but its leather case clearly marks it as a travelling clock. But an astronomer's clock made in 1795 by Ferdinand Berthoud, in the National Maritime Museum at Greenwich, shows a brass carrying handle for what is essentially a working, and normally static, clock.

Pendule Régence :
The shortest period of the Regency in France (1715-23) was truly a transition period, the massive grandeur of Louis XIV designs softening, but not yet forming the new, lighter curves of Louis XV clocks. Forms such as the tête de poupée persisted as did the large pedestal clocks. Boulle Marquetry and combinations of ebonized wood with gilt-bronze mounts continued popular.

Pendule Religieuse :
The French bracket clock of the late 17th century, of plain architectural form. The name probably derived from their simplicity or by analogy with the architectural form of churches. These clocks are sometimes called Louis XIII clocks, but this is misleading for clocks not popular until 20 years after his death in 1643. Such late 17th-century bracket clocks, whether French, English or Dutch, developed as a result of the invention of the pendulum. The plainer type of casing takes the form of a portico with flankind pillars or pilasters, with pediment above. It is derived from Italian cabinets of the 16th century and Dutch cabinets of the mid 17th century. Decoration tended to greater flamboyance as the 17th century progressed. Early examples were of ebonized wood with simple pierced brass mounts in place of pillars, and a pierced brass pediment. More elaborate forms had pilasters and segmental pediments, sometimes inlaid with Boulle marquetry or decorated with black or red lacquer with brass or gilt-bronze, including flambeau finials or small figures in the Renaissance manner. The dial, covered wth black or dark-colored velvet, occupied the whole of the front. The chapter ring was marked for each minute and the hands were of delicately pierced gilt metal. Below the chapter ring the dial might be mounted with a gilt-bronze lambrequin carrying the maker's name, or with a fanciful mount such as Father Time.

Pendule Sympathique :
One of the most intriguing inventions of Abraham-Louis Breguet, first made c. 1805-10. The pendule sympathique consisted of a table or mantel clock with a special clip above to hold a watch during the night hours, in the manner of a watch stand. At a fixed hour the clock not only set the watch to time but also regulated any error. The clock was capable of regulating an error of up to 7 1/2 minutes and, as it was used daily, greater error was unlikely. Few of these clocks were made. Some were designed to wind the watch as well as to regulate it and set it to time. They appear to have been designed by Breguet to satisfy a challenge and to promote his business intersts, for Breguet was more than capable of making watches which did not require this kind of attention.

Pendule De Voyage :
A travelling clock, normally with a cylinder form of lever escapement mounted on a separate platform, developed in France in the early 19th century and made in great numbers in that country in the later 19th and early 20th centuries. The form began to evolve at the end of the 18th century, the fashion led by Abraham-Louis Breguet who produced small square clocks with glass sides owing something to the shape of pendules d'officier or Capucines, but most perhaps to the four-glass clocks or small régulateurs. The general form remained constant, though thousands of variations were made in details of panels and frames - or in size, which might vary in height from 2 or 3 in. to 12 in.

Pendulum :
A clock weight hung from a fixed point, which swings back and forth in a regular beat to regulate a clock's movement.

Pendulum Aperture :
A feature of the design of bracket-clock dials during the first half of the 18th century. A curved hole was cut in the dial above the center to show the small engraved brass disc attached to the verge escapement arbor which moved from side to side as the clock was going.

Pendulum Bob :
The adjustable weight at the lower end of a pendulum. The lenticular-shaped pendulum bob, often in cast iron for turret clocks, is probably the most common; it has the advantage of offering the lowest air resistance and therefore requires less energy from the train to maintain it in oscillation. The cylindrical pendulum bob found in many high-quality regulators and electrical impulse master clocks gives excellent results. The cylindrical shape has more air resistance, but this may be used to counteract changes in rate due to circular error. By the 19th century many turret-clock pendulums had become cast-iron cylinders with domed tops to prevent dust settling. Weights of several hundred pounds were not uncommon, as this was found to overcome the action of wind and weather on the hands. The bob of the Great Clock of Westminster ('Big Ben'), for example, weighs 700 lbs. Some 18th-century and earlier clocks have the major axis of a bun-shaped bob at right angles to the pendulum rod.

