126 THE CULTURE OF FARM CROPS. 



Basalt Hornblende. Syenite Hornblende. 



Silica 42.24 45.69 



Alumina 13.92 12.18 



Lime 12.24 13.83 



Magnesia 13.74 18.79 



Oxide of iron 14.59 7.32 



Oxide of Manganese 0.33 0.22 



Fluoric acid 1.50 



97.06 99.53 



, This variety of granite is distinguished by the absence of 

 potash and the presence of lime in notable quantity. 



Granite also contains a number of other minerals in veins, 

 or scattered through the mass. Among the most important 

 of these are apatite or phosphate of lime; marble or crys- 

 tallized carbonate of lime ; tourmaline ; epidote and cryso- 

 lite. These furnish to the soil the phosphoric acid, which 

 is indispensable for vegetable life and growth, and contrib- 

 ute lime, magnesia, potash and soda as well. Where these 

 minerals abound, the soil is fertile and bears abundant crops. 

 The greater parts of New England ; northern New York ; 

 eastern Canada; Pennsylvania, parts of New Jersey, West 

 Virginia and southward along the mountains and eastward 

 to their feet, are covered with soil produced by the decom- 

 position of this class of rocks and prove by the high culture 

 and value of the soil, how well it is furnished w r ith the ele- 

 ments of plant food. 



The same may be said of all the other rocks of this class; 

 which consist of similar minerals varying more or less in 

 proportion. This variation naturally has an effect upon 

 the character of the soils derived from these rocks. For 

 when phosphoric acid is deficient, no surplus of other ele- 

 ments will make up a fertile soil ; and when the lime or 

 potash has been washed from the soil on the higher lands 

 into the valleys, the sandy land which remains has no good 

 quality to attract the husbandman. 



The most fertile soils are those derived from the decom- 

 position of limestone rocks. When the traveller across the 

 < o:i:inent passes the Appalachian mountains, he enters the 

 .grand valley of the Mississippi and Missouri rivers, and 

 traverses a vast region of the utmost fertility, renowned as 



