Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/918

 after the formation of the lowland plains, and during a period when all the hollows in the much-denuded glacial deposits, both in Lancashire and in the Isle of Man, were occupied by lakes, which threw down the grey silt which I have called the " Lower Cyclas-clay," and in which the Cervus megaceros is so often found entombed.

4. It appears probable that glaciers still lingered in the deep valley of the Lake-district during the whole of the period occupied by the rising of the land, the pause, and its subsequent denudation and the connexion of England with the Isle of Man and Wales with Ireland. The climate would probably be rather colder than during the Esker-drift period, owing to the greater extent of land cooling the air ; but the temperature, apart from local causes, was no doubt becoming warmer.

5. At the close of the pause in elevation, before the lake-period, when the sea still occupied the low plains of Western Lancashire, the Shirdley-Hill sand and the Preesall shingle banks came into existence, forming a line of old sand dunes, from which sand was blown over the face of the country around Ormskirk, covering up the " lower peat " formed during the period of the pause. Below these old sand dunes in the plain, flats of this sand are occasionally found, forming the actual sea-bottom of the Shirdley-Hill-sand sea. The surface of the sand is worn, more or less, into channels by brooks, or small rivers, which no doubt flowed into the lakes, which, gradually increasing in size, afterwards covered the whole of these low-lying plains, not only between Liverpool and Southport, but between Fleetwood and Lancaster, and all the broad estuaries of the rivers flowing down from the Cumberland mountains, on the north side of Morecambe Bay, with the freshwater " lower Cyclas-clay."

6. During the formation of the Cyclas-clay, the entrance, or outlet, of all the river- and brook-valleys appears to have been choked and obstructed ; for freshwater lacustrine marls almost invariably form the base of the alluvium of the valleys in Lancashire and Cheshire. On the surface of the clay, on the plains and in the valleys, a forest of Scotch firs and oaks came into existence, the former sometimes appearing first, and being succeeded by the latter. The trees attained an immense size, owing probably to the continental conditions prevailing.

7. The country began to subside; drainage became still more obstructed ; the growth of peat ensued ; the sea encroached upon the land, and gradually worked its way eastwards over the sea-bottom of postglacial times — a movement yet in progress, the lowland of Western Lancashire and Cheshire being preserved from it only by artificial means. In a few places the ground has, partly naturally, partly artificially, been reclaimed from the sea, as at the mouth of the Alt and Wyre, where it has deposited an Upper Scrobicularia- clay on the peat.

8. Here and there, also, sand has begun to blow during the last three or four hundred years, the lines of sand dunes helping to keep the sea out. Everywhere the sand, when it first began to form, was blown into fresh water.