part 1] ANNIVERSARY ADDRESS OF THE PRESIDENT. 1.XXV 



and the position of the Palaeozoic platform and the effect of earth- 

 movement upon it have been ably dealt with by your former 

 President, Sir Aubrey Strahan, in his Address for 1913. 



In these publications the principal features of the deep-seated 

 geology revealed by the operations have been described, and much 

 detailed information is given respecting the buried formations. 

 It is my purpose now not to enter again into these particulars, but 

 to discuss as broadly as possible the bearing of the new evidence 

 upon the Wealden structure considered as a whole. 



The borings have shown conclusively that on the northern side 

 of the Weald the anticlinal northward dip dies out in the Cretaceous 

 strata and is replaced in the underlying Jurassic strata, wherever 

 these are present, by a counter-dip to the southward. The 

 Jurassic and Lower Cretaceous formations together form a huge- 

 recumbent wedge tapering away to the north ; and the northern 

 limb of the Wealden anticline, as seen at the surface in the Upper 

 Cretaceous rocks, is simply the slope on the upper plane of this 

 wedge ; while the lower plane, resting on the Paheozoic floor, dips 

 downwards in the opposite direction under the Weald. The 

 structure of this limb is illustrated by the section, tig. 1 (p. Ixxvi), 

 drawn across the North Downs from the Thames shore between 

 Heme and Whitstable to Romney Marsh north of New llomney. 

 As is indicated, the line traverses the position of deep borings 

 towards both ends, and passes not far from another site near the 

 middle. These borings supply the evidence on which this particular 

 section is plotted; but any parallel line drawn to the eastward of 

 this, through the district where the borings are most numerous, 1 

 gives almost precisely similar results, so that the section may be 

 regarded as typical. It must be remembered, however, that in this 

 and in the three later sections it has been necessary to exaggerate 

 the vertical scale to about 9 times the horizontal, therefore the 

 true dips are not nearly so steep as they are drawn ; also, I have 

 nowhere attempted to show faults or minor folds, but have merged 

 all such details into the simpler elements of the structure. The 

 general accuracy is not, I think, in any case seriously impaired 

 by this broad treatment, while the essential factors are conveniently 

 accentuated. 



Without recapitulating the particulars of the succession, which 

 have been elsewhere described, I will draw attention to the fact 



1 See sketch-map and section in my account {supra cit.) in ' Summary of 

 Progress of the Geological Survey for 101G." 



