BEACHES, ETC., OF THE SOUTH OF ENGLAND. 327 



which could have been produced only by the sweep of a far-reaching 

 broom. Further, debris (and bones more especially), if carried down 

 by swollen streams, and subject to frequent and much exposure, 

 must inevitably have been more or less worn, whereas both retain 

 the sharp angles of fracture. All observers agree upon the sharp- 

 ness of the harder debris and the absence of wear on the bones. 



With regard to deposits formed on a Chalk surface these objections 

 are of still greater force, for the wear of the rock would be more 

 rapid, and more deeply cut gullies would result. In either case it 

 is not easy to see how the delicate land-shells found in this rubble 

 could have escaped without injury, or rather destruction, or how to 

 account for the presence of the mammalian remains in the condition 

 in which they are found. Their presence there at all is unac- 

 countable, whether on the supposition that the animals were carried 

 down by freshets, or that their remains had been left after death 

 on the spot where they died. In the one case rhey would not have 

 been dispersed as they now are, and in the other, if by chance they had 

 escaped injury from predaceous animals, they must have been more or 

 less weathered — but of neither do they, as a rule, show any traces. 



2. The agency of ice and snow is open to fewer objections. By 

 this means debris might be propelled over the edge of the cliff 

 along its whole face, without wearing very definite channels, but in 

 times of thaw the escape of the surface-waters must have ended 

 in producing results analogous to those caused by heavy rainfalls. 

 By ice and snow the rubble might also have been driven over 

 smaller gradients and to a gre^iter distance beyond the cliff, but I doubt 

 whether it could, as at Godrevy (antea, p. 281), have been propelled 

 for a distance of above 200 feet from the face of a cliff; for the cliff 

 is not more than 40 feet high, and the hill at the back does not rise 

 higher than 150 feet, and that at a distance from it of some 250 feet. 

 Besides, the slope of the rubble does not exceed an angle of 10° to 

 12°, whereas the angle of repose of loose gravel is 40° and that of 

 rubble 45°, though these would be somewhat diminished, but not to 

 that extent, by the greater fluidity of the mass produced by the 

 snow. Nor would a sludge of ice, snow, and rock-debris in motion 

 be more favourable than running water for the preservation of the 

 land-shells and mammalian bones. 



Another difficulty in the way of the ice-and-snow hypothesis is 

 the small size of the areas (at times to be measured by acres, — see 

 PL YII. figs. 3, 5) that form the centres of dispersion, and the small 

 gradients and short lengths of the slopes. It is very different in a 

 mountainous district, where the frozen masses are large and the 

 slopes steep ; but with the gentle slopes of the South Downs 

 (PI. YII. fig. 2) how would the winter's ice and snow on them have 

 been equal to the propulsion of the debris of flints and loam across 

 the Sussex Coast plain — a distance of from 2 to 5 miles over a com- 

 paratively level surface ? Or, to take the case of the Isle of Portland, 

 is it likely — with its length of 3 miles and its gradient of about 

 1 in 40 feet — that the ice and snow could have forcibly driven down 

 the Head in one direction over the Eaised Beach southward, and in 

 the other direction have sent the large mass of Chesilton debris north- 



Q. J. G. S. No. 190. z 



