随着一声『土地公公到』,天上掉下个馅饼砸到你头上,
你获得了『土地公公』赠送金钱41个M。
30 The origin of Refrigerators
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, taverns, and hospitals, and by
some forward-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 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.
Making an efficient icebox 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 economize ice
included wrapping up 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, and ingenious Maryland farmer, Thomas Moore, had
been on the right track. He owned a farm about twenty miles outside the
city of Washington, for 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 would no longer have to
travel to market at night in order to keep their produce cool.