202 CORALS AND CORAL LSLANDS. 



the side fronting east. But the north and north-east sides of 

 lari-tari are only a bare reef, through a distance of twenty 

 miles, although the south-east reef is a continuous line of ver- 

 dure. The small island of Makin, just north of Tari-tari, is 

 the breakwater which has protected the reef referred to from 

 the heavier seas. 



Coral island accumulations have an advantage over all other 

 shore deposits, owing to the ready agglutination of calcareous 

 grains, as explained on a following page. It has been stated 

 that coral sand-rocks are forming along the beaches, while the 

 reef-rock is consolidating in the water. A defence of rock 

 against encroachment is thus produced, and is in continual 

 progress. Moreover, the structure built amid the waves will 

 necessarily have the form and condition best fitted for with- 

 standing their action. The atoll is, therefore, more enduring 

 than hills of harder basaltic rocks. Reefs of zoophytic growth 

 but " mock the leaping billows," while other lands of the same 

 height gradually yield to the assaults of the ocean. There are 

 cases, however, of wear from the sea, owing to some change 

 of condition in the island, or in the currents about it, in 

 consequence of which, parts once built up are again carried off. 

 Moreover, those devastating earthquake-waves which overleap 

 the whole land, may occasion unusual degradation. Yet these 

 islands have within themselves the source of their own repair, 

 and are secure from all serious injury. 



The change of the seasons is often apparent in the distribution 

 of the beach sands covering the prominent points of an island. 

 At Baker's Island (near the equator, in long. 176° 23^, W.) 

 this fact is well illustrated. J. D. Hague states {Aih.Jouj: Sci., 

 II., xxxiv: 237), that the shifting sands change their place twice 

 a year. " The western shore of the island trends nearly north- 

 east and south-west ; the southern shore, east-by-north. At 

 their junction there is a spit of sand extending out toward the 

 south-west. During the summer, the ocean swell, like the wind, 

 comes from the south-east, to the force of which the south side 

 of the island is exposed, while the western side is protected. 

 In consequence, the sands of the beach that have been accu- 



