part 1] ANNIYERSARY ADDRESS OF THE PRESIDENT. lxxiii 



The Structure of the Weald and Analogous Tracts. 



Amid the turmoil of recent events, so momentous for humanity, 

 it has not been easy to concentrate attention upon the history of 

 the distant ages when there were no men on the Earth. But our 

 studies of the silent past, apart from their practical consequence, 

 have, in times like these, a particular value in releasing us tem- 

 porarily from the spell of the present ; and it is in this mood that 

 I now invite your reconsideration of some familiar features in 

 English stratigraphy. 



The Wealden Anticline. 



There is no structure in Britain that is more widely known to 

 geologists in general than the Anticline of the Weald. The dis- 

 tinctive rock-types and surface-features in which the structure is 

 revealed stand out with such bold simplicity that, from the early 

 days of our science, the Weald has been accepted almost uni- 

 versally for all purposes of illustration as the type of a broad 

 uncomplicated anticline. And, if we confine our attention to the 

 surface, no better example of the structure could be anywhere 

 found. But, when William Topley nearly half a century ago 

 began to consider the detailed stratigraphy of the area as a whole, 

 in the preparation of his great memoir on the geology of the 

 Weald, 1 he soon perceived that there were factors present which 

 had not been taken into account in the current explanation, and 

 that the origin and structure of this apparently slight and simple 

 fold deserved further study. As a result of his study, he brought 

 a short paper before this Society in 1874, entitled ' On the 

 Correspondence between some Areas of Apparent Upheaval & the 

 Thickening of Subjacent Beds '. 3 In this paper, he urged that 

 the anticlinal dip of the Wealden strata might be, at least in part, 

 accounted for without earth-movement, because of the much greater 

 thickness of the Lower Cretaceous sediments in the axial area than 

 on the flanks ; and he showed that the same explanation could be 

 applied to several other tracts of gently-inclined rocks in England. 

 At the time when his paper was read, the Sub-Wealden Boring had 

 not been carried out ; and Topley pursued his argument with the 



1 Mem. Geol. Surv. 1875. 



2 Q. J. G. S. vol. xxx, pp. 186-95. 



