132 CORAL FORMATIONS. 
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dence, in all its characters, with those of atoll reefs. Should sub- 
sidence now cease, the reefs, no longer increasing in height, would 
go on to widen, and the accumulations produced by the sea, would 
commence the formation of dry land, as exhibited in figure 6. Ver- 
dure may :oon after appear, and the coral island is finally com- 
pleted. It is not impossible that the land should form, in certain 
favourable spots, while the subsidence is in progress, if it be not 
beyond a certain rate. The following figure represents the effect 
Fig. 7. 
of a cessation or diminution of subsidence on the barrier reef, about a 
high island, represented in figure 1, II, page 127. ‘The barrier reef has 
become a finished island, and forms a green belt to the land. The 
fizure shows a section of this belt. 
All the features of atolls harmonize completely with this view of 
their origin. In form they are as various and irregular as the outlines 
of barrier reefs. Compare Angau of the Feejees, with Tari-tari of 
the Tarawan Group (page 50); Nairat or Moala with Tarawa; 
Nanuku with Maiana or Apamama. ‘The resemblance is close; 
and in the same manner we might find all the forms of lagoon reefs 
represented among barrier reefs. We observe all those configurations 
which would be derived from land of various shapes of outline, 
whether the narrow mountain ridge, (as at T'aputeouea, one of the 
Tarawan Islands,) or a wide area of irregular slopes and mountain 
ranges. Among the groups of high islands, we observe that abrupt 
shores may occasion the absence of a reef on one side, as on Moala; 
and a like interruption is found among coral islands, (Tarawa.) Many 
of the passages through the reefs may be thus accounted for. 
The fact that the submerged reef is often much prolonged from the 
capes or points of a coral island, accords well with these views. These 
points or capes correspond to points in the original land, and often to 
the line of a prominent ridge; and it is well known that such ridge- 
lines often extend a long distance, with slight inclination compared 
with the slopes or declivities bounding the ridge on either side. 
Coral islands or reefs often lie in a chain like the peaks of a single 
