vi CONTENTS. 



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 . Pages 232-261 



CHAPTER VI. 



THE DENUDATION OF THE LAND — Continued. 



Denudation aided by recently ejected castings flowing 

 down inclined grass-covered surfaces — The amount 

 of earth which annually flows downwards — The 

 effect of tropical rain on worm-castings — The finest 

 particles of earth washed completely away from 

 castings — The disintegration of dried castings into 

 pellets, and their rolling down inclined surfaces — 

 The formation of little ledges on hill-sides, in part 

 due to the accumulation of disintegrated castings — 

 Castings blown to leeward over level land — An 

 attempt to estimate the amount thus blown — The 

 degradation of ancient encampments and tumuli — 

 The preservation of the crowns and furrows on land 

 anciently ploughed — The formation and amount of 

 mould over the Chalk formation . . 262-307 



