Ch. xx.] 



ON SOUTH COAST OF ENGLAND. 



531 



vertical position, and in a direction east and west. This 

 chalk forms the projecting promontory of Cnlver Cliff 



on 



Needle 



Bay on the one side, and Compton Bay on the other, have 

 been hollowed out of the softer sands and argillaceous strata, 

 which are inferior, in geological position, to the chalk. 



omena 



Handfast 



fa 



promon 



excavation made by the waves in the softer strata, corre- 

 sponding to those of Sandown Bay. 



11 



a 



le bank — progressive motion 



sea beaches. 



Although the loose pebbles and grains of sand composing 

 any given line of sea-beach are carried sometimes one way, 

 sometimes another, they have, nevertheless, an ultimate 

 motion in one particular direction."* Their progress, for 

 example, on the south coast of England, is from west to east, 

 which is owing partly to the action of the waves driven east- 

 wards by the prevailing wind, and partly to the current, or 

 the motion of the general body of water caused by the tides 

 and winds. The force of the waves gives motion to pebbles 

 which the velocity of the currents alone would be unable to 

 carry forwards ; but as the pebbles are finally reduced to 



mud 



matter 



rmme 

 I from 



Mr. Palmer and 



the course which the main body of 

 wasting cliffs will eventually take. 



It appears, from the observations 

 others, that if a pier or groin be erected anywhere on our 

 southern or south-eastern coast to stop the progress of the 

 beach, a heap of shingle soon collects on the western side of 

 such artificial barriers. The pebbles continue to accumu- 



after which 



late till they rise as high as the pier or groin 



t 



The western entrance of the Channel, called the Solent, is 



* See Palmer on Shingle Beaches, 

 Phil. Trans. 1834, p. 568. 



t Groins are formed of piles and 

 wooden planks, or of faggots staked 



down; and are used either to break the 

 force of the waves, or to retain the 

 beach. 



M M 2 



