A. Sirahan's Address to Section C, Geology. 461 



anticline of the Isles of Wight and Purbeck, not only lie in the 

 range of the axis, but show an increasing intensity southwards, 

 towards what we may suppose to have been the most active part of 

 ■that axis. A similar structure prevails in the Oolitic rocks also. 

 They too had been thrown into east and west folds before the 

 'Cretaceous period, and this earlier set of movements also grew in 

 intensity towards the south. It would seem, then, at first sight that 

 the structure of the later rocks gives an easy clue to the structure of 

 the older rocks buried beneath them. This is by no means the case. 

 That the movements manifested in the Oolitic and Cretaceous rocks 

 followed the same general line as the older movement admits of 

 'little doubt, but that the later structures correspond in detail with 

 the earlier is improbable. 



A brief examination of the region where the Carboniferous rocks 

 disappear under the Secondary formations will give the grounds 

 for this statement. There we find that the Trias passes over the 

 ■complicated flexures of the Mendip axis in undulations so gentle 

 as to prove that those flexures had been completed before it was 

 deposited. Nor, again, do the members of the Oolitic group of the 

 rocks cropping out in succession further east show any such folds 

 as those visible in the Carboniferous, and it is not till we have 

 passed over a considerable tract of Secondary rocks in which 

 there are no signs of east and west folding that we reach the 

 anticlines of the Vales of Pewsey and Wardour. Nor can we 

 then fit these folds in the Cretaceous formation on to any visible 

 axes in the Carboniferous rocks. Under these circumstances it 

 would be unjust to suppose that such synclines and anticlines as 

 those of the London and Hampshire basins, or of the Weald, 

 coincide with previously formed synclines and anticlines in the 

 older rocks. They give a clue to the position of the old axis, but 

 not necessarily to the details of its structure. Yet it is upon the 

 determination of the position of the older anticlines and synclines, 

 and of their intersection with the north and south disturbances, 

 that we must depend for locating concealed coalfields. So far but 

 little has been done in the forty - eight years since the question 

 was first mooted by Godwin-Austen. The existence of a coalfield 

 in Kent has been proved, and what appears to be a prolongation 

 of a disturbance from the Pas de Calais along the south-western 

 side of it. The other borings which have reached the Palseozoic 

 floor round London and at Harwich have thrown but little light 

 on the details of its structure. By far the greater part of the ground 

 remains yet to be explored. 



In this brief review of the earth-movements of one period, as 

 manifested in one small part of the globe, we have found reason to 

 conclude that they were the result of compression and upheaval ; 

 that the crust yielded to the compression by overthrusting and 

 buckling along certain belts ; that these belts in the north of 

 England and the Midlands ran for the most part north and south, 

 ■diverging, however, to the south-west and to the south-east, while in 

 'the south of England they took an east and west direction and 



