But if you want to set the clock it is easy to do so by reason of the fact that the minute hand is not fixed to the arbor, but only to the slieve on the cogwheel that fits on the arbor, and is held somewhat tight to the arbor by means of the spring. The hands can thus be turned, but they are a little stiff. A washer on the minute hand arbor keeps the slieve on the cogwheel pressed tight against the spring, being secured in its turn by a very small lynch-pin driven through a hole in the minute hand arbor. It remains to explain a few subsidiary arrangements, not always found upon all clocks, but which are useful. In order to prevent the overwinding of the clock (see Fig. 43), which would cause the cord to overrun the drum, an arm is provided, fitted with a spring. As the weight is wound up the free part of the cord travels along the drum or the fusee; and the cord, when it is near the end of the winding, comes up against the arm and pushes it a little aside. This causes the end of the arm to be pushed against a stop on the axis of the fusee, and thus prevents the clock being further wound up. The stop, being ratchet-shaped, does not prevent the weight from pulling the ratchet wheel round the other way, and thus driving the clock; it only prevents the rotation of that wheel when the string is near it, and the winding is finished. Another arrangement is the “maintaining spring.” It will be remembered that during the process of winding the clock the hand twisting the key takes the pressure of the ratchet wheel off the pall, so that during that operation no force is at work to drive the clock. In consequence the pendulum receives no impulse, but swings simply by virtue of its former motion. If the process of winding were done slowly enough the clock might even stop. To avoid this, a very ingenious arrangement is made to keep the cogwheel mounted on the winding shaft going during the winding-up process. This is called a maintaining spring. The arrangement shown in Fig. 53 will explain it. [Illustration: FIG. 53.]