100 1T(,\V C:nOPS FEED. 



which is remarkable for its extraordinary and persistent 

 fertility. The prairies of our own West, the bottom lands 

 of the Scioto and other rivers of Ohio, arc other examples 

 of peculiar soils; while on every farm, almost, may bii 

 found numerous gradations fi-om clay to sand, from ve<^e- 

 table mould to gravel — gradations in color, consistence, 

 composition, and productiveness. 



CHAPTER II. 



ORIGIN AND FORMATION OF SOILS. 



Some consideration of the origin of soils is adapted to 

 assist in understanding the reasons of their fertility. 

 Geological studies give us reasons to believe that what is 

 now soil was once, in chief part, solid rock. We find in 

 nearly all soils fragments of rock, recognizable as such by 

 the eye, and by help of the microscope it is often easy to 

 perceive that those portions of the soil which are impal- 

 TDable to the feel are only minuter grains of the same rock. 



Rocks are aggregates or mixtures of certain minerals. 



Minerals, again, are chemical compounds of various ele- 

 ments. 



We have therefore to consider : 



I. The Chemical Elements of Rocks. 



II. The Mineralogical Elements o.f Rocks. 



III. The Rocks themselves — their Kinds and Special 

 Characters. 



IV. The Conversion of Rocks into Soils ; to wliich we 

 may add : 



V. The Incorporation of Organic Matter with Soils. 



