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III] of this sand lay a few stray valves of the estuarine Scrobicularia and of Tellina. The bottom deposits were probably laid down in a tidal river; but whether within the influence of the salt water is doubtful.

As far as the Tilbury evidence goes it suggests a maximum elevation of the land of about 80 feet above its present level; but we will return to this question when we have dealt with the other rivers flowing more directly into deep sea. The animals and plants found at Tilbury were all living species.

It is unnecessary here to discuss more fully the submerged forests seen in dock and other excavations in the Thames flats, for they occupy a good many pages in the Geology of London published by the Geological Survey. Even 250 years ago, the hazel trees were noticed by the inquisitive Pepys during one of his official visits to the dockyards, and later writers are full of remarks on the ancient yew trees and oaks found well below the sea-level. Most of these early accounts are, however, of little scientific value. 

It is not our purpose to describe in detail the many exposures of submerged land-surfaces which have been seen on the shores of the North Sea. This