326 CORALS AND CORAL ISLANDS. 



it at 1,150 feet — possibly 1,750. These islands, therefore, 

 although toward the limits of the subsiding area, were still far 

 within it. The valley -bays of the islets of the lagoon are of 

 great depth, and afford additional evidence of the subsidence. 



Tahitian Islands. — 'The Tahitian Islands, along with Sa- 

 moa and the Feejees, are near the southern limits of the area 

 pointed out. Twenty-five miles to the north of Tahiti, within 

 sight from its peaks, lies the coral island Tetuaroa, a register 

 of subsidence. Tahiti itself, by its barrier reefs, gives evidence 

 of the same kind of change ; amounting, however, as we have 

 estimated, to a depression of but two hundred and fifty or 

 three hundred feet. The northwestern islands of the group 

 lie more within the coral area, and correspondingly, they have 

 wider reefs and channels, and deep bays, indicating a greater 

 amount of subsidence. 



Samoan or Navigator Group. — The island of Upolu has 

 extensive reefs, which, in many parts are three-fourths of a 

 mile wide, but no inner channel. The subsidence is estimated 

 on page 158, at one or two hundred feet. The volcanic land 

 west of Apia, declines with an unbroken gradual slope of 

 one to three degrees beneath the sea. The absence of a low 

 cliff is probable evidence of a depression, as has been else- 

 where shown. The island of Tutuila has abrupt shores, deep 

 bays and little coral. It appears probable, therefore, that it 

 has experienced a greater subsidence than Upolu. Yet the 

 central part of Upolu has very similar bays on the north, 

 which would afford apparently the same evidence ; and it is 

 quite possible that the facts indicate a sinking which either 

 preceded the ejections that now cover the eastern and west- 

 ern extremities of Upolu, or accompanied this change of level. 

 The large island of Savaii, west of Upolu, has small reefs, 

 small because, probably, of volcanic action ; for it bears, every- 



