THE AIR 



147 



siderable force, especially if the wind is blowing toward 

 him. Everyone has experienced the force of the wind 

 when he was passing around the corner of a building on 

 a stormy day. You have seen balloons ascend or other 

 objects float in the air. The balloon ascends because it 



does not weigh as much as 

 the air which it displaces. If 

 a pine board is placed at the 

 bottom of a tank of water 

 and then released, it will soon 

 rise to the surface of the 



AIR PUMP 



water. Because the pine board is not so heavy as the 

 water which it displaces, the water forces it to the top. 

 An object which is not as heavy as the air that is dis- 

 placed by it will ascend for the same reason that the 

 board does in the water. These everyday experiences 

 give some evidence that the air is composed of matter. 

 Matter is anything which has weight, and as air has 

 weight it is composed of matter. 



If air has weight then it should be possible to weigh 

 it. Let us see if we can weigh air on scales. Get a 

 rubber bladder from a football or basket-ball, force all 

 the air out of it, and balance it on delicate scales or get 



