FORMATION OF CORAL REEFS AND ISLANDS. DAW 
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 cal- 
careous 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 con- 
tinual progress. Moreover, the structure built amid the | 
waves, will necessarily have the form and condition best fitted 
for withstanding 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 occa- 
sion unusual degradation. Yet in ordinary seas these islands 
have within themselves the source of their own repair, and 
are secure from all serious mjury. 
The change of the seasons is often apparent in the distri- 
bution 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 
(Am. Jour. Scr, IL., xxxiv, 237), that the shifting sands 
change their place twice a year. ‘The western shore of the 
island trends nearly northeast and southwest; the southern 
shore, east-by-north. At their junction there is a spit of sand 
extending out toward the southwest. During the summer. 
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