AIR 



a fresh supply. If we try to stop breathing we 

 begin to choke, and after a very short while we 

 are obliged to give in and draw a deep breath 

 of this air. Animals breathe also ; we can listen 

 to any dog or cat that is lying asleep. They 

 breathe as regularly as we do. We see their 

 sides moving, just as we feel our own sides do. 

 Trees and plants also breathe, although they 

 do it in a different way, and it is more difficult 

 to find out about them. What then is this air 

 we are all breathing ? Certainly it is a very 

 important thing, worth taking a good deal of 

 thought about, for we can none of us live 

 without it. 



Let us go up to a window on a cold day, or 

 take up a piece of glass and breathe out upon 

 it two or three good deep breaths. What do 

 we find ? Tiny drops of water have formed on 

 the surface, and have evidently come out with 

 our breath. If the glass had not been there to 

 catch them they would have gone out into the 

 space around us, as they usually do ; so there 

 must be water in some form in this air, and 

 water also in our breath. Again, let us go 

 into a room where the windows have not been 

 opened for a long time, or a room in which 

 there are a great many people. "What bad 

 air!" we exclaim, and at once open the doors 

 and windows to let in fresh air. Some people 

 will faint if they have to stay long in a hot, 

 close building, and only recover themselves 



(17) 



