(112') 



tion, or breaking down, from various causes, of rocks. 

 Through the great convulsions of nature this triturated dust 

 is mingled together, so that every species of rock formation 

 is represented in every handful of clay. Were this not the 

 case, we would have over limestone rocks a great mass of 

 unproductive pulverized carbonate of lime ; or over granite^ 

 we would see nothing but the sparkling atoms of quartz and 

 mica, and over each stratum there would be the constituents 

 of that rock, and hence no vegetation would charm the eye 

 or delight the heart, to say nothing of our digestive wants.^ 

 Through the agency of perfectly natural causes (water prin- 

 cipally), the soils have been intimately mingled. By this 

 ■wise provision vegetation in every spot in the world finds 

 some elements necessary to its existence. But it sometimes 

 happens that there is a deficiency of some of the elements^ 

 and again that there is a surplus. In the great alluvial 

 swamps decayed vegetable matters exist to such an extent 

 that some cereals do not thrive well, and on the other hand, 

 on the steep mountain sides, by the action of washing rains, 

 this matter has been carried off. Again, in many sections, 

 the fertile matters have been exhausted, or so nearly so, that 

 the products of the soil cease to be remunerative. It is the 

 province of scientific agriculture to point out these deficien- 

 cies and direct the remedy. 



The soil originally consisted simply of the debris of the 

 rocks or clay. It is composed of the elements of the rocks, 

 together with an intimate admixture of some mineral sub- 

 stances. In limited patches the soil partakes of the charac- 

 ter of the formations underneath. Thus, in iron districts, 

 the soil in places shows the presence, in considerable quan- 

 tities, of iron, making the earth red or brown. In sand- 

 stone countries the clay has a quantity of sand overlying it, 

 and among the primitive rocks scales of mica glisten on 

 every side. The weight of a cubic foot of thoroughly dried 

 soil averages as follows : 



