Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/908

 or spring tides happened to be in the ascendant. This state of things is going on at the present time in the marshes of the Ribble, between Preston and Southport, where, after heavy rains or floods, freshwater shells may be found, during neap tides, in the hollows in the Scrobicularia- mud, and where, after spring tides, crabs may be found living in all the ditches for one or two miles inland.

In Section 2, and, in fact, in all other sections where the junction of the sand dunes with the underlying peat is visible, the base of the blown sand is found to be stratified (a"), and to contain freshwater shells, especially Bithinia tentaculata. It would therefore appear that when the sand commenced to be blown, both in Cheshire and in Lancashire, the surface of the country was a freshwater morass or bog, which was gradually filled up by the sand ; indeed, in Cheshire and at Southshore, near Blackpool (but not, so far as I am aware, between Liverpool and Southport, or at Lytham), seams of peat, from the tenth of an inch to 3 inches in thickness, occur in the first four or five feet of the sand dunes (a"), sometimes as many as ten or eleven seams occurring in a foot, always in strictly horizontal layers. This stratified sand I have called, for convenience, the " Bithinia-tentaculata sand."

West of Section 2, and about 50 yards east of Leasowe Embankment, the Tellina-sand has thinned out, but reappears on the other side of the sea-wall — the two beds of peat, again coalesced, reaching a thickness of five feet ; beneath, a thick bed of grey clay occurs, full of valves of Scrobicularia piperata. This I have called the " Lower Scrobicularia-clay," as a bed with Scrobicularia lies above the thick peat of Lancashire. In this section the first six feet of the sand dunes is the " Bithinia-sand," with seams of peat, at every 10 or 12 inches. Above the last seam of peat the sand contains worn marine shells, blown in and associated with freshwater and land-shells, which lived and died on the spot.

Still further west, at a point about ten yards north-east of the north-east end of the embankment, the peat is about 5 feet thick, resting on 9 feet of Scrobicularia-clay, the latter resting on the Upper Boulder-clay, which is of a deep purplish red, with blue seams, and, under the action of the waves, has been furrowed into long grooves, running at right angles, or slightly obliquely to the shore. It is honeycombed by marine organisms, and here and there bored by Pholades. All the pebbles are erratic ; and occasional large boulders are seen overgrown with tangle. The surface of the grey Scrobicularia- clay is, as before, a marshy growth ; but it is penetrated by the large and massive roots of a perfect forest of trees, found at the base of the peat above.

Further west, in the centre of the embankment, these various beds thin very much, the Boulder-clay rising higher, in a kind of boss or dome ; and it is therefore probable that the beds above described lie in a hollow cut in the Boulder-clay by the Mersey when this tract was its estuary.

Behind the embankment a thin bed of blown sand is found resting on peat, near the Leasowe Lighthouse. About 6 feet of this is visible