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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 agri- 
culture ; 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 contain at least g 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 sili- 
ceous. The term clayey soil should not be applied 
to any land which contains less than £ of impalpa- 
ble 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 a decomposed 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 decomposing basalt, 
it may be denominated basaltic soil. If fragments 
of quartz and mica be found abundant in the mate- 
rials 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 
