58 Conservation Reader 



aside the dish containing the muddy water and examine 

 what remains in the bottom 6f the dish that once contained 

 • the earth or soil. This is mostly sand, but with it are rough 

 fragments of rock which can be crumbled in the hand. The 

 greater number of the little sand grains are quartz.' Some 

 of them are clear like glass, others are reddish. In this 

 quartz sand are a few grains of iron which the magnet picks 

 out, and a number of scales of yellow mica. 



After standing a few hours the muddy water has become 

 clear, and a deposit of a yellowish substance has collected 

 in the bottom of the dish. We will carefully pour off the 

 water and examine what remains. This fine soft mud we 

 call clay. As it dries and becomes hard it shrinks and 

 cracks, and thus breaks up into little pieces. Clay forms 

 a greater or lesser part of all soil. Clay soil is very sticky 

 when it is wet, as you will be sure to remember if you have 

 tried to walk over it. When soil is formed largely of clay 

 we speak of it as a heavy soil. In the West it is called adobe 

 and is sometimes used in making houses. When adobe 

 soil dries, great cracks form in it. These cracks are some- 

 times large enough for small animals to fall into. When 

 there is a large amount of sand, we speak of the soil as light 

 or sandy. A soil composed of sand and clay is sometimes 

 called loam. If it is nearly all clay it is a clay loam; if there 

 is much sand it is a sandy loam. 



Soils found in low, swampy places are sometimes formed 

 almost wholly of decaying vegetable matter. Such soils 

 are known as peat soils. They are usually very fertile. 



We have now learned about three things that the soil 

 contains that are bulky and easy to discover : decaying 

 vegetation, sand, and clay. These are, however, far from 



