and on the Basins of London and Hants. 125 



Bion, that rot only many inclosed valleys similar to that of Kingsclere, but also^ 

 in a less degree^ many open valleys similar to that of Pewsey and tlie great 

 central valley of Kent and Sussex^ though largely modified by denudation, 

 owe their origin to an antecedent elevation and fracture of their component 

 strata ; and these phajnomena may be regarded as of frequent occurrence 

 in the formations of all ages, and as indicating the multitude of disturbing 

 causes by which the earth's surface has been affected. 



Another question of some moment derives much light from the evidence af- 

 forded by the valley of Kingsclere and the contiguous district along the line of 

 junction of the plastic clay with the subjacent chalk, viz. whether the chalk was 

 disposed in its present form of troughs or basins before the deposition of the 

 tertiary formations now inclosed in them ? or (to speak more locally) whether 

 the basins of London and Hants existed in their present relative position to each 

 other and to the chalk, before the epoch of such deposition ? and I think the 

 evidence we here find, shows as decisively for the basin of London, as that 

 which we collect at the two extremities of the Isle of Wight and near Corfe 

 Castle does for the basin of Hants and Dorset, that the present inward inclina- 

 tion of the southern edges of both these basins has taken place since the depo- 

 sition of the Plastic, and also, probably, of the London, clay. 



The sections near London afford us no means of judging of this question, as 

 all the tertiary strata are here nearly horizontal and parallel to those of the hori- 

 zontal chalk. But where it happens (as it does near Highclere) that thin and 

 regular beds of sand, gravel and clay, are disposed at a high angle, and exactly 

 parallel to the strata of the subjacent chalk, along a considerable tract of coun- 

 try, it is no less certain that the movement of both these formations, whether 

 by elevation or depression, was contemporaneous, than it is clear from the sec- 

 tion at Alum Bay, that in the Isle of Wight the vertical and parallel position 

 of the same formations on the south frontier of the Hampshire basin was 

 posterior, not only to the deposition of the plastic, but also of the London, 

 clay. 



Assuming then, that the London and Hampshire basins did not hold their 

 present relations to each other and to the intermediate elevated plains, at the 

 time of the deposition of the plastic clay, the next inquiry is, whether on 

 these plains there be any evidence to show that the tertiary strata which now 

 repose almost exclusively within these basins, have been originally more con- 

 tinuous than they are at present, or perhaps united together. 



Now it happens that the space dividing the basin of London from that 

 of Hampshire is almost wholly occupied by an elevated plain of chalk, the 

 average level of which exceeds that of the tertiary hills within the area of 



