Page:The Formation of Vegetable Mould through the Action of Worms (1881).djvu/12

vi 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 millstones—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

CHAPTER VI.

THE DENUDATION OF THE LAND—continued.