Constantius and his more famous son, Constantine the Great, resided for long periods in Britain, and, partly to this circumstance, partly to the renewed peace brought about by the protection of the fleet of the Saxon Shore, the province enjoyed another lease of prosperity. Indeed, there is some reason to believe that the period 296-350 was the most prosperous that Roman Britain ever knew. Building was going on vigorously. When Constantius II. rebuilt Augustodunum in Gaul he levied artisans for the work in Britain, a circumstance which points to a condition of great prosperity. The western mines were being actively worked; Damnonia (Devon and Cornwall) was evidently being drawn much more closely into the Roman sphere of civilization. Something of the same kind seems to have been taking place north of the Wall, though here the Imperial influence was of a much fainter character. Something must be said of the towns. They were not numerous or specially important. It must be remembered that Britain as a province was comparatively poor and unsettled as compared with Spain or Asia Minor. Its relative prosperity at this period was thrown into relief by the fact that Gaul had long been suffering from barbarian invasions; it is not improbable that there had been immigration from the Continent. To return to the towns: Camulodunum seems never to have recovered from its destruction by Boudicca. When it was rebuilt, its walls enclosed an area less than that of several other places. Glevum, and probably Lindum, were _colonia_; Verulam had been a _municipium_ since the commencement of the Roman epoch. Eboracum was undoubtedly the principal place north of the Trent; Corinium, Viroconium, Calleva, Isca Silurum, and other places, had considerable local importance. Aquæ Sulis was much frequented as a health resort; but the most important city of the province from the time of Carausius onwards was undoubtedly London, which about 340 received the title of Augusta, with, in all probability, exceptional privileges. Its name was far too ancient to be ousted by a mere honorary appellation, but Londinium Augusta was certainly the largest and most important, if not the finest, of Romano-British towns. Its walls enclosed an area of some 380 acres. The average of population per acre in modern London is about sixty, but in Berlin it is one hundred. Sanitation was ill-understood in those days, and in a commercial centre like London the crowding was probably often dense. The normal population may have been about 50,000. The area of Verulam was about 203 acres; its population, perhaps, 20,000. Such importance as it still retained may have been largely due to the fact that it was a pleasant place of resort from busy and overcrowded London. Viroconium, with an area of 170 acres, and Calleva with 102, can hardly be credited with more than 10,000 and 5,000 inhabitants respectively. Population does not flock into places of no special commercial importance.