Pendulum, Compound :
Generally, a pendulum having part of its weight above the point of suspension. The greater the proportion of weight above the suspension, the longer the period of vibration of the compound pendulum. A theoretically perfect pendulum has all the matter composing it at its center of oscillation. This is, of course, impossible in practice. The pendulum rod, for example, however thin, must have some weight which is not concentrated at the pendulum bob's center of oscillation. All practical pendulums are partially compound, because the weight of the components cannot by concentrated at the center of oscillation.

Pendulum, Conical :
A pendulum with a bob describing a horizontal circle, used in some Victorian novelty clocks and also to control the driving mechanism of equatorially mounted telescopes. The pendulum is normally driven at its lower end by a slotted arm which allows the pendulum to move away from the central position which it occupies when the clock is stopped. The time taken for one circle to be completed is the same as that required for one complete cycle of a normally oscillating pendulum of equivalent length.

Pendulum, Ellicott :
Temperature errors, caused by expansion of the pendulum rod in heat slowing the clock's rate, led John Ellicott, probably after seeing John Harrison's gridiron compensation, to the idea of using levers to magnify the differential-expansion effect of brass and steel rods, so as to reduce the number required in a pendulum to two brass and one steel. A brass ring is secured to the central steel rod by a screw, and it carries the pivots. The levers are free to move on the pivots, and carry the pendulum bob supported by the screws. All three rods are fixed in the block at the pendulum's upper end. As the temperature rises, the brass rods expand more than the steel rod, moving the inner ends of the levers downwards and raising the pendulum bob, maintaining the pendulum's effective center of oscillation in its original position. The action is reversed on a fall in temperature. Owing to friction this system was not entirely satisfactory.

Pendulum, Free :
It has been known for a long time that a 'free' pendulum clock will achieve perfect timekeeping. A pendulum, to achieve this, would maintain its arc and do no work, without ever receiving impulse - perpetual motion, clearly impossible! Early this century, William Hamilton Shortt, in collaboration with Frank Hope-Jones, prouced an almost free pendulum clock system which was used as the time standard in observatories throughout the world until superceded by the quartz-crystal clock in the late 1930s. Briefly, in the Shortt clock system, a synchronome master clock is used as a slave. The master free pendulum receives impulse released by the slave clock and in turn controls the slave clock's rate by a hit and miss governor. The master pendulum operates in a steel cylinder at a constant temperature and reduced atmospheric pressure; small changes in operating pressure are used to make minute adjustments to rate by air-friction loss and circular error.

Pendulum, Gridiron :
It was apparent to John Harrison that the greatest error to be counteracted in pendulum clocks fitted with a good escapement was that due to expansion or contraction of the pendulum rod in heat or cold. The Harrison brothers measured the coefficients of expansion of most metals and alloys available then and discovered that brass expanded relative to steel in the ratio approximately of 10 to 6. They made pendulums working on this principle, incorporating four brass rods acting upwards, and five steel rods acting downwards. The upwards expansion of the brass rods compensated for the downwards expansion of the steel rods and maintianed the center of oscillation of the pendulum at a constant distance from the suspension point. This principle was used in their early marine chronometers to alter the effective working length of the balance spring, thus compensating for their temperature errors.

Pendulum, Mercurial :
George Graham, with his mercurial compensation pendulum, preceded John Harrison by a few years in solving the problem of temperature error caused by the expansion or contraction of the pendulum rod in heat or cold. Graham discovered that the upward expansion of mercury in a cylindrical jar, used as the pendulum bob, approximately 2 in. in diameter and 7 1/4 in. high, will compensate for the downward expansion of a one-second pendulum rod. Pendulums are sometimes made with two or more jars containing mercury. The increased surface area exposed to the air speeds the transfer of heat on change of temperature. Glass jars, usually adopted for appearance's sake, are not the best substance to contain the mercury. Steel or iron jars allow quicker heat transference because of their higher conductivity.

Pendulum, Rhomboid :
A form of pendulum sometimes seen on turret clocks, though rarely on domestic clocks, in which the rod takes the form of a diamond-shaped frame composed of four steel strips connected horizontally across the center by a strip of brass. Any increase in length of the steel due to heat is compensated for by an outward expansion of the central brass strip.

