Wrist-watch. Coloured X-ray of a 17-jewel wrist- watch, showing the internal mechanism. Internal cogs and gears of the watch escapement can be seen. Some of the small circles contain ruby jewels used in bearings. An escapement is a device within a watch which provides periodic impulses to the balance wheel that helps to regulate time- keeping. Jewels, whether natural or man-made, are used in watch bearings because their smooth surfaces offer little friction resistance and are hard-wearing.