D. Mackintosh — The Drifts of the Lake District. 



305 



Most of the lines visible to the naked eye point N.E. or obliquely 

 across the valley of the Duddon. Most of the few strongly-marked 

 grooves run between N. and N. 35° E., or approximately in the main 

 direction of the Duddon valley. The ramifying rough crevices in 

 the limestone would appear to have existed before the glaciation 

 occurred. They are partly filled with sand and fine gravel, which 

 may belong to the Middle Drift period, and which may have once 

 covered the whole rock-surface, and furnished the ice with grinding 

 material. If so, its removal by the ice must have been followed by 

 the accumulation of the Upper (?) Eed Boulder-clay which covered 

 the glaciated rock-surface, and still covers it where quarrying 

 operations have not extended. But this clay did not result from the 

 grinding up of the limestone, for (according to an analysis made by 

 Mr. Heywood, of Millom) it contains silica 62-97, and alumina, 

 17-50 per cent. Nearly all, if not all the stones and boulders in this 

 clay, have come from directions which cross the grooves and strise (a 

 few of the microscopic lines excepted), and the main direction of 

 the ice-marks (N.E.) is nearly at right angles to the main direction 

 of the drift- carriage (N.N.W.). The glaciating agent, therefore, 

 could not have been the carrying agent, though it may have been of 

 the same nature. The boulders are chiefly Eskdale granite and 

 Eskdale or Wast dale granilite, granular felstone apparently from 

 Wastdale, etc. The existence of the stride under a covering of 

 Boulder-clay furnishes an illustration of one of the fundamental 

 principles of geology, namely, that the sea preserves the most 

 delicate marks on rocks in areas of deposition, a principle which Mr. 

 de Eance overlooked when he asserted that the roclie moutonnee at 

 Grange Bridge could never have been touched by the sea (Geol. 

 Mag., March, 1871). 



Fig. 7. — Glaciated Block of Limestone from the Eock-surface of a Quarry near 

 Millom. Scale, one-fifth of original. 



Limestone Sculptured by the Sea.— 'Not far from the above quarry, 

 at Hodbarrow Point, the pebbles and boulders of the red clay are 

 used by sea-waves to hollow out the originally rough and uneven 

 surface of limestone strata, and the effect produced is a perfect fac- 



TOL. VIII. — NO. LXXXV. 



20 



