CHAPTER YL 



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 com- 

 pletely away from castings — The disintegration of dried cast- 

 ings 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. 



We are now prepared to consider tlie more 

 direct part wliicb vrorms take in the denuda- 

 tion of the land. When reflecting on sub- 

 aerial denudation, it formerly appeared to 

 me, as it has to others, that a nearly level or 

 very gently inclined surface, covered with 

 turf, could suffer no loss during even a long 

 lapse of time. It may, however, be urged 

 that at long intervals, debacles of rain or 



