114 Bay— Ancient Beach and Submerged Forest. 



the tract ; and these, during the course of centuries of exposure to 

 the heavy seas that break upon the coast, must have tindergone some 

 considerable amount of destruction. Formerly, therefore, this shoal 

 must have formed a natural breakwater, and have rendered the 

 channel within it a convenient harbour. The gradual destruction of 

 this barrier has probably been accompanied by a gradual silting up 

 of the depression within. The accompanying map is taken from the 

 Admiralty chart ''copied from the Pilote Francais of 1836, and in a 

 later chart (1848) the depth of water at points here marked 3^ and 

 3| fathoms is marked as only being 3 fathoms, so that if any 

 reliance is to be placed on these data, the process of silting up is 

 progressing very rapidly. It occurs to me, as by no means im- 

 probable, that a change of level of the land, by a slight sinking, 

 may have at the same time lowered the barrier, and by increasing 

 the general depth of water in the bay have, to some extent, 

 counteracted the effect of this very rapid silting up of the old 

 harbour. But this is mere conjecture, and I only throw out these 

 remarks in the hope that some archaeologist may, perhaps, be 

 induced to search out any evidence of the cause why Wissant has 

 ceased to be a port ; geologists may thereby be enabled, perhaps, to 

 form some idea of the nature and amount of the changes that have 

 taken place in and around this interesting bay during the period 

 of history. 



But to revert to the more ancient history, the raised beaches 

 (or that of Sangatte, at least) prove a period when the land was 

 depressed below its present level, and the peat bed shows one of 

 re-elevation. The sand above and the second layer of mould 

 indicate a second alternation of movement ; and I am inclined to 

 think that the growth of the present dunes took place during 

 yet another upheaval ; and their partial destruction, as already 

 suggested, during a final and very modern period of depression,, 

 which has left the submerged forest where we now find it. Such 

 a succession of oscillatory movements is, at the present day, well 

 understood, and is in perfect accordance with facts observed else- 

 where.^ De la Beche tells us also that the dunes of the Cornish 

 coast are composed of two parts of different ages.^ This gives us an 

 example parallel to that above described, where the two portions 

 appear to have been separated by a period during which, what must 

 have been at the time, an abundant vegetation covered the older. 

 Where this stratum of mould has not been preserved we lose all 

 clue to the fact that these dunes are not throughout of one date, but 

 belong to epochs, probably separated by a long interval of time. 

 By such perishable evidences are the remarkable events of the 

 world's history preserved to us in the Geological Eecord ! If the 

 pages that we have before us are so fragmentary we may well 

 judge how many must have been altogether destroyed ! 



^ Vide, for one instance, De la Beche's Eeport, etc.. pp. 401, et seq. ; also the 

 Abstract of Mr. Godwin Austen's paper "On Submerged Forest" (Geol. Mag., 

 vol. ii. p. 556. 



2 Supra, p. 426, et seq. 



