1870.] DE RANCE—LANCASHIRE AND CHESHIRE POSTGLACIAL. 663 
probably swept away by after-denudation. Neither does any repre- 
sentative of the «‘ Shirdley-Hill sand” occur in the Ribble estuary 
or valley, possibly because the latter was not so deep or fully formed 
during that period as now. But much further north, on the north 
shore of Morecambe Bay, at the top of a low cliff of Upper Boulder- 
clay, at Rampside near Barrow, is a well-known postglacial deposit, 
containing species of marine shells, which have been enumerated by 
Miss Hodgson, of Ulverstone. ‘This deposit appeared to me in some 
measure to resemble a raised beach, or rather sea-bed, occurring on — 
the southern shore of the bay, west of Pilling, between Fleetwood 
and Lancaster, which I found to underlie the main or thick peat of 
that area, and to abut against a high cliff of Upper Boulder-clay on 
the top of which the village of Preesall is built. The sand and 
shingle contain Cardium edule, Natica, and other marine shells, and 
fragments of hzmititic iron-ore from the Furness district. The de- 
posit is but rarely seen; but there can be little doubt that the whole of 
the immense peat-moss plain forming the country on the southern 
side of Morecambe Bay, between the sea and the glacial-drift covered 
Fylde, was once the postglacial sea-bottom, and that Morecambe Bay 
was shaved across by the sea at the same period as the plains between 
the Dee and Mersey and the Alt and Douglas—the only difference 
being that, with the exception of the peat-moss plain between Pilling 
and Fleetwood, the whole of the Morecambe plain is again beneath 
the waves, while all the skill of the engineer has to be exerted to 
prevent the Alt and Douglas portion sinking below them. 
When the bottom of the bay is examined, it is found to consist of 
red-sandstone rock, covered with a thin bed of red Boulder-clay ; 
this, again, is covered with a freshwater blue clay, on which grew a 
forest, which is covered with peat. Itis clear, then, that after the 
postglacial sea had formed a plain in the glacial deposits, leaving 
cliffs all round of Boulder-clay, the whole bay became land, drainage 
was obstructed, and freshwater-beds were thrown down. These after- 
wards became terrestrial surfaces, supporting a forest, afterwards 
destroyed by the growth of peat,—a result exactly similar to that 
obtained from an examination of the estuary of the Mersey, men- 
tioned above. 
The light-coloured blue clay, occurring under the main thick peat, 
I have called the “‘ Lower Cyclas-clay,” as, in the neighbourhood of 
Southport and Formby, where it is well developed, being about 20 feet 
thick, it contains the shell Cyclas cornea, occasionally to the almost 
total exclusion of any other form. The clay does not extend east- 
wards under the whole of the moss, but gradually thins out along a 
line nearly parallel with the coast, at a distance of from three to four 
miles from it. To the east of this line the peat is about 12 feet thick, 
resting on the Shirdley-Hill sand. It is drier and more friable than 
where resting on the “ Cyclas-clay,” and is made chiefly of layers of 
more or less decomposed heather-stems and leaves, instead of Sphag- 
num and other mosses, as is the case with the peat on the clay. At 
the base of the peat, in both instances, a submerged forest is found. 
Near Halsall the trees are chiefly oak, some of them of very large 
VOL. XXVI.—PART I. 3 
