PRACTICAL AGRICULTURE. 25 



largest possible quantity of corn from the same plant. — 

 Peculiar methods must be used for the production of 

 nitros^on in the seeds ; others for giving strength to the 

 straw ; and others again, when we wish to give such 

 quahties to the straw as will enable it to bear the weight 

 of the ears. 



We must proceed in the artificial rearing and forcing 

 of plants precisely as we do in the fattening of animals. 

 The llesh of wild animals is devoid of fat, or nearly so. 

 The production of flesh and fat may be artificially in- 

 creased : all domesticated animals are easily fattened. — 

 To do this, we add to the quantity of food, and lessen 

 (as in the stall-fed ox) the waste occasioned by the in- 

 creased action of the lungs, (as consequent upon motion,) 

 together with the waste which such muscular exertion 

 uould produce by increased action of the skin. 



Arable land is originally formed by the crumbling of 

 rocks, and its properties depend on the nature of its com- 

 ponent parts. 



Sand, clay, and lime, are the names given to the prin- 

 cipal constituents of the different kinds of soil. 



Pure sand, and pure limestone, in which there are no 

 other unorganized substances except the earth of flint, 

 chalk, or silicic acid combined with lime, form absolutely 

 barren soils. But clay always forms a part of fertile 

 soils. Whence is the origin of clay earths in arable 

 land 7 What are their constituents ? and what part do 

 they play in favoring vegetation ? They are produced 

 by the breaking down of aluminous minerals by the ac- 

 tion of the weather. These minerals are found, mixed 

 with other substances, in granite, mica-slate, porphyry, 

 clay slate, the volcanic rocks, and others. Mountain 

 limestone is remarkable for the quantity of clayey earths 

 which it contains. In grauwacke we find pure quartz, 

 clay slate, and lime; in the sandstones, quartz and 

 loam ; and in the transition limestone there is an inter- 

 mixture of clay, feldspar, and clay slate. These exam- 

 ples may be sufficient. 



It is known that aluminous minerals (that is to say. 

 minerals containing the metal "aluminum," which, com- 



