460 PROCEEDIIfGS OP THE GEOLOGICAL SOCIETY. [May 24, 



Part II. Ojs" the Denttdation of the Weald. 



Having noAY described the chief phenomena connected with the 

 superficial beds of the Medway valley, we will pass on to consider 

 the Hght which they throw upon the much-disputed question of the 

 " Denudation of the Weald." We think it will be conclusively 

 shown that " rain and rivers " have been the main agents in pro- 

 ducing the present form of the ground. 



We propose to treat the subject in the following manner : — 

 a. Short sketch of previous theories, with objections to the theory 

 of fracture, and to the marine theory, 



1. Theory of Fracture. 2. Marine theory. 

 /3. Bearing of the river-gravel on the question, 

 y. On the mode of deposition of beds of gravel and loam, and on 



the action of streams and rivers in modifying their channels. 

 ^. On the origin of escarpments. 



n. Short Sketch of previous Theories, tvith Objections to the Theory 

 of Fracture and to the Marine Theory. — In the Introduction pre- 

 fixed to Conybeare and Phillips's ' Outlines ' *, Mr. Conybeare gives 

 an account of the combination of longitudinal and transverse valleys, 

 or those running respectively along and across the strike, of which 

 the Weald is an excellent example. He attributes their formation 

 to running water ; but adds, " it is easy to show that the phe- 

 nomena attendant on valleys are very commonly of such a nature 

 that to believe them to have been formed by their actual rivers, 

 however long their action may have endured, involves the most direct 

 physical impossibilities." Mr, Conybeare also points out (p. 145) 

 that, if the tranverse valleys were filled up, the whole drainage of 

 the country would pass out by Romney Marsh and Pevensey 

 Level. 



Mr. Scropef, in 1825, in speaking of the results of volcanic 

 action, alludes to the Weald as the result of upheaval, during which 

 " a longitudinal crack opened across the beds parallel to the axis of 

 elevation. • The chalk, resting on beds of clayey marl, slipped away 

 on either side from the axis, leaving bare the lower strata of green- 

 sand. Again, the partial subsidence of this formation upon the 

 slippery beds of the Weald Clay disclosed in turn the iron-sand, 

 which forms the visible axis of this ridge." Such valleys the author 

 proposed to call " valleys of elevation and subsidence, or anticlinal 

 valleys" J. He considers that they may have been " subsequently 

 enlarged and otherwise modified ; and many others, perhaps indeed 

 a far greater number, wholly and entirely excavated by the slow 

 but constant and powerful action of the same causes which are still 

 continually in force ; amongst which the fall of water from the sky, 

 and its abrasive power as it flows over the surface of the land from 

 a higher to a lower level, is the principal " (p. 214). 



* ' Outlines of the Geology of England and Wales,' 1822, p. xxiii. 

 t ' Considerations on Volcanos,' chap. 10, p. 213. 



\ Dr. Bucbland, in 1825, proposed to call tlie Weald and similar valleys^ 

 "valleys of elevation" (Trans. Geol. Soc. 2nd series, vol. ii. p. 119). 



