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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 25, 



To the east of Farnham there is a depression of the chalk-strata 

 for an interval of a mile ; towards this point one of the upper branches 

 of the Wey, known as the Farnham River, comes down in a direct 

 course from its source, near Alton, and would flow out into the 

 London basin but for an intervening difference of level of very small 

 amount, and which causes the stream to turn away at a right angle 

 in the direction of Waverley. The line of valley from Farnham to 

 Alton belongs to the system of disturbances which attended the 

 Wealden elevation *. In this upper portion of the valley of the Wey 

 we have a repetition of all the phenomena of the Guildford Valley 

 with respect to the limited distribution, composition, and arrangement 

 of the gravel-beds, so that it will not be necessary to give any detailed 

 description of them ; and for the same reason, the gravel-beds of the 

 valley of the Mole, at Dorking and Betchworth, will need only inci- 

 dental notice. It would require a great extent of illustration to show 

 the detail of the distribution of these gravels from Alton to Reigate, 

 and their dependence on the external configuration of the district. 

 Such detail cannot be attempted here, besides which independent 

 observers need no longer trouble themselves to map out and define 

 the boundaries of geological groups, inasmuch as the Government 

 has undertaken the task. 



Sir R. Murchison has lately (in a paper read before the Society 

 May 14, 1851) brought forward some views respecting the convulsive 

 character of the Wealden elevation, and has appealed to certain lines 

 of gravel-beds as the evidences of such forces : another distinguished 

 geologist has long supported his theory of the Wealden denudation 

 by a reference to an accumulation of the same age as that of the beds 

 to be here noticed f. I neither propose in this place to offer any 

 observations on these views, nor to substitute any speculations of my 

 own as to the Wealden area; but simply to show that the accumula- 

 tions in question are perfectly distinct, as to age and origin, from 

 those which resulted immediately from the spoil of the Wealden de- 

 nudation, and that this area had acquired its main physical character 

 at some time anterior to the distribution of these gravel-beds. I am 

 the more anxious that this fact should be fully appreciated by geolo- 

 gists, from its connexion with the physical geography of the South 

 of England during the Upper Tertiary period. 



The external physical features of the valley south of the break in 

 the chalk at Guildford are represented on the Map, fig. 1, and its 

 geological structure has been already described %. The slopes of the 

 hills which surround this area are remarkably steep. When viewed 

 from their summits, the bottom of the valley has the appearance of 

 a perfectly level plain ; it consists, however, of two platforms — an 

 upper and outer one, and a lower or central, along which the river 

 Wey now takes its course : the difference of level is trifling, not more 

 perhaps than 1 2 feet, but it is marked by an abrupt descent from 

 one to the other. The whole of this area, to the base of the steep 



* Quart. Journ. Geol. Soc. vol. iv. p. 260. 



f Principles of Geology, 1833, vol. iii. p. 285 et seq. ; Manual, 1851. 

 X Proc. Geol. Soc. vol. iv. p. 170. 