Pendulum, Royal :
The verge escapement, being virtually the only one known when the pendulum was introduced, calls for a large pendulum arc, unless gearing is introduced between the escapement and pendulum, or the escapement is very much modified, as in 18th-century Comtoise clocks. Verge-pendulum clocks usually have short pendulums swinging through a large arc. When the anchor escapement was introduced, the smaller pendulum arc enabled much longer pendulums to be used, and led to better timekeeping because of the reduction in circular and escapement errors. This led to the title of 'royal' pendulum being given to the pendulum beating seconds with an effective length of 39.139921 in.

Pendulum, Simple :
Scientifically, a theoretical pendulum, the mass of which is all concentrated at its center of oscillation. The term is also often used to describe a pendulum without any form of temperature compensation.

Pendulum, Torsion :
A form of balance suspended by a thin narrow metal strip. As the balance rotates, the suspension strip is twisted, moving an arm situated near the upper end of the suspension. The arm communicates its movement to a form of anchor escapement which, on release, causes the impulse to twist the suspension a little more, thus maintaining the balance in oscillation. Torsional pendulums are commonly found in 400-day or anniversary clocks. Because of escapement error and poor temperature compensation, timekeeping is usually poor.

Pendulum, Turret-clock :
Early turret clocks used wrought-iron pendulum rods, which were forged bars of rectangular section. The rating nuts were wing nuts formed from a long thin rod wound into spirals. Wooden rods were in frequent use, as wood has a very small coefficient of thermal expansion and, provided it is properly sealed, suffers little from humidity. Pitch pine and hickory were often used, in more recent years mahogany. Compensated pendulum rods on turret clocks were introduced in the 19th century. They are nearly always a combination of zinc and steel and are tubular in construction. A steel rod hangs from the suspension; at its lower end a collar supports a zinc tube running upwards the appropriate length. From the top of this tube a further steel tube descends and, fitting snugly over the bottom collar, carries the pendulum bob. This system was first devised by Edward Troughton. Although turret-clock pendulums beating seconds are the most common, the location of turret clocks provides scope for longer rods. Rods beating 1 1/4 or 1 1/2 seconds are common and at one time rods of astonishing length were introduced. Many beat 2 seconds and thus have a theoretical length of over 13 ft., while there are a few recorded beating 1 1/4, 1 1/2 and even 3 seconds. It was thought that these long pendulums exercised 'dominion over the clock', evening out irregularities caused by friction and other imperfections in the train. Recent studies have shown that this view was erroneous, for the performance of a clock depends on the drain of energy in the pendulum due to windage and friction in comparison with the total energy in the system.

Photographer's Clock :
A clock with a large dial and center sweep seconds hand moving over a 0-60 graduated scale, with a subsidiary hand to indicate elapsed time on a second scale graduated 0-60 or 0-100 minutes; expressly designed for photographic darkroom use. Generally, the hands are coated with luminescent paint to allow them to be seen in total darkness. A simple clock movement with a balance wheel is used, often fitted with pull winding but sometimes wound from the rear, which can be set to zero, started and stopped by other cords, pushbuttons or levers. An alarm bell may be fitted to remind the user that the required period has elapsed. These clocks are mounted in circular drums, often of tin plate or plastic; synchronous electric clock movements are also used.

Photozenith Tube :
Since 1955 Greenwich Observatory near London has employed the photozenith tube (PZT) for checking its standard clock against the stars. Selected stars which transit near the zenith are automatically photographed on the same plate twice before and twice after crossing the meridian, at times dictated by the standard sidereal clock. The time of transit according to this clock can then be found by interpolation.

Picture Clock :
In the early 19th century it became the fashion to own an oil painting of a town or village scene incorporating the tower of a church or similar building bearing a clock dial. The dial was not part of the painting but an actual clock dial, the mechanism of which was concealed in a space behind the picture. Some of these clocks also had music and mechanism to make the sails of a windmill rotate, fishermen mend nets, and so on. They usually have good French or Swiss mechanisms, and the musical and automata work is also of high quality, though the paintings as works of art may leave something to be desired.

