314 SCIENCE OF AGRICULTURE. Pakx II. 



Sect. II. Classification and Nomenclature of Soils. 



2116. Systeviatic order and an agreed nomenclature are as necessary in the study of 

 soils as in that 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. 



2117. A correct classification of soils may be founded on the presence or absence of 

 organic and inorganic matter in their basis. This will foi-m two grand classes, viz. 

 primitive soils, or those composed entirely of inorganic matter, and secondary soils, 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 car- 

 bonic 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 colour, or texture ; and sub-varieties 

 founded on moisture, dryness, richness, lightness, &c. 



2118. I?i 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, &c. When one earth prevails, the generic 

 name should be taken from that earth, as clayey soil, calcareous soil, &c. ; 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, &c. The great thing is pre- 

 cision 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 which effervesce with acids should be distinguished by the name of calcareous 

 sandy soil, to distinguish them from those that are silicious. The term clayey soil should 

 not be applied to any land which contains less than one sixth of impalpable earthy matter, 

 not considerably effervescing with acids ; the word loam should be limited to soils, con- 

 taining at least one third of impalpable earthy matter, copiously effervescing with acids. 

 A soil to be considered as peaty, ought to contain at least one half of vegetable matter. 

 In cases where the earthy part of a soil evidently consists of the decomposed matter of 

 one particular rock, a name derived from the rock may with propriety be applied to it. 

 Thus, if a fine red earth be found immediately above decomposing basalt, it may be de- 

 nominated basaltic soil. If fragments of quartz and mica be found abundant in the 

 materials of the soil, which is often the case, it may be denominated granitic soil ; and the 

 same principles may be applied to other like instances. In general, the soils, the 

 materials of which are the most various and heterogeneous, are those called alluvial, or 

 which have been formed from the depositions of rivers ; and these deposits may be de- 

 signated as silicious, calcareous, or argillaceous ; and in some cases the term saline may 

 be added as a specific distinction, applicable, for example, at the embouchure of rivers, 

 where their alluvial remains are overflown by the sea. 



2119. In naming the species of soils, greater nicety is required to determine distinctions 

 than in naming the genera ; and there is also some difficulty in applying or devising 

 proper terms. The species are always determined by the mixture of matters, and never 

 by the colour or texture of that mixture which belongs to the nomenclature of varieties. 

 Thus a clayey soil with sand is a sandy clay, this is the name of the species ; if the mass 

 is yellow, and it is thought worth while to notice that circumstance, then it is a yellow 

 sandy clay, which express at once the genus, species, and variety. A soil containing 

 equal parts of clay, lime, and sand, would, as a generic term, be called clay, lime, and 

 sand ; if it contained no other mixture in considerable quantity, the term entire might 

 be added as a specific distinction ; and if notice was to be taken of its colour or degree of 

 comminution, it might be termed a brown, a fine, a coarse, a stiff, or a free entire clay, 

 lime, and sand. 



2r20. The following Table enumerates the m,ore common genera, species, and varieties 

 of soils. The application of the terms will be understood by every cultivator, though to 

 attempt to describe the soils either chemically or empirically (as by sight, smell, or touch), 

 would be a useless waste of time. From a very little experience in the field or garden, 

 more may be gained in the study of soils, than from a volume of such descriptions. This 

 Table corresponds with the nomenclature adopted in the agricultural establishments of 

 Fellenberg at Hofwyl in Switzerland, and of Professor Thaer at Moegelin in Prussia, 

 with the nomenclature employed by Professor Thouin in his lectures at Paris, and in 

 general with that of all the Continental professors. It is therefore very desirable that it 

 should become as generally adopted as that of the Linnean system of nomenclature 

 in botany. The principle of the Table may be extended so as to include any otlier soil 

 whatever. 



