232 DISINTEGRATION Chap. V. 



CHAPTER Y. 



THE ACTION OF WORMS IN THE DENUDATION 



OF THE LAND. 



Evidence of the amount of denudation which the land has 

 undergone — Sub-aerial 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 levi- 

 gated 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 



