Caption

Watch cogs. Internal cogs and gears of a watch escapement. The red circles are 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. Photograph of a 17-jewel Roamer watch from Switzerland.