v.] ACTION OF WORMS 85 



rearrangement of the particles, some washing-down of 

 the finest material, until the large fragments which are 

 unmoved by the rain are left on the surface. 



Nor are such inanimate agencies as the wind and 

 rain alone effective in moving soil ; animals play their 

 part, even ants and moles are capable in time of 

 bringing about considerable shifting of fine soil from 

 below to the surface. That some such action does go 

 on may be concluded from the fact that even when the 

 soil is stony the surface of an old pasture is quite devoid 

 of stones, to find which it may be necessary to dig down 

 for a foot or two. This characteristic of old grass land 

 is chiefly due to the action of worms, which are always 

 swallowing the finest soil particles, and then ejecting 

 them as wormcasts on the surface. At first sight such 

 an action seems trivial, but one has only to collect and 

 weigh on some autumn morning the wormcasts from a 

 square yard of ground to find what a considerable 

 shifting of earth has taken place. Darwin has shown 

 that from this cause alone large stones, and even old 

 buildings of the time of the Romans and later, have 

 been completely buried ; he found that in one case 

 burnt marl, spread on the surface of grass land, had been 

 buried 3 inches in fifteen years, and in another case that 

 a layer of chalk had sunk 7 inches in twenty-nine years. 

 A hole cut in an old grass field will often show at some 

 little depth layers of chalk or ashes or burnt soil, each 

 layer representing material which had been spread on 

 the surface years before. Soils of transport are formed 

 in exactly the same way as sedentary soils, they have 

 merely travelled a little farther and been subjected to a 

 certain amount of sorting ; in all cases we have to look 

 upon soil as the product of the weathering — the dis- 

 integration and decay — of certain fundamental minerals 

 out of which the primitive rocks and the earth's crust 



