Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/902

 but all traces of this have now disappeared through the wasting of the cliff by the waves, and by the progress of the embankment, undertaken in, the hopeless task of stopping their devastations. Beds of sandy silt occur in various horizons in the Middle Drift, as well as occasionally in the Upper Boulder-clay.

Summary and General Conclusions.

From an examination of the facts and inferences brought forward it appears probable : — 1. that before the Glacial epoch the N.W. of England was higher above the sea-level than it is at present, and that the sea stood further out, possibly forming a narrow channel between England and Ireland, which were probably more or less connected from Miocene times down to the period immediately preceding the Glacial epoch. Before the commencement of this epoch the land commenced gradually subsiding, the Irish Channel was no longer narrow, and the waves were rapidly denuding across the ends of the various longitudinal hills and valleys, wearing them back and back, until the plains of Wirral and Western Lancashire came into existence, part of the great plain, extending from Liverpool to Lancaster, being since obscured by the deposition of Glacial deposits 200 feet thick. These longitudinal valleys, running in the strike of the Triassic strata, appear to have been formed by the agency of running water, aided by atmospheric causes ; and wherever, by natural sequence or subsequent faulting, hard beds rest upon or are thrown against soft, on the eastern sides of these valleys, or on the western sides of the hills, there the dissolving power of western storms of wind and rain have formed long lines of escarpment, running parallel with the strike.

2. That the Mersey occupies at Liverpool a longitudinal valley, or rather a tidal channel excavated at the bottom of one ; but its outfall, in Preglacial times, appears from some reason to have been checked or closed, forcing it to turn abruptly westward, flowing over what is now Wallasey-pool gorge, a transverse valley terminating to the west by escarpments running north and south respectively, which were continuous before the river Mersey cut the transverse gorge in question. The river must have thrown itself over the escarpment, wearing its bed backwards and downwards at the same time. This action probably began to take place before the sea had removed the western side of the valley of which the escarpment lying north of the gorge was the eastern slope.

3. That when the Glacial period commenced, the hilly country became covered with immense glaciers, or possibly an ice-sheet, which, as the cold increased and the land sank, gradually extended over the lower country and reached the sea, by this time covering the lowland plains above referred to, and that the Lower Boulder- clay, with angular local fragments, is due to this land-ice, and may be called terrestrial Lower Boulder-clay.

4. That this portion of the N.W. of England continued subsiding until the land stood 100 feet lower than at present, and that the lowlands of Lancashire and Cheshire were submerged to a depth of