THE SOIIi. G5 



different degrees of hardness. Both of tliese qualities 

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

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

 tions are exactly aliJce, the soils formed from thon 

 will he of the same natural fertility^ and in propor- 

 tion as the chemical character of roclis changes., in 

 the same proportion will the soils differ in fertility. 



In most districts the soil is formed from tlie rock 

 on whicli 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 

 banks of rivers consist of matters brought from the 

 country through which the rivers liave passed. The 

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

 deposits large quantities of mud brought from the un- 

 inliabited upper countries. The prairies of the West 

 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 mattei-s which ^\\ov\(i follow such under- 

 standing. 



