181 Mr. S. V. Wood on the Formation of the River- 



Inasmuch as the lateral displacement should be greatest in the 

 case of the uppermost beds, from the greater length of the exte- 

 rior curves over a dome of elevation to those more interior, as 

 shown by Mr. Hopkins in the case of the Weald, the greatest 

 results would be looked for where the uppermost beds were pre- 

 sent. But against that we have the greater mobility of the 

 soft sandy Eocene strata over the more rigid chalk ; so that the 

 latter, with a less displacement than the former, might produce 

 at greater distances equal or even greater flexures than the latter. 

 The same observation applies equally to the varying rigidity of 

 the lower cretaceous and oolitic beds. We have a concurrence 

 of evidence to show that these movements took place when the 

 sea of the upper drift covered the island ; and it would be a 

 subject of much interest to discuss how far the influence of a 

 superincumbent sea would conduce to an increase in the pasty 

 or pliable condition of the strata beneath it, did space permit me 

 here to enter on that subject. I will only observe, therefore, 

 that it appears to me that this influence would be great, since, 

 if the impervious clays did not completely overlap the sandy 

 beds, the pressure of the water must reduce the porous beds of 

 sand to the condition of quicksands, by filling every interstice 

 between the grains with water. We know also how great is the 

 quantity of water that chalk will as land absorb ; and this 

 quantity may be capable of large increase under the pressure of 

 a sea, and the pliability or pasty consistency of the mass pro- 

 portionately augmented. These are the causes to which, as it 

 appears to me^ the inclination of the oolitic and cretaceous strata, 

 that in sections attached to early geological maps were repre- 

 sented as arising from an upheaval in the north-west, is really 

 due; that is to say, in lieu of such elevatory action from the 

 north-west, they have been produced by a lateral pressure radia- 

 ting from a centre in the South-east of England; and in sup- 

 port of that view I call particular attention to the manner in 

 which the circles abruptly cease against the Triassic outcrop 

 generally, and most conspicuously so where that outcrop, backed 

 by the close neighbourhood of the palaeozoics, presents most the 

 character of a wall stopping the outspread, as in the region 

 skirting the eastern side of the Somersetshire coal-field. 



It should of course follow, if these views are sound, that all 

 the ridges which the surface presents should be alternations of 

 anticlinal and synclinal, however faint these may be. Much of 

 the valley system of the East of England consists of lines of 

 hills produced by denudation, as the chief and almost the only 

 apparent cause, so that it is not easy to determine whether these 

 lines of hills are really anticlinals. On the coast, where the 

 hills are in section, the alternation of anticlinal with synclinal 



