124 SHORES CHANGE WITH LEVEL OF LAND. 



though partly to the ease with which the sea could encroach on the 

 loose clayey and sandy formations, when, owing to a different level of 

 the land, circumstances were more favourable for its work of excava- 

 tion. The most important class of inlets occupies the positions of 

 what were formerly dome-shaped or anticlinal folds. 



The Shore. As a district became depressed and the sea admitted, 

 every portion of the land must in succession have been a shore, and 

 the shore moved gradually with the depression of the land to a level 

 which was progressively higher. When we remember the power 

 which the sea possesses of throwing up around our coast in stormy 

 seasons not merely the spoils of life but masses of rock from great 

 depths, a mechanism becomes discernible which has brought gravel 

 beds and our pebble beaches gradually into their present position in 

 times antecedent to the final shaping of the contours of the coasts. 

 The beach follows the shore, and it may be that much of the material 

 thus brought back again had previously been scoured from the present 

 seaward slopes of the country in an antecedent age, when its level 

 was higher. These materials are ever reinforced with the hard frag- 

 ments worn from the nearest local source, and with pebbles driven 

 along the shore by waves lashed by the wind. A remarkable 

 instance, however, of the mode of origin of such pebble beds is 

 furnished by the Chesil Bank, which stretches for about eleven 

 miles on the Dorset sea-board from Portland to Abbotsbury. Port- 

 land Bill has arrested the movement of pebbles to the east like an 

 artificial groin, but when their nature is examined, and the large 

 size of the pebbles in the eastern end of the bank near Portland is 

 considered, there is no sufficient reason for believing that they travelled 

 out of Cornwall and Devon along the existing shores when the rocks 

 of the floor of the English Channel could so easily have furnished an 

 assemblage of this kind, which would equally have become embedded 

 in the ledge of Kimmeridge Clay which forms the foundation of the 

 bank, and there became heaped up as the land descended to- its present 

 position. 1 The same agencies which have brought the pebble beds to 

 our shores have been chiefly concerned in the production of sea-cliffs. 

 We know the rapid waste of certain parts of the coast, where noble strips 

 of land have in historic times passed, often with towns and villages 

 upon them, back into the sediments of which they were originally com- 

 posed, and have been swept out over the floor of the German Ocean. 

 But all our coasts happily do not crumble away like those of Yorkshire, 

 and though the changes which take place from year to year prove 

 that the existing aspect of many cliffs is of very recent origin, yet 

 their geological structure often makes it probable, even when proof 

 is wanting, that they too have come down to us from an immeasurably 

 distant past. Some coasts are especially favourable to the formation 

 of cliffs, because the rocks are hard and not easily worn away, while 

 the land which they form rises to a fair height from the sea. Sea- 

 side towns generally occur where gaps appear between cliffs, though 

 there are many exceptions. The gap furnishes a ready means of 

 1 Prestwich on the Chesil Bank, Institute of Civil Engineers, vol. xl. 



