Fire was discovered many thousands of years ago. The first time humans saw fire was probably when a tree was destroyed by lightning(闪电).Humans soon learned how to make a fire. They probably made the first fire by rubbing (摩擦)two sticks together. Fire was very important to humans. They needed fire to keep warm at night. They used fire to cook food. ⑶They used fire to keep enemies and wild animals away. In some parts of the world fire was used to send messages. The Indians in America, for example, used fire to make smoke as a message. In some other countries people lit fires to warn their friends of danger. ⑷Fire was also used to give light. Before the invention of the oil lamp(灯), humans burned sticks to get light. One man even used fire to tell the time. He invented a candle clock. He made a candle that took exactly twelve hours to burn. Then he marked this candle in twelve equal(相等的) parts. He lit the candle and could tell the time by counting the number of parts left of the burning candle. But the candle clock did not always work well. If there was a wind blowing on the candle, it burned too quickly.
