Rc'id : Coast-Erosion. 327 



of hills running- from Tickhill throug-h Bawtry to the Trent near 

 Gahisboro' ; and on this rang^e a similar assemblag^e of Permian 

 and Carboniferous boulders is found at Gring^ley-on-the-Hill, 

 which is ten miles east of Tickhill, and, like Tickhill, about forty 

 miles south of York. 



COAST=EROSION.* 



CLEMENT REID, F.R.S. 



The erosion of our coast must be studied in conjunction with 

 the deposition of the material eroded. When examined in this 

 wa}' we find in England that it has not been a continuous 

 process, varying when short periods are studied, but averaging- 

 the same from century to century. Instead of this regular 

 process, the rapid accumulation in certain places teaches us 

 that coast-erosion, as we now see it, began at a definite date, 

 before which conditions were entirely different. If this were 

 not so, the area of the new lands, accumulations of shingle,, 

 and of sand-dunes would be much greater. It does not seem 

 practicable to obtain exact measures, but the rates of accumula- 

 tion of various recent deposits, and of the silting-up of our 

 harbours, suggest that the cliff-erosion only began 3000 or 

 4000 years ago, or about the date when our harbours were 

 already in use and Stonehenge was being raised. 



In order to understand the nature of the changes that are 

 now going on, it is necessary to look back to the Neolithic 

 period to see what the country was then like, otherwise the 

 existing irregularities of our coast-line will be quite unintelligible. 

 It is not needful to go back further, but we must picture the 

 country as it looked when the sea stood 60 feet lower. 



A close study of the buried land surfaces, or ' submerged 

 forests,' found in the alluvium of all our estuaries at various 

 levels down to about 50 feet below the present sea level, shows 

 that oak trees flourished on the lowest of these ancient soils. 

 This proves that the sea then stood so far below its present 

 level that the highest tides could not reach the roots of the 

 trees. These old land-surfaces seem all to be of Neolithic date. 

 During this period the seaward end of all our valleys was 

 deepened till the channel reached about 60 feet below its present 



* Abstract of a paper read to Section E of the Meeting- of the British 

 Association, York. 



1906 SepteiuLer i. 



