BARREL HOLLOW—A sink cut either into the top plate or the pillar plate of a watch to allow the barrel freedom. BARREL HOOK—A bent pin in the barrel to which the mainspring is attached. BARREL RATCHET—A wheel on the barrel arbor which is prevented by a dog from turning backward while the mainspring is being wound and which becomes the base against whose resistance the train is driven. BARTLETT, P. S.—One of the early watchmakers of America. Connected with the Waltham factory at first and later with the Elgin Company. It is said that he first proposed the formation of the company at Elgin. His name became familiar as a household word throughout the country from being inscribed upon a full-plate model which attained widespread success. BEAT—The strike or blow of the escape wheel upon the pallet or locking device. BEAT PINS—The pins at the ends of the pallets in a gravity escapement which give impulse to the pendulum. BECKETT, SIR EDMUND—See _Denison, Edmund Beckett_. BEROSUS—A Chaldean historian who lived at the time of Alexander the Great, about 200 B. C., and was a priest of Belus at Babylon. Said to have been the inventor of the hollow sun-dial. He was the great astronomer of his age. BERTHOUD, FERDINAND, 1727-1807— An eminent French watchmaker and writer on horological subjects. Among his books are: "Essai sur l'Horlogerie," "Traite des Horloges Marines," and "Histoire de la mesure du Temps." He was a Swiss by birth, but lived most of his life in Paris. BEZEL—The ring of a watch or clock case which carries the glass or crystal in an internal groove. BIG BEN—The great bell which strikes the hours on the clock at Westminster. BIZZLE—A corruption of Bezel. See _Bezel_. BLOW HOLES—Places where the brass and steel of a compensation balance are not perfectly united, when they are put together with silver or solder. BOB—The metal mass forming the body of a pendulum. BOETHIUS, ANCIUS MANLIUS SEVERINUS, A. D. 480-524—A Roman philosopher and statesman to whom is sometimes attributed the invention of the clock. He did make a sun-dial and a water clock which latter may have contained a germ of the idea later developed into our modern clock. BOSS—A cylindrical prominence or stud. The minute hand is carried on the boss of the center wheel. BOTTOM—Of a Watchcase—The cover outside the dome of the case. Commonly called the "back." BOUCHON—The hard brass tubing of which pivot holes in watch and clock plates are made; known commonly as "bushing wire." The short sections cut off for a pivot being called the "bushing." BOW—The ring of a watch case to which the guard or chain is attached; also known as "pendant bow." [Illustration: BOW AND BUTTON] BOX CHRONOMETER—A marine chronometer. BOXING-IN—Fitting the watch movement in its case; applied chiefly to the encasing of stem-winding movements.