322 SYLVA AMERICANA. 



unless in crevices, where they have been washed in by rains ; 

 and in cultivated soils their depth is generally the same as that 

 to which the implements used in cultivation have penetrated. 



Classification and Nomenclature of Soils. 



Systematic order and an agreed nomenclature are as necessary 

 in the study of soils as of plants or animals. The number of 

 provincial terms for soils which have found their way into the 

 books on cultivation, is one reason why so little use can be made 

 of their directions. A correct classification of soils may be 

 founded on the presence or absence of organic or inorganic 

 matter in their basis. This will form two grand classes, viz. 

 primitive soils, or those composed entirely of inorganic matter, 

 and secondary soih, or those composed of organic and inorganic 

 matter in mixtures. These classes may be subdivided into 

 orders founded on the presence or absence of saline, metallic 

 and carbonic matter. The orders may be subdivided into genera 

 founded on the prevailing earths, salts, metals, or carbon ; the 

 genera into species founded on their different mixtures ; the 

 species into varieties founded on color, texture ; and sub-varieties 

 founded on moisture, dryness, richness, lightness, etc. 



In naming the genera of soils, the first thing is to discover the 

 prevailing earth or earths ; either the simple earths as clay, lime, 

 sand, or the particular rocks from which the soil has been 

 produced, as granite, basalt, etc. When one earth prevails, the 

 generic name should be taken from that earth, as clayey soil, 

 calcareous soil, etc. ; when two prevail to all appearance equally, 

 then their names must be conjoined in naming the genus, as clay 

 and sand, lime and clay, basalt and sand, etc. The great thing 

 is precision in applying the terms. Thus as Sir H. Davy has 

 observed, the term sandy soil should never be applied to any soil 

 that does not contain at least seven-eighths of sand ; sandy soils 

 that effervesce with acids should be distinguished by the name 

 of calcareous sandy soil, to distinguish them from those that are 

 siliceous. The term clayey soil should not be applied to any 



