SOILS. 



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variety of mineral species, generally has all the chemical require- 

 ments of a good soil. 



But we must recollect that the drift material is frequently found 

 assorted according to the fineness of its particles, and that this 

 assorting is sometimes carried to such a degree as to be detrimental 

 to the quality of the material as a soil. A bed of pure clay, or of 

 sand, or of clean gravel will not make a soil of itself, but a 

 mixture of all constitutes the most fertile that we have. The 

 fertility of a soil is, however, not alone conditioned upon its chemi- 

 cal constituents; it depends in a great measure upon its porosity, 

 adhesiveness, and the state of comminution of its molecules. To 

 learn the chemical composition of soils and their molecular structure, 

 analyses of the most complicated kind have been made, which, 

 taking a purely scientific view of the question, are highly interest- 

 ing, but are, practically, of a value not in proportion to the labor 

 and expenditure of time in making them. The soil of one and 

 the same farm, or of a single acre of ground, often differs so much 

 that a few analyses would not give a correct idea of its quality, 

 at least none more correct than could be reached by a superficial 

 examination, so that, in buying a farm, I would advise one rather 

 to rely on the judgment of an experienced farmer than on the re- 

 sults of a chemist's laboratory. 



The good quality of a soil covered by a thrifty vegetation of cer- 

 tain herbs and trees is immediately recognized. The barrenness 

 of a spot, likewise, needs not to be first ascertained by finding out its 

 chemical deficiencies; and, provided we are acquainted somewhat 

 with the elements of vegetable physiology, we will also soon be able 

 to guess at a proper course for its improvement. 



A plant draws a great proportion of its nourishment through its 

 roots from the soil. The roots can only take up nutritive parts when 

 in solution. Easily soluble salts must be highly diluted, or they 

 would injure the plants ; usually soils contain little of these, and the 

 mineral substances composing them are of themselves so insoluble in 

 water that the roots could draw no benefit from them, if by the ad- 

 mixture of humic acid, which almost every good soil contains, the sol- 

 ubility of these substances were not induced. This acid is a brown 

 substance, originating from the decomposition of vegetable matter 

 in the soil. It has the peculiarity of forming with all earths 

 combinations which are soluble in water ; it displaces carbonic 

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