ORIGIN OF CONTINUOUS BEACHES 6 1 



shore of North America to the southward, the pocket-beaches 

 increase in chmcnsions, and contain more sand. Going 

 toward the tropics, this famihar clement of the sea border 

 becomes constantly more and more abundant, until l)e\ond 

 Cape Cod the hard rocks are rarely visible, and the pebbles, 

 if they occur, are altogether from the glacial waste, either 

 that which is excavated from the shore or that brought in by 

 the sea-weed. From New York to Florida, and thence to the 

 Rio Grande, there are no firm materials from whicli pebbles 

 can be made. We pass from the northern type of pebbly 

 pocket-beaches to the straight sand-coasts of the south by a 

 somewhat gradual transition. The accumulations of detritus 

 become more extensive, here and there the horns of the 

 re-entrant bays no longer project far enough into the sea to 

 contain the large amount of material which finds its way into 

 the depression ; so a portion of the matter flows out and 

 streams down the shore to the next bay ; this in turn is more 

 completely filled, and finally we come to the conditions of 

 continuous beaches. 



The change in character of the shore which is brought 

 about by the passage from the cliff- and pocket- to the con- 

 tinuous beach, is caused by the alteration in the geological 

 conditions of the continent in the district in which the shore- 

 line is laid. The hard rocks of the high north, because of 

 their resistance to the action of the waves, yield but slowly to 

 the sea. The water next the shore is deep, and the bottom 

 either of firm stone, close-set pebbles, or dense clay ; all these 

 conditions are opposed to the formation of sandy shores. 

 Although the pebbly beaches grind up a great deal of rocky 

 matter, they convert the greater part of it to fine material 

 which forms clay. In the region south of New York, and 



