GLACIAL BEDS. 493 



In Cardiganshire, near Aberystwitli, etc., and over much of Central Wales, there 

 are accumuhitions of Glacial Drift, consisting of Boulder Clay overlaid by loam, 

 sand, and gravel. The materials are of local derivation. Perched blocks, and 

 Eskers have been noticed.' 



In South Wales, near Cardiff, Cowbridge and Bridgend, there are extensive 

 deposits of Drift gravel and ckay with boulders, which are connected with the 

 Glacial period. West of Llantrissant, Gwaun Ynysplwm might be taken for an 

 old moraine-dammed pool, for it is almost hemmed in on the south by a bank of 

 Drift gravel, exposed in the railway-cutting.^ In describing the evidences of 

 Glacial action in South Brecknockshire and East Glamorganshire, Mr. J. W. E. 

 David has pointed out grooves and stride on the surfaces of the Pennant sandstones 

 and Millstone Grit, and /^oc/ies fnoiiro>i>ttrs were ohservedhy him in Brecknockshire. 

 (See Fig. 82, p. 475.) The Boulders in the Drifts appear to be almost entirely of 

 local derivation, but Chalk-flints are met with in places.^ 



SOUTH-WESTERN COUNTIES. 



There is very little Drift on the Cotteswold Hills, but in the neighbouring vales 

 there is much gravel ; this has been divided by Mr. W. C. Lucy* and Mr. E, 

 Witchell^ into the Angular Gravel of the slopes, the rolled Oolitic Gravel of the 

 river valleys, and the Northern Drift. The older or ' Northern Drift ' gravel 

 occurs at various elevations and contains fragments of Greensand, Chalk and 

 Chalk-flint, in addition to the more abundant fragments of older rocks. Thus an 

 isolated hill, at Limbury near Hartpury, in the Vale of Gloucester, showed 8 feet 

 of gravel, composed for the most part of pebbles of quartzite, with fragments of 

 Silurian and other strata, besides eruptive rocks. Mr. Lucy has noticed the 

 occurrence of rocks from the North of England ; these might have been derived 

 from the Boulder Clay of Cheshire and Shropshire, for the gravel is not of Glacial 

 formation, though it may be connected with the Glacial period. The Oolitic 

 gravel is for the most part modern river gravel, and the Angular gravel is due to 

 the subaerial waste of the hills and escarpments. Quartz pebbles have, however, 

 been found here and there on the higher parts of the Cotteswold Hills, from the 

 neighbourhood of Cheltenham to Bathampton and Farley Downs near Bath. 



The Mendip Hills are remarkably free from Drift, but there are deposits 

 of loam and clay, with here and there a boulder of some local rock, whether Old 

 Red Sandstone or Millstone Grit, whose position cannot well be accounted for 

 by the action of rain, rivers, or sea.^ Near Watchet and at Minehead possible 

 evidences of Glacial action have been described.'' 



In Devonshire and Dorsetshire, on tlie summits of the hills and high lands formed of 

 the Chalk and Upper Greensand there is generally found an accumulation of materials 

 derived chiefly from those formations. The Chalk itself, as is well known, 

 is frequently capped by a bed called Clay-with-flints, due in part to the dissolution 

 by carbonated water of the Chalk, whereby the insoluble portions and the flints 

 remain (see sequel) ; and in part to the former presence of Eocene clays. This 

 Clay-with-flints is found in many places near Seaton and Axminster, but it is 

 associated frequently with deposits of Chert detritus, the fragments being some- 

 times rolled, and transported to a distance (though not necessarily a great one) 



1 W. Keeping, G. Mag. 1878, p. 532, 1882, p. 251. 



2 Science Gossip, Sept. 1880 ; G. Mag. 1872, p. 574. 



^ Q. J. xxxix. 39. See also Lyell, Address to Geol. Soc. 1836; Murchison, 

 Proc. G. S. ii. 230, and Silurian System ; Trimmer, Q. J. ix. 282 ; W. S. 

 Symonds, Geol. and Nat. Hist. Repertory, i. 148, Records of the Rocks, 1872. 



* Proc. Cotteswold Club, 1870, and vii. 50; see also Murchison, Proc. G. S. 

 ii. 231. 



^ Proc. Cottesw. Club, vi. 146 ; see also Hull, Q. J. xi. 487. 



^ Geol. E. Somerset (Geol. Survey), p. 162. 



' W. C. Lucy, G. Mag. 1874, p. 256; /i/ul p. 573; T. M. Reade, Proc. 

 Liverpool Geol. Soc. 1881. 



