Outside the wall, encircling it closely, is the ditch, the most striking feature in the whole fortress. This is in general plan not unlike the long section of a pear, the northern end being the smaller, and the western side flattened so as to be nearly straight. The counterscarp of this ditch includes an area of about 5 acres. The ditch itself, measured from the level of the foot of the wall crowning its scarp, is about 60 feet deep, with slopes of 1 foot horizontal to 2 feet vertical, and about 70 feet broad. It is only just not too steep to be covered with short turf. The crest of the counterscarp is a ridge about 6 feet broad, and about 20 feet below the level of the foot of the wall. From it descends another slope, equally steep, but much deeper; on the west side descending about 150 feet to the bottom of the valley, and on the east to a rather less depth, as here this “glacis” is succeeded by a sort of broad terrace of pasture land, which falls gently towards the river, the level of which may be 250 feet below the platform of the castle. In many respects these defences resemble those of Bramber, in Sussex. At the north-west end the ditch is traversed by a very modern causeway of earth, which supersedes the earlier drawbridge. At the south end, where the ground is highest and the ditch about 50 feet deep and 80 feet broad, there remain two engaged piers upon the scarp and counterscarp, and between them two detached piers, of which the outer has fallen against the inner. All are rectangular; and the inner of the detached two is considerably the larger, and probably carried a tower for the protection and working of a double drawbridge. These piers are of flint rubble, cased with ashlar, of which a small part only remains. At the outer end is the earthwork of a _tête du pont_, or ravelin, of triangular plan, the passage from which was a little to the east side of the apex. This work was evidently constructed when artillery was in use, and is attributed to Henry IV., during the campaign of 1589. It no doubt represents an earlier barbican, also of earth and timber. There are no traces of masonry beyond the bridge. This work opens upon the ridge of the promontory, which widens and rises somewhat higher to the south. The ground is scarred with banks and ditches, the remains of fieldworks of various dates, both of attack and defence.