Pigeon-racing Clock :
For recording the arrival time of racing pigeons, developed originally in the 19th century by W. H. Turner. The birds are taken to the point of departure and released at a given time, their homing instinct compelling them to return to their home loft as rapidly as possible. On arrival the identification ring each pigeon carries is detached and placed in a small thimble for insertion into a slot in the pigeon clock, and a lever is pressed which causes the time of insertion to be recorded on a paper tape. The rings are stored in a container in the order in which they are inserted into the clock. Various devices are fitted to prevent tampering and the clocks aare sealed. After the race the records are removed to determine the exact time of arrival of the birds. Early pigeon clocks were made in Britain, others in Belgium where the sport is also popular.

Pillar Clock :
Early Gothic clocks usually stood on brackets fastened to the wall, or were hooked to the wall, but such clocks were made to stand on hollow pillars, which contained the weights. As clocks on pillars generally stood lower than wall clocks, more frequent winding was necessary. After the Renaissance, table clocks with astronomical dials began to be made with the dials on both sides, and similar weight-driven clocks were also produced; they needed to stand on a pillar so that the dials at the rear could be easily seen.

Pillar Clock, Japanese :
Pillar clocks, often referred to as 'stick' clocks, were made to hang on the supporting column of a Japanese house, since the screen walls were not designed to support heavy objects. Pillar clocks were usually long and narrow, hence their nickname. They had simple four-wheel weight-driven movements at the top. Very early ones have a foliot; most have balance wheels; occasionally, later ones have short-bob pendulums. The single hand was attached to the weight and as the weight descended the hand passed a graduated scale, or dial indicating the time. More elaborate pillar clocks have a striking mechanism in the weight, activated by pins projecting inwards from the hour plates on the vertical dial. The striking pattern of Japanese clocks is unique; it proceeds backwards from nine to four starting at sunset (6): 6-5-4-9-8-7-6-5-4-9-8-7.

Pillar-and-Scroll Clock :
A shelf clock attributed to Eli Terry, having a column on each side, a scroll-cut pediment and three finials on top.

Pinion :
A small toothed wheel driven by a gear. In clock gear trains a pinion is usually the smaller driven member, and normally has less than 20 teeth, which are termed 'leaves'. The hypocycloidal form is mostly used for pinion leaves. A hypocycloidal curve is that traced by a point on the circumference of a circle rolling inside another circle.

Pinion, Lantern :
A form of pinion construction in which the pinion leaves are made from round steel pins, held by brass discs. In some cheap clocks the steel pins are held at one end only, by a die-casting technique which also forms the wheel collet. Lantern pinions are also found in high-quality clocks, and they are often used in turret clocks. The gear action between a lantern pinion driven by a correctly formed wheel, is excellent, but a lantern pinion is unsatisfatory as the driver.

Pinion, Rolling-leaf :
To reduce friction, lantern pinions are sometimes made with the leaves pivoted to allow them to rotate.

Pinion-facing Tool :
A tool for finishing and polishing the end face of a pinion. A facing tool is made of soft steel or bell metal and used with coarse red stuff for squaring up the pinion face. For finishing or polishing it is made of bell metal and used with slightly moistened diamantine. In form the tool is a short tube with a slightly tapered hole to allow the pinion arbor just to pass through the small end, the end wall of the tube being the finishing face, having itself been finished dead square. When facing a pinion, the pinion arbor is supported at one end in the turns and at the other by the facing tool, the pinion being rotated by use of a ferrule and bow. To keep the facing tool true to the work, the tube itself may be pivoted in a hand frame.

Pinion-milling Machine :
Pinions for watches and sometimes also for small clocks were usually made from pinion wire, but for larger clocks pinions were milled from a cylinder of steel left standing when the clock arbor was turned on the lathe. Determination of the dividing of the pinion was done by using a dividing plate in a manner rather similar to that used on a wheel-cutting engine, though the dividing plate for pinions had a much smaller range of divisions marked on it. Early pinion-cutting machines employed a simple hand-operated file cutter running parallel with the pinion arbor, the cutter being guided by a frame which also held the pinion being cut between centers; later, machines were devised on the same principle but using revolving cutters, travelling longitudinally to form the pinion leaves. Factory methods employed milling machines in which the pinions to be cut were presented to the revolving cutter by automatic means, each slot between the leaves being milled out in turn.

