The encampments, Roman and British, are thus described. In the Roman camp, the plan is invariably the same--a rectangular area, surrounded by a ditch, the earth thrown inwards, forming a high mound, defended on the top with wooden palisades, but of these all vestiges have disappeared: in the middle of each side the entrance, from which a way led to the opposite gate; and at or near the outer action of the two ways, was the Prætorium, the remains of which may frequently be traced. These camps are not usually found on very high hills. The Britons, on the other hand, always occupied the highest ground, frequently an isolated hill, which they surrounded with deep trenches and a series of low terraces scooped out of the side of the hill, rising one above another, not in an unbroken line, but forming, in some places, a network of flat forms, commanding every approach to the entrances, with advantageous positions for the sling, in the use of which the Britons peculiarly excelled. Every inequality of the ground was taken advantage of: the entrances sometimes opened into one of the trenches, through which the approach to the interior leads, so as to expose an enemy to an overwhelming storm of darts and stones from the heights above. Our early historians mention four great roads by which South Britain was traversed, and these usually have been considered as the work of its conquerors; but recent researches have led to the conclusion that the Romans only kept in repair, and perhaps improved, the roads which they found in use on their settlement in the island. Along the course of the great roads, or in their immediate vicinity, are found the principal cities, which, in pursuance of their usual policy, the Romans either founded or re-edified; and to which, according to the privilege bestowed, the various names were given of colonies, municipalities, stipendiary, and Latian cities. Many other Roman roads exist. "The old British roads, or trackways, were not paved or gravelled, but had a basis of turf, and wound along the tops or sides of the chains of hills which lay in their way. Surrey furnishes a remarkable example of such an appropriation of one of its chalk ridges; and it may be inferred that the agger called the Hog's Back presented to the earliest inhabitants of Britain a natural causeway of solid chalk, covered with a soft verdant turf, peculiarly suited to the traffic of the British chariots, and connecting the western Belgæ with the Cantii, and affording through them an access towards the continent at all seasons of the year. These advantageous peculiarities, no doubt, rendered it the grand strategic route by which an invading army would have penetrated to the westward; and Vespasian may be supposed, with great reason, to have marched along it."[7]