英文科学读本 第一册·Lesson 12 Clay—Its Uses Ⅰ
Lesson 12 Clay—Its Uses Ⅰ
I never knew till today, said Fred, "what a useful thing clay is. It is useful because it is pliable."
You know we made a saucer and a basin with our pieces of clay?
Yes, said Norah, "here they are. I put them on the shelf."
Do you know, he said again, "that all our saucers and basins, and cups and jugs, and plates and dishes, are made of clay too?
Yes, and so are the bricks and tiles and chimney-pots for building our houses, the drainpipes for taking away waste, and the flowerpots for our gardens.
All these things are made of clay. Clay is earth. This is why we sometimes call the things earthenware.
What a useful substance clay is, said Norah. "I suppose all these things are molded into the right shape while the clay is moist and pliable. But how are they made hard, like this plate?"
They have to be baked in very hot ovens. said Fred. "Bricks, after they are molded, are piled in a great heap, and a big fire is made in the middle of them. This fire is kept burning for weeks. When the baking is over, the things are hard and firm, and will always keep their shape."
If we drop the cups and saucers on the floor they break into pieces. They are brittle as well as hard. The moist clay was not brittle, for we could throw it down, or even strike it with a hammer, without breaking it.
Did the baking make it brittle, Fred?
Yes, it did, said Fred, "and it did something more. The moist clay was pliable. But could I mold this piece of flowerpot into any other shape?"
No, said Norah.
Willie, who had been very quiet for some time, joined in now and said, "Don't forget, Norah, that the clay, after it is baked, will never be pliable again."
SUMMARY
Cups and saucers, plates and dishes, basins and jugs are made of clay; and so are bricks, tiles, chimneypots, and flowerpots. We call these things earthenware. While the clay is moist and pliable, the men mold it into the proper shape for all these things, and then bake them in hot ovens till they are hard.
