WATCH

the construction of pocket timepieces was first made po ible by the invention of the mainspring as a substitute for suspended weights. The early history of watches is uncertain, but probably they were first made at Nuremberg about the beginning of the i6th cent. These watches had on'y an nour-hand, the minute-hand being added late in the 17th cent. The flat, round form was introduced early in the 17th cent., and repeating watches were invented in 1676. The practice of setting the pivots in precious stones originated about 1700. The force of a mainspring weakens as the spring uncoils, and to equalize this force the ‘fusee’ was invented about 1530. In most Eng. watches the fusee is now superseded by the going barrel, which is cheaper to make and more suitable for the popular, keyle type. The motion of a watch is regulated principally by the escapement and balance-wheel. Variations in temp. affect watehes even more than clocks, and to compensate for these the balance wheel is constructed partly of bra and partly of steel, on the same principle as the ‘gridiron’ pendulum (see Cuiocx). In watches the lever escapement is largely used... Chronemeters are simply watches made with special accuracy, usually fitted with the detached escapement.