lxvi PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [vol. lxxvi, 



On the west coast we enter the region of the drift again on the 

 north side of the Bristol Channel. Along the shores of South and 

 Central Wales, and in Anglesey, the sea would gain limited access 

 in many places by the removal of the Pleistocene deposits ; hut it is 

 not until we reach North Wales that the shape of the land would 

 be radically altered. Here most of the broad Vale of Clwyd would 

 become an arm of the sea, stretching southward nearly to Euthin ; 

 most of the Flintshire coast would be invaded ; and the estuary of 

 the Dee would be prolonged by a deep inlet, running past Wrexham 

 nearly to the entrance to the Vale of Llangollen. 1 



In Cheshire and West Lancashire the marine invasion would be 

 similar in many respects to that between the same latitudes in the 

 east of England, and broadly extensive ; so that the distance 

 across the land, between tide-water and tide- water, would be reduced 

 to 60 miles or less. A large portion of the Wirral peninsula 

 would be submerged, together with much of the low country to 

 the north-east and south-east, the estuary of the Mersey being 

 prolonged far to the eastward, with narrow branches continuing 

 into the salt-field and neighbouring tracts, and a long arm 

 probably running southwards between Chester and Tarporley. 2 



Between the Mersey and the Ribble, and between the Bibble 

 and the Lune, practically the whole of the West Lancashire plain 

 would become sea, continuous with Morecambe Bay. North cf 

 this bay the changes would be comparatively insignificant, being 

 confined to some narrow strips along the open coast, 3 together 

 with an enlargement of the Solway Firth. 



In the Isle of Man the northern plain would be wholly sub- 

 merged, reducing the size of the island by about a fifth. 



For the proof that the solid rock lies below sea-level in these 

 areas we are dependent, of course, mainly upon the evidence of 

 borings ; and this evidence, while explicit in a broad sense, is rarely 

 so full as to enable us to define the limits exactly. Upon a rough 

 estimate, however, we may conclude that, in the aggregate, a little 



1 L. J. Wills, ' Late Glacial & Post-Glacial Changes in the Lower Dee 

 Valley' Q. J. G. S. vol. lxviii (1912) pp. 180-97 & pi. si. 



2 The buried valley- system of the Cheshire and Lancashire plain is com- 

 plicated, and has not yet been worked out in detail. The ' Buried Valley of 

 the Mersey' is discussed by T. Mellard Reade, Proc. Geol. Soc. Liverpool, 

 14th Session, 1872-73, pp. 42-65. 



3 For a recent account of the drifts of the rising ground north of the 

 Duddon estuary, see Bernard Smith, ' The Glaciation of the Black Combe 

 District (Cumberland) ' Q. J. G. S. vol. lxviii (1912) pp. 402-48 & pis. xli-xliii. 



