59 



fertilize; thirdly, we must supply, in the unfertile, the 

 ingredients which it lacks, in order to become the same 

 as the fertile. A perfect soil is composed of many 

 ingredients, such as organic matter, silica, alumina, 

 magnesia, lime, oxide of iron, potash, carbonic acid, etc., 

 etc. Consequently, if potash is wanting, potash must 

 be supplied ; if magnesia is wanting, magnesia must be 

 supplied, etc. 



Organic manner is a sine qua non of fertility, but if 

 more than fifty per cent, be contained in a soil, it be- 

 comes sour, and requires manuring. In a cold climate, 

 color should not be forgotten, as a dark soil will absorb 

 heat better than a light one. Plowed fields loose their 

 covering of snow sooner than meadows. In manuring, 

 therefore, care should be taken that the soil assume a 

 dark appearance. Organic matter administers food to 

 plants through their roots ; consequently, land which 

 has been long cultivated, and scantily manured, becomes 

 poor, through the absorption of organic matter. Organic 

 matter disappears in two ways : 



First. — By sustaining plants, as aforesaid. 



Second. — By decomposition through exposure to the 

 atmosphere ; therefore, it must be artificially supplied, 

 or the land grows poor. 



The best way, when land runs down, is to cultivate 

 crops to be plowed under, such as clover, buckwheat, 

 etc. 



The different soils which appear on the earth's sur- 

 face may be generally classified into three kinds, with 

 their mixtures. They are — 



