BOW SOILS ABE MADE 6? 



PART Hl-SoiLS 



CHAPTER XIII.— How Soils are Made 



67. General Definition of Soils. — Many persons im- 

 properly speak of soil as "dirt." Soil may be defined 

 as the finely pulverized portions of the earth's surface 

 in which plants may grow. Dirt means something un- 

 clean or filthy, and the word should never be applied to 

 soil. Soil, it is true, may become dirty, but fresh, pure 

 soil is clean and destroys <lirt and filth. 



Soil, as the word is ordinarily used, refers to only the 

 first C to 12 inches of the earth's surface. The portion 

 below this depth is called the subsoil. There is usually 

 a marked difference between the soil and subsoil. 



Land is made up of soils, rocks, stones, and beds of 

 mineral 01 - are the great beds of hard minerals 



which may often be seen projecting through the soil 

 and sometimes making up whole mountain ranges. Beds 

 of granite, marble, sandstone, and limestone are called 

 rocks. 



Scattered through the soil are coarse, broken frag- 

 ments of the rock masses called -stones. Rocks and 

 stones are made up almost exclusively of mineral mat- 

 id when they decay they form soils. It is hard to 

 realize that the surfaces of rocks, which appear to be 

 almost everlasting, are constantly being worn away to 



