CH. l] EARTHWORMS AND LEECHES 25 



Archaeologists are indebted to worms for the preserva- 

 tion of many ancient objects, such as coins, implements, 

 ornaments, and even the floors and remains of ancient 

 buildings that have become buried by the soil thrown up 

 as worm-castings. The process of disappearance is of 

 course hastened by the excavations effected by the worms 

 below the surface, for the collapse of the burrows slowly 

 but surely allows objects on the surface to sink down- 

 wards. 



In the disintegration of rocks, and the denudation of 

 the land, worms play an important part. The penetration 

 of the burrows, and the lining with castings, carries down 

 the humus-acids to a considerable depth and exposes the 

 underlying rocks to their solvent action. Within the 

 body of the worm itself small stones and grains of sand 

 are reduced to yet finer dimensions and rendered the more 

 easy of transport by wind or water. On sloping surfaces 

 the upturned castings, at first semi-fluid, flow down, and 

 when dry roll down the incline, or are washed by the rain 

 into the valleys and ultimately carried out to sea, while 

 on level ground the dried castings are blown away to lower 

 spots by the wind. The more or less parallel ridges that 

 are frequently found on the sloping sides of grass-clad hills 

 are in part, at any rate, formed by the material derived 

 from worm-castings, which has temporarily lodged against 

 tufts of grass, etc., and in turn furnished a richer and 

 deeper soil for stronger growth which arrests yet more and 

 so increases the ledge. All land surfaces, whether level 

 or sloping, provided they are occupied by worms, are reduced 

 in altitude by their action. In no small degree then may 



