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physical properties of their source very necessary 

 before we can fully understand the various opera- 

 tions of husbandry, and their relation to the nutri- 

 tive processes of plants. 



A soil, to be capable of developing vegetable 

 life, must, of necessity, not only contain all those 

 substances which we have found to constitute 

 the inorganic parts of plant-food, but must 

 contain them in a certain condition in which alone 

 they can be assimilated by the plant. For 

 the mere presence of inorganic plant-food in 

 the soil is not sufficient to make it fertile, even 

 though the quantity may suffice for a thousand 

 harvests ; it is only when these inorganic substances, 

 through the powerful action of heat, moisture, and 

 atmospheric air, have assumed a certain form 

 and condition, that they are able to serve as plant- 

 food. A rock, even when pulverized, will be 

 unable to support vegetable life, although its chemi- 

 cal composition may be the same as of a fertile soil. 



A mere chemical analysis of a soil, therefore, 

 cannot enable us to judge of its quality, and 

 the figures of such analysis can have no value in 

 the eyes of the practical husbandman ; for plants 

 depend for their development upon the physical 

 condition of the soil, and upon a certain physical 

 form of its constituents which is but imperfectly 

 revealed by chemical analysis. This fact cannot 

 be made too widely known, for a firm belief still 



