But the former enemies, when they perceived that the Roman soldiers were gone, immediately coming by sea, broke into the borders, trampled and overran all places, and like men mowing ripe corn, bore down all before them. Hereupon messengers were again sent to Rome miserably imploring aid, lest their wretched country should be utterly blotted out, and the name of a Roman province, so long renowned among them, overthrown by the cruelties of foreign races, might become utterly contemptible. A legion was accordingly sent again, and, arriving unexpectedly in autumn, made great slaughter of the enemy, obliging all those that could escape, to flee beyond the sea; whereas before, they were wont yearly to carry off their booty without any opposition. Then the Romans declared to the Britons, that they could not for the future undertake such troublesome expeditions for their sake, and advised them rather to take up arms and make an effort to engage their enemies, who could not prove too powerful for them, unless they themselves were enervated by cowardice. Moreover, thinking that it might be some help to the allies, whom they were forced to abandon, they constructed a strong stone wall from sea to sea, in a straight line between the towns that had been there built for fear of the enemy, where Severus also had formerly built a rampart.(79) This famous wall, which is still to be seen, was raised at public and private expense, the Britons also lending their assistance. It is eight feet in breadth, and twelve in height, in a straight line from east to west, as is still evident to beholders. This being presently finished, they gave the dispirited people good advice, and showed them how to furnish themselves with arms. Besides, they built towers to command a view of the sea, at intervals, on the southern coast, where their ships lay, because there also the invasions of the barbarians were apprehended, and so took leave of their allies, never to return again.