Regulator

(rěg'u-la-tōr.) [ From L. regulo, I direct. ] (Mech.) That part of a machine which produces an equable or uniform movement, such as the fly-wheel, the governor, the throttle-valve of a steam -engine, & c. - (Horol.) An apparatus attached to the hair-spring of a watch, which, by practically lengthening or shortening the spiral spring attached to the balance, causes the watch to go slower or faster; in modern watches it is generally a mere index; in those of older date, it is a pinion and segment. In each case, one end of the spring pa es freely, but in contact, through an aperture in a small piece which is movable along the spring. [s. 761]