THE PwAISED BEACHES, ETC., OP THE SOUTH OF ENGLAIS^D. 263 



10. llie Eaised Beaches, and ' Head ' or EcrBBLE-DRiri', of the SoriH 

 0/ England: their E elation to ^/«6 Yalle? Drifts ancZ to the 

 Glacial Period ; and on a late post-Glacial Submergence. 

 By Joseph Prestwich, D.C.L., E.E.S., F.G.S. 



[Plates VII. & VIII.] 



Part I. (Eead February 10th, 1892.) 



Contents. p^^^ 



§ 1. Objects of the Paper 263 



§ 2. Range of the Raised Beaches and ' Head,' or Rubble-drift, on the Coast 

 of Kent ; Sussex ; Hampshire ; Dorset ; South Devon ; South Corn- 

 wall ; North Cornwall ; North Devon ; Somerset ; and South Wales. 264 



§3. Origin of the Foreign Boulders in the Raised Beaches 295 



§ 4. The Mollusca of the Raised Beaches , 298 



I 5. The Relation of the Raised Beaches to the Valley Drifts 302 



§ 1. Objects of the Paper. 



I HAVE been led of late years to conclude that, besides the subaerial, 

 marine, and river-valley drifts of Glacial and post-Glacial age, there 

 is another which cannot be referred to any of the causes to which 

 those drifts owe their origin. Nevertheless this drift is not only of 

 common occurrence, but it is found in positions and with characters 

 at one time simulating the Valley Gravels, and at another presenting 

 features more analogous to those due to Glacial or to Subaerial action. 

 It is therefore desirable, in order to prevent confusion, that the place 

 of this Drift should be defined before proceeding, as I had intended, 

 with the other Quaternary series in their due order. 



I described long ago one phase of the Eubble-drift — as I propose 

 for the present to term this drift — in the Sangatte Cliff,^ namely that 

 long know;n as the ' Head,' which is associated with all our Eaised 

 Beaches ; and more recently I have briefly discussed some of the 

 theoretical questions connected with its origin.^ Since then I have, 

 however, materially enlarged the scope of the enquiry and arrived at 

 more' definite conclusions. 



I purpose, therefore, in this paper — Istly, to give the range of the 

 Eaised Beaches and Head in the South of England and South Wales ; 

 2ndly, to show their relation to the Valley Drifts ; 3rdly, to define 

 the characters and position of the Head or Eubble-drift, and to 

 determine its several phases inland ; and, 4thly, to enquire into the 

 origin and age of this special drift. 



As the Eaised Beaches have a general uniformity of structure, and 

 have been often described, I may pass over them rapidly, and om.it 

 details except where there are new points to notice or where, in a 

 few cases, no description has been previously given. With the 



1 Quart. Journ. Geol. Soc. vol. vii. (1851) p. 274, and vol. xxi. (1865) p. 440. 



2 Brit. Assoc. Rep. for 1880 (Swansea Meeting), p. 581 ; and Bull. Soc, geol. 

 France, 3me ser. vol. viii. (1880) p. 547. 



Q.J.G.S. No. 190. T 



