Vol. 6S.] GLACIATTON OF THE BLACK COMBE DISTEICT. 413 



The section^ which he drew of the drifts between Elack Combe 

 and the sea gives a fairly correct impression of their general 

 relations; but these general relations seem to be best explained on 

 the assumption that the drifts are all the product of an ice-sheet 

 which was resting upon the shelving shore of the Irish Sea Basin. 



(i) Thickness of the drifts. — There seems to be, on the 

 whole, little available evidence as to the thickness of the drifts 

 near the sea-border, yet the records obtained show that, in general, 

 they descend far beloAV sea-level. At Thornflat, Drigg, about 50 

 feet above sea-level, a boring passed through 160 feet of Boulder 

 Clay, with seams of running sand, without reaching its base ; 

 but near Bootle, Aveline mapped sandstone in sifa (p. 405) at 

 nearly 150 feet above sea-lovel. In many places between Bootle 

 and Silecroft it seems likely that the inland drifts may descend 

 below sea-level, as they do in the coasfc-sections. If this be so, 

 the sea, in pre-Glacial times, assuming the present level to be the 

 «ame, may have washed the western slope of Black Combe, forming 

 a sea-cliff now concealed. 



A boring, recorded by Mackintosh,^ at the south-western end of 

 the AVhicham Valley, was stopped in 300 feet of sand, but we are 

 not informed whether this sand is Glacial or not ; the lower part 

 of the boring may well have been in Trias. I have been informed 

 that many borings through the alluvium, close to and east of, 

 Silecroft, in search of haematite, have failed, sand only being 

 encountered. Off Hodbarrow Point,^ south-east of Millom, a 

 boring proved 132 feet of clay, and others, farther in the estuary, 

 passed through a great thickness of sand (? estuarine), sometimes 

 resting on clay. Near Burnfield, about a mile and a quarter 

 north of Millom, gravel extends to 70 feet below sea-level, when 

 slate is encountered. 



East of the Daddon, at Irleth, near Askham in Furness, the 

 total thickness of the three drifts was 291 feet, resting upon lime- 

 stone some distance below sea-level. 



(ii) St. Bees Head to Hycemoor. — Aveline says of the 

 St. Bees Sandstone area : — 



* Mucb of the ground under which the sandstone lies is covered with super- 

 ficial matter, this matter being foreign-derived stones and boulders mixed up 

 with sand and fragments disintegrated from the red sandstone itself. In 

 many cases it may be said to be buried in its own waste. In nmny quarries 

 the breaking up of the higher beds may be observed.' (MS. Eeport.) 



Hebert states'* that on the sandstone there are large tracts of 



1 ' On the Drifts of the West & South Borders of the Lake District, and on 

 the Three Grreat Granitic Dispersions ' Greol. Mag. vol. viii (1871) p. 255. 



- Q. J. G. S. vol. XXV (1869) p. 428. 



2 Geological Survey 6-incli map. 

 4 MS, Eeport. 



