534 



THE CHESIL BANK. 



[Ch. XX. 





fifty feet perpendicular. The extent of ground that moved 

 was about a mile and a quarter from north to south, and 600 



from 



>/ 



Portland is connected with 



the mainland by the Chesil Bank, a ridge of shingle about 

 seventeen miles long, the first part of which, near Portland, 

 for a length of about five miles, has the sea on each side of 

 it. It then continues seven miles farther in a north-easterly 

 direction as far as Abbotsbury, sloping steeply on the one 

 side towards the sea, and on the other towards a narrow 

 channel called the Fleet, which may be regarded as an estuary 

 the waters of which are brackish. It then stretches for five 

 miles farther as a pebbly beach thrown against the coast of 

 Dorsetshire. 



The pebbles 



forming 



this immense barrier are chiefly 



to view during storms. 



siliceous, all loosely thrown together, and rising to the height 

 of from twenty to thirty feet above the ordinary high-water 

 mark; and forty feet at the south-eastern end, which is 

 nearest the Isle of Portland, where the pebbles are largest. 

 Here its width is about 600 feet, which diminishes to about 

 500 at Abbotsbury. 



That part of the bar which attaches Portland to the main- 

 land rests on Kimmeridge clay, which is sometimes exposed 



The clay may have formed a shoal, 

 and the set of the tides in the narrow channel may have ar- 

 rested the course of the pebbles, which are always coming 

 from the west. 



Chesil Bank, the pebbles increase gradually in size as we 

 proceed south-eastward, or as we go farther from the quarter 

 which supplied them. Had the case been reversed, we should 

 naturally have attributed the circumstance to the constant 

 wearing down of the pebbles by friction, the beach along 

 which they are rolled being seventeen miles in length. But 

 the true explanation of the phenomenon is doubtless this : 

 the strongest currents or movements of the sea during storms, 

 when a gale from the south-west co-operates with the tide, 

 act with greater power in the more open channel or farthest 

 from the head of the bay ; within the bay the land affords 

 more shelter from the wind and waves. In other words, the 



It is a singular fact, that, throughout the 











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