184 On the Geology of the Cliffs at Brighton, [March, 



On Sept. 24, 1817, I examined the structure of the cliff at 

 Brighton. From the dirt and rubbish thrown over it, it is impos- 

 sible to make any observations on the west part of the town, nor 

 is the structure clearly to be perceived on the east till you arrive 

 at the last groin, which is near the termination of the houses on 

 the east cliff. 



Here there is a passage cut in the cliff to descend to the shore, 

 and a little in advance of this a good idea may be gained of the 

 structure of the whole of the cliff between this place and Rotting- 

 dean. 



From the top to about four feet above the level of the shingle 

 (as it then was) the cliff consists of fractured chalk flints inter- 

 mixed with small, mostly rounded, fragments of chalk, cemented 

 togetlier by a very pale ferruginous clay ; the cohesion of these 

 materials, though not very firm, is sufficiently strong to make it 

 difficult to pull out a projecting flint by the hand, and also to 

 allow the cliff to be absolutely perpendicular, which is mostly the 

 case : the fragments of flints, though they appear to have been 

 subjected to the action of water, are nevertheless by no means 

 rounded; they are merely deprived of their sharp edges and 

 angles. 



Under this stratum, which, as I have said, occupies the whole 

 of the cliff to within about four feet of the level of the shingle, is 

 a bed or layer of perfectly rounded pebbles ; they appear to be 

 mostly chalk flints, are quite loose, and rest upon a thin layer of 

 fine silicious sand, and this asrain rests upon the solid chalk. 

 The latter circumstance cannot, however, at present be seen till 

 you have advanced about a mile east from this spot. 



These rounded pebbles are mostly of a large size, and have no 

 intermixture of clay or other substance to bind them together : 

 this may be said generally of the bed. In several spots, how- 

 ever, and particularly a little cast of the groin in the upper part 

 of the bed, the interstices are filled up by calcareous matter in a 

 state of very distinct crystallization : hence these pebbles falling 

 from the cliff, form masses of considerable firmness ; in other 

 parts, the calcareous matter is in an earthy state : further to the 

 eastward, they are not unfrequently mixed with clay or sand, 

 but still continue loose. 



This bed may be distinctly traced to within about one-eighth 

 of a mile of Rottingdean ; it may always be distinguished from 

 the superior stratum by the rounded form of the pebbles ; it is 

 about six feet in thickness, and from this it does not vary, 

 except near its termination, and in one or two other places. 

 After continuing for about two miles from Brighton, on a level 

 with the present bank of shingle, it begins to rise very gra- 

 dually, and the solid unaltered chalk appears on which it is 

 Been to rest, except where the thin layer of fine sand occurs, and 

 this is in some places mixed up with the pebbles. About a 



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