唐朝国庆

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The world’s first compass That the world’s first compass was invented by the Chinese people is a well-known historical fact. Many centuries ago, the people of China made the discovery that natural magnets have attracting properties[性质] and that a freely suspended[悬挂] magnetized bar always points north and south. Thus they found that such an instrument[仪器] could be used for the purpose of determining[决定] direction.. It was recorded in ancient books that the earliest compass was shaped like a spoon and mounted [安置]on a graduated plate. About the end of the eleventh century the Chinese people used the compass in navigation. In the twelfth century a compass of the floating-needle type came into use. It was recorded that this early sea-going compass was in use on Chinese ships up to the seventeenth century. From the Chinese the Arabs learned to make compasses and to use them in navigation. The Arabs in turn introduced the compass to Europe. In the bands of the Chinese, Arabs and Europeans, the great invention of the ancient Chinese was further developed. That is how the compass finally reached its present[相当] perfection. Magnets Do you know what magents do? Magnets pick up things made of iron or steel. The ends of a magnet are called poles. It has been proved[证明] by experiment that one end of the magnet always points to hte north and is called the "N" pole. The other end always to the south and is called the "S" pole. if the N pole of one magnet is held toward the N pole of another, the magents will push away from each other. If the N pole of one magnet is held toward the S pole fo another, the magnets will pull together. This is why one magnet will sometimes pick up another magnet and why sometimes it will not. You may wonder why the magnet’s poles point north and south. the fact that the carth has two magectic poles tells us the reason. The two poles of the earth attract the poles of all magnets.