朗文3L看听学英语第四册 Lesson 47

（单词翻译）

　　Lesson 47 Television Day: The sea
TV Commentary¹:
If you looked at the Pacific from a space-capsule you might think that the world was all water. You would hardly be able to see any land at all. Water covers most of the earth's surface.
The sea contains a large number of substances, besides common salt. If you boiled away some sea-water, you would find over forty different materials. For instance², out of a cubic mile of water you would get ninety-four tons of silver and three tons of gold! If it were possible to do this, it still wouldn't be worth the trouble. It would cost more to obtain these precious metals than they are worth. But the sea provides us with a great many materials which we can obtain easily and which we use a lot. For instance, we use huge quantities of sand in industry to make glass, detergents³ and cement⁴.
Besides materials like salt and sand, we obtain a great deal of food from the sea. One day we may even have undersea farms. We have hardly begun to explore the sea. In some ways it is less familiar than outer space.