108 



"ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



islets, to show where the gaps existed, and finally is overwhelming the beach 

 rock conglomerate, which only juts out in strips or points separated by 

 reaches of sand of greater or less extent. 



Some of our photographs of coral shingle and coral boulders driven 

 inland between shrubs and trees show that they penetrate a considerable dis- 

 tance over the summit of the land rim (PI. 64). They also show how coral 

 fragments, from the size of one's head to the merest chips, collect and 

 become cemented together to form a conglomerate or breccia merely from 

 the action of the wind and rain, and not under the influence of the sea, 

 thus gradually covering the old ledge, whatever might be its composition, if 

 it should constitute the foundation of an island. 



Our examination also shows how all the low land of the rim of an atoll 

 is absolutely at the mercy of waves of great height, or even of a common 

 storm, and how the material from the outer beach, and all kinds of coral 

 shingle fragments, are pushed across between the shrubbery and large trees, 

 killing some of those nearest the shore, and how the sea may cut gullies into 

 the low land, either on the sea face, or through it, or down the lagoon slope. 



There is a fine sink on the southern point of the entrance to Makemo, 

 behind the great shingle beach dam which has shut off from the sea the 

 extensive flat area of that end of the island. 



Many blow-holes occur on the outer edge of the reef platform ; this is 

 cut up by numerous shallow digitatious, many of which are bridged to form 

 tlie blow-holes. 



Gap across the Land Rim of Makemo. 



