THE ORIGIN OF THE SOIL 5 



5. Wind. — ^The wind does its greatest work in distributing 

 soil, but it has a part in the making of it as well. Where 

 particles of sand are blown against solid rock, the solid 

 part is gradually worn away and becomes soil. The. friction 

 between the rock and the sand which is being blown about 

 has a tendency to rub off pieces, just as is the case in the 

 bottom of the stream. 



From the above we see that there are many agencies at work 

 making soil. These have been working and will continue to 

 work for centuries. It is likely that they are as active now 

 as they ever were and soil is being made just as fast now as 

 it was centuries ago. We shall see in the next chapter how 

 much of the soil is wasted. 



6. Distribution. — The greater part of the soil that we see 

 in the fields has not always been there. In that part of the 

 country which was once covered by glaciers most of the soil 

 has been brought from some . other place. South of the re- 

 gion covered by ice much of the soil has been formed from 

 the rock underlying the region. However, little of the soil 

 lies where it was formed, but has been moved by water and 

 wind. Soils may be divided into two classes: sedentary and 

 transported. Where the natural rock has decayed and the 

 soil has gradually become deeper and deeper we have 

 sedentary soils. Muck soils belong to the sedentary class 

 because they are found in the place where they have been 

 formed. 



Transported soils are found everywhere. Water is one of 

 the greatest agencies in carrying soil from place to place. 

 We see its work along every stream wherever the bank is low 

 enough to allow overflow. When it rains some water gener- 

 ally runs off the sloping parts of the fields and finds its way 



