Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/906

 50 feet high : these, however, in the neighbourhood of Leasowe, were washed away by the continual encroachment of the sea many years ago, and their place artificially supplied by an embankment, which has to be continually repaired, and, after heavy storms, even partially rebuilt, the cost of which is paid by an acreage-toll levied on the landowners of the district.

The drainage of the district is naturally much obstructed. Deep sluices, like small canals, often from 16 to 20 feet deep, carry the water into the river Birket, which falls into Wallasey Pool, an arm, or tributary, of the Mersey. In the sections exposed in the Birket and sluices, beds of peat, often as much as 16 feet in thickness, are seen resting on grey clays ; and on the northern portion of the tract a bed of sandy marine silt occurs on the peat, caused by recent inroads of the sea. The sand dunes, when their bases are seen, are found almost invariably to rest upon a surface of peat. At New Brighton, on the Mersey, there is a slight exception, the sand resting on the bare rock, belonging to the Bunter Pebble-beds. A little further west, the red beds of the Upper Mottled Sandstone occur, jutting out into the sea, forming the picturesque cliffs known as the " Red Noses."

Walking along the sea-coast from the Bed Noses towards Hoylake, a little before reaching Leasowe Castle, the section given in fig. 1 is reached. The sand-dunes (a) are about 35 feet in height, rest on a flat-surface peat (b) about 2 feet thick, which runs out seawards about five yards, forming a terrace, resting on a bed of pale, pure, grey-coloured clay (c), containing Cardium edule, and with a marshy growth at its surface. This clay rests upon a thin bed of peat (e) resting upon another bed of grey clay, covering still another seam of peat, which is believed to rest on the Boulder-clay, here covered up with sea-sand.

In fig. 2 a greater thickness of peat is observed, and it is split in two by a bed of olive-green-coloured sand (B'), containing Tellina balthica and Cardium edule. A sand of probably the same age occurs in Lancashire, north of Southport, and I shall hereafter, for convenience, call it the " Tellina-balthica sand."

The peat below the sand (b") is about 2 feet in thickness, and rests upon the usual grey clay (c) with a marshy growth at the top. Its base is concealed by sand, and it is doubtful whether it is marine or fluviatile at this point, as these conditions vary in a few yards. There can be little doubt that the whole of the silts of the Birket plain were deposited when this tract was an estuary of the Mersey, that river having, even in historical times, flowed through the gorge, at the bottom of which now runs Wallasey Pool into the sea, between Leasowe and New Brighton, until, through the outlet being choked by the deposition of alluvium, the drainage has to a certain extent been reversed. Whilst this deposition went on, freshwater forms might have lived in pools of fresh water in hollows of the Boulder-clay, simultaneously with marine forms in other pools filled by high tides a few feet distant, — fluviatile and marine forms of life preponderating horizontally and vertically in the silts, according to whether freshets