340 CORALS AND CORAL ISLANDS. 
Captain Beechey mentions, however, that at forty-one fath- 
oms, near Sala-y-Gomez, he found a bottom of sand and 
coral. 
The Paumotus commence in longitude 130° W., and em 
brace eighty coral islands, all of which, excepting about eight 
of small size, contain lagoons. Besides these, there are, near 
the southern limits of the archipelago, the Gambier Islands 
and Pitcairn, of volcanic or basaltic constitution. The for- 
mer in 23° §., have extensive reefs. About the latter, in 25° 
S., there are some growing corals, but no proper reefs. 
The Marquesas, in latitude 10° S., have but little coral 
about them; and this is the more remarkable, since they are 
in close proximity to the Paumotus. But their shores are 
mostly very abrupt, with deep waters close to the rocks. An 
island which, before subsidence has commenced, has some ex- 
tent of shallow waters around, might have very bold shores 
after it had half sunk beneath the waves. This would be the 
case with the island of Tahiti; for its mountain declivities 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 afterward, on the ces- 
sation of the subsidence, others failed to form again on ac- 
count of the deep waters. 
The Society Islands have extensive coral reefs, with dis- 
tant barriers. The reefs of Tahiti extend, in some parts, a 
mile from the shores. Tetuaroa, 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 represented as a collection of rugged peaks without coral 
shores. The Rurutu and Hervey Islands, just northwest of 
