464 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 24, 



by a strip of water in the "Weald Clay valley, then a long ridge of 

 Greensand country ; beyond this a second strip of water washing 

 the foot of the Chalk escarpment. " This form of ground would 

 certainlj'' be peculiar, and ill- adapted for the beating of a powerful 

 surf, so as to produce on one side only the cliffy escarpment that 

 forms the inner edge of the oval of Chalk"*. 



ft. Bearing of the River-gravel on the question. — ^We have endea- 

 voured to show that there are many objections both to the " fracture 

 theory," and to the " marine theory," and we will now proceed to 

 discuss the arguments in favour of the " atmospheric theory" which 

 may be derived from an examination of the superficial deposits, de- 

 scribed in the first part of our paper. 



"We have shown that deposits of river-gravel occur at various 

 heights, sometimes even 300 feet, above the level of the Medway. 

 All this gravel we consider as having been deposited by the River 

 Medway, when its bed was at a much higher level f, and the follow- 

 ing are the reasons for this supposition. No one would hesitate to 

 say that the Aylesford gravel is a fortner bed of the Medway, or, in 

 other words, that the Medway once fiowed 40 feet above its present 

 level. When we find similar gravel and brick-earth of river origin, 

 and containing similar fossils, gradually creeping up the hills, we 

 find that we cannot stop at 40 feet, and we are constrained to admit 

 that the Medway flowed at 100, 200, and even 300 feet above its 

 present level, and in the same direction as at present ; for the river- 

 gravel lying on the Lower Greensand and Gault contains pebbles of 

 Wealden sandstone which must have been brought from areas south 

 of the Greensand escarpment. As the gravel is found at all levels 

 from the 300 feet to the present level of the Medway, we must sup- 

 pose that the river deepened its bed gradually, and that since the 

 Medway flowed at the 300 -feet level no agents, except rain and 

 rivers (and possibly river-ice), can have been working at the denu- 

 dation of the rocks contained within the basin of the Medway. The 

 next question is, What is the amount of denudation that has been 

 effected since the Medway flowed at the 300-feet level at East Mai- 

 ling? The area shaded on the Map (fig. 9) represents roughly J 

 what part of the Medway basin souili of East Mailing is below the 

 300-feet level. "When the Medway was depositing the East Mailing 

 gravel, of course all this area must have been above the 300-feet 

 level. Therefore, since the Medway ran at the 300-feet level at 

 East Mailing all this area has been denuded. When we add that 

 a large part of this area is 200 and even 250 feet below the gravel 

 at East Mailing, the vast amount of the denudation will be perceived. 



* Eamsay, ' Physical Geology and Geography of Great Britam,' 2nd edit. p. 

 79. 



t Relatively to the strata it was flowing over, though not necessarily higher 

 above the sea-level than it is at present ; for, if the river worked its way down- 

 wards as fast as the Wealden area was raised upwards, no alteration of its posi- 

 tion with regard to the sea-level would take place. 



X Untn the New Ordnance Survey of Kent is completed, it wiU be impossible 

 to show exactly how much of the country is below the 300-feet level ; but a 

 rough map is sufficient for our purpose. 



