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VI] been so complete, that we are apt to forget how altered is the appearance of the English coast. Even so recently as the time of Caesar's invasion flat muddy shores or low gravelly plains occupied many parts of the coast where we now see cliffs and rocky ledges.

We will not labour this point, which must be obvious to anyone who has noticed how little the low terrace which still fringes great part of the Sussex coast can resist the waves, and how quickly it is eaten away during storms. Any restoration of our coast-line for the time of Caesar must take these changes into account.

The material thus being removed by the attacks of the sea is partly Pleistocene gravel, partly alluvium of later date; and the alluvial strata with their accompanying buried land-surfaces resemble so closely those already described that we need not linger long over their description.

If we commence at the Strait of Dover we are immediately confronted with clear evidence of the change of sea-level. Submerged forests are well seen between tide-marks in Pegwell Bay, and valleys with their seaward ends submerged and forming harbours are conspicuous in Kent. Owing to local conditions, the valleys are mostly narrow and steep, and the small harbours therefore soon filled up, or were lost through the cutting back of the cliffs on either side.