Sussex forms the western half of a chalk basin. The chalk rises in a long, narrow, lofty, and very steep ridge, forming the northern, eastern, and southern margins of the area, its height, reaching to 800 feet, being known as the Downs. The North Downs divide Sussex from Surrey, the South Downs are the frontier towards the sea. This latter ridge extends from near Chichester to Beachy Head, while the North Downs extend to Folkestone and Dover. The deep wooded area thus enclosed between them is the well-known weald of Sussex. The basin is cut across obliquely by the sea, and the south-eastern frontier of the county thus laid open for a length of about fifty miles. In former days, however, the broad marshes of Pevensey, Winchelsea, and Romney closed this opening with a barrier as effective as the downs themselves. Upon these downs, and especially upon the range to the seaward, the early sea-kings seem to have pitched their resting-places. Here are still found such hill-camps as Woolstonbury, Caburn, Rookshill, and Cheukbury, circular in form, and therefore neither British nor Roman, and besides these, several others, as Newhaven, Seaford, and Burling, which are segments of circles, and, like Flamborough Head, enclose headlands, and are attributed, with some probability, to the Danes. It seems the general opinion that these circular or segmental earthworks preceded the mounds and banks found in the interior of the country and upon lower ground, the work of the same people after their settlement and civilisation. Sussex is the only county the primary divisions of which bear the names of rapes; of these it contains six: Hastings, Pevensey, Lewes, Bramber, Arundel, and Chichester, subordinate to which are sixty-five hundreds; each rape contains a portion of seaboard, a river, a haven, and a fortress. The rivers are the Lavant, which nearly encircles the city of Chichester, and falls into one head of the Bosham estuary, the port of Chichester—the name is thought to be a corruption of the Saxon _hlifian_, a rising, because the springs rise annually from deep sources;—the Arun, which descends the dell bearing its name, cleaving the chalk-range, and reaches the sea at Little Hampton; the Adur, the river of Bramber, which, also by a pass in the chalk, reaches the sea at Shoreham; the Ouse, the river of Lewes, which, through a narrow gorge, now joins the sea at Newhaven, instead of, as formerly, flowing out at Seaford. The Cuckmere is the river of Pevensey, but it leaves that haven far to the east, and descends, also by a gap in the chalk, to the sea, west of Beachy Head; and, finally, the Rother, the river of the rape of Hastings, but the common boundary of Sussex and Kent, and which falls into the sea at Rye. Pevensey Haven, though deprived of the Cuckmere, is the receptacle for a number of lesser streams, by which the upland waters formerly flooded that extensive level.