英国学生科学读本 第94期:一副风箱(1)

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　　Have you a pair of bellows at home? 你的家里是否有一副风箱呢?

　　If you have, I hope that you will examine them carefully, and try to see how they are made, and to understand their use. 如果有的话, 希望你能够仔细观察它的构造并了解它的用途。

　　Perhaps you have heard of the boy who cut the bellows open to see where the wind came from. 也许你听说过, 有的孩子会拆开风箱, 看看这些风到底是从哪里来的。

　　If you will read what I have to tell you, you will not need to do anything so foolish. 如果你看了我的介绍, 就不会做出这样的傻事了。

　　A pair of bellows consists of two rounded pieces of thin wood, which are joined together at the edges by a folded piece of leather. 一副风箱包括两块轻薄的圆形木片, 通过边缘处一片交叠的皮革固定在一起。

　　Each board has a short handle by which the bellows can be opened and closed. 两块木片各有一个短短的把手, 利用把手, 我们可以开闭风箱。

　　In the centre of the under or lower board there is a round hole, 在下方木片的中心位置上有一个圆孔,

　　and if you put your finger into this hole, you can feel that it is closed inside by a loose flap² of leather. 你把手指伸入孔中, 就会感觉到其内部被一个松动的皮革盖板所封闭。

　　This leather flap is called a "valve³. " It opens inwards. 这个皮革盖板就是“阀门”, 它朝里打开。

　　When you separate the handles of the bellows and make the space inside larger, 如果你拉开风箱的把手, 使得内部空间变大,

　　the air outside forces open the valve, rushes in through the hole, and fills the bellows.  外部空气就会迫使阀门打开, 冲出圆孔, 进入风箱内部。

　　But when you push the handles together, the air inside presses down the valve and closes the hole; 然而, 当你将两个把手靠近时, 内部的空气就会压下阀门并关闭圆孔；

　　so that the air has to pass out through the metal spout⁴ or "nozzle, " which is placed at the end of the bellows opposite to the handles. 如此一来, 空气就只能通过把手反方向另一端的金属喷口或者“喷嘴”透出。

　　A valve is somewhat like a trap-door, and is used for allowing a fluid—usually air or water—to pass through in one direction but not in the other. 阀门是一种类似活板门的设施, 通常用于确保流体——一般是空气或水——能够向某一个固定的方向流动。

　　You can make a valve by cutting a hole through a big cork⁵, and then covering the hole with a piece of paper a little smaller than the cork. 你也可以制造阀门：在大木塞上钻一个洞, 然后利用一张比木塞稍小的纸来挡住这个洞。

　　You must pin down or gum the paper to the cork at one side only. 必须将这张纸钉在或者黏贴在木塞的一面。

　　You will then find that you can blow through the hole in the cork in one direction, but not in the other. 随后你就会发现, 你只能从一个方向上通过这个洞向木塞吹气, 而另一个方向则不行。

　　If you keep your finger inside the hole in the bellows by which the air enters, the bellows will not do their work properly; 如果你将手指堵在风箱中空气进出的圆孔上, 风箱就无法正常工作了。

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