Glacial Events in England and Wales. 273 



whicli is a perched esker, 950 feet above the sea-level ; of " a very 

 striking array of gigantic eskers " between Bodfari and Mold, a 

 number of which on or near to a watershed reach a height of 

 between 120 and 150 feet, and which often rise at an angle of 45° ; 

 of the eskers enclosing swamp- and lake-basins near Gresford, and 

 around EUesmere. The latter are often as abrupt as artificial earth- 

 works, and rise to a height of quite 150 feet al)0ve the very beautiful 

 and pellucid sheets of water which repose in the intermediate hollows. 

 These eskers and lake-basins form quite a feature on the Ordnance 

 map. A few of them are capped with clay. After considering the 

 causes of the retention of water in the esker hollows (which 

 generally appear to consist of sand or fine gravel), and preferring 

 the theory that "the decay of vegetation artificially planted or 

 naturally grown in the basins may have increasingly acted as a 

 retainer of water," the author proceeds to assign reasons for re- 

 garding the forms of post-glacial river-courses "as the effect of 

 unequal deposition, tidal scour, and freshwater floods." Among 

 mountains near the sources of drift-supply, valleys were often filled 

 up to a certain height with drift extending imiformly and con- 

 tinuously across ; but in the greater part of the district described in 

 the paper, the filling up of the valleys (according to the author) 

 must have been very partial and unequal, so that the rivers, 

 generally sjoeaking, found ready-made channels after the final 

 emergence of the land. " In many places the denudation (effected 

 by the rivers) would amount to cutting a slice out of the side of 

 one knoll, and leaving a knoll or drift-slope on the other side of 

 the valley unscathed, or it would take the form of a lateral encroach- 

 ment on a knoll or slope, so as to leave either a straight or horse- 

 shoe-shaped cliff-line, the opposite side of the valley still retaining 

 the shape given to it by the sea." After supporting his ideas by 

 referring to phenomena in the courses of the Dee, Alyn, and Ceiriog, 

 in Morecambe Bay, the estuary of the Mersey, the pits in the Irish 

 Sea, English Channel, etc., the author concludes with the following 

 general account of the north-west of England and AVales : — " I 

 believe this area includes a variety of phenomena which are more 

 calculated than those of any other British area to suggest the true 

 sequence of glacial and interglacial events. Within a small compass 

 it embraces plains, wide and narrow vallej'^s, cwms, lakes, table- 

 lands, groups and ranges of mountains, and neighbouring sea-beds. 

 In ascending order it contains, (1st) pre-glacial white clay and sand ; 

 (2nd) two if not three kinds of lower boulder-drift which in different 

 districts go under the names of rammel (ground moraine of Mr. 

 Mellard Eeade), blue clink, pinnel or sammel, in addition to a 

 shelly lower boulder-clay ; (3rd) coarse esker-gravel-and-sand of 

 hilly or adjacent districts ; (4:th) fine sand and gravel of low-level, 

 plains; (5th) uj^per boulder or brick-clay. Southward the area 

 under consideration graduates into a non-glacial district. Northwards 

 it graduates into the Lake District, and westwards into the Snow- 

 donian and Merionethshire Districts, in both of which are to be 

 found the sure signs of great sheets of land-ice and glaciers — namely, 



DECADE II. — VOL. III.— NO. VI. 18 



