AUSTEN TERTIARY DEPOSITS OF THE SUSSEX COAST. 41 



exactly with the breadth of the series of yielding oolitic strata, along 

 which line the rate of destruction and removal is now so great as to 

 warrant the supposition that this particular portion of the south 

 coast has been mainly produced within a comparatively recent period. 

 Weymouth Bay is partly due to a line of depression and partly to 

 sea- waste. From Portland to Durlston the coast-line presents 

 advancing cliifs of hard strata ; but, whenever yielding beds come in, 

 as to the east of Swanage, the coast-line recedes. At some time 

 therefore, not very remote, the line of this part of the south coast of 

 England must have been less irregular, or more linear in an east and 

 west direction than at present. 



The remains of Elephants and other large Mammalia occur in all 

 the valleys which open out into Charmouth Bay, from the Exe to 

 the Brit ; the gravel-beds in which these occur are much above the 

 present sea-level, and have been cut through, at some time subsequent 

 to their original accumulation, along the central hues of these valleys. 

 These valley-gravel-beds are quite distinct from those, with pebbles 

 of quartz and granite, which cap the Haldon, Blackdown, and other 

 ranges which run down to the coast as far east as the Bridport valley, 

 and which gravel-beds do not contain mammalian remains. 



The beds of peat with timber-trees which are to be seen at low 

 icater opposite the openings of some of these valleys, as at the mouth 

 of the Char, must not be taken as indications of recent changes of 

 level, but only as serving to mark the continuation of those vallej's 

 before the coast-hne had been cut back. A little caution is necessary 

 ■vsith respect to numerous local deposits of a terrestrial character 

 which are exposed between tide-levels round the whole of the east 

 end of the English Channel, but I am not aware of any special cha- 

 racter by which these accumulations can be distinguished from those 

 older land-surfaces which were coeval with the large Mammalia, and 

 older than the gravels containing their remains. 



The accumulations of shingle on this part of our coast consist 

 principally, as in the great Chesil Bank, of chalk-flints and chert ; 

 but it is deser\*ing of notice that the so-called *' raised beach" at 

 Portland Bill is mainly composed of local materials, and with only a 

 few flints : so that, at the time the water-level stood at the line thus 

 mdicated, materials were not available for flint-shingle as at present : 

 the cause of this must obviously be sought for in the change of level 

 itself. 



The flint-shingle of the beaches of Studland and Christ Church 

 Bays is derived from the gravel-beds which cover the adjacent parts 

 of Dorset and Hants : this is the case with respect to the shingle- 

 beaches of the whole of the eastern extremity of the English Chan- 

 nel, — the great bulk of the material is old gravely which has been 

 worked over again and again during various successive periods. 



Some peculiar features in the parts of the Isle of Wight and South 

 Hants, bordering the Solent, will be noticed in the sequel. 



Sussex. — Further east, the Chalk Downs of Sussex present a ridge 

 from three to six miles broad, trending from Beachey Head in a 

 direction about E. bv S., W. bv N. ; from this headland to Selsea 



