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74 are quite unlike the undulating flats which occur higher up.

The flat of Selsey Bill yields evidence of submerged land-surfaces opposite each of the shallow valleys; but here we meet with the same difficulty which confronted us in the Thames Valley and on the east coast. Pleistocene land-surfaces and alluvial deposits of early date are seen on the foreshore side by side with the more modern Neolithic alluvium and submerged forests. Unless great care is taken it may be thought that the well-preserved bones of rhinoceros and elephant, and the shells of Corbicula fluminalis, come from the same alluvium that yields Neolithic flint-flakes, or that plants such as the South European Cotoneaster Pyracantha flourished in Britain up to this recent date. Except for the sake of warning against these sources of error the submerged forests of Selsey Bill need not detain us.

Still travelling westward we next arrive at the series of tidal harbours opening into Spithead, Southampton Water and the Solent. All of these are obviously continuations of the valleys which lengthen them inland; and this is amply proved by dock excavations and borings.

Even Southampton Water and the Solent themselves are nothing but submerged valleys. A well at the Horse Sand Fort—one of the iron forts which rises out of the sea at Spithead—showed a band of