BALANCE

A CIRCULAR, MOVING PART WHICH OSCILLATES ON ITS ROTATIONAL AXIS. IT IS COUPLED TO THE BALANCE-SPRING WHICH GIVES IT THE TO-AND-FRO MOTION THROUGH WHICH IT DIVIDES TIME INTO STRICTLY EQUAL PARTS. EACH TO-AND-FRO MOVEMENT (“TICK-TOCK”) IS CALLED AN OSCILLATION, AND EACH OSCILLATION COMPRISES TWO VIBRATIONS.
A CIRCULAR MASS (RIM) HELD BY SPOKES. COMBINED WITH THE SPIRAL IT FORMS THE REGULATING ORGAN OF THE WATCH.