Ixxviii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [March I913, 



results of the Sub-Wealden boring, we are justified iu supposing that 

 the declivity shown by the —1000 and 1500-foot contours on the 

 map represents the marginal part only of a prolonged slope. It is 

 significant that the only boring which has reached the Palaeozoic 

 platform below the declivity shows the existence of Trias ; at 

 Erabourne 81 feet of marls and conglomerates lay unconformably 

 on the steeply tilted Palaeozoic rocks. It seems, therefore, that that 

 formation circles round the elevated tract on its southern, as well 

 as on its western and northern sides. 



Prom this fact and from the development of the Jurassic rocks, 

 it appears that the sag in the Palaeozoic platform had been in 

 progress more or less all through Mesozoic times, and that the 

 superimposing of the Wealden Anticline upon it has been a minor 

 incident upon the margin of the sagging area, not materially 

 changing its character as a dominant factor in the structure of 

 Southern England. It is remarkable, too, that the London syncline 

 has been superimposed upon what had been for long a tract of . 

 elevation. 



One of the results of the elimination of the post-Oligocene move- 

 ments has been to accentuate the importance of the elevated tract 

 of Eastern England at the expense of the Palaeozoic areas of 

 Western England and Wales : for, of course, the general tilt of the 

 Upper Cretaceous rocks towards the west has been eliminated, as 

 well as the synclines and anticlines. The evidence on which the 

 relative levels of the London area and the western areas could have 

 been estimated has perished with the denudation of the Upper 

 Cretaceous rocks ; but, if it is right to suppose that those rocks 

 extended continuously over the western areas, we are confronted 

 with a distribution of Palaeozoic tracts in pre-Gault times which 

 differs widely from the distribution now in existence. 



At any rate, the existence of the elevated tract in early Cretaceous 

 times explains several points that were obscure. It provides a 

 probable source for some Palaeozoic material which enters largely 

 into the composition of some of the Lower Cretaceous rocks, and 

 has clearly not travelled far. It explains also the attenuation of 

 the Jurassic rocks and the littoral character assumed by them in 

 its neighbourhood. 



On the other hand, it must be admitted that there still is no 

 obvious connexion between the configuration and the structure of 

 the platform. Though little has been done as yet towards tracing 

 the outcrops of the rocks which compose the Palaeozoic platform, we 



