英文科学读本 第二册·Lesson 01 Porous Bodies

Lesson 01 Porous Bodies

Fred and Willie came home very proud from school one afternoon. "What do you think, Norah?" said Fred. "We have both been put up into the next class. Teacher picked out a few of the best boys to go up. I am so glad Will was put up with me."

And only think, Norah, said Willie. "We shall still have our jolly object lessons. We had a lesson this afternoon about porous bodies. Shall we tell you all about it, Norah?"

Oh, do, please. said Norah.

Well then, said Fred, "you must first tell us all the porous bodies you can remember."

Oh yes, said Norah. "Sponge, bread, sugar, chalk, dry clay, charcoal, and coke are all porous. They all suck up liquids into their pores."

Quite right, said Fred. "Now watch me. This is a tumbler about half-full of turpentine. This piece of cane has been standing in the tumbler a few minutes. See what happens when I put a match to the top of the cane."

Why, it bursts into a flame at once, said his sister. "How is that?"

I'll show you, said Fred, "just as teacher showed us. Look at the holes in the bottom of the cane."

Then I suppose, said Norah, "the pores of the cane absorb the turpentine, and take it up to the top."

That's just it, said both the boys. "The cane is porous. "

Now look here. Do you know what this is? said Fred.

It is a piece of the wick of the lamp, said Norah.

See, said Fred, "I will dip it into this water. Now when I take it out and squeeze it, some water runs out of it. What does that prove, Norah?"

It proves, said she, "that the wick is porous, and that it absorbs liquids."

Quite right, said Fred.

Now think of the wick in the lamp itself. The lower part of the wick is in the oil, but it is the upper part that gives the light.

Oh, I think I see, said Norah, "The wick must be something like the cane. I suppose it absorbs the oil, and carries it up to the top, where it burns."

That is right, Norah, said Willie, "And a candle burns in the same way. The heat melts the tallow into a liquid. The wick absorbs the liquid tallow, and carries it up to the top, where it burns."

SUMMARY

Porous bodies absorb liquids. Turpentine rises through the pores of the cane and burns at the top. The wicks of the candle and the lamp are porous. The tallow and the oil rise through the pores of the wick and burn at the top.