Fire A gift of the gods. According to an old Greek myth, Prometheus and his brother, Epimetheus, heroes of a race of giants called the Titans, were given the task of creating man. Epimetheus was also to provide all the animals with means of defense or flight. To some he gave courage, strength, and claws with which to fight, and to others long legs, nimble feet, or wings with which to escape. So lavish was he with these gifts to the lower animals that he had nothing left to give to man. Prometheus, however, was determined that man should not be neglected and so, according to the myth, he gained access to heaven and lighted his torch at the chariot of the sun. Returning to earth, he presented fire to man, and with this gift came mans dominion over all the earth. The first cook. It took a long time, however, to learn how to use this gift. For centuries men lived like wild animals. Their food consisted of nuts, herbs, fruit, and the flesh of animals. Cooking was unknown, and when a wild animal was captured, the savage tore it apart and ate the raw flesh. According to one legend, a hunter, after a long tramp, succeeded in catching a rabbit. On his way home he found a smoldering fire which had been started by lightning. Throwing his rabbit on a log, he lay down and went to sleep. When he awoke, he found that his rabbit had fallen into the fire. In attempting to rescue it, the savage got some of the juice of the roasted rabbit on his fingers. By instinct, he put his burnt fingers to his mouth, and the taste was so pleasing that he immediately finished the rabbit, and this is how man learned to cook. Reduction of metals. Ages later, man began to use fire to make metals and to form them into spears and hatchets for hunting and fighting. The alchemists, as we know, used fire in their attempts to change the base metals into gold, and today fires are burning in many furnaces producing, if not gold, metals of far greater value to the progress of civilization. Copper, bronze, iron, and steel, produced by fire, have been the stepping stones of mans progress through the ages. The chemistry involved in the extraction, purification, and alloying of metals is so interesting and of such great importance that volumes have been written on this subject. Heating homes. We are so accustomed to living in heated homes that it is only when something goes wrong with the furnace that we give any thought to the blessed fire. To the savage shivering in his cave, however, a fire was a real blessing, even if it did fill his eyes with smoke. Keeping the home fires burningwas a difficult task for the American Indian, who delegated this to his wife. Woe be to the squaw who let the fire go out. In the wintertime, the fire was built on the ground in the center of the tent, which had a small hole in the top to act as a smokestack. Even the palaces of the wealthy in the Middle Ages were cold and damp, the fireplaces being so inefficient that only a portion of one room could be heated at a time. Not until a comparatively recent date were stoves invented, and furnaces were unknown even when your grandfather was a boy. How fires are started and stopped. You have learned that burning is rapid oxidation which gives off light and heat. In order to start a fire, three conditions are necessary: something to burn; something to support the combustion; and a means of lighting the fuel . Having lived all his life in a home where the furnace is kept burning all winter, the average person seldom thinks of the difficulty of starting a fire.
GRE数学模拟练习题(4)
如何解决GRE数学粗心问题?
GRE数学考试常见词汇归纳列举
GRE数学考试技巧:难题并非重点
GRE数学难题解析(1)
GRE数学核心知识点归纳
GRE数学专项考试辅导书推荐
GRE数学练习题及答案(1-5)
GRE数学图表题高分方法
GRE数学三大题目分析
GRE sub数学考试要点介绍
GRE数学考试重点试题:算术(6)
GRE数学在GRE考试中的重要性
GRE数学常考题型举例分析:排列组合
GRE数学考前7大注意事项
GRE数学考试重点试题:算术(3)
GRE数学运用方法介绍:最小值代入检验法
GRE数学经常考查的概念:几何部分
GRE数学经典题目讲解:几何
GRE数学常见专业术语
GRE数学注意事项+复习方法
GRE数学需要注意的难点
GRE数学冲刺阶段复习三大方法
GRE数学疑难问题解答思路(1)
GRE数学模拟练习题(3)
GRE数学专项考试全攻略(1)
GRE数学考试题型+形式介绍
GRE数学常见问题分析
GRE数学易错题型解析(1-10)
GRE数学最常用的概念罗列
| 不限 |
| 英语教案 |
| 英语课件 |
| 英语试题 |
| 不限 |
| 不限 |
| 上册 |
| 下册 |
| 不限 |