AUSTEN TERTIARY DEPOSITS OF THE SUSSEX COAST. 47 



island, have been found to contain the remains of the Elephas pri- 

 migenius. 



The changes which are recorded in the section here given, and 

 which may be taken as a type of the relations of two sets of accu- 

 mulations, both having an extensive range, are as follow : — 



1. The older gravel-beds were accumulated, partly in some old 

 valleys (which will be found to be mostly in lines of disturbance) and 

 in part over an extended level surface. 



2. The next result indicated is that of excavation, by which the 

 beds along the old valleys were cut out along a central line ; the 

 broader expanses were also greatly denuded, and this- process in some 

 cases extended deep into the subjacent strata. 



3. Terrestrial conditions followed. This was the period of the 

 Elephas lorimigenius and associated fauna ; and it was during the long 

 lapse of time which is indicated by the great abundance of these re- 

 mains, that the older gravel-beds became cemented and charged by 

 peroxide of iron, from the percolation of surface-water. 



4. This surface was submerged to as great as, or even to a greater 

 extent than the subsidence that existed during the accumulation of 

 the older gravel-beds : the valleys which had been cut out were again 

 filled with detritus that caught up with it the harder and more per- 

 sistent portions of those animals which had left their remains there. 



These gravel-beds were themselves excavated as we now find them, 

 and nearly along the same lines as before. In these changes each pro- 

 cess of accumulation corresponds to a period of gradual depression, 

 and each denudation to a rise. 



C. The highest or newest beds, which are referable to a state of 

 things somewhat different from such as exists at present, are those 

 described as the *' brick-earth," which is a subaerial accumulation, 

 and therefore necessarily at places cotemporary with fluviatile and 

 lacustrine depositions : such, for instance, in the Isle of Wight, are 

 the beds of sand, clays, and marl which are to be seen in the cliff sec- 

 tion of Tolland's Bay*. 



Gravel Beds of the Sussex Levels. — No detritus whatever is found 

 along the base of the escarpment of the South Downs, as from Cocking 

 to Duncton, whereas chalk-flints form broad and thick accumulations 

 at the foot of their outer slopes. 



The tract beneath the chalk-downs, of which Chichester may be 

 taken as the centre, has been described as a plain, which it is to the 

 eye ; but, though the diff'erence of level may be slight, it will readily 

 be seen that it presents two levels ; and that, bordering on the chalk, 

 there is an upper zone composed of flint-gravel, as at West Hampuet. 

 In places this gravel has a banded arrangement, from the presence of 

 seams of sand ; but where it contains much clay, as is often the case, 

 no such arrangement can be traced. The whole is coloured and often 

 cemented by iron. 



Of this age are the gravel-beds of the Broile, thence extending 

 eastwards. They usually overlie lower tertiary clay strata. 



* Mem. Geol. Surv. Isle of Wight, pp. 8 & 105. 



