CHAPTER HI. 



THE AMOUNT OF FINE EARTH BROUGHT UP BY 

 WORMS TO THE SURFACE. 



Rate at which various objects strewed on the surface of grass- 

 fields are covered up by the castings of worms — The burial of 

 a paved path — The slow subsidence of great stones left on the 

 surface — The number of worras which live within a given 

 space — The weight of earth ejected from a burrow, and from 

 all the burrows within a given space — The thickness of the 

 layer of mould which the castings on a given space would 

 form within a given time if uniformly spread out — The slow 

 rate at which mould can increase to a great thickness — 

 Conclusion. 



We now come to the more immediate subject 

 of this volume, namely the amount of earth 

 which is brought up by worms from beneath 

 the surface, and is afterwards spread out more 

 or less completely by the rain and wind. The 

 amount can be judged of by two methods, — 

 by the rate at which objects left on the 

 surface are buried, and more accurately by 

 weighing the quantity brought up within a 



