264 TROF. J. PRESTWICH OX THE RAISED 



overlying" Enbble-drift the case is different ; for the deposit varies in 

 composition, not only according to the locality, but also according to 

 the distance from its source — variations often so great as to have 

 given rise to wide differences of opinion as to its origin. 



The first distinctive but purely local name applied to this drift was 

 given at Brighton by Mantell, who termed it the 'Elephant Eed,' 

 as it contained the remains of the Mammoth/ De la Beche applied 

 the term 'Head' to a similar angular detritus overlying the 

 Eaised Beaches of Devon and Cornwall.^ Godwin-Austen adopted 

 the same term, but gave it an extension inland beyond the limits of 

 the Beaches.^ Murcbison looked upon the Head as merely one form 

 of a drift which he took to be general over the whole of the South 

 of England, and in which he included other so-called post-Glacial 

 Drifts/ To this he gave the name of ' the angular Elint-drift.' For 

 convenience' sake I shall, in speaking of this drift, use the term Head 

 or Eubble-drift, meaning both that portion lodged on the Raised 

 Beaches and that which exists independently in other areas. 



§ 2. Eange of THE Eatsed Beaches akd ' Head,' or Eubble-drift, 

 ON the Coast. (See Map, PI. VIII.) 



The encroachment of the sea in recent times on the south-eastern 

 coast of the Channel has been so great that only a few remnnnts of 

 the Eaised Beaches, which we have reason to believe extended all 

 round the South Coast of England, now remain; but of the Head, 

 with which they are commonly associated, frequent traces are to be 

 met with apart from the Beach. 



(1) The Isle of Thanet. — Small sections of the Eubble-drift are to 

 be seen at the Margate (South Eastern) Eailway-station ; again, on 

 either side of the North Foreland, in the gaps at Joss Stairs and 

 Stone Stairs, and in the cliffs west of Eamsgate. In all these places it 

 consists merely of chalk-and-flint rubble, mixed with Tertiary flint- 

 pebbles, green-coated flints from the base of the Thanet Sands (which 

 once spread over that island), and with occasional patches of brick- 

 earth. This rubble exists also on the slope of the cliff of the South 

 Foreland adjacent to Kingsdown, near Walmer. I am not aware 

 that any organic remains have been found at these places. 



(2) Dover and Folkestone. — A. more important mass of Head lies 

 at the base of the West Cliff of Dover, just behind the South Eastern 

 Eailway-station. It consists of chalk-and-flint rubble of local origin, 

 containing some remains of the Mammoth. It attains a thickness 

 of 40 feet or more ; and, as it descends to the level of the shore, it 

 is possible that a Eaised Beach may be hidden under it or may have 

 existed at a short distance in front of it. 



^ ' Geology of the South-east of England ' (1833), p. 32. 



2 ' Eeport on the Geology of Cornwall, Devon. &c.' (1839) p. 432. 



^ ' On the Superficial Accumulations of the Coasts of the English Channel, 

 and th.e Changes they indicate,' Quart. Jouru. Geol. Soc. vol. vii. (1851) p. 118. 



^ ' On the Distribution of the Flint-Drift of the South-east of England, on 

 the Flanks of the Weald, and over the Surface of the North and South Downs,' 

 Quart. Journ. Geol. Soc. vol. vii. (1851) p. 349. 



