ancient land-surface seen between tide-marks. A boring is not altogether satisfactory evidence for the occurrence of a land-surface at such a depth; but if it is trustworthy it points to a subsidence of about 60 feet, an amount identical with that observed in the Thames Valley.
The estuaries of the Ribble, Mersey, and Dee tell a similar story, for on their shores and under their marshes are found some of the most extensive submerged land-surfaces now traceable in Britain. Many accounts of these have been published; but the alternations of marine with freshwater strata and with land-surfaces are so like those already described that a short account will suffice.
Carefully plotted engineer's sections will be found in Mellard Reade's papers, and his account of the succession is so interesting that it is worth quoting. He postulates two periods of elevation, alternating with three periods of depression; but in this area, as in the Thames Valley, it appears as though all the phenomena can be accounted for by one long period of intermittent depression. His generalised section of the deposits in these estuaries is as follows:—
| 3rd period of depression |
Blown sand Recent silts with beds of peat; Scrobicularia, occasional
freshwater shells, red-deer, horse, Bos primigenius, Bos longifrons, and human skull | |
| 2nd period of elevation |
Superior peat- and forest-bed |