Pinion Wire :
The basic material from which steel or brass pinions are made for small clocks, brass pinions sometimes being used in clock motion work. The pinion wire is produced by drawing wire through drawplates. When making a pinion, a length of pinion wire of the desired diameter, having the required number of leaves, is mounted in a lathe or turns and cut to form the pinion and arbor in one piece. To do this a cut is first made at each end of the pinion and the surplus leaves broken off before the final turning. Pinions made from wire require to have their leaves finished to shape by filing along the flutes, and steel pinions are finally finished by hardening and polishing.

Pintongs, or Pinvice, or Pinchuck :
Pintongs are used to hold wire, drills, broaches and for other purposes. Sliding and screw-nose pintongs or pinvices have a small loose or fixed split chuck at the end of a hollow handle through which wire can be passed and gripped true in the center of the tool. The chuck is closed either by a ring which slides on the tapered body of the chuck, or by a knurled nut which has part of its hole tapered and screws over the chuck jaws. The tool is made in a range of sizes, either for hand use or for fitting into the jaws of a large machine chuck. When made with a back center point it can be fitted with a ferrule, driven by a bow and used for turning.

Pipe :
Any extended hollow boss, as in a key. The key-pipe is the hollow squared part which fits the winding arbor.

Pivot :
The reduced-diameter arbor end which turns in the hole made in the clock plate (or jewel) to receive it.

Pivot, Conical :
Cheap alarm-clock balance staffs often utilize a cone-shaped pivot. In higher-grade work the term also applies to pivots designed to run in capped jewel holes. The acting part is parallel; the conical section is used to blend the small-diameter pivot into the larger staff and reduce the chance of pivot breakage.

Pivot Hole :
The bearing in which a pivot runs.

Planetary Clock :
It has been suggested that such clocks were originally devised to provide a driving mechanism for models showing the planetary system, and that telling the hours of the day was a secondary consideration. See Planetarium.

Planetarium :
A mechanically operated device in which the revolutions of the Earth and the other planets around the sun are represented on a dial or dials; they may be hand-operated or clock-driven. Richard of Wallingford's astronomical clock of 1336 was also a planetarium, for although the part of his manuscript describing it is missing, John Leland, who saw the clock during the reign of Henry VIII, states that the planets were depicted. The first planetarium of which we have full knowledge was the machine designed and made by Giovanni Dondi of Padua between 1348 and 1364. The weight-driven clock movement was contained in a seven-sided bronze vertical frame above which were mounted seven main dials on which were displayed the movements of the sun, moon, and five other known planets, moving in epicycles according to the Ptolemaic system. In 1561 Eberhart Baldewein of Kassel made to the order of Wilhelm IV of Hesse a somewhat similar planetarium mounted in a square vertical gilt-metal case, with planetary dials on all four sides, still on the geocentric principle. This fine example had a celestial globe on top. The first English planetarium after Wallingford's was one built nearly 350 years later by Samuel Watson of Coventry. It was ordered by Charles II in 1681 and completed by Watson six years later; this also is geocentric. A relatively simple but effective heliocentric planetarium was made for Christiaan Huygens in 1681 by Johannes van Ceulen of the Hague. It is spring-driven and controlled by a balance with spiral balance-spring, as invented by Christiaan Huygens in 1675. Another elaborate planetarium was made in England by Henry Bridges. It has a geocentric upper dial and a planetary heliocentric lower dial which shows the eccentricity of the planetary orbits, the latitude of each planet and the position of its perihelion and aphelion. During the present century elaborate and effective planetaria employing optical projection have been made, mainly by the firm of Carl Zeiss, for showing to large audiences. Spectators sit below a dark dome on which images of stars, sun, moon and planets are projected from an instrument situated at the center of the dome, with very realistic effect.

Planishing :
The operation of working a metal surface to a smooth, evenly rounded or flat shape, usually in soft metal such as copper, silver or brass. The metal is hammered with a planishing hammer on an anvil, the anvil and hammer having specially shaped and polished working surfaces. For clock plates the work can be finished with a wide-edged chisel-shaped tool with the edge squared off to act as a scraper, but rounded forms in casework are completed with the hammer when hand-produced.

