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It is evident from what has been said concerning 

 the production of soils from rocks, that there must be 

 at least as many varieties of soils as there are species 

 of rocks exposed at the surface of the earth ; in fact 

 there are many more. Independent of the changes 

 produced by cultivation and the exertions of human 

 labour, the materials of strata have been mixed to- 

 gether and transported from place to place by various 

 great alterations that have taken place in the system 

 of our globe, and by the constant operation of water. 



To attempt to class soils with scientific accuracy, 

 would be a vain labour ; the distinctions adopted by 

 farmers are sufficient for the purposes of agriculture ; 

 particularly if some degree of precision be adopted in 

 the application of terms. The term sandy, for instance, 

 should never be applied to any soil that does not con- 

 tain at least J of sand ; sandy soils that effervesce with 

 acids should be distinguished by the name of calcare- 

 ous 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 of im- 

 palpable earthy matter, not considerably effervescing 

 with acids : the word loam should be limited to soils, 

 containing at least one third of impalpable earthy mat- 

 ter, 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 



