176 Geological Society. 



magmatic solution consists of such molecules, and that the norm of the 

 " Quantitative System " is a fairly representative set of these compounds. 



'The actual mineral and textural characters of igneous rocks are variable 

 qualifiers of each chemical unit, and should be applied as such to terms indi- 

 cating magmatic character.' 



2. ' The Denudation of the Western End of the Weald/ By- 

 Henry Bury, M.A., F.L.S., F.G.S. 



There are two main theories of Wealden denudation : — 

 (1) attributing the removal of most of the Chalk to marine planation ; 

 and (2) denying planation, and relying solely on subaerial denudation. 

 Prof. W. M. Davis's suggestion of a subaerial peneplain forms a sort 

 of connecting link between the two. 



The evidence in favour of planation which Ramsay and Topley 

 brought forward is inconclusive, and might plausibly, if it stood 

 alone, be attributed to pre-Eocene causes. On the other hand, 

 Prestwich's arguments against planation are equally weak, while 

 the Chalk plateau to which he draws attention strongly supports 

 Ramsay's views. The distribution of chert is fatal to Prof. Davis's 

 hypothesis, and very difficult to account for, except on the marine 

 theory. 



In the case of the River Blackwater it can be proved that, long 

 after the Hythe Beds of Hindhead were uncovered, the river-system 

 remained extremely immature ; and this affords very strong grounds 

 for the acceptance of the marine hypothesis. 



The evidence of the other western rivers is less conclusive, 

 though the Wey and the Mole both provide minor arguments 

 pointing in the same direction. The anomalous position of the 

 Arun, at the foot of the northern escarpment of the Lower Green- 

 sand on either side of the Wey, is almost certainly due to com- 

 paratively recent captures from the latter river, and affords no 

 ground for assuming a river-system of great age matured on a 

 Miocene peninsula. 



There is no proof that any of the existing connexions between 

 rivers and longitudinal folds are of a primitive character ; and, on the 

 other hand, there are many alleged examples of transverse distur- 

 bances having served as guides to consequent rivers. This again, 

 on the whole, supports the marine hypothesis, especially if, as there 

 are reasons for believing, the longitudinal folds are older than the 

 transverse. 



