PACIFIC OCEAN. 
215 
best chart of the numerous islands of this group was that 
in the atlas of the Astrolabe's Voyage ; but now the islands 
have been surveyed during the U.S. Exploring Expedition, 
and full information respecting them and the reefs has 
been given by Dana. Many of the islands are bold and 
mountainous, and are surrounded by reefs, lying far from 
the land, and outside the ocean appears very deep. The 
Astrolabe sounded with 90 fathoms in several places about 
a mile from the reefs, and found no bottom. It is evident 
that the water within many of the encircling reefs is deep : 
as indeed I was formerly assured was the case by Dillon. 
Beyond the high and encircled islands there are numerous 
atoll-formed reefs. Hence the whole group has been 
coloured blue. In the S.E. part lies Batoa, or Turtle 
Island of Cook (Second Voyage, vol. ii. p. 23, and chart ; 
4to edit.), surrounded by a coral-reef, ‘which in some 
places extends two miles from the shore ; ’ within the reef 
the water appears to be deep, and outside it is unfathom- 
able ; coloured pale blue. At the distance of a few miles, 
Captain Cook [ibid. p. 24) found a circular coral-reef, four 
or five leagues in circuit, with deep water within ; ‘ in 
short, the bank wants only a few little islets to make it 
exactly like one of the half-drowned isles so often men- 
tioned,’ — namely, atolls. South of Batoa lies the high 
island of Ono, which appears in Bellingshausen’s Atlas to 
be encircled ; as do some other small islands to the south ; 
coloured pale blue : near Ono, there is an annular reef, 
quite similar to the one just described in the words of 
Captain Cook ; coloured dark blue. 
subsidence, and the reef is breached opposite to the principal inlet on 
the land. At Ngaloa harbour, Kandava, the map of this part of the 
island suggests subsidence, but there are also indications of slight 
upheaval. There is a barrier-reef. The soundings 150 fathoms 
from the edge of the reef were 80 fathoms, the slope for the first 65 
fathoms from the shore being 1 in 1, then 1 in 1-4, diminishing to 1 in 
2 till 300 fathoms was reached.] 
