58 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



as compared with masses of subangular gravel, implies lengthened 

 attrition in places, such as bays, where the materials remain long 

 impounded. If we assume that the rounded granitic and other 

 shingle, now found in the beds of the Sussex-levels, may have fol- 

 lowed the coast-line from Cornwall and Devon eastwards, it should 

 happen, that all these materials should be water-worn, that similar 

 pebbles should occur along the intermediate space, and that they 

 should increase in bulk and in number westward ; but such is not 

 found to be the case. 



Again, under the supposition that these materials may have been 

 derived from our own western districts, it is necessary that all the 

 different rocks above enumerated should occur in that quarter. In- 

 stead of this, some only of the granites, greenstones, fibrous slates, 

 and limestones are referable to rock-masses occurring between Torbay 

 and the Land's-end. On the other hand, if the fragments contained 

 in the yellow drift-clays of Sussex be compared with a series taken 

 from the rocks composing the Cotentin and the Channel Islands, the 

 agreement will be found very close and striking, so much so, that I 

 was at one time disposed to think that they must have been derived 

 directly from that quarter ; and it was very reluctantly, and from 

 the insuperable difficulties which such a supposition involved, that 

 I abandoned it in favour of the view which is here taken. 



With respect to the perfectly rounded materials, or shingle, we 

 know that, previous to its removal to where it now occurs, it must 

 have been formed and accumulated on some coast between tide-lines ; 

 on one side of the Channel such spot could not be less than seventy 

 miles distant ; and although, as has been stated, the materials them- 

 selves lead us to look to the French coasts of the Channel, it by no 

 means happens that the whole of the series from which they may 

 have been derived is to be met with at the coast-line there. This 

 view involves the supposition of a condition of the Channel-area such 

 as it presents now, — under such conditions no one part of its coast, 

 nor even the whole of the present coast-line taken together could 

 have furnished all the foreign materials now buried beneath the 

 Sussex-levels. 



Even were this otherwise, the law regulating the distribution of 

 coast-shingle renders the supposition of derivation from the French 

 coast wholly inadmissible. Shingle can only travel to any distance 

 in the direction of the coast-line on which it has been formed. A 

 section across the Channel from the Cotentin to Selsea shows an 

 undulating surface of sea-bed, and deep troughs of 300 feet, across 

 which such materials could not have been so moved. 



But, admitting that the smaller shingle from some distant coast 

 might have found its way to our Sussex-levels, by some possible 

 application of the drifting powers of the sea along its marginal line, 

 such powers become wholly insufficient with reference to the more 

 bulky masses which have been here noticed. 



The dimensions of the boulder now exposed near Pagham, and the 

 many others of scarcely inferior size which must have been met with, 

 seem to admit but of one supposition with reference to the mode 



