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“I never knew till today,” said Fred, “what a useful thing clay is. It is useful because it is plastic. 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 drain-pipes for taking away waste, and the flower-pots 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 moulded into the right shape while the clay is moist and plastic. But how are they made hard, like this plate?”
“They have to be baked in very hot ovens,” said Fred. “Bricks, after they are moulded, 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 in 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 plastic. But could I mould this piece of flower-pot 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 plastic again.”
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