Bacteria can make foods go bad. This is true of cooked foods as well as fresh foods. The problem is especially dangerous when the air around food is warm. High heat kills bacteria. But warm, wet conditions help bacteria grow.

细菌能使食物变坏。这对于熟食和新鲜食物都是如此。当食物周围的空气很温暖时，这个问题尤其危险。高温杀死细菌。但温暖潮湿的环境有助于细菌生长。

So, the best way to protect food is to keep it in a cool place. There are several ways to keep food cool without the need for electricity. Some refrigerators, for example, are powered by gasoline motors.

所以，保护食物最好的方法就是把它放在凉爽的地方。有几种方法可以使食物保持凉爽而不需要电力。例如，一些冰箱由汽油发动机驱动。

There are less costly ways than refrigeration to keep food cool. An ice box is a simple device. It is made mostly of wood. The inside walls are covered with metal. A big piece of ice is placed in the bottom. Millions of homes had ice boxes until refrigerators became common in the nineteen forties.

有比冷藏更省钱的方法来保持食物的凉爽。冰盒是一种简单的设备。它主要由木头制成。里面的墙被金属覆盖着。一大块冰被放置在底部。在20世纪40年代冰箱普及之前，数以百万计的家庭都有冰盒。

An ice box will keep food from spoiling for several days if the outside temperature is not too warm. If the box is kept out of sunlight, the ice will last longer.

如果外面的温度不太热，一个冰盒可以防止食物腐烂几天。如果把盒子放在阳光下，冰就会变长。

Probably the best method to keep food cool without electricity is a device called the evaporative cooler. Evaporation is the natural change of water from liquid to gas as the water mixes back into the atmosphere. An evaporative cooler is easy to make. And it does not need ice.

如果没有电，保持食物凉爽的最好方法可能是一种叫做蒸发冷却器的装置。蒸发是水从液体到气体的自然变化，因为水又回到了大气中。蒸发式冷却器很容易制造。它不需要冰。

One common evaporative cooler is built as a tall box. Food is kept on several shelves inside. The shelves are made from pieces of metal with many small holes. All four sides of the box are covered with thick cloth. A container of water is placed at the bottom. Another container of water is placed at the top.

一个普通的蒸发冷却器是作为一个高盒子建造的。食物被放在里面的几个架子上。这些架子是用有许多小孔的金属片做成的。盒子的四面都铺上厚厚的布。一容器的水放在底部。另一个容器的水被放置在顶部。

The top and bottom of each piece of cloth is placed in the water. This keeps the cloth wet.

每一块布的顶部和底部都放在水里。这把布弄湿了。

Put the cooler out in the open air, but not in the sun. Air will pass through the wet cloth. This keeps the inside of the box several degrees cooler than the outside air temperature. And this is often just cool enough to keep foods fresh.

把冷却器放在室外，但不要放在阳光下。空气将穿过湿布。这使得盒子的内部温度比外面的温度低几度。而这通常只是为了让食物保持新鲜。