430 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 23,
what is already known, are merely intended to stimulate to further
research*.
8. Connexion between Boulder-drifts and Superficial Accumulations at high Levels.
I have not seen any Lower Boulder clay or pinel in the Furness peninsula at a higher level than nearly 800 feet above the sea (between Ulverstone and Beckside). In the valleys and on the slopes of the Coniston Old Man, I have traced it up to about 900 feet near Paddy-End Copper Works, and to about 1200 feet on the Walna Scar road and between it and Goat's Water. The Upper Boulder-clay of Furness may be traced up to at least 700 feet (above Soutergate). On the Old Man I have traced a coarse rubbly clay overlying either pinel or sand and gravel up to at least 1200 feet above the sea. On the same mountain, rounded gravel may be found up to 1000 feet†. In south Lancashire Mr. Hull has not been able to trace the undoubted Lower Boulder-clay up to any considerable height. The middle drift rises higher‡, and the Upper Boulder-clay higher still, while erratics may be found on the Pennine hills up to 1800 feet, proving a submergence of north-central England to that extent§. I believe I saw a patch of erratic Upper Boulder-clay, at least 1000 feet above the sea, at the entrance of the railway tunnel north of Dove Holes (near Buxton), Derbyshire. But from an examination of the extent to which drift deposits, with erratic stones, graduate upwards into deposits with angular stones of local derivation, and from a comparison of the superficial accumulations at low and high levels in Lancashire and Derbyshire, I have been led to the following conclusions:—
(1) During the period of the great north and south flow of land-ice, superficial detritus, either loose or closely packed, was left in hollows or on the lee side of rocky projections and knolls; but no extensive and continuous spread of Boulder-clay resulted from its action.
(2) During the succeeding submergence the sea rearranged the previously existing surface-detritus, and combined with land-ice in giving rise to a variety of superficial phenomena of denudation and deposition, which will require much research to decipher.
(3) The principal part of what are called drift deposits was derived from the waste of local rock formations, and accumulated by the ordinary action of the sea. In most places, especially at a distance from hills, comparatively little of the finer part of drift deposits
- The Rev. Mr. Thornber informed me that Connemara Marble (?) had been
found in the Boulder-clay at Blackpool; and a workman once showed me a specimen of Gryphoea incurva he had picked up on the beach. The latter may possibly have been brought to Blackpool as ballast in a vessel.
† For an account of the drifts of the Old Man see 'Scenery of England and Wales,' by the author of this paper.
‡ It is well known that shell-bearing middle drift has been found in the neighbourhood of Macclesfield, and on the Macclesfield and Buxton road, up to 1200 feet above the sea.
§ Mem. Lit. and Phil. Soc. Manchester, vol. ii. 3rd series.