Planting :
Positioning and marking out the parts of a clock between or on the clock plates, so that they will function correctly. It includes the correct positioning of the hands and winding squares on the dial.

Plate :
The front and back of the clock's movement or works.

Plate Clock :
The Telleruhr or dish clock was popular in south Germany and Austria in the late 17th century, and the idea was revived in the 20th using a china plate instead of a metal one. The movements were similar to the going part of an alarm clock with an open mainspring and were controlled by a balance, but the mainspring arbor had a winding square allowing the clock to be wound through a hole in the dial. These clocks were mass-produced by the Black Forest factories in the 1920s, and were, in effect, a development of the china dials found on Black Forest wall clocks of the mid 19th century. Their fragility has greatly reduced their numbers and they are now seldom seen.

Plates, Latched :
To make dismantling and assembly easier, some late 17th-century makers used small latches to secure their pillars and plates. The idea is still occasionally used and during the 1960s the makers of the Section clock used latches to secure the sub-assemblies.

Plates, Pinned :
Taper wedging pins have been used from the earliest times to secure mechanical assemblies. In the usual pillar and plate assembly the pillars are riveted to the backplate and are reduced in diameter, forming a shoulder to support the front plate, which is secured by a tapered pin passing through a small hole pierced in the protruding pillar end.

Plates, Screwed :
Occasionally clocks are found in which the pillars are screwed into the clock backplate, rather than riveted. This makes cleaning the clock much easier. Modern clocks usually have the pillars threaded at both ends and secured to the plates by washers and nuts.

Plates, Split :
Assembling a large three- or four-train clock often presents great difficulty. High-quality clocks sometimes have the front or backplate divided, so that each train may be assembled independently.

Platform :
A plate carrying a sub-assembly which may be removed for attention without disturbing the main frame of the clock. The platform escapement of a carriage clock is an example.

Pliers :
Hand tools for gripping or holding material which is to be bent, twisted, pulled, pushed, etc. There are many different types of plier jaws for different purposes, and the two levers are pivoted or 'boxed' to ensure that the jaws meet accurately. Sometimes the jaws are lined with brass to prevent damage to parts held in them.

Polishing :
There are several methods of producing a smooth or glossy surface on clock parts made from metal, glass, stone, plastic, wood, etc. Almost all the metal parts in a clock movement can be polished; parts such as pallets, pinions and pivots are polished to reduce friction on their working surfaces, allowing the parts to slide easily together and reduce the possibility of injurious material clinging to them. Other clock parts such as brass weights, pendulum bobs, bezels, frets and finials are polished for the sake of appearance. Metal surfaces are polished with a polisher of soft steel, iron, bell metal, tin, zinc, lead or wood according to circumstances. In all cases the polisher is softer than the surface being polished, and is charged with compounds ranging from carborundum and oilstone dust to rouge and diamantine.

Polishing, Pinion :
The flutes and leaves of a pinion are polished in a pinion polishing tool; it consists of a frame in which the pinion is mounted between centers and free to rotate. The frame is fitted to slide on a base which has a wooden disc pivoted to a block, adjusted so that the edge of the disc is slightly askew to the pinion axis. As the disc is rotated the pinion revolves, cutting a screw thread in the edge of the disc, which is charged with polishing material. During the operation the pinion is made to slide back and forth so that its whole length is polished.

Polishing Mills, or Laps :
Tools with a revolving disc charged with a polishing compound. These are of various designs, some being made for the specific purpose fo polishing one type of componenet. Depending on the work, the mill or lap disc can be made of wood, copper, nickel, bell metal, iron or steel.

Polishing Muller, or Stake :
A block of steel with a flat polished surface on which a polishing medium such as rouge is mixed with oil. It is usually contained in a wooden box to keep out dust and grit.

Porcelain Case :
Porcelain is a hard translucent material of which an important ingredient is china clay (kaolin), with various other materials added according to type, and fired to a high temperature in a potter's kiln. Most porcelain clock cases are of hard-paste porelain and are of French or German manufacture. The material is adaptable to the making of ornamental cases combining modelled figures, flowers or other decorative features, and it can be colored by painting and firing enamels on its urface. Individual decorative figures, or sometimes complete cases, are made in biscuit (unglazed) porcelain, and such cases are normally protected from dirt by glass domes or shades. Porcelain, like all ceramic materials, shrinks and is inclined to distort during firing, and for this reason clock movements are fitted to porcelain cases with screws from loosely fitting rings at the back.

