Page:St. Nicholas, vol. 40.1 (1912-1913).djvu/104

  

power to keep in motion the machinery of a watch is supplied by the mainspring. In winding a watch, this spring is coiled in the central part of its holder, known as a “barrel.” The mainspring in its constant endeavor to uncoil turns this barrel in one direction, and its power is transmitted through the teeth on the outer rim of the barrel to the “train” of wheels.

The motion is prevented from being too fast by what is known as an escape-wheel, the cogs of which work in connection with the “pallet and fork.” This lets the motion “escape” in a series of short stoppings, well known as the ticking of the watch. In connection with the “pallet and fork” is the balance-wheel, whose vibrations regulate the speed at which all shall move. This balance-wheel serves the same purpose in a watch that the pendulum does in a clock.

The vibrations of the balance-wheel are the result of the action of two forces, one being the force of the mainspring acting through the “train” of wheels and the escapement, to turn the balance-wheel on its axle, and the other being the opposing force of a very small spring, known as the hair-spring, coiled loosely about the balance-wheel, and which thus tends to regulate the power of the mainspring.

The bearings for the ends of the tiny shafts of the wheels give better service if they are not made of metal but of some hard mineral or jewel, as, for example, garnet, chrysolite, ruby, etc. The lower-priced watches have these jewels in only some of the most important bearings. The better classes of watches have more jewels. If all the important wheel bearings have these minerals, the watch is said to be “full-jeweled.” The jewels are held in place by screws so small as to be almost invisible without the aid of a microscope. Very small screws are also used in other parts of the watch.

Ask some one you know to let you look at the works of his watch, or, better still, as watches nowadays are often made with a protecting plate that conceals all but a few parts of the mechanism, ask some friendly jeweler to let you see the machinery of a watch from which he has removed this outer plate, and to explain it to you.