1.Have you a pair of bellows at home？If you have，I hope that you will examine them carefully，and try to see how they are made，and to understand their use.Perhaps you have heard of the boy who cut the bellows open to see where the wind came from.If you will read what I have to tell you，you will not need to do anything so foolish.
2.A pair of bellows consists of two rounded pieces of thin wood，which are joined together at the edges by a folded piece ofleather.Each board has a short handle by which the bellows can be opened and closed.
3.In the centre of the under or lower board there is a round hole，and if you put your finger into this hole，you can feel that it is closed inside by a looseflap of leather.This leatherflap is called a “valve.”It opensUNDER SIDE OF BELLOWS（风箱底面）
inwards.When you separate the handles of the bellows and make the space inside larger，the outside air forces open the valve，rushes in through the hole，and fills the bellows.
4.But when you push the handles together，the air inside presses down the valve and closes the hole；so that the air has to pass out through the metal spout or “nozzle，”which is placed atthe end of the bellows opposite①to the handles.
5.A valve is somewhat like a trap-door，and is used for allowing②a fluid-usually air or water-to pass through in onedirection but not in the other.You can make a valve by cutting a hole through a bigcork，and then covering the hole with a piece of paper a little smaller than the cork.You must pin down or gum the paper to the cork at one side only.You will then find that you can blow through the hole in the cork in one direction，but not in the other.
6.If you keep your finger inside the hole in the bellows by which the air enters，the bellows will not do their work properly；for when you shut the bellows，the valve cannot close the air-hole because of your finger，and most of the air then escapes through this hole instead of going out through the nozzle.
①Opposite，at the other side or end of.
②Allowing，permitting；giving leave to.
7.Every one knows that we use the bellows to make the fire burn more brightly.But how do they do this ？It is by causing more air to pass among the hot coals.Air is a mixture of several gases，and one of these gases-oxygen -is necessary for making the coals burn.
8.If your mother has no bellows，what does she do when she wants the fire to burn more brightly ？She opens either the door or the window，to let more air into the room，or she stirs the fire with the poker，to let the air pass freely among the coals.
9.Have you ever watched a blacksmith working at his forge①？
He needs a very hot fire to heat the iron bars which he makes into horse-shoes and many other things；and he could not have this without using bellows.If you look carefully，you will see that there is a difference between the bellows of the blacksmith‘s forge and those which you use for your kitchen fire.The air comes out of your kitchen bellows in puffs，but it comes out of the blacksmith’s bellows in a steady stream.
