THE ISLAND BEACHES 175 



not nearly so great, and so the product formed is beach sand- 

 stone, or beach sandstone in which are embedded coral fragf- 

 ments after the manner of conglomerate. All degrees of 

 fineness and consolidation of the beach sandstone are to be 

 found. A fine loose sandstone represents the minimal product 

 of the process — the hard mosaic breccia, the maximal ; and 

 all intermediate grades are to be found, their composition 

 depending entirely upon the wave force that was exercised in 

 their making. Some specimens show an interesting stratifi- 

 cation, and tell of different forces which have been brought into 

 play on the lagoon beaches at different periods of the island 

 building. 



On the lagoon shores, where there is an exposure to strong 

 currents, as on some parts of Pulu Panjang and the western 

 end of Pulu Tikus, the sand accumulation cannot take place, 

 and here the wide areas of the beach are made up of broken 

 coral fragments. These fragments are water-worn from their 

 ceaseless movement upon each other, and they remain entirely 

 uncemented ; but this condition gives way to the normal, even 

 sandy stretches wherever the normal conditions of the lagoon 

 shore prevail. 



The sandy lagoon beaches outrun the islands, and at their 

 extremities form sand spits stretching towards the lagoon. 

 This is a very characteristic feature of the atoll islands. The 

 islands tend to be crescents ; the lagoon beaches exaggerate 

 this crescent shape, and so the extremities of the islands 

 curve to the lagoon as tapering sand spits. Between these 

 sand spits the ocean communicates, across the barrier flats, 

 with the lagoon. On the southern or windward side of the 

 atoll it is only natural that the light sand should have been 

 driven to its farthest extent, by wave action across the flats, 

 and by Avind action across the islands ; and here it is that we 

 find the broadest stretches of sandy beach, the highest sandy 

 shores, and the most extensive lagoon shallows. Here, too, 

 are found the island lagoonlets with wide areas of coral silt, 

 but this more fittingly belongs to the description of the island 

 than the beach. 



