230
DISINTEGRATION
Chap. V.
CHAPTER V.
THE ACTION OF WORMS IN THE DENUDATION OF THE LAND.
Evidence of the amount of denudation which the land has undergone—Subaerial denudation—The deposition of dust—Vegetable mould, its dark colour and fine texture largely due to the action of worms—The disintegration of rocks by the humus-acids—Similar acids apparently generated within the bodies of worms—The action of these acids facilitated by the continued movement of the particles of earth—A thick bed of mould checks the disintegration of the underlying soil and rocks. Particles of stone worn or triturated in the gizzards of worms—Swallowed stones serve as mill-stones—The levigated state of the castings—Fragments of brick in the castings over ancient buildings well rounded. The triturating power of worms not quite insignificant under a geological point of view.
No one doubts that our world at one time consisted of crystalline rocks, and that it is to their disintegration through the action of air, water, changes of temperature, rivers, waves of the sea, earthquakes and volcanic outbursts, that we owe our sedimentary formations. These after being consolidated and sometimes
