3>art 1] ANNIVERSARY addrkss of THE PRESIDENT. lxxxiii 



That the structure of certain other areas of sedimentary rocks in 

 England resembled to some extent that of the Weald, was incident- 

 ally urged by Topley in the exposition of his idea that apparent dip 

 need not imply unequal earth-movement. He cited in particular 

 the Jurassic and Triassic rocks of Central England, and the Oolitic 

 rocks of Yorkshire, with further illustration from the Carboni- 

 ferous rocks of Yorkshire and of Derbyshire. I propose now to 

 follow him in regard to the first two examples, with the advantage 

 .of information procured since he wrote. 



The South Midland Structure. 



In the South Midland area the Jurassic sequence affords the only 

 practicable basis for comparison, owing to our inadequate knowledge 

 of the Trias of the Weald, although, if we could have included this 

 formation also, I believe that the similarity of structure would 

 have declared itself more obviously. 



The great eastward attenuation of the thick sedimentary pile 

 which constitutes the Jurassic succession in Gloucestershire and 

 neighbouring counties was brought into prominence by Hull, in a 

 valuable paper contributed to this Society so long ago as 1859, ' On 

 the South-Easterly Attenuation of the Lower Secondary Formations 

 of England, &C.,' 1 and my present discussion of the matter will be 

 practically a restatement of Hull's case, with some additional 

 evidence. As an illustrative section I have taken a west-to-east 

 line from the Cotteswold escarpment above Gloucester, through mid- 

 Oxfordshire, to the neighbourhood of Aylesbury in Buckinghamshire 

 (fig. 3, facing p. Ixxx), as this line runs close to the Burford Boring 



(Depth below sea-level to 

 (Borings.) Palaeozoic floor.) 



Feet. 



Strouanne 453 



Tardinghen 604 



Framzelle 1306 



PasdeGay 1263 



Wirwignes 689 



Samer 440 



' What is the age of this Palaeozoic depression ? How has a lower 

 orographic syncline changed into an upper geotectonic anticline P These 

 questions will be answered, it is hoped, by a study of the Jurassic rocks 

 traversed in the above-mentioned borings.'] 



1 Q. J. G.S. vol. xvi, pp. 69-81. 



