ELEMENTS OF AGRICULTURE. 
4l 
are totally inert and would so remain for centuries, with¬ 
out encouraging vegetation. Carbonate of lime possesses 
the property of decomposing a. 1 these remains, and of ren¬ 
dering them fit to serve the nutrition of plants. It also 
destroys the acidity of certain soils. We shall, however, 
jave occasion to recur to the effect of mineral manures. 
38. Certain plants seem to prefer calcareous to all othe- 
soils, as sainfoin and lucerne, both forage plants. The fa¬ 
mous vineyards of Champagne are on a soil eminently cal- 
eareous. 
39. Potatoes, turnips, beets, cabbages, Jerusalem arti¬ 
chokes, grow finely in calcareous soils; as do peas, com, 
barley, tobacco, etc. 
QUESTIONS. 
1. What is the composition of carbonate of ilme 1 
2. What is understood by calcareous earth ? 
3. What is the effect of too much carbonate of lime ? 
4. What the effect when it exists in the right proportion ? 
5. What are the calcareous substances most commonly met with ? 
6. What occurs when carbonate of lime is exposed to the action of he£3 s 
7. What is the effect of calcareous substances upon the soil when th ’f 
are rendered friable by frost ? 
8. In what state must the carbonate of lime be to produce the prop- ' 
effect 1 
9. What is the effect of carbonate of lime on clay soils ? 
10. On soils containing- organic remains of difficult decomposition ? 
11. On acid soils ? 
12. What plants prefer calcareous soil 1 
LESSON VI. 
PLASTER, MARL, MAGNESIA, IRON. 
40. Among the mineral substances that enter into t>*. 
composition of soils, there are some of more rare occur¬ 
rence, and in smaller quantitv, than silica and claf 
4 # 
