At some late period in the Roman domination this magnificent harbour was found to be silting up. Many things have changed since those remote days, but the prevailing winds and the general set of the sea-currents in the Channel remain unaltered. Even then the westerly gales and the march of the shingle from west to east were altering the geography of this coast, just as they are active in doing now, adding as they do in every year great deposits of shingle to that projecting beak of Dungeness which was not in existence in the Roman era. The consternation of the merchants and the shipping interest of Portus Lemanis at this gradual silting up of the harbour must have been great, but we know nothing of it, nor of the measures that must needs have been taken to prevent it. Probably it was the clearing of the wooded inland country that caused these changes, quite as much as the set of the shingle; for it was the dense woods that gave the Rother and the Limen their once robust existence, and when they were cut down and the moisture they generated was lost, those rivers would lose that strength of current necessary to scour away the shingly bars that began to accumulate in the estuaries. The mischief was, of course, long in the doing, and probably two hundred years passed before it was seen that the harbour and the port were doomed. When that fact became at last impressed upon the Romans, they altered their policy. Ceasing any attempt they had made to keep the waterway open, they allied their efforts to the forces of nature, and, building walls to keep the sea out and the rivers within their courses, began that sustained work which has at last, after some sixteen hundred years, made Romney Marsh what we now see it. It was they who first built upon the shingle where Dymchurch Wall now keeps the sea at bay, and their work was the "Rhee Wall"--the _rivi vallum_ of their language--that, running from Appledore to Romney, kept the fresh water out of the land it was now their earnest endeavour to reclaim. Portus Lemanis, of course, was ruined, but, equally of course, not at once. How rarely does one actually picture the real length of the Roman stay in Britain, which actually comprised over four hundred years; or, to put it in a picturesque comparison, a period of time equal to that between our own day and the reign of Henry VIII. For half of their colonial period--say from a time corresponding to that between the reign of Queen Anne and that of Edward VII.--they were engaged in enclosing and draining the marsh, and there must have been ample time for the inhabitants of Portus Lemanis to realise the position. Did the Roman scheme, we wonder, allow them compensation?