Each of us drinks about three pints of fresh water every day, and we use a great deal of water for washing, for cooking, and for other purposes. 我们每个人每一天都会饮用3品脱左右的淡水, 而日常生活中的清洗、烹饪与其他诸多活动都离不开用水。

　　Where does all this water come from? 这些水都是从哪里来的呢?

　　In some places we get water from wells, and in other places from rivers or lakes. 在有些地方, 人们从井中取水, 而在另外一些地方, 人们从河流或湖泊中取水。

　　But from whatever source we get the water, it is quite certain that at one time or another it must have fallen from the clouds as drops of rain. 然而, 无论我们从哪里取水, 可以肯定的是, 天上的云朵时不时就会降下雨水。

　　Have you ever been in a cloud? 你看到过云朵吗?

　　Perhaps you have climbed to the top of a high hill, and have seen a white cloud come scurrying towards you, 也许你曾经爬到山峰之上, 看到一块白云快速朝你飘来,

　　till it has covered the hill-top and everything above, below, and around you. 直到它将山顶与周围空间中的万物, 包括你在内, 全部包裹起来。

　　The cloud was no longer white, but of a dull grey colour, like the mistwhich we see on a foggy morning. 这时, 云朵不再是白色, 它变成了昏暗的灰色, 就像是朦胧的清晨时分天空的那层薄雾。

　　Indeed a fog is simply a cloud resting on the ground. 实际上, 雾气就是落在地面上的云朵。

　　But what are the clouds made of? 然而, 云朵究竟由什么构成呢?

　　They are just like the clouds of white steam, as we call it, that you see rising from a boiling kettle. 其实, 它们与那些从沸腾的水壶中冒出的白色水蒸气一样。

　　The white steam and the clouds are both composed of extremely small specks of water, so small that they have been called water-dust. 白色蒸汽与云朵均是由很小的水粒构成, 因为它们的体积实在太小, 所以我们称之为水雾。

　　When a number of these water-specks join together, they form a drop of rain, 当许多水粒凝聚在一起时, 它们就变成了雨滴。

　　and then the weight of this rain-drop makes it come pattering quickly to the earth. 随后, 雨滴的重量使得自己迅速落到了地面。

　　How did all this water which forms the clouds and the rain get into the air? 这些构成云朵和雨水的水分是怎样进入到空气中的呢?

　　It was evaporated by the heat of the sun from the surface of the oceans and seas, and rivers and lakes. 它们由海洋、河流与湖泊表面的水在太阳热量的作用下蒸发而成。

　　Three-quarters of the surface of the great globe on which we live is covered with water. 在我们生活的这个巨大星球中, 四分之三的表面都被海水所覆盖。