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 burning was 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.
To get some idea of the difficulty of starting fires, imagine yourself shipwrecked like Robinson Crusoe upon an uninhabited island. To build a fire, the first condition would be met by collecting some wood. The second condition would be no problem as air is always present to support combustion. The third condition, raising the fuel to its kindling temperature, would offer a real difficulty. Two methods have been used. The first is to employ the heat of friction caused by rubbing two dry sticks together. This sounds simple, but much skill and practice are essential to the success of this operation. The second method is to make sparks by striking two pieces of flint together. This may work if the operator is persistent and if his fuel is sufficiently fine and dry. But before he succeeds in getting a fire started by either method, our Robinson Crusoe will do some thinking about the usefulness of the common match.
英语四级备考:选词填空之带项检查
大学英语四级备考:仔细阅读题型简介
12月大学英语四级冲刺精讲-选词填空篇(5)
12月英语四级阅读冲刺练习及答案(4)
12月大学英语四级冲刺精讲-长篇阅读篇(4)
大学英语四级备考:长篇阅读样题分析
6月大学英语四级备考:选词填空技巧二
大学英语四级备考:选词填空技巧六
大学英语四级备考:仔细阅读如何出奇制胜
12月英语四级阅读冲刺练习及答案(2)
英语四级备考:选词填空之综合解题
英语四级备考:选词填空之解题方法
高频短语大盘点 聚焦12月英语六级考试阅读
12月大学英语四级冲刺精讲-长篇阅读篇(1)
12月大学英语四级冲刺精讲-仔细阅读篇(1)
大学英语四级备考:选词填空技巧四
12月英语四级阅读遇到不会题目怎么办
12月英语四级阅读冲刺练习及答案(6)
12月英语四级阅读冲刺练习及答案(5)
大学英语四级备考:选词填空技巧五
12月英语四级阅读强化训练(7)
12月大学英语四级冲刺精讲-仔细阅读篇(4)
大学英语四级备考:仔细阅读解题步骤
大学英语四级备考:长篇阅读题型概览
大学英语四级备考:长篇阅读答题技巧
12月英语四级段落信息匹配题强化训练(3)
12月英语四级阅读冲刺练习及答案(8)
12月大学英语四级冲刺精讲-选词填空篇(2)
12月英语四级阅读冲刺练习及答案(1)
12月大学英语四级仔细阅读考前充电
不限 |
英语教案 |
英语课件 |
英语试题 |
不限 |
不限 |
上册 |
下册 |
不限 |