1849.] AUSTEN ON THE VALLEY OF THE ENGLISH CHANNEL. 91 



ing oif at nearly the same level against a central area, over which no 

 trace whatever of such gravels is to be found, and thus insulating it in 

 the pleistocene sea. At Dorking the geological phaenomena of the 

 Guildford valley are repeated. 



A series of raised marine beds, as already described, surround the 

 West of England on the south-west and west ; and except at inconsi- 

 derable heights, we find no traces whatever of any drift beds over this 

 area. Here again the highest drift beds with elephants' remains are 

 above the pleistocene beds with shells, as they are on the Sussex coast : 

 such was the position of the Plymouth beds described by Dr. Moore*. 



The whole of the South of England, from the Wealden area on the 

 east, to the Land's End, does not appear to have been a continuous 

 line of dry land during the pleistocene period. Between the two 

 tracts here noticed we find a wide interval over which water-worn 

 materials of distant origin occur abundantly. The whole of the valley 

 of the Exe is filled with an accumulation of this sort, derived from 

 the rocks of North Devon ; these beds spread out over the country 

 east and west of the actual course of the river, and have afforded 

 elephants' remains from a variety of places and elevations. Dr. Buck- 

 land was the first to call attention to the curious fact of the occurrence 

 of pebbles of milky quartz over the highest levels of the Blackdown 

 range. I have described elsewhere the characters by which the bed 

 which contains these pebbles is to be distinguished from all other ac- 

 cumulations of the district, as also the fact of its distinct superposi- 

 tion f; and in spite of the present elevation of the Blackdowns, I see 

 no solution of the difficulty but by supposing that the whole of that 

 area was submerged during the latest portion of the pleistocene 

 period. 



The western boundary of this interval of depression, or perhaps 

 better the coast-line of this western island in the latest and highest 

 range of the pleistocene sea, is well defined along the northern extre- 

 mity of Great Haldon, by a clean outline of water- worn materials and 

 immense blocks, which occur from that point by Whadden Barton, 

 Chudleigh, round the Bovey valley, particularly at Pen Wood, Staple 

 Hill, and thence to Newton. For the evidence that all this material 

 has travelled south — that all the remarkable faults and fissures of the 

 Chudleigh district were produced before the dispersion of this gravel ; 

 as well as that the difference of level which it occupies in the Bovey 

 valley and on the summit of the Haldons, is due to changes of 

 level which have taken place since their accumulation, I must refer 

 to a former notice of the district |. The strongest proof of all, that 

 the highest levels of the Haldons and Blackdowns (900 to 1000 feet) 

 must have occupied a low level with respect to the Dartmoor group, 

 is, that the summit gravel contains pebbles of its schorly granite. 



The two areas of the South of England which thus seem to have 

 been insulated in the pleistocene sea, have certain physical features 

 in common, the prominent one being the east and west axes of their 

 mineral masses. The boundary -line of the pleistocene drift from the 



* Report of Brit. Assoc. 1841, p. 62. 



t Geological Transactions, vol. v. I Ibid. 



