MACKIE — RAMBLE IIS" THE NORTH OF FRANCE. 



127 



ances. If correct, it should be of value in determining the com- 

 paratively modern origin of that great diluvial mass of angular flints, 

 and the debris of the chalk, and of the Tertiaries, we find so exten- 

 sively spread over the area of the Chalk. 



If no error exists in my examination of the recent shell sand at 

 Havre, the section there goes to show the recent origin of the " flint- 

 drift," since not only the recent species of mollusks lived there, but 

 even the configuration of the coast of Normandy must have had a 

 near approximation to its present state before the drift gravel was 

 deposited. 



The undulating surface of the valley of the Seine must have ap- 

 proached nearly to its present line, although some differences either 

 in the prevalent direction of the winds, or the outline of the shore, 

 are required to account for the accumulation at that spot of so nu- 

 merous a collection of shells, the mollusca and their debris being 

 now on that side of the Seine, but sparingly distributed in conse- 

 quence of the washing-away action of the boisterous seas, although 

 such shells, as before stated, are abundant on the quieter shores of 

 Honfleur, Trouville, and Dives. 



If nothing more important be proved from this bed of sand, it must 

 be admitted that an elevation of some feet has taken place in this 

 district within a very restricted period. Of such an elevation we 

 have also evidences on the English side of the Channel. 



So like in mineral character is the flint-drift seen on the top of the 

 cliff's of Cap La Heve with that shown at the roadsides of the upper 

 part of the valley of St. Addresse, that there seems no doubt of the 

 continuity of the deposit over the shell-sand. 



The mass of craie against which it abuts is not however in situ. 

 The base of the cliff's of Cap La Heve consists of marls, sands, and 

 clays of the Gault, Greensand, Wealden ? and Kimmeridge periods, 

 by the rapid wearing away of which, the craie glauconeuse of which 

 the upper portion of the cliff" consists, is constantly falling or rather 

 sliding down in enormous masses forming an extensive undercliff*, as 

 at Folkestone and the Isle of Wight in our own country. The di- 

 rection of the dip shows that some of these beds would naturally be 

 continued on the site of the "shell-sand," and this buttress of craie 

 debris — for it consists of blocks and the regenerated material of several 

 strata of the craie glauconeuse, as indicated by the mineral characters 

 of the materials, the fossil shells, etc. — has slipped or been brought 

 down from a higher level to its present position ; and it is this which 



