Chap. VL MOULD OVER THE CHALK. 803 



thickness. On the north-west side of tlie 

 bill, either no embankment had ever been 

 thrown up above the ditch, or it had subse- 

 quently been removed ; so that here there 

 was nothing to prevent worm-castings, earth 

 and stones being washed into the ditch, at the 

 bottom of which the mould formed a layer 

 from 11 to 22 inches in thickness. It should 

 however be stated that here and on other 

 parts of the slope, the bed of mould often con- 

 tained fragments of chalk and flint which 

 had obviously rolled down at different times 

 from above. The interstices in the under- 

 lying fragmentary chalk were also filled up 

 with mould. 



My son examined the surface of this hill to 

 its base in a south-west direction. Beneath 

 the great ditch, where the slope was about 

 24°, the mould was very thin, namely from 

 1^ to 2^ inches ; whilst near the base, where 

 the slope was only 3° to 4°, it increased to 

 between 8 and 9 inches in thickness. We 

 may therefore conclude that on this artificially 

 modified hill, as well as in the natural valleys 

 of the neighbouring Chalk Downs, some fine 



earth, probably derived in large part from 

 14 



