ELEMENTS OF AGRICULTURE, 
73 
wet. Though calcareous substances correct the defects 
of lands that retain water, it is when these defec.ts pro¬ 
ceed from their composition, and not from their situation. 
45. It is generally in autumn that marl is hauled upon 
the land, because then it becomes rapidly friable from the 
effects of rain and frost, and can be more easily and evenly 
spread. 
QUESTIONS. 
1. Does marl agree with calcareous soils ? 
2. What species of marl should be employed on calcareous soils ? 
3. What species should be used on gravelly and sandy lands ? 
4. Should marl be used in large quantities on light lands ? 
5. To what soil is marl, properly so called, best adapted 1 
6. Is a marly soil fertile in itself 1 
7 . Are there certain plants that by their presence indicate the existence 
of marl ? 
8. On what does the action of marl depend ? 
9. On what does the quantity of marl to be employed depend ? 
10. Does marl improve wet lands ? 
11. At what time is marl usually hauled out! 
LESSON VII. 
CLAY AND SAND AS AMELIORATORS. 
46. It is important here to correct an error frequently 
met with in works that treat of the improvement of the 
soil. Almost all of them recommend clay as an amelio 
rator of sandy soils, and sand for clay soils. Here again 
practice is in contradiction to theory, and has proved that 
clay and sand can not serve as ameliorators one to the 
other, as they will not combine; or at least they do so 
with great difficulty. 
47. Let us examine the effect that each of these bodies 
is destined to produce upon the different soils. Sand 
ought to act upon soils in which clav predominates; for 
7 
