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 know the minimum extent of the change of level; but its full amount has to be ascertained from other localities. This difficulty has seemed of far greater importance than it really is, and some geologists have suggested that at this period of maximum elevation, England stood several hundred feet higher above the sea than it does now. I doubt if such can have been the case. Granting that the sea may have been some 300 miles away from Tilbury, measured along the course of the winding river, this 300 miles would need a very small fall per mile, probably not more than an inch or two. The Thames was rapidly growing in volume, from the access of tributaries, and was therefore flowing in a deeper and wider channel, which was cut through soft alluvial strata; it therefore required less and less fall per mile. Long before it reached the Dogger it probably flowed into the Rhine, then containing an enormous volume of water and draining twice its present catchment area. The clean gravel and sand which occupy the lower part of the ancient channel at Tilbury require to be more closely examined, for it is not clear that they are, as supposed, of fluviatile origin; they may quite well be estuarine. In the sand Mr Spurrell found the freshwater shells _Bythinia_ and _Succinea_, and in it was also found the human skeleton described by Owen; but, according to Mr Spurrell, on the surface 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.