After the balance has been started, its momentum at each turn starts the lever when the jewel-pin strikes it, but unless the balance was constantly supplied with new power it would soon stop, and the watch would not run. It will be noticed, however, from the illustration, that the teeth of the escape-wheel are peculiar in shape and very different from those of the other wheels. The ends of the pallet-jewels are also cut at a peculiar angle. Now, each time just before the jewel-pin starts to shift the lever from one side to the other, the latter is in such a position that one of the pallet-jewels is thrust in so that its side is against that of one of the teeth of the escape-wheel, keeping it from turning. But the instant the lever commences to move it begins to draw this pallet-jewel outward from the tooth until the corner of the jewel passes the corner of the tooth. Then the escape-wheel is released and the power that is behind it makes it turn quickly, and on account of the shape of the tooth, it gives the pallet-jewel a sharp push outward, swinging the lever, causing it at the other end to impart a quick thrust to the jewel-pin, thereby accelerating the speed of the balance and renewing its momentum. Thus the balance receives the power to keep it in motion, swinging it as far as the hairspring allows. The hairspring then reverses it and swings it until the jewel-pin again starts the lever in the other direction, releasing the escape-wheel from which it receives another "impulse" and so on as long as the mainspring is kept wound. A watch in perfect time ticks five times to the second. That means 18,000 swings of the balance every hour, or 432,000 in a day. And in that time, the rim of the balance travels about ten miles. A clock is essentially only a larger and stronger watch, just as a watch is a clock made small enough and light enough to be carried about conveniently. But the working of the two is practically the same. They are but different members of the same family, varying types of one time-keeping machine which is among the most ingenious and valuable things that man has made. One interesting thing to know about a watch is that if it is keeping good time, it will serve for a fairly accurate compass. So if you are ever lost in the woods, your watch may help you out again. Lay it flat face upward, and point the hour hand toward the sun. Then South will be in the direction half way between the hour hand and the figure 12, counting forward as the hands turn in the morning hours, and backward in the afternoon. This is because the hour hand moves around the dial just twice as fast as the sun moves around the sky, making a full circle in twelve hours while the sun makes its half circle from horizon to horizon.