222 SUPERFICIAL DEPOSITS. 



described a bed of this kind in Cambridgeshire, at about 

 407 feet above the sea level.* 



Belt, in describing the superficial deposits of Devon and 

 Cornwall,! says that " near Okehampton, on the northern part 

 of the moors, the bed rock is composed of hardened shales and 

 sandstones. The sides of the hills are covered with a stony 

 clay, sometimes as much as 30 feet in thickness, containing 

 many large angular blocks of stone, especially near to and on 

 the surface. Amongst these, blocks of granite, which must 

 have been brought at least two miles, are not infrequent." 



He says that on the eastern side of Dartmoor Mr. St. 

 Omerod has noticed beds of gravel reaching up to 900 feet 

 above the sea, and has given instances of many transported 

 blocks of granite and carboniferous rocks. Mr. Belt thinks 

 that floating ice was the transporting agent. 



The south-east of England is largely covered with gravel 

 and drift, with brick earth and loam. Many of the beds have 

 been traced to fluvialite action, but those on the high ground, 

 reaching sometimes to 800 or 900 feet above the sea level, the 

 " pebble gravel," the " plateau drift," the " southern drift " 

 must be referred to other and more general causes, and, with 

 regard to this, there is a variety of opinions, t Most geolo- 

 gists seem to believe these beds to be of pre-glacial or glacial 

 date, while Prestwich thinks the rubble drift is post-glacial. 



It is to be noted that blocks of rock foreign to the locality 

 have been found in these high level drifts. Also, long ago, 

 Dr. Mantell, in his " Geology of Sussex," pointed out the 

 existence of rolled stones of porphyry, greenstone, granite and 

 other far transported rocks in the raised beach near Brighton, 

 which underlies the celebrated " Elephant Bed," a deposit of 

 rubble drift. Prestwich states that in the rubble drift, or its 

 equivalent, on Hayling Island and near Worthing there are 



* "On a Peculiar Bed of Angular Diift on the Lower Chalk High Plateau 

 between Upton and Chilton." Quarterly Journal Geological Society, May, 1882. 



t " On the Drift of Devon and Cornwall." Quarterly Journal Geological Society. 

 Feb. 1876. 



t Murchison : " On the Distribution of the Flint Drift of the south-east of Eng- 

 land, &c." Quar. Jour. Geo. Soc, Vol. VE, p. 349. 



Austen : Op. cit. 



Reid : " On the origin of Dry Chalk Valleys, and of Combe Rock." Quar. Jour. 

 Geo. Soc, Aug., 1887. 



Prestwich : " On the relation of the Westleton Beds, or Pebbly Sands of Suffolk, 

 and those of Norfolk, &c." Ibid, Feb. and May, 1890. 



Irving ; " Note on the Plateau-Gravels of East Berks and West Surrey." Dbid, 

 Nov., 1890. 



Prestwich : " On the Formation and Drift Slopes of the Darent Valley." Ibid, 

 May, 1891. 



Elsden: "On the Superficial Geology of the Southern Portion of the Wealden 

 Area." Ibid, Nov. 1887. 



Whitaker : " Geology of London," in Mem. of Geological Survey, 1889. 



Monkton : "On the occurrence of Boulders and Pebbles from the Glacial Drift 

 in Gravels south of the Thames." Ibid, Aug., 1893. 



Shrubsole : " On the Plateau Gravel south of Reading." Ibid, Aug., 1893. 



