1822.] On the Geology of the Cliffs at Brighton. 185 



mile and an half from Rottingdean, where the bed is about four 

 feet above the level of the shore (these four feet consisting of 

 solid chalk) large rounded pieces of chalk begin to occur in it, 

 and these gradually increase so much, that in some places they 

 form the greater part of the bed, and are of a very large size. 

 This intermixture continues for about a mile ; the bed then 

 gradually becomes thinner, and less regular, appearing to have 

 some intermixture with the upper stratum, and, continuing to get 

 thinner and thinner, is lost about one-eighth of a mile from the 

 ravine of Rottingdean. 



In some places, a good deal of clay is mixed with the pebbles ; 

 in others, they are small, but always preserve their character of 

 roundness. I found a rounded piece of granite among them, 

 and saw several rounded fragments of the primitive rocks lying 

 on the shore which were probably all derived from this source. 

 I likewise found a bone of an animal, of the class mammalia, in 

 two places distinctly imbedded in the pebbles : in both cases, it 

 was in a very soft and decomposed state. Pieces of argillaceous 

 iron stone are not of unfrequent occurrence in it. 



The frequent falling of the cliff on this shore is I think to be 

 almost entirely attributed to this loose bed of pebbles, near 

 Brighton, where it is on a level with the shore. It is readily 

 washed away at spring tides, and the cliff undermined, but that 

 part of the cliff on which the town stands is now well defended 

 by a low wall built against it : this covers the bed of loose peb- 

 bles, and prevents the sea from undermining the cliff. Towards 

 Rottingdean, where it is elevated by the solid chalk above the 

 reach of the waves, the shore is much narrower ; but even here, 

 the action of the weather causes the pebbles frequently to fall 

 out, and deprives the upper part of the cliff of its support : 

 hence there is at this part a projecting ledge of chalk about four 

 feet in height, which continues to resist the sea, though the 

 cliff above it has fallen away. 



The stratum which forms the upper and main part of the cliff 

 is tolerably uniform throughout, merely varying in this ; that in 

 some parts the flints are more abundant, but always of the angu- 

 lar description above mentioned ; in others, the fragments of 

 chalk and agglutinating clay are most predominant, sometimes 

 to the total exclusion of the flints. At about one-eighth of a 

 mile from Rottingdean, the solid chalk is seen to form the 

 whole of the cliffy but it is very difficult to say at what exact 

 . point the debris ceases and the chalk begins, owing ])robably to 



H^ the washing down of the surface by the rains, which, in many 



^B| parts, conceals the real structure of the cliff. 



^^- Although I have described this stratum and the bed of peb- 

 bles as continuing the whole way from Brighton to Rottingdean, 

 yet it must be particularly noticed that about half way between 

 the two places, for about 100 yards, the cliff is formed entirely 



