PACIFIC AND BEERING’S STRAIT. 
181 
tween the lake and the sea larger, so as to admit of the water finding 
its level, the period of low water might be determined, as there is a 
change of tide in the entrance. 
The strip of low land enclosing the lagoon is nearly seventy miles 
in extent, and the part that is dry is about a quarter of a mile in width. 
On the inner side, a few yards from the margin of the lake, there is a 
low bank formed of finely broken coral ; and, at the outer edge, a much 
higher bank of large blocks of the same material, long since removed 
from the reach of the waves, and gradually preparing for the reception 
of vegetation. Beyond this high bank there is a third ridge, similar to 
that skirting the lagoon ; and outside it again, as well as in the lagoon, 
there is a wide shelf three or four feet under water, the outer one 
bearing upon its surface huge masses of broken coral ; the materials for 
an outer bank, similar to the large one just described. These appear- 
ances naturally suggest the idea of the island having risen by slow 
degrees, d'hus the sand dispersed over the lagoon indicates a period 
when the sea rolled entirely over the reef, tore up blocks of coral from 
its margin, and by constant trituration ground them to powder, and 
finally deposited the particles where they now rest. The bank near the 
lake must have originated at a subsequent period, when the outer edge 
becoming nearer to the surface, moderated the strength of the waves, 
and the wash of the sea reached only far enough to deposit the broken 
coral in the place described. At a still less distant period, when the 
island became dry, and the violence of the sea was wholly spent upon 
its margin, the coral, which had before escaped by being beneath 
the surface, gave way to the impetuous wave, and was deposited in 
broken masses, which formed the high ridge. Here the sea appears 
to have broken a considerable time, until a second ledge gradually ex- 
tending seaward, and approaching the surface, so lessened the effect of 
the waves upon this ledge also, that they were again only capable of 
throwing up an inferior heap similar to the one first mentioned. In 
process of time this outer ledge will become dry, and the many large 
blocks of coral now resting near its edge will form another heap similar 
to the large one ; and thus the island will continue to increase by a sue- 
