150 CHILDREN'S GARDENS 



gives a pumping effect to the air in the soil, and 

 helps to keep it moving and changing around the 

 plant roots. This can be illustrated by placing a small 

 square of paper under the fingers, and blowing hard 

 through one of the spaces between the fingers. While 

 the blowing is continued, part of the pressure will be 

 removed from the top of the paper, and the pressure 

 of the air below it will hold it against the hand. As 

 soon as the blowing stops, the paper will fall. An- 

 other way is to make a sucker. Boys are familiar 

 with making use of the washer of soda water bottles 

 by putting a screw through the hole, and sticking this 

 against windows or walls. This, or a larger piece of' 

 rubber, may be used for this experiment, and by using 

 one with several square inches of surface and slightly 

 wet, and pressing it down firmly so that there is no 

 air under it, quite a heavy weight may be lifted, and 

 held so long as no air gets under the sucker. A piece 

 of heavy glass will usually give the smoothest surface 

 and best results, but a piece of old chinaware or tin 

 plate will also serve. This can be held on the floor 

 between the feet, and the children can try to pull 

 the sucker loose. This will give them a very definite 

 idea of how hard the air presses downward, when 

 there is no air on the opposite side to press upward. 



It is this air and the carbon in it, which the leaves 

 and the sunlight make into the wood of the trees, and 

 the flowers and fruits, and perfumes and beautiful 

 colors of the plants. 



The need for fresh air and sunlight does not seem 



