SERRATED BEACHES 57 



mile, we find at Cape Florida old and rounded grains of 

 sand, worn out by a journey which they have made from 

 hundreds of miles to the northward. 



The studious observer of the shore must often have 

 noticed that when the section between high and low water 

 mark is composed of pebbles, as is the case with nearly all 

 the pocket-beaches, the bits of stone are generally arranged 

 in successive ridges, the crests of which lie at right angles 

 with the shore and rise perhaps a foot above the general 

 plane of the beach, the intermediate bays having a breadth 

 of a score or more feet. Where these ridges and furrows 

 are well developed, the whole shore-line may have a curious 

 scalloped aspect. The origin of these peculiar structures is 

 not easily accounted for ; to attain the explanation we should 

 note certain evident facts concerning them. In the first place 

 they are extremely impermanent. By placing a mark in the 

 centre of one of the elevations, we easily find that they 

 change their position with almost every storm. Sometimes, 

 indeed, when the currents which move along the shore are 

 very strong, they may entirely disappear, to be rebuilt in a 

 few hours in another time of high waves. If we smooth 

 them away with a shovel, we may see them reconstructed 

 before our eyes. 



The way in which these pebbles are brought into this 

 order seems to be as follows, viz.: The crests of the billows 

 which form the breakers do not tumble down at the same 

 moment along any extended line. A glance at them shows 

 us that at every few feet of their length the surge falls to the 

 beach at a different instant. Hence the swash-wave, which 

 slips up the beach, has an extremely irregular front ; it 

 ascends not as a straight line, but in separate broad tongues 



