Tham khảo tài liệu 'reading knowledge 5', ngoại ngữ, anh ngữ phổ thông phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | D A good scientist needs to be creative Questions 11-21 By the mid-nineteenth century the term icebox had entered the American language but ice was still only beginning to affect the diet of ordinary citizens in the United States. The ice trade grew with the growth of cities. Ice was used in hotels Line taverns and hospitals and by some forward-looking city dealers in fresh meat fresh 5 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 the ice sold in New York Philadelphia and Baltimore and one-third of that sold in Boston and Chicago went to families for their own use. This had become possible because a new household convenience the icebox a precursor of the modern refrigerator had been invented. 10 Making an efficient ice box was not as easy as we might now suppose. In the early nineteenth century the knowledge of the physics of heat which was essential to a science of refrigeration was rudimentary. The commonsense notion that the best icebox was one that prevented the ice from melting was of course mistaken for it was the melting of the ice that performed the cooling. Nevertheless early efforts to 15 economize ice included wrapping the ice in blankets which kept the ice from doing its job. Not until near the end of the nineteenth century did inventors achieve the delicate balance of insulation and circulation needed for an efficient icebox. But as early as 1803 an ingenious Maryland farmer Thomas Moore had been on the right track. He owned a farm about twenty miles outside the city of Washington for 20 which the village of Georgetown was the market center. When he used an icebox of his own design to transport his butter to market he found that customers would pass up the rapidly melting stuff in the tubs of his competitors to pay a premium price for his butter still fresh and hard in neat one-pound bricks. One advantage of his icebox Moore explained was that farmers
