Chap. VI. MOULD OVER THE CHALK. 305 



carried further down the valley. Closely 

 similar results, with respect to the thickness of 

 the mould, were obtained in a neighbouring 

 valley. 



St. Catherine's Hill, near Winchester, is 

 327 feet in height, and consists of a steep 

 cone of chalk about i of a mile in diameter. 

 The upper part was converted by the Romans, 

 or, as some think, by the ancient Britons, into 

 an encampment, by the excavation of a deep 

 and broad ditch all round it. Most of the 

 chalk removed during the work was thrown 

 upwards, by which a projecting bank was 

 formed ; and this effectually prevents worm- 

 castings (which are numerous in parts), stones, 

 and other objects from being washed or rolled 

 into the ditch. The mould on the upper and 

 fortified part of the hill was found to be in 

 most places only from 2^ to 3^ inches in 

 thickness ; whereas it had accumulated at the 

 foot of the embankment above the ditch to a 

 thickness in most places of from 8 to 9| 

 inches. On the embankment itself the mould 

 was only 1 to 1| inch in thickness; and 

 within the ditch at the bottom it varied from 

 2^ to 3|, but was in one spot 6 inches in 



