298 JOSEPH PEKSTWICH, F.R.S.^ P.G.S., ON A POSSIBLE 



single bones and fragments mingled pellmell. The conclusion 

 is that all these various cases ai-e part of one gi^eat earth movement 

 downwards and upwards, and that this theorj offers the best 

 solution and co-orHnates all the observed facts. 



With regard to Mr. Allen Brown's suggestion during tbe dis- 

 cussion, tbat tbe phenomena considered by Professor Prestwich 

 were caused during a " pluvial" period following the Glacial epoch, 

 I would point out that such a period would not account for 



(1) the phenomena at Chesilton, for instance, where the slope of the 

 nearest height is too abrupt to allow of such an explanation, since 

 the natural drainage would besouthward, andnottowards Chesilton ; 



(2) such a raiuAV ish, however abundant, would sort the materials, 

 whereas the Rubble-drift is unsorted ; (3) a "pluvial" period does 

 not account for the unworn character oE the angular debris; nor, 

 (4) can we imagine a sufficient mass of water to be dammed up 

 on such ridges as exist at Les Noires Mottes or Portland to 

 deve'op sufficient kinetic energy to produce such tremendous 

 tumuUuary results as the respective Rubble-drifts at Sangatte and 

 Chesilton present. 



I cannot conclude without expressing my admiration of the 

 sagacity which marks Dr. Prestwich's papers to the Geological and 

 Royal Societies, and the fairness which has led him scrupulously 

 to reject evidence which to his mind was not absolutely conclusive. 



Admiral H. D. Gkant, C.B., R.JST., writes : — 



It will possibly be interesting to the readers of Dr. Prestwich's 

 very valuable paper if I state the result of some observations I 

 made in tlie Red Sea twenty-four years ago. I was surveying 

 Riis Gharib, Gulf of Suez, for a lighthouse, and noticed to the 

 north of the point a very remarkable beach of conglomerate com- 

 posed of numerous small pebbles and stones unUke anything in 

 the vicinity. The adjacent hiiloc^ks averaging 50 and GO feet 

 high were entirely sand, the point itself and hills in the neighbour- 

 hood were chiefly sandstone and limestone. The beach, now about 5 

 or 6 feet above high water mark, extended below the water for 

 some distance. 



In referring to this survey I should like to mention an interesting 

 fact. On the island of Shadwan, at the entrance of the Gulf of 

 Suez, are to be seen some extraordinary evidences of both violent 

 upheavals and more geiitle action — with very deep water-worn 

 gullies — which caused much astonishment to our party, as the 

 dimensions and formation of the island would not admit of such a 

 storage of water as to form so great toirential streams, which the 

 well-marked water-courses would indicate. 



In one part of the is'and, in the centre of a well-mfirked crater, 

 is a hillock of an elevation of about 50 feet, which is a mass of 

 fossilised sea shells, embedded in argillaceous soil, and has under- 

 gone a process of disintegration. In breaking oif a piece of the 



