2 Mr. Hopkins on the Structure of the 



When I came, however, to examine the descriptions which we already possessed of 

 the geological structure of the district, I found them too imperfect and frag- 

 mentary to enable me to detect with certainty the accurate laws of the phseno- 

 mena, or to allow me to appeal to them as tests of the accuracy of my theoretical 

 views. 



The general anticlinal structure of this tract has been long known. Dr. Mantell 

 and Mr. Lyell recognized also the existence of several longitudinal anticlinal lines, 

 running generally in an east and west direction. Dr. Mantell had also made several 

 insulated observations on the dip of the strata in different localities ; but I am not 

 aware that either of these gentlemen so far directed his attention to observations 

 of this kind, as to determine accurately the position or extent of any one of the 

 lines of elevation, the existence of which they had recognized, much less to detect 

 the true law by which (as we shall see hereafter) these lines are related. Dr. Fitton 

 has also made several observations on the structure of the Weald, and has given 

 some valuable sections in his memoir " On the Formations below the Chalk," a 

 work to which I have constantly referred in my own investigations. Only one 

 part of the Wealden district, however (the south-western), has been hitherto 

 examined, with reference to its structure, in much detail. This portion, lying 

 more especially in the neighbourhood of Pulborough, was carefully investigated by 

 Mr. Martin, and described by him in a memoir published some years ago. The 

 author in this memoir enters into some speculations concerning the general cha- 

 racter of the whole tract comprised within the limits of the Wealden denudation, 

 and especially directs attention to its transverse drainage. Almost every one of its 

 rivers, in some parts of its course, passes nearly perpendicularly through one or 

 more of the longitudinal ridges of the district, and finally escapes from it by 

 passing transversely through the bounding chalk escarpment. It seems almost im- 

 possible to render any account of this frequent transverse direction of the river- 

 courses, without referring it to the original existence of transverse fissures, as Mr. 

 Martin has done. He appears to have been the first to recognize distinctly what 

 I conceive to be the real structure of the district in this respect, but his views 

 were for the most part conjectural, except so far as they were applied to the 

 neighbourhood of Pulborough. With respect to other parts of the district, they 

 appeared to rest principally on analogy, and not on facts furnished in detail by 

 direct observation. I determined therefore to attempt to supply the deficiency 

 of evidence in that large portion of the Wealden district which had not been 

 examined in sufficient detail ; and since the analogy which the denudation of the 

 Bas Boulonnais bears to that of the Weald, and the relative positions of the two 

 districts, indicate the great probability of their elevations having been contempo- 

 raneous, I considered it necessary, in order to render the investigation complete, 



