138 CORAL FORMATIONS. 
would be the case with the island of Tahiti; for its mountain declivi- 
ties are, in general, singularly precipitous, except at base. The Mar- 
quesas may, therefore, have once had barrier reefs, which were sunk 
from too rapid subsidence ; and afterwards, on the cessation of the 
subsidence, others failed to form again, on account of the deep waters. 
The Society Islands have extensive coral reefs, with distant bar- 
riers. ‘The reefs of Tahiti extend, in some parts, a mile from the 
shores. ‘Tethuroa, to the north of Tahiti, and Tubuai, near Bolabola, 
are lagoon islands. Maitea, east of Tahiti, is a sugar-loaf truncated 
at summit, four miles in compass, and is said by Forster to have an 
encircling reef.* 
South of the Society Islands, near 25° S., is Rapa, which is repre- 
sented as a collection of rugged peaks without coral shores. The 
Rurutu and Hervey Islands, just northwest, have coral reefs fringing 
the shores. There is no evidence of recent volcanic action among 
them. Some of them are elevated coral islands, as Mitiaro, Atiu, 
Mangaia and Mauki, and also, according to Stutchbury, Rurutu. 
Okatutaia is a low coral island but six or seven feet out of water. 
Between the Paumotus and the longitude of Samoa, are nume- 
rous small islands, all of coral origin. 
The Samoan Islands have extensive reefs. About Tutuila they 
are somewhat less extensive than around Upolu, owing to its abrupt 
shores ; and about Savaii they are still smaller, as already explained. 
The influence of abrupt shores may also be seen in some parts of 
Upolu; for example,—to the west of the harbour of Falifa, where, for 
several miles, there is no reef, except in some of the indentations of 
the coast. Manua is described as having only shore reefs. 
The Tonga Islands, south of Samoa, for the most part, abound in 
coral reefs, and Tongatabu and the Hapai Group are solely of coral. 
Eoa is a moderately high island, with a narrow reef. ‘Tafoa, an 
active volcano, and Kao an extinct cone, are mthout reefs. Vavau, 
according to Williams,t is an elevated coral island. Pylstaarts, near 
Eoa, is a naked rock, with abrupt shores, and little or no coral. 
Sunday Island, farther south, (29° 12’ S.,) is beyond the coral-reef 
limits. 
North of Samoa are several scattered islands, of small size, all of 
coral. 
* Darwin, op. cit. p. 153. t+ Narrative, ii. 65. { Miss. Enterprises, p. 427, Amer. ed. 
