SPANDRELS—The corners of a square face outside the dial of a clock. Formerly very beautifully decorated. The age of the clock can be told approximately from the form of ornamentation employed. [Illustration] SPLIT SECONDS—A chronograph in which there are two center-seconds hands—one under the other—which can be stopped independently of one another. SPRING-CLOCKS—Clocks whose driving power is a coiled spring instead of a weight. [Illustration] STACKFREED—The derivation of the word is obscure; it is possibly Persian. A device to counteract the difference in power of the mainspring at the different stages of its unwinding. Fixed to the mainspring arbor above the top plate is a pinion having eight leaves, which gears with a wheel having twenty-four teeth, which do not quite fill out the circumference of the wheel. Fastened to the wheel is a cam, concentric for about seven-eighths of its circumference and indented for the remainder. Into a groove in the concentric portion of the edge is pressed a roller which is pivoted at the free end of a strong curved spring. When the mainspring is fully wound the roller rests in the curved depression of the cam and the effort required to lift the roller up the incline absorbs some of the mainspring's power. On the other hand when the mainspring is nearly run down, the roller is descending an inclined plane and absorbs less of the power. Not an acceptable device and now rarely met with. STEM-WINDING—The ordinary method of winding keyless watches by means of a stem running through the pendant. STOP WORK—An arrangement for preventing the overwinding of a mainspring or a clock weight. _Stratton, N. P._—One of the early watchmakers connected with American manufacture. He was an apprentice of the Pitkin Bros., and was sent by the Waltham Company to England in 1852 to learn gilding and etching. He was made assistant superintendent of the Waltham Co. in 1857. He invented a mainspring barrel and a hair-spring stud which were later adopted by the Waltham Company. STRIKING-WORK—The part of a clock's mechanism devoted to striking. The chief forms are _Rack_, and _Locking-plate_, or _Count-wheel_. See separate articles. STRIKING-WORK, LOCKING-PLATE, OR COUNT-WHEEL—Used in turret clocks where there is no occasion for the repeating movement. This form of striking work does not allow of the repetition or omission of the striking of any hour without making the next one wrong. STRIKING-WORK—RACK—A form of striking work used largely in house clocks; the number of blows to be struck depends merely on the position of a wheel attached to the going part. In this form the striking of any horn may be omitted or repeated without deranging the following strikes. STUD—1. A small piece of metal pierced to receive the outer or upper coil of a balance spring. 2. The holder of the fusee stop-work. 3. Any fixed holder used in a watch or clock, not otherwise named, is called a stud.