The combination of natural processes by which soils are formed.
1Finally, the _plants _growing in soils are powerful agents of soil formation.
2The most effective water impurity, considering soil formation, is the gas, _carbon dioxid.
3The second great chemical agency of soil formation is the oxygen of the air.
4We have learnt these things about soil formation.
5While, therefore, the physical agencies of soil formation are most active in arid climates, the same cannot be said of the chemical agencies.
6It is clear, then, that the second great agency of soil formation, which always acts in conjunction with temperature changes, is _freezing water.