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106 much neglected period in geological history and to suggest directions in which further research is likely to be profitable. We have, however, made out several points, and can give an approximate answer to some of the questions.

It is quite clear that at the opening of the period with which this volume deals, the greater part of England stood fully 70 feet above its present level, for the oldest deposit we deal with is a land-surface covered with oak-forest and lying 60 feet below tide-level. The oaks cannot have flourished lower, but they may have grown on a soil well above sea-level. Perhaps taking the whole of the evidence into account, a subsidence of nearly 90 feet is the most probable measure of the extent of the subsequent movement.

We do not yet know whether in England this movement was a depression of the land or a rise of the sea; but the fact that the relative levels seem to have been quite different in Scotland and in Scandinavia seems to indicate that it was the land that moved, not the sea.

We begin, therefore, with a period when the whole of the southern part of the North Sea was an alluvial flat connecting Britain with Holland and Denmark, and to some extent with France. The Isle of Weight was connected with Hampshire, and the Channel Islands with France. Probably the Isles of Scilly were islands even then, for the channel between them