AUSTEN TERTIARY DEPOSITS OF THE SUSSEX COAST. 69 



waste which the land of this part of the coast has experienced within 

 the historical period; and, when to this are added the eflFects produced 

 during that long period antecedent to such records, it is not too 

 much to speculate on a time when a low level plain extended over 

 the rocky ledges of the Middleton, Bognor, and Barn rocks, and 

 from Selsea so as to include the Owers. (See p. 64.) 



§ V. Summary. 

 It was only a very short time since, and that, too, in the most 

 advanced treatises on systematic geology, that certain superficial accu- 

 mulations of every European district were grouped together, as be- 

 longing to " the diluvial period." Recent investigations are now 

 beginning to assure us of the great amount of physical change which 

 is referable to that period, and also that it was not transitory, nor 

 convulsive, as it has been frequently represented. Already it is 

 separable into stages and subdivisions, whereby the lapse of time is 

 becoming clearly marked out. 



The knowledge we possess of the history of these later changes is 

 as yet a very imperfect one, and it is not perhaps too much to assert, 

 that, of all geological periods, that which comes nearest to our own 

 times is the one which is the least understood. If the accumula- 

 tions themselves in these regions are wanting in those vertical di- 

 mensions which speak directly to the eye as to the vast duration of 

 the older palaeozoic, secondary, and tertiary periods, the very fact of 

 great physical changes having taken place during comparatively 

 much shorter periods of time is in itself a consideration which 

 renders the earth's recent history even more strange than its re- 

 moter one. 



The amount of change which took place in the relative distribu- 

 tion of land and water over the whole northern hemisphere of the 

 globe during this same "Diluvial period" will be found to be as 

 great, if estimated according to area, as that indicated at any earlier 

 times ; whilst it presents moreover such a wonderful uniformity in the 

 direction in which the change took place, that, when fully worked 

 out in all its details, it may perhaps enable us to arrive at a cosmical 

 law for the cause of such changes on the earth's surface. 



In the introductory observations on the land bordering on the 

 English Channel, the superficial accumulations were particularly 

 alluded to, in order to point out, that even in places where these had 

 all been considered as of one age, yet two or more intervals, marked 

 by great changes in the configuration of the surface, were clearly in- 

 dicated. The interest which attaches to the deposits of the Sussex 

 levels consists in this, that through them several more terms are 

 intercalated in the series -of superficial accumulations, and are there 

 characterized by forms of life, whereby the conditions of the stages 

 are clearly marked. This circumstance is owing to the very re- 

 markable fact, that a portion of the Sussex coast has been placed 

 at several periods, dating back to the oldest tertiary times, in precisely 

 the same position with respect to the sea-level. 



The high-level gravel-beds, which in their extension from the south- 