Portico Clock :
A portico is a classical porch with a decorated entablature supported on columns, and often completed by a triangular pediment. On modern buildings in classical style, the pediment sometimes contains a clock dial. The term 'portico clock' is also applied to the style of French clock usually known by the name 'Empire'. Here the entablature is supported by four columns on a base, and the movement is suspended below it with the pendulum exposed. This design can also be seen in earlier examples from Austria, the essential feature being the entablature supported by columns. Other Austrian designs, especially in the Biedermeier period, include columns, but do not necessarily qualify as portico clocks.

Position Clock :
Also called a regulator clock.

Postman's Alarm :
The Black Forest industry was hard hit by American competition in the years 1842-60 and in the 1860s began to make clocks on the American pattern in factories. The old type of wall striking clock, with the striking train behind the going train, had sometimes included a small alarm mechanism placeed at the side of the movement. When striking clocks began to be replaced by the new American type, the manufacturers of the 'hang-up' clocks remodelled the design to place alarm work where the striking train had been, providing it with a long chain to give a protracted ring. The mechanism was more solid than before, and the clocks competed successfully with the American clocks with alarm work because of their greater accuracy. No one know how the name 'postman's alarm' came to be applied to these clocks, but as late as 1948 a faded inscription could be seen on a shop wall in Islington, London, 'The original Postmens' Alarms'. Sometimes these clocks were made without a separate glass, the dial itself being glass with the figures behind it. Various sizes were made, and the type did not die out until c. 1914.

Potence :
A bracket or cock mounted between the clock plates. In a verge clock the potence is the bracket carrying the lower escape-wheel pivot.

Precession of the Equinoxes :
The positions of the equinoxes are determined by the position of the Earth's axis, and if this was constant in direction the equinoxes would remain fixed in position in relation to the fixed stars. Owing to a gyroscopic effect produced by the gravitational pulse of the moon and sun on the Earth's equatorial bulge, the Earth's axis, though remaining always at the same angle to the plane of its orbit, changes its direction, making one complete revolution in approximately 26,000 years. From the Earth, therefore, the equinox points in the heavens move slowly around the equinoctial or equatorial circle. The spring equinox in the early Christian era was in the constellation of Aries and was termed the 'first point of Aries'. It has now moved back into the constellation of Pisces, a movement of nearly 30º of Right Ascension.

Projection Clock :
A form of night clock incorporating an internal light and projection lenses to throw an image of the dial and hands on a wall or other convenient surface. The idea dates back to the 18th century, and some models with oil lamps were made early in the 19th century. Even with the introduction of electric lighting, however, the idea was never exploited to any large extent, since any form of artificial illumination can be adapted to reading a clock at night without the complication of projection apparatus.

Pulley :
A wheel grooved on its circumference to retain a rope or line. The weight of an eight-day clock is usually hung from a pulley. The line passes from the barrel round the pulley and is attached to the seat board. This arrangement halves the weight's fall, but demands a weight twice as heavy to drive the clock as one hung directly from the line without using a pulley.

Punch :
A steel or brass rod, used to transmit pressure or a sharp blow to a required point. Punches are made for many purposes, e.g. making centers before drilling, and for riveting, chasing, matting, blanking and stamping out shaped holes or parts. Serial letters and numbers are marked on clock parts with punches. Punches may be solid, hollow, flat, round or otherwise shaped at the working end. Many of them are designed to be used in a staking tool in which the punch is held in a guide for accurate positioning in relation to an anvil or stake.

Punch, Bell :
A self-centering punch, with a center punch point at one end, designed to slide down a tube or sleeve which has a cone- or bell-shaped mouth. With the bell mouth placed directly over the end of a rod, the center of the rod can be accurately marked with the punch, provided that the end of the rod is itself square to the rod's axis and the axis of the bell punch is correctly in line with the axis of the rod. Bell punches are available in various sizes and are used to center-punch a rod prior to turning it between male centers in a lathe. Some bell punches have the center punch fitted with a return spring.