1865.] 



FOSTER AND TOPLEY JIEDWAY GRAVELS, 



443 



On the Superficial Deposits of tlie Valley of the Mebway, ivith 

 Remarks on the Denudation of the Weald. By C. Le Neve 

 Foster, B.A., D.Sc, F.G.S., and William Topley, F.G.S., of the 

 Geological Survey of Great Britain. 



Contents, 



Introduction. 



Part I. Description of the superficial 

 deposits. 

 a. General description of the vaUey 



of the Medway. 

 /3. Superficial deposits. 



1. Subaerial beds. 



2. Modern alluvium. 



3. Kiver-gravelandbrick-earth. 

 a. The Medway. 



h. Tributariesof theMedway. 



4. Pipes of gravel and brick- 

 earth. 



5. Disturbances. 



Part IT. Denudation of the Weald. 



a. Short sketch of previous theories, 

 with objections to the theory 

 of fi'acture and to the marine 

 theory. 



/S. 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. 



S. On the origin of escarpments. 

 Conclusion. 



Introduction. 



During the last few years the subject of river-gravel has so much 

 occupied the attention of geologists, that a short description of the 

 gravel and brick-earth of the valley of the Medway will not be with- 

 out interest, especially as those deposits have a most important bear- 

 ing on the denudation of the Weald. In the present paper we 

 propose, firstly, to describe the superficial deposits of the valley of 

 the Medway, and, secondly, to show what light those deposits throw 

 on the theory of the denudation of the Weald. 



Part I. Description of the Superficial Deposits. 



a. General Description of the Valley of the Medium/. — Before de- 

 scribing the superficial deposits it will be well to devote a few lines 

 to a concise account of the basin of the Medway; the position of the 

 beds will then be more readily understood. As we intend to treat 

 of only so much of the basin as lies within and south of the Chalk 

 escarpment, we can confine our description to that part. The escarp- 

 ment of the Chalk forms on the north a well-marked boundary to 

 our district. On the east the line of watershed separating the vaUey 

 of the Medwaj' from that of the Stour passes south from the Chalk 

 by Lenham to Pluckley and Shadoxhurst; thence the watershed 

 turns westwards, and, passing Cranbrook, Ticehurst,Wadhurst, Crow- 

 borough, and West Hoathly*, divides the waters of the Medway 

 from those of the Bother and the Ouse. From West Hoathly a 

 line passing northwards by Copthorn Common and Bletchingley to 

 the Chalk escarpment, north-west of Godstone, separates the Medway 

 basin from that of the Mole ; the boundary of our basin then follows 

 the Chalk past Titsey, turns south-east and runs eastwards along the 

 high ground of the Lower Greensand to Ightham Common, and then 



* This high ground forms part of the prominent chain of liills known as tlie 

 Forest Ridge. The highest point, Crowborough Beacon, is SO-i feet above 

 low-water mark. 



