T. BELT ON THE DjRIFT OF DEVON AND CORNWALL. b / 



10 to 12 feet in depth contain palaeolithic flint implements, which 

 occur principally at the base of the deposit. 



Sussex, Kent, and Surrey. — Sir Roderick Murchison very fully 

 described the surface geology of these counties, and followed Sedg- 

 wick and De la Beche in ascribing the formation of the Lowland 

 deposits to cataclysmal action. Of late years, however, the evidence 

 that abounds of violent and tumultuous deposition has been almost 

 ignored under the influence of the teachers of the theory of subaerial 

 denudation. 



In the distribution of the gravels between the escarpments of the 

 North and South Dowus there are two points to be explained — the 

 complete denudation of many large tracts lying above 200 feet above 

 the sea, and the outspread of the gravel in great sheets below that 

 level and especially below 100 feet above the sea. To the former 

 of these distinct yet complementary phenomena my attention was 

 first drawn by Mr. J. H. Farrer, who pointed out to me from the 

 top of Hawkhurst Down the remarkable absence of flints from 

 between the chalk escarpment and the top of Leith Hill, and urged 

 that if the Chalk that once covered the greensand slope had been 

 removed by subaerial denudation, the flints would still have been left 

 behind, and asked what force had cleared them away. In every 

 county of the area to which this paper is confined there are Upland 

 gravels, with transported stones, showing signs of gradual and 

 tranquil deposition, and Lowland gravels affording evidence of sud- 

 den and tumultuous formation. Nowhere are there any marine 

 remains or old sea-beaches, excepting near the present shore-line. 

 In Cornwall and in Devon, as well as in Sussex and Surrey, inde- 

 pendent observers, including the most illustrious of our geologists, 

 have published their convictions that great currents of water poured 

 across the country. I do not know what other geological conclusion 

 has more evidence to support it. Tet because no acceptable theory 

 has been advanced to account for the origin of such a tumultuous 

 and overwhelming flood, the evidences of its occurrence have of late 

 been neglected. Can we have a stronger argument of the necessity 

 of a good theory of origin to enable us to appreciate the importance 

 of the facts with which we have to deal? 



5. Classification of the glacial phenomena. — I have in former 

 papers* urged that Mr. Alfred Tylor's theory that the sea-level 

 was greatly lowered in the Glacial period through the vast quantity 

 of water that, in the form of ice, was piled up around the poles is 

 borne out by much geological, physical, and biological evidence. 

 Possibly a point of departure for the commencement of the Glacial 

 period may be found in the first evidence of the lowering of the sea- 

 level. Thus, in the Weybourne sands, the Portland-Bill marine 

 beds, and the Bridlington Crag we have evidence of the sea rising 

 to about the same level as it now does ; and these deposits are 

 clearly of older date than the overlying glacial beds. 



The first stage of the Glacial Period, as thus defined, is marked by 



* Naturalist in Nicaragua, p. 266 ; and Quarterly Journal of Science, Oct. 

 1874. 



