BALANCE COCK—The standard which supports the top pivot of the balance. In old watches often elaborately pierced and engraved. BALANCE SPRING—In America usually called the "hair-spring." A long slender spring that governs the time of vibration of the balance. One end of the balance spring is fastened to a collet fitted friction-tight on the balance staff, the other to a stud attached to the balance cock or to the watch plate. The most ordinary form is the volute, or flat spiral. The other form used is an overcoil. See _Bréquet Spring_. The principle of the isochronism of a balance spring was discovered by Hooke, and first applied to a watch by Tompion. The name hair-spring comes from the fact that the first ones are said to have been made from hog bristles. BALANCE SPRING BUCKLE OR "GUARD"—A small stud with a projecting tongue attached to the index arm and bridging the curb pins so as to prevent their engaging two of the balance spring coils. Used chiefly in Swiss watches. BALANCE STAFF—The axis of the balance. The part of a watch most likely to be injured by a fall. BALANCE WHEEL—A term often incorrectly applied to the balance itself, but properly it is the escape wheel of the verge escapement. BAND—Of a Watchcase—The "middle" of the case to which the dome, bottom and bezel are fastened; the last sometimes screwed, sometimes snapped. BANK—Banking-pin. BANKING—In a lever watch the striking of the outside of the lever by the impulse pin due to excessive vibration of the balance. In a cylinder or verge movement the striking of the pin in the balance against the fixed banking-pin. BANKING-PIN—A pin for restricting the motion of the balance in verge and cylinder watches. BANKING-PINS—1. In a lever watch, two pins which limit the motion of the lever. 2. In a pocket chronometer, two upright pins in the balance arm which limit the motion of the balance spring. 3. In any watch, the curb pins which confine the balance spring are sometimes called banking-pins. BARLOW, EDWARD (BOOTH)—A clergyman of the Church of England, born in 1636. He devoted a great deal of time to horological pursuits. He invented the rack repeating striking works for clocks, applied by Tompion in 1676. He invented also a repeating works for watches on the same plan. And he invented the cylinder escapement which he patented with Tompion and Houghton. When he applied for a patent on his repeating watch he was successfully contested by Quare, who was backed by the Clockmakers' Company. He died in 1716. BAR MOVEMENT—A watch movement in which bars take the place of the top plate and carry the upper pivots. Sometimes termed a "skeleton" movement. Not generally adopted because its many separate bearing parts promote inaccuracies where large quantities are to be produced. BARREL—A circular box which confines the mainspring of a watch or clock. BARREL ARBOR—The axis of the barrel around which the mainspring is coiled.