CHAPTER NINE 



THINGS OF WHICH SOIL IS MADE 



Let us take a spadeful of soft, dark earth from the garden 

 and see if we can find of what it is made. 



We will first put the earth in a dish of water and stir it 

 thoroughly. We notice that the water at once becomes 

 muddy and that little particles of a dark substance rise to 

 the surface. These particles appear to be pieces of stems 

 and leaves. 



This crumbHng vegetation is peat, a substance which fills 

 many swamps and, when cut into blocks and dried, is used 

 for fuel. When scattered through the earth peat has a very 

 different use. As the leaves and stems. of plants die and 

 slowly mingle with the earth, they give it the dark color, 

 which usually extends down for two or three feet. As this 

 vegetation changes, or decays, as we usually say, it fur- 

 nishes a number of substances which supply food to the 

 roots of growing plants. One of the most important of 

 these is nitrogen, an invisible gas. 



The decaying vegetation which we find mixed with the 

 soil has other uses. It holds water and so helps to keep the 

 soil moist. It makes the soil loose and more easy to culti- 

 vate. It absorbs heat from the sun and so helps to warm 

 the soU. This vegetable matter, when it is completely de- 

 cayed, we call humus. Soils that are rich in humus are 

 usually very fertile. 



We will now turn the muddy water into another, dish, 

 pour more clear water upon the material that remains in 

 the bottom of the dish, and wash it again, repeating the 

 work until the water is no longer muddied. We will set 



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