英国学生科学读本 Lesson 43 一块粘土(1)
第43课 一块粘土
Do you know where clay comes from? If you take a long walk near the town in which you live, you will very likely find some deep hole or pit in the ground from which men are digging out the stuff we call clay.
你知道粘土是从哪儿来的吗?如果你在居住的城镇附近走上一段很长的路，就很可能发现地上有一些深洞或者深坑，人们就是从这些洞里，把一种叫“粘土”的东西挖出来的。
Clay is found in thick beds or layers in the earth, and we may therefore call it a rock. We may also call it a mineral.
粘土在一些很厚的泥土层中可以找到，我们也可以管粘土叫“岩石”或者“矿物”。
Let us ask the men in the clay-pit to give us a lump of clay. Its colour will most likely be brown. Pure clay is white, but a little red iron-rust is often found mixed with it. As we press the clay between our fingers, we find that we can mould or knead it into any shape we please.
咱们朝挖粘土的人要一块粘土吧。粘土的颜色大部分是棕色的。纯粹的粘土是白色的，但经常混有少量的红色铁锈。我们把粘土放在手指之间捻一下，发现可以把它“塑成”或者“捏成”任何我们想要的形状。
Let us make the clay into a ball. Now let us try to play a game of cricket with our clay ball. We shall soon find that the clay ball will not bounce as the leather ball does.
咱们把粘土团成一个球吧，用这个粘土球来玩玩板球!我们很快就会发现，粘土球不会像皮球那样弹跳。
When we press a piece of clay out of shape, it does not spring back to its old shape again as a ball made of leather or of india-rubber does. We therefore say that clay is not elastic.
我们把一块粘土捏得变形之后，粘土不会弹回原来的形状，而皮子或者天然橡胶做的球，就可以弹回原来的形状。所以我们说，粘土“没有弹性”。
We shall next put our lump of clay in the oven, and let it dry for several hours. The dry clay will break into powder, if we drop it on the ground; so we say that dry clay is brittle.
然后，我们把那个粘土大块，放进炉子里，烤上几个小时。干燥的粘土，一掉到地上就会碎成粉末。所以我们说，粘土很“脆”。
But let us put the dry clay into a saucer half full of water. Soon all the water will disappear, while the clay will become soft once more.
不过，咱们再把干燥的粘土，放进盛了一半水的碟子里。用不了多久，所有的水就都不见了，而粘土又会变软了。
