THE SOIL. 65 



different degrees of hardness. Both of these qualities 

 must affect the character of the soil, but it may be 

 laid down as a rule that, when the rocks of two loca- 

 1'>n$ are exactly alike, the soils formed from them 

 will be of the same natural fertility ', and in propor- 

 tion as the chemical character of rocks changes, in 

 the same proportion will the soil* <7 ///</ in f> /'t'dity. 



In most districts the soil is formed from the rock 

 on which it lies ; but this is not always the case. 

 Soils are often formed by deposits of matter brought 

 by water from other localities. Thus the alluvial 

 b:u iks of rivers consist of matters brought from the 

 country through which the rivers have passed. The 

 river Xile, in Egypt, yearly overflows its banks, and 

 deposits large quantities of mud brought from the un- 

 inhabited upper countries. The prairies of the AVr-t 

 owe their soil chiefly to deposits by water. Swamps 

 often receive the washings of adjacent hills ; and, in 

 these cases, their soil is derived from a foreign source. 



We might continue to enumerate instances of the 

 relations between soils and the sources whence they 

 originated, thus demonstrating more fully the impor- 

 tance of geology to the farmer ; but it would be be- 

 yond the scope of this work, and should be investi- 

 gated by scholars more advanced than those who are 

 studying merely the elements of agricultural science. 



The mind, in its early application to any branch 

 of study, should not be charged with intricate subjects. 

 It should master well the rudiments, before investi- 

 gating those matters which should follow such under- 

 standing. 



