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II] (9) of the engineer represent a true growth in place, like the main peat; it is somewhat irregular and tends to abut against banks of sand (9*) rising from below. In one of these banks, according to Mr Spurrell, the human skeleton was found.

The contents of the sand (other than the skeleton) included Bythinia and Succinea; and as Mr Spurrell calls it a "river deposit," it apparently did not yield estuarine shells, like the silts above. The sub- angular flint gravel (10) below has all the appearance of a river gravel; it may be from 10 to 20 feet thick, and rests on chalk only reached in borings.

The floor of chalk beneath these alluvial deposits lies about 60 or 70 feet below the Ordnance datum in the neighbourhood of Tilbury and Gravesend, and in the middle of the ancient channel of the Thames it may be 10 feet lower; but there is no evidence of a greater depth than this. We may take it therefore that here the Thames once cut a channel about 60 feet below its modern bed. We cannot say, however, from this evidence alone that the sea-level then was only 60 feet below Ordnance datum, for it is obvious that it may have been considerably lower. If, as we believe, the southern part of the North Sea was then a wide marsh, the Thames may have followed a winding course of many miles before reaching the sea, then probably far away, in the latitude of the Dogger Bank. This must be borne in mind: we