﻿364 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Here, however, a new feature presents itself, in the surface of the 

 chalk not being deeply grooved and eroded as it is wherever the drift 

 is immediately superposed to it, and in its being separated from the 

 drift by beds of pebbles, each of which has a thoroughly rounded 

 and water- worn aspect. The pebbles, which are very regularly stra- 

 tified, in layers with sand, are hardly to be distinguished from those 

 now accumulated by the action of the sea, like which they contain 

 here and there a large fragment of chalk, and occupy a thickness of 

 about 8 or 10 feet. It is manifest, therefore, that they were formed 

 under tidal and wave influences of a former epoch. Dr. Mantell, 

 indeed, suggested this, and also pointed out that this pebble- or 

 shingle-bed contained fragments of granite, porphyry, greenstone, 

 quartz rock, and greywacke-slate, &c. — detritus now foreign to the 

 coast. Again, from the condition of the pebbles and the presence of 

 some marine shells of existing species (together with portions of a 

 whale, BalcEna mysticetus, afterwards discovered) he very properly de- 

 duced, that the beds must have been aggregated by long-continued 

 action of waves, — the more so as fragments of chalk among them had 

 been perforated by Pholades. Here, therefore, we have distinct evi- 

 dence of a true old beach, which, although subsequently raised up, 

 had been tranquilly and naturally formed upon a bare chalk shore 

 during a long period, just as the present shingle is accumulated, at a 

 lower level, on the reefs of chalk seen at low water. It is also to be 

 noted that Dr. Mantell further detected in this old marine shore-bed, 

 some remains of the same quadrupeds which occur much more abun- 

 dantly in the overlying " Elephant-breccia." 



This raised beach has here, however, but a small persistence inland ; 

 and its termination eastwards on the coast, which is a little beyond 

 the Preventive Station, is distinctly seen in the vertical cliff. 



For the space of the half-mile where it is exposed, the old beach is 

 everywhere immediately covered by drift, which, from its brecciated and 

 tumultuous condition, presents the most lively contrast to the former, 

 see fig. 7. The lower part of this detritus at Kemp Town is in one 

 part made up of large fragments and angular pieces of chalk, almost 

 in situ, and confusedly heaped together, with some flints, indicating 

 that they must have resulted from violent dislocation. The mass 

 above these consists in some parts of a whitish, chalky admixture or 

 broken rubble, in which a rude undulation is seen, accompanied 

 however (when viewed as a whole) by numerous convolutions of every 

 sort of irregularity, whether as regards the materials or the contour 

 of the laminae. Farther east, these appearances are very prevalent, 

 where the mass, particularly in its upper part, has a yellow sandy 

 matrix, and where the thickness is not less than 50 feet. At Kemp 

 Town, for example, the re-aggregated beds have been formed chiefly 

 out of the detritus of the chalk, but towards the Preventive Station 

 they consist, to a great extent, of sands (with a few large fragments 

 of grey-wether-sandstone) derived from the Tertiary Rocks*. This 



* Since the observations recorded in the text were made, a fall of a portion of 

 the cliff, about 300 paces east of the walks at Kemp Town, has laid open a clean 

 vertical section of the lower part of the drift which lies on the ancient raised 



