ELEMENTS OF AGE [CULTURE. 
33 
QUESTIONS. 
1. What is the soil 
2. What is the sub-soil ? 
3. May the depth of the soil be increased ? 
4. Intc how many classes do we divide the constituents of the soil ? 
5. That a soil may be fertile, what is necessary ? 
6. What is the defect in too rich a soil ? 
7. How is the vegetation in a poor soil ? 
8. What are the qualities to the value of a soil ? 
9. Can a soil be classed according to the relative proportion of its consti& 
rent parts ? 
10 Which is the best way to determine the value of a farm ? 
LESSON II. 
THE MINERAL PARTS OF THE SOIL. 
8. As we have before said, the soil is composed of some 
substances of mineral and others of vegetable and anima] 
origin. These last accrue from the organic remains of the 
vegetable and animal kingdoms, and are decomposed upon 
and under the surface of the earth, or have been thrown 
upon the fields by the cultivator. That they may produce 
a proper effect, it is necessary that they should be mixed 
with mineral substances ; for alone they would be injurious 
to plants, as they would render vegetation too active. 
9. Among the mineral substances that enter into the 
composition of soils, and those that are the most frequently 
found, and in the greatest quantity, are, silex , or siliciom 
sand ; alumine ; and the carbonate of lime.* 
10. The other bodies that also enter into the composi¬ 
tion of the soil, but less frequently and in less quantity, 
are, sulphate of lime,f or plaster ; carbonate of magnesia?; 
* Carbonate of lime is formed by the union of carbonic acid with oxyde 
of calcium, or with lime. All bodies thus formed by the union of an acid 
and an oxyde, take, as we have said before, the name of a salt. 
t A salt formed by the union of sulphuric acid and lime- 
l 
