The next question we have put—What light do these submerged forests throw on the antiquity of man in Britain, or on the race-problems of Britain?—is a difficult one to answer in the present state of our knowledge. Valuable evidence has been lost through the failure to preserve most of the human remains that have been found; but both Owen and Huxley recognised the peculiar type of the “river-drift man.” Unfortunately few implements have been collected, and the pieces of wood shaped by man, though recorded, have not been preserved. One implement of polished stone has certainly been found in the latest submerged land-surface, but it is not clear that anything except flakes has been obtained in the older deposits. Still the stratigraphical relations seem to indicate that all these deposits are of Neolithic age and later than the Palaeolithic terraces. The relations of Palaeolithic to Neolithic are still very obscure in this country, and the reason is perhaps to be sought in a submergence which has tended to carry many of the transition deposits beneath the sea-level, or has caused them to be silted up under more modern alluvium. The lowest submerged forest requires careful search before we can be certain of its true position in the sequence; but it is seldom exposed, and then only in dock-excavations soon again hidden. Before we can attempt to answer the other questions, it is important to get an estimate of the amount of time occupied in the formation of these deposits, and of the lapse of time since the last of them was formed. The newest of them belongs certainly to the age of polished stone, and the earliest also probably comes within the Neolithic period. We have already seen that within the period represented by the submerged forests there has been a rise of the sea-level, or depression of the land, to the extent of 80 feet, perhaps a few feet more. If we can obtain some measure of the time occupied in the formation of such a series of deposits, this should give us some idea as to the length of the Neolithic period, and also of the rate at which changes of the sea-level sometimes can take place. It is unfortunate that for these calculations so many of the factors are of uncertain value. We may estimate from the present rate of erosion of the coast the amount that has been lost since the sea-level became stationary, or we may take the rate of accumulation of sand-dunes or shingle-spits; or the rate at which our estuaries, harbours, and broads are silting up. It all comes, however, to this—no exact figures can be given; but so many rough calculations lead to approximately the same date, that the date arrived at may be trusted to give some idea of the length of the period which has elapsed since the downward movement ceased.