280 DILUVIUM. 



forming the base of the chiF. The shingle bed succeeds ; and imme- 

 diately above it, is a heap of chalk in a state of ruin ; the latter is invested 

 by the calcareous bed, of which the upper part of the cliff is composed. 

 This appearance is curious, but the manner in which it has been produced 

 is easily explained, by a reference to those natural operations that stiU 

 continue in full activity on our coasts. Were a bed of calcareous rubble 

 to be deposited over the ruins of the chalk chifs that are scattered along 

 the shore, a collection of materials would be formed, corresponding in 

 every respect with those above described ; and a vertical section would 

 exhibit an appearance precisely similar ; namely, a stratum of solid chalk 

 at the base ; then a layer of sand and of shingle ; and lastly, a heap of 

 displaced chalk, surrounded by calcareous diluvium. In corroboration of 

 this opinion, it may also be remarked, that while in general, the variations 

 observable in the colour and composition of the calcareous bed, are nearly 

 Jiorizontal, in the circumstances under discussion, they are no longer 

 conformable to the subjacent deposit, but rise over the heaps of chalk 

 rubble ; as in Tab. iv. fig. 2. These interspersions of pure chalk are 

 frequent in other parts of the bed, but the present example is one of the 

 most remarkable. 



Proceeding eastward, at the distance of two miles and a half from 

 Brighton, the cliff is composed of the Upper chalk, to the extent of three 

 hundred yards. This remarkable change in the structure of the cliff has 

 evidently been occasioned, partly from the destruction of the diluvial 

 deposits by the inroads of the sea, and partly from a projection of the 

 chalk, which formed their ancient boundary ; for there appears to have 

 been but Httle correspondence in the sinuosities of the ancient and modern 

 shores. An abrupt recess marks this alteration in the face of the cHff ; 

 and here the calcareous bed rises suddenly to the summit of the chalk, 

 over which it is continued in a layer of inconsiderable thickness (vide 

 Tab. V. fig. 1). The shingle bed, which at a short distance to the west 

 contains large masses of chalk, here suffers a remarkable contraction, and 

 is divided by thin seams of sand and fine rubble. At the curvature of 

 the recess, the shingle diminishes very abruptly, and soon entirely dis- 



