30 Mr. Hopkins on the Structure of the 



dresselles, the dip, as seen in the cliff, is to the south, which shows the valley to be 

 here formed by a synclinal arrangement of the beds, since on the south of the 

 valley the dip is northerly. The same arrangement is also maintained more to the 

 east, as shown by the section (Diagram No. 30.) of the hill at Basinghen already 

 described. On the east of Marquise the valley is bounded by the older formations, 

 and a transverse section of it is altogether different. 



I have already mentioned the general structure of Mont Lambert near Boulogne. 

 The hill appears to have originated in a local disturbance. On the side towards 

 Bainctun, the beds dip very rapidlv into the hill, an arrangement of the strata 

 which brings up the coral rag at the foot of the hill, and the Oxford clay in the 

 valley at Bainctun as shown in Diagram No. 27. The general dip of the hill 

 on the western side is small and towards the coast. On the north it has already 

 been stated that the dip is with the general declination of the surface in that 

 direction. 



On the south of the Liane there are no indications of distinct lines of elevation. 



In the portion of the Bas Boulonnais more remote from the sea, and occupied 

 by the oolites, the indications of elevatory movements are much less sensible than 

 in the tract already described. I was not able there to trace the lines of elevation 

 above described to points more remote from the coast than those above indicated. 

 There is, however, some evidence of a transverse dislocation close to the borders 

 of the chalk near Henneveux, which is perhaps deserving of mention. It has been 

 stated in a former part of this paper, in tracing the course of the Oxford clay, that 

 the hill on which Alinctun is situated projects its eastern escarpment as far east as 

 Henneveux and Brunembert, -very near to the opposite chalk escarpment. It 

 appeared to me probable that the Oxford clay dipped with some rapidity to pass 

 under the chalk. This must necessarily be the case if the present difference of 

 elevation between the top of the Oxford clay escarpment and the bottom of that of 

 the chalk was produced by the elevatory movement which took place after the de- 

 position of the oolites. Assuming this to be true, there must here be a transverse 

 line of flexure, such as would almost necessarily be attended by a corresponding 

 dislocation. Such a fracture is indicated by a deep valley which cuts directly across 

 tbe high plateau of Oxford clay near its eastern extremity. The course of the 

 valley is marked by a small stream which falls into the Liane near the village of 

 Bournonville. It would be extremely difficult to account for it, I conceive, in any 

 other manner. Still, it is possible, though I think improbable, that the surface of 

 the Oxford clay might have been approximately the same as at present before the 

 unconformable deposition of the cretaceous system, in which case its actual con- 

 figuration may have been due to denudation, and not to elevation. 



Structure of the North-eastern Portion of the District. — This is the tract occupied 



