详情

　　今天小编为备考英语四级的同学们整理了英语四级听力美文，希望可以为大家带来帮助，一起来看看吧。
　　英语四级听力美文第53篇:The Origin of the Refrigerators
　　By the mid—nineteenth century, the term icebox had entered the American language, but icewas still only beginning to affect the diet of ordinary citizens in the United States. The ice tradegrew with the growth of cities. Ice was used in hotels, taverns, and hospitals, and by someforward—looking city dealers in fresh meat, fresh fish, and butter. After the Civil War (1861-1865), as ice was used to refrigerate freight cars, it also came into household use. Even before 1880 half of the ice sold in New York, Philadelphia, and Baltimore, and one—third of that sold inBoston and Chicago, went to families for their own use. This had become possible because anew household convenience, the icebox, a precursor of the modern refrigerator, had beeninvented. Making an efficient icebox was not as easy as we might now suppose. In the earlynineteenth century, the knowledge of the physics of heat, which was essential to a science ofrefrigeration, was rudimentary. The commonsense notion that the best icebox was one thatprevented the ice from melting was of course mistaken, for it was the melting of the ice thatperformed the cooling. Nevertheless, early efforts to economize ice included wrapping up theice in blankets, which kept the ice from doing its job. Not until near the end of the nineteenthcentury did inventors achieve the delicate balance of insulation and circulation needed for anefficient icebox. But as early as 1803, an ingenious Maryland farmer, Thomas Moore, hadbeen on the right track. When he used an icebox of his own design to transport his butter tomarket, his butter, still fresh and hard in neat, was worth one—pound a brick. One advantageof his icebox, Moore explained, was that farmers would no longer have to travel to market atnight in order to keep their produce cool.