CLASSIFICATION AND DESCRIPTION OF SOILS. 231 



lutely essential to an intelligent understanding and success- 

 ful practice of agriculture as an art. 



But as such a classification may not be intelligible to those 

 who are wholly ignorant of geology, the more common clas- 

 sification of agricultural writers is added, in which no refer- 

 ence is had to the geological origin, but only to the chemical 

 character of the soil. It will be seen that both modes corres- 

 pond in many important particulars, and it is hoped, that the 

 infinite importance of an exact knowledge of soils to the prac- 

 tical farmer, will be a sufficient apology for adopting a method 

 which must necessarily lead to some degree of repetition. 

 Perhaps we ought to urge this as a peculiar excellence, inas- 

 much as each mode will throw light upon the other, and en- 

 able the careful student to obtain a clearer and more com- 

 prehensive view of the subject, than either mode taken by it- 

 self. 



Geological Classification and Description of Soils. 



Geologists make two general divisions of the rocks : 

 1. Stratified, or those rocks which are found in regular lay- 

 ers, like the leaves of a book, and which appear to have been 

 deposited from a mechanical and chemical suspension in wa- 

 ter. 2. Unstratified, or those which have no marks of strata, 

 but appear, from their texture and resemblance to the lava of 

 volcanoes, to have once been in a fused or melted state. The 

 stratified rocks are divided into Aluvium, Diluvium or Drift, 

 Tertiary, Secondary and Primary. Each of these divisions 

 are variously subdivided. The chemical distinction was 

 pointed out page 187. Geologically, then, soils may be di- 

 vided into the five following classes : Alluvial, Diluvial, Ter- 

 tiary, Secondary and Primary soils. 



I. Alluvial soils. These are of two kinds ; those formed 

 by rivers, and those resulting from peat-swamps, or growing 

 vegetables. 



1. Alluvial soil of rivers consist of particles of every kind 



