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fresh fish, and butter. After the Civil War, as ice was used to refrigerate freight cars, it alsocame into household use. Even before 1880, half the ice sold in New York,Philadelphia, and Baltimore, and one-third of that sold in Boston andChicago, went to families for their own use. This had become possible because anew household convenience, the icebox, a precursor of the modern refrigerator, had been invented. Making an efficient icebox was not as easy as wemight now suppose. In the early nineteenth century, the knowledge of thephysics of heat, which was essential to a science of refrigeration, wasrudimentary. The commonsense notion that the best icebox was one thatprevented the ice from melting was of course mistaken, for it was the meltingof the ice that performed the cooling. Nevertheless, early efforts toeconomize ice included wrapping the ice 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 andcirculation 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 twentymiles outside the city of Washington, for which the village of Georgetown wasthe market center. When he used an icebox of his own design to transport hisbutter to market, he found that customers would pass up the rapidlymelting stuff in the tubs of his competitors to pay a premium price for hisbutter, still fresh and hard in neat, one-pound bricks. One advantage of hisicebox, more explained, was that farmers would no longer have to travel tomarket at night in order to keep their produce cool. | 
