From the coast side it presents a number of clearly-defined harbours, from which it has evidently been colonised, and from which we know it to have been invaded; these harbours are the mouths of its small, parallel, characteristic rivers--the Arun, the Adur, the Ouse, the Cuckmere, and the Rother. Of natural harbours other than the mouths of the rivers it now has none, though it is probable that in the remote past plains, which are now dry land guarded by small elevations (as for example, Pevensey and Winchelsea), formed natural harbours afterwards artificially developed. These harbours are small for our modern scale of shipping, and the strong tide that runs in them is rather a disadvantage than otherwise for those who use them to-day. But in early times such tides were nothing but an advantage, and the smaller draft and beam of the shipping found ample accommodation in the river mouths. It is also to be noted that these river mouths stood at fairly even distances one from the other. There is not in the whole length of the coast of England, from the South Foreland to Penzance, a strip of coast so exactly divided by refuges set at regular distances into which small craft can run. Moreover, Sussex also provides a multitude of those even, sloping, and safe beaches which were of such immense importance to early navigators, with whom the beaching of a whole fleet was among the commonest ways of effecting a landing. The typical Sussex example of this early advantage and of a town springing around it is, of course, to be discovered at Hastings. It may next be inquired what limits eastward and westward existed to form natural boundaries for the county. This is a point of great interest which has been but little examined, but which a consideration of the geography of Sussex should make sufficiently plain. The early settlements along the river mouths were grouped together in one countryside by the comparative facility of communication along the sea-plain, and again by the comparative facility of communication along the well-watered belt to the north of the Downs. It may be imagined that the settlements around the harbours of the Ouse, of the Arun, and of the Adur, would, from the earliest times, have been in touch with each other along the flat of the coast, and that their extensions along the river valleys to [Illustration: HASTINGS--FISHING FLEET] the north of the hills, as also the separate harbour at the mouth of the Rother, would equally have been in communication by that ancient track most of which subsists to this day, and of which further mention will be made later on in these pages. But, when the primitive inhabitant attempted a similar communication eastward into what is now Kent, or westward with what is now Hampshire, his way was barred by two great tongues of marsh. [Sidenote: THE MARSHES]