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Bird's-eye View of Covered Homestead. 



AGRICULTURE. 



MAN is the sole inhabitant of the earth that 

 selects, for the purposes of cultivation, 

 other plants than what the soil naturally brings 

 forth. The spontaneous growth of nature afford- 

 ing but a limited quantity of food for man, he 

 supplements the supply by capturing the wild 

 animals, which often feed upon what is unsuited 

 for his sustenance. But even in the most favour- 

 able circumstances, a given area of territory can- 

 not maintain many of the human family, so long 

 as they depend upon the natural vegetation or on 

 the chase. It is only after those plants which 

 yield man an abundant supply of food are made 

 the objects of cultivation, that population aug- 

 ments, and civilisation begins. 



In temperate latitudes, the cereals, or corn- 

 bearing grasses, have always been the chief 

 plants from which civilised man has drawn his 

 subsistence. But excepting in a very few spots, 

 none of these are found growing in a wild state. 

 To give full possession of the ground to the 

 cereals, man must wage a perpetual warfare with 

 the indigenous plants which are ever ready to 

 spring up and occupy the ground. 



It was a profound observation of Adam Smith, 

 that 'the most important operations of agri- 

 culture seem intended not so much to increase, 

 though they do that too, as to direct the active 

 fertility of nature towards the production of the 

 plants most profitable to man. A field overgrown 

 with briers and brambles may frequently produce 

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as great a quantity of vegetables as the best culti- 

 vated vineyard or cornfield. Planting and tillage 

 regulate, more than they animate, the active fer- 

 tility of nature.' To yield such results, the 

 plants of nature must possess certain advantages 

 over those which man cultivates. To comprehend 

 the nature of these differences in the requirements 

 of plants, and to enable us more readily to under- 

 stand the philosophy of the practices of agricul- 

 ture, the sciences connected with that art will each 

 shortly occupy our attention. 



CHEMISTRY OF AGRICULTURE. 



The elementary substances occurring in plants, 

 whether wild or cultivated, are oxygen, hydrogen, 

 nitrogen, carbon, sulphur, phosphorus, chlorine, 

 iodine, bromine, fluorine, potassium, sodium, cal- 

 cium, magnesium, aluminum, silicium, iron, man- 

 ganese. These eighteen elements are rarely all 

 combined in one plant It is supposed that certain 

 of them can be substituted for one another. Thus, 

 sodium and potassium, being somewhat similar in 

 their nature, are sometimes found in varying pro- 

 portions in the same kinds of plants that have 

 grown on different soils. But the presence of 

 many of them is indispensable, and there can be 

 no substitution in their case. In this position 

 stand the first-named six elements. 



The principal mass of all plants is made up of 

 oxygen, hydrogen, nitrogen, and carbon. When 



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