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_. [Illustration] 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_, _Top Plate_, _Half 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.