The dwellers in the soil 



55 



with soil to which eartli worms have been added, one 

 worm to every pound of soil. Leave them out of 

 doors where the rain can fall on to them. You can 

 soon see the burrows and the heaps of soil or "casts" 

 thrown up by the worms: these casts wash or blow 



Fig. 24. 



Soil in which earthworms have been living 



and making burrows 



over the surface of the soil, continually covering it with 

 a thin layer of material brought up from below. Con- 

 sequently the soil containing earthworms always has 



