56 DEKIVATION OF SOILS. 



other crops taken off'. Above all he must not, as soon 

 as his land is so far recovered that his clover or other 

 green crop begins to be heavy, yield to any temptation 

 to cut it off"; for this is returning to the old system of 

 exhaustion. The object should be to keep the land 

 steadily improving; and to that, for the few first years, 

 all other considerations should give way. When it 

 is fully established as a fertile and well stocked soil, 

 constant watchfulness will keep it in that condition 

 without much expense; and the farmer will soon find 

 that it is far cheaper to cultivate good land and keep 

 it good, than to live on a farm where every thing is 

 taken out and nothing put in. 



SECTION III. OF THE DERFVATION OF SOILS, AND THEIK 

 CLASSIFICATION. 



I have already said that the mineral part of soils is 

 derived from the decomposition or crumbling down of 

 the solid rocks. In every neighborhood may be seen 

 instances of this crumbling down : with some rocks, 

 as granite, it is very slow, scarcely perceptible from 

 one year to another; with others it is more rapid, as 

 some sandstones and limestones; with others still al- 

 most immediate, as some slates which fall to pieces 

 whenever they are brought to the surface. However 

 quickly or slowly this crumbling takes place, a soil is 

 at last made, and of course resembles in its composition 

 that of the rock from which it was formed. 



The greater part of the rocks which appear on the 

 surface of our earth, are varieties of sandstones, lime- 

 stones or clays, or mixtures of the three*. 



1. Sandstone is often known as freestone, and is 

 common in many parts of this country, being a va- 

 luable building material. Our light sandy soils were 



* This is a popular ami not strictly scientific classification, and 

 is to be considered only as a general description. 



