ELEMENTS OF AGRICULTURE, 
7i 
vessel. After this, the residuum is nothing more than 
clay and silica, the weight of which is easily ascertained 
by the scales. Tf we then compare it with the original 
quantity operated on (that is, the hundred grains), the 
difference will be the exact quantity of carbonate of lime 
contained in the marl; for the diminution is occasioned 
by the escape of the carbonic acid gas, besides the lime 
that was expelled with the nitric acid. 
QUESTIONS. 
1. Why do we distinguish several kinds of marl ? 
2. Which are the principal kinds of marl ? 
3. Can we distinguish marl simply by the eye ? 
4. Why has so little marl been employed? 
5. What is the effect of marl applied to lands that do not contain a suffi¬ 
ciency of organic remains ? 
6. What is the effect of marl on the fertility of lands ? 
7. Where does it most abound in the United Slates ? 
8. What is it well to know before using marl? 
9. How do we ascertain the quantity of carbonafe of lime contained in a 
soil ? 
10. What advantage does marl generally possess over lime ? 
LESSON VI. 
MARL AS AN AMELIORATOR (CONTINUED). 
36. In the preceding lesson, we have made known the 
different species of marl, and also the means of distinguish¬ 
ing them. The question now to be examined is, to which 
species of earth is each kind particularly suited ? 
37. In general, as marl is only employed on account of 
the carbonate of lime it contains, it is without effect upon 
calcareous soils, unless the object is an amelioration by 
clay. The action of the farmer, as regards the ameliora¬ 
tion of calcareous as well as other soils, depends upon the 
object that he wishes to attain. 
