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 unlocked it turns a little. This allows the barrel to turn. The cord and weight pull on the barrel, too, to help it turn. And this sets all the other wheels in motion. You didn’t know that all the wheels in a clock are called a "train of wheels" did you? They are all coupled together, just as a train of cars are, and travel together. The pendulum seems to be the engineer; the locked wheel is the throttle; the barrel, cord and weight are the engine, furnishing the power to pull the train. The locked wheel is a safety valve, too, as well as a throttle.

The little saw-toothed wheel and the anchor, or lever catch, are there to tell all the other wheels not to go too fast. Every time the pendulum swings, a tooth of this wheel is let go. Then another tooth is caught and held an instant. This catching and letting go make the clicking or ticking sound in watches, and the solemn tick-tock of big clocks. The wheel and the catch are called the "escapement," because the wheel turns around, or escapes, only one tooth at a time. At every tick the escapement says: "Not-so-fast," and at every tock, "Go-ahead." You see, when the cord and weight begin to pull on the barrel, it would whirl over and over, as fast as it could, if nothing held it back. Then all the wheels would fairly race, until the weight had dropped to the bottom. There would be a grand smash-up, if the escapement wasn’t there to hold them all to a steady gait.

The whole duty of a  good clock is to drive the hour hand at a regular rate of travel around the dial, twice in twenty-four hours. So the barrel turns entirely over twice, letting down two coils of cord. In an eight-day clock the cord is wound around the barrel sixteen times. On the rear end of the barrel is fixed the hour wheel. Both turn together. The minute wheel and the second wheel are fitted there, too. All of these turn on other wheels and pinions. The axles of the pinions are extended and pushed through the dial to carry the hour, minute and second hands. So these hands just have to turn when the wheels turn.

Sometimes a clock goes too fast or too slow, and must be regulated. A grandfather’s, or other pendulum clock, is regulated. by pushing the "bob" of the pendulum up or down on the rod. The. time it takes a pendulum to swing, depends upon the length of the rod. In a watch, or a spring clock, there is a key-stone shaped I indicator plate r right over the coiled spring. One side is marked S (slow) and the other F (fast). A movable pin over this plate regulates