Ohap. VI. CASTINGS BLOWN TO LEEWARD. 287 



will never be removed as long as the wood 

 lasts ; and mould will here tend to accumulate 

 to the depth at which worms can work. I 

 tried to procure evidence as to how much 

 mould is blown, whilst in the state of cast- 

 ings, by our wet soTithern gales to the north- 

 east, over open and flat land, by looking to 

 the level of" the surface on opposite sides of 

 old trees and hedge-rows ; but 1 failed owing 

 to the unequal growth of the roots of trees 

 and to most pasture-land having been formerly 

 ploughed. 



On an open plain near Stonehenge, there 

 exist shallow circular trenches, with a low 

 embankment outside, surrounding level spaces 

 50 yards in diameter. These rings appear 

 very ancient, and are believed to be contem 

 poraneous with the Druidical stones. Castings 

 ejected within these circular spaces, if blown 

 to the north-east by south-west winds would 

 form a layer of mould within the trench, 

 thicker on the north-eastern than on any other 

 side. But the site was not favourable for the 

 action of worms, for the mould over the 

 surrounding Chalk formation with flints, was 

 only 3 '3 7 inches in thickness, from a mean of 



