Page:The Formation of Vegetable Mould through the Action of Worms (1881).djvu/316

 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 ¼ 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 2½ to 3½ 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 9½ inches. On the embankment itself the mould was only 1 to 1½ inch in thickness; and within the ditch at the bottom it varied from 2½ to 3½, but was in one spot 6 inches in