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 . Page 230—258 



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 

 ])ellets, 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 . . 259-304 



