232 FORMATION AND GROWTH OF 



with foreign substances. It may be said that on 

 pasture-land the vegetable products are not allowed 

 to decay. This is partly true; but if such pro- 

 ducts are eaten off by the cattle, they are returned 

 again to the surface ; their fertilising quality being 

 increased from their having been used as animal 

 food. 



In a comparison between meadows and pasture- 

 land the difference between sole worm-work and the 

 conjoint effects of vegetation decay and of the earth- 

 worms appears evident. Examine a meadow-field 

 after the hay is cut, and the worm-casts are found to 

 be few and far between ; but if the after-grass is 

 allowed to rot on the land, the worms will be more 

 numerous, working among the decayed vegetable mat- 

 ter. In pasture-land there will be a hundred worms 

 for every one in a meadow; the greater number being 

 found under and associated with the decayed vege- 

 table matter in the droppings from the cattle. 



In some soils, such as alluvial loam, earthworms 

 will burrow to a great depth ; but they seem usually 

 incapable of penetrating into the ordinary subsoils 

 that occur in Ireland. The gravelly subsoils formed 

 by the esker-drift ought to be soft enough for them 

 to work into, yet they are never found in it. The 

 usual subsoil, boulder-clay drift, they never burrow 

 into, and a not uncommon subsoil in some places, 

 namely, a stratum of bog iron-ore, they could not 



