416 C. E. De Bance — Glaciation of N. W. of England. 



. In the Till, or land-ice Lower Boulder-clay, the matrix and 

 included fragments have often the same origin, and the pebbles 

 and boulders are invariably angular or sub-angular, glaciated, and 

 scratched, and comparatively local/ In North Wales I have de- 

 scribed it as being eroded, denuded, and overlain by the ordinary 

 marine Lower Boulder-clay, but in Lancashire the latter is absent at 

 high levels, and the former does not generally occur at low levels, 

 though in going north its level gradually descends. 



Mr. Mackintosh mentions a " blue clay" under the Lower 

 Boulder-clay, and states that it may be inferred from the facts given 

 in his eight papers that it was formed in a " shallow sea and denuded 

 (if not upheaved and again depressed) before it was overlaid by the 

 Pinel " ; and, further, in his " Drift-Deposits of the West Eiding of 

 Yorkshire," describes the sea as acting at a level principally between 

 300 and 600 feet above the present sea, during a period of subsi- 

 dence. If this clay be really marine, as he states, and deposited 

 when the land stood at 650 feet lower than at present, then it 

 follows that the true Lower Boulder-clay, which in Lancashire, 

 Cheshire, Cumberland, and Carnarvonshire, often occurs heloio the 

 present sea-level, must have been formed in water of 650 feet depth, 

 and when the Lake District and Lancashire were submerged under 

 the sea to that amount. Unless it can be proved that an elevation of 

 at least 600 feet took place between the depositions of the two clays, 

 of which he gives no proof, — and as it is clear that the parent rocks 

 from which all erratics found in the Lower Boulder-clay must have 

 been, with the rarest exceptions, above the sea-level, — no Boulders 

 should be found in it that occur in situ at an elevation of less than 

 600 feet; but an examination of the stones and boulders of the Lower 

 Boulder-clay of Lancashire has convinced me, that at least eight to 

 ten per cent, are derived from portions of hills to the north, imder 

 300 feet in height. 



I, therefore, see no reason to change the opinion, stated in my 

 paper on the "Glacial Phenomena of Western Lancashire, etc.,"^ 

 that the Lower Boulder-clay was deposited when the land forming 

 the sea-bottom was not more than 100 feet lower than at present, 

 and that the movement of subsidence continued during the Middle 

 Sand period, so that the shells found near Macclesfield at 1200 feet, 

 and on Moel Tryfaen, are newer than those of Blackpool at 50 feet 

 above the sea, by the period of time which the land took to subside 

 that amount. 



If, as Mr. Mackintosh states, these sands were formed during an 

 elevation, it follows that the Moel Tryfaen and Macclesfield are older 

 than those of Blackpool, and that the country was submerged twelve 

 or thirteen hundred feet before the deposition of the Lower Boulder- 

 clay ceased, and that of the sands in the high districts commenced ; 

 and it therefrom follows that before the sands of Western Lancashire 



1 For my descriptions of this clay in North Wales, see Nature, vol. ii., p. 391 ; 

 in Lancashire, Quart. Journ. Geol. See, vol. xxvii. ; Geol. Mag., Vol. VIII., 

 pp. 108, 116, and 310. 



2 Quart. Journ. GeoL Soc, vol. xxvii., part i., p. 652. 



