Book III. CLASSIFICATION OF SOILS. 311 



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 mix- 

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

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



2068. 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 thg 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 preci- 

 sion 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 land which contains less than one sixth of impalpable 

 earthy matter, not considerably effervescing with acids ; the word loam should be limited 

 to soils, containing 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 de- 

 composed matter of one particular rock, a name derived from the rock may with pro- 

 priety be applied to it. Thus, if a fine red earth be found immediately above decom- 

 posing basalt, it may be denominated 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 deposi- 

 tions of rivers ; and these deposits may be designated as siliceous, calcareous, or argil- 

 laceous ; 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. 



2069. 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 color or texture of that mixture which belongs to the nomenclature of varieties. 

 Tlius 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, tlien it is 

 a yellow sandy clay, which express at once the genus, species, and variety. A soil con- 

 taining 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 color 

 or degree of comminution, it might be termed a brown, a fine, a coiarse, a stiff, or a free 

 entire clay, lime, and sand. 



2070. The following Table enumerates the more 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, of Professor Tbaer at Mcegelin in Prussia, of 

 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 Linnasan system in botany. The principle of the table may be extended so 

 as to include any other soil whatever. 



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