Allaiison-Winn : Sea's EncroacJnnent on the East Coast. 307 



about six or seven miles distance — a marked flattening of the 

 g-radient of the sea bottom occurring- at the seventeenth or 

 eighteenth mile, and in about twenty fathoms (Figs. 3 and 4). 



Is it not possible that the chalk may have been reached in 

 this 1 20 ft., and that the erosion is going on steadily in the softer 

 material of the strata above ? ' 



In all cases, where the material is of a soft and easily eroded 

 nature for a considerable depth below low water level, we have 

 to consider the following : — 



Chief Causes. 



(i) Surf and wave action on visible 

 shore between higrh and low 



•t3 ' 



water. 



Causes. 



(2) The erosion" going on below low 

 water level many miles out to sea 

 and in 5 to 10 fathoms. 



^ ( (3) The action of countless borers, 



Contributory | , ^ , 



worms, eels, shell-fish, etc., etc. 



(4) The action of submarine springs. 



It has been so long customary to speak of 'beach,' 'shore,' 

 or 'foreshore,' as quite distinct from 'sea-bed' or 'sea-bottom,' 

 that we may get into the habit of regarding them as not being 

 continuations of the same surface. One has, for example, been 

 in the habit of regarding the shore as a natural bank with a very 

 flat gradient, the toe of which extends to low water mark. It 

 would be more correct to look upon the junction of the glacial 

 drift or other erodible material with the chalk, rock, or other 

 hard material as the toe of the bank under consideration. Off" 

 the Holderness coast this toe is to be found in many fathoms of 

 water and miles out to sea. 



We should arrive at a clearer view if we would regard 

 the sea as water held in a great basin which, in consequence of 

 the tides, seems to us to be more full at certain times than it is 

 at others. The visible shore — i.e., the portion exposed between 

 the tides — is the rim of the basin, but none the less part of the 

 same vessel. 



It will, therefore, appear more correct to regard as ' sea-bed ' 

 all surfaces actually beneath the sea at highest spring tides. 

 If this view be accepted we can more readily eliminate from our 

 minds the popular fallacy that all our troubles begin and end 

 in the changes we observe on the little strip of visible shore 

 between high and low water marks. 



1904. October 



