Time Telling through the Ages

Pendulum, Gridiron – Invented by Harrison in 1726, and still with slight improvements an effective timekeeper. The rod of this pendulum is constructed of five steel and four brass rods so arranged that those which expand most are counteracted by those of less expansion, and the length of the pendulum remains constant.

Pendulum, Mercurial Compensation – A pendulum having for a bob a jar of mercury which expands upward with the increase of temperature thus counteracting the lengthening of the rod from the same cause. Invented by Graham about 1720. With slight improvements still in use and keeps time very accurately.

Pendulum, Torsion – A pendulum vibrating by the alternate twisting and untwisting of an elastic suspension. The body is a horizontal disc weighted around its edges, and its suspension a steel or brass wire. The period of a torsion pendulum being much longer than a vibrating pendulum of the same length, the time of running is longer. Clocks fitted with torsion pendulums have run a year on one winding.

Pendulum Swing – The short ribbon of spring steel which suspends the pendulum of a clock.

Penetration of Gearing – The depth of intermeshing of the teeth of pinion and wheel.

Phillips Spring – A balance spring with terminal curves after rules laid down by M. Phillips, an eminent French mathematician. A term seldom used though his curves are generally followed.

Pillar – The three or four short brass posts which keep the plates at their proper distance apart. In early days made in very artistic and elaborate shapes. Later they became plain straight cylindrical columns.

Pillar Model – A type of movement in which the works are hung between two plates supported and separated by posts or pillars and forming all the principal bearings of the movement. Only average adjustment is possible in this model. In this model the plate is sometimes cut away to imitate a "bridge model." The opposite extreme in construction to the "bridge model."

Pillar Plate – The lower plate of a watch movement – the one nearest the dial – to which the pillars are solidly fixed, in a "pillar model."

Pinchbeck, or "Pinchbeck Gold" – An alloy of three parts zinc to four of copper which "resembles gold in color, smell and ductility." So called from its inventor Christopher Pinchbeck (1670-1732) who during his life guarded the secret of its composition very jealously.

Pinion – The smaller of two toothed wheels that work together. The teeth of a pinion are called leaves. See also Lantern Pinion (#Pinion_Lantern).

Pinion, Lantern – A pinion consisting of two circular metal plates joined by short steel wires.

Pitch – The length of the arc of the circumference of the pitch circle from center to center of two adjacent teeth.

Pitch Circle – The geometrical circle traced with the center of the wheel as its center and at which the curved tips of the teeth begin. The diameter is proportional to the number of teeth determined upon. The proportion of the pitch circles of a wheel and a pinion gearing together is determined by the ratio of revolutions desired.

Pitkin, Henry – With his brother, James F., he started at Hartford, Conn., in 1838, the first factory for machine-made watches in the United States. They made their own machinery, which was very crude. After making about 800 watches they were forced to abandon the project, being unable to compete with cheap foreign watches. He died in 1845.

Pivots – The ends of the rotating arbors in a watch that run in bearings.

Planetarium – An astronomical clock which exhibits the relative motions and positions of the members of the solar system. Has no regulating system and usually no driving power but is run by turning a crank by hand.

Plates – In watches and small clocks the circular discs of brass to which the mechanism of the watch is supported. In large clocks the plates are usually square-cornered oblong. See Pillar Plate (#Pillar_Plate), Top Plate (#Top_Plate), Half Plate (#Half_Plate), Full Plate (#Full_Plate), etc. In half-plate, and three-quarter-plate types of watches part of the disc is cut away.

Pocket Chronometer – A watch with a chronometer escapement.

Polos – A basin in the center of which the perpendicular staff or gnomon was erected, and marked by lines for the twelve portions of the sun-lit day. Herodotus ascribes its invention to the Babylonians, Phavorinus claims it for Anaximander and Pliny for Anaximenes. Also called "Heliotropion."

Potance or Potence – A vertical or hang down bracket, supporting the lower end of the balance staff in full-plate watches.

Prescot – A town in a remote part of Lancashire for years the center of the movement trade in England.

Push Piece – 1. The milled knob pushed in from the pendant to open the case. 2. The boss pushed in when the watch is to be set.

Quare, Daniel – 1649-1724 – Claimed the invention of the repeater, and backed by the Clockmakers' Company obtained the patent against Barlow from James II. Also credited with the invention of equation clocks. He was master of the Clockmakers' Company in 1708. He first used the concentred minute hand in England, but Huyghens had preceded him in this in the Netherlands.

Quarter – 1. A term in common use for the period of three months – a quarter of the year. 2. The fourth part of an hour – 15 minutes.

Quick Train – A watch movement balance vibrates 18,000 times per hour. Unequal mainspring pull is less felt in the quick train. Used generally in Switzerland and America, and a feature of practically all modern watches.

Rack – A straight bar, or segment of a circle, with teeth along one edge. It has a reciprocating motion.

"Radiolite" – Trade name adopted by Robt. H. Ingersoll & Brothers. for their watches having black faced dials with luminous hands and numerals. Composed of a substance in which genuine radium is used in minute proportions.

Radius of Gyration – The distance from the center of gyration to the axis of rotation.

Ramsey, Davis – One of the earliest British watchmakers of renown. He was appointed "keeper of clocks and watches" to James I, and appears to have retained his appointments after the death of the latter. He was the first master of the Clockmakers' Company tho he seems to have taken little active part in the management thereof. Scott introduces him into his story – "The Fortunes of Nigel" as a Keeper of a shop a few yards east of Temple Bar. Without doubt he was the leading clockmaker of his day. He died in 1655.

Ratchet – The pawl, or dog, which engages in the teeth of a ratchet wheel and prevents it from turning backward. It is held lightly against the periphery of the ratchet wheel by a small spring known as the ratchet spring.

Ratchet Wheel – A wheel with triangular teeth fixed on to an arbor to prevent the latter from turning backward. The fronts of the teeth are radial, the backs straight lines running from the tip of one tooth to the base of the next. In going-barrel, keyless watches the ratchet has epicycloidal teeth. By "the ratchet" in a watch, chronometer or clock with mainspring is meant the ratchet fastened to the barrel arbor to prevent the mainspring from slipping back when it is being wound.

Recoil – In recoil escapements the pallets not only stop the escape wheel but actually turn it backward a slight distance. This backward motion is called the recoil.

Regulator – 1. A standard clock with compensated pendulum with which less accurate movements are compared. 2. The lever in a watch by which the curb-pins regulating the swing of the hairspring are shifted.

Remontoire – An arrangement in the upper part of the going train by which a weak spring is wound up or a small weight is lifted that gives impulse to the escape wheel at short intervals. Its use is to counteract the irregularities in impulse due to the coarse train, etc. They are delicate and complicated and now superseded by the Double Three-legged Gravity Escapement.

Repeater – A striking watch or clock which by the pulling of a string or the pressing of a button could be made to repeat the last hour and part hour, struck. In vogue during the 18th century. Credit for the invention was disputed by Daniel Quare and Edward Barlow. James II gave the decision in favor of Quare whose mechanism was a trifle simpler.

Repousse – A kind of chasing in which the metal is punched or pressed from the back bringing the design into higher relief than by the usual method of indenting.

Ring-Dial – See Sun-dial, Portable (#Sun_Dial_Portable).

Richard, Daniel Jean – A Swiss watchmaker, born at La Sagne in 1665. At fifteen a watch having come into his hands, he constructed a similar one unaided. That was the first watch made in Neuchatel. After a time in Geneva he set up business in La Sagne, afterwards moving to Locle. He created the watch industry of Neuchatel and saw it grow to a neighborhood of five hundred workers. He died at Locle 1741. In 1888 a bronze statue was erected to him there.

Robbins, Royal E. – Born in Connecticut 1824. He was essentially one of the "fathers" of American watchmaking because it was through his financing and clever management that the first watch company finally succeeded in making a financial success.

Roller – The circular plate in a lever escapement, into which the ruby pin is set.

Roller-Jewel – Same as "impulse pin."

Roman Indiction – A period of fifteen years appointed by the Emperor Constantine 312 A. D. for the payment of certain taxes.

Rose Engine – A lathe in which the rotary movement of the mandrel is combined with a lateral, reciprocating movement of the tool rest; used for ornamenting the outside cases of watches with involved curved engraving.

Ruby Pin – The impulse pin in a lever escapement, made of a ruby.

Ruby Roller – The roller in a duplex escapement against which the teeth of the escape wheel are locked.

Run – In the lever escapement, the extent of the movement of the lever toward the banking pins after the "drop" on to the locking.

Sabinianus – Pope from 604 to 606. Said to have invented a clock in 612 A. D., but the clock he is supposed to have built was probably only another of many forms of clepsydrae, or water clocks.

Safety Pinion – A center pinion in a going-barrel watch which allows the recoil of the barrel if the mainspring breaks.

Sand-Glass – (Clepsammia) – A dumb-bell-shaped glass globe containing sand, and with a small aperture through which the sand flows in a certain fixed time. The most common form is the hour-glass but many others are in use as the three-minute glass for boiling eggs, the two-minute glass used by the British Parliament, etc. Dried and finely powdered eggshell sometimes used in place of sand. The principle is the same as that of the simplest form of clepsydra. See Hour-Glass (#Hour_Glass).