PACT FTC OCEAN. 
225 
notices collected by Horsburgh, it appears that some of the 
many islands composing it are high, with a bold outline ; 
and others are low, small, and interlaced with reefs. All 
the high islands appear to be fronted by distant reefs rising 
abruptly from the sea, and within some of which, there is 
reason to believe that the water is deep. I have therefore 
little doubt that they belong to the barrier class. In the 
southern part of the group, we have Elisabeth Island, 
which is surrounded by a reef at the distance of a mile ; 
and two miles eastward of it (Krusenstern, Append. 1885, 
p. 42) there is a little island containing a lagoon. Near 
here, also, lies Circular Eeef (Horsburgh Direct, vol. ii. 
p. 796, 8th edit.), ‘ three or four miles in diameter, having 
deepwater inside with an opening at the N.N.W. part : the 
reef on the outside is steep to.’ I have from these data, 
coloured the group pale blue, and Circular Eeef dark blue. 
— The Anachorites, Echequier, and Hermites consist of in- 
numerable low islands of coral formation, which probably 
are atolls ; but not being able to ascertain this, I have not 
coloured them, nor Durour Island, which is described by 
Carteret as low. 
The Caroline Archipelago is now well known, chiefly 
from the hydrographical labours of Lutke : it contains 
about forty groups of atolls, and three encircled islands, 
two of which are engraved in Figs. 2 and 7, Plate I. 
Commencing with the eastern part, the encircling reef 
round Ualan appears to be only about half a mile from the 
shore ; but as the land is low, and covered with mangroves 
(Voyage autour du Monde, par F. Lutke, vol. i. p. 339), 
its margin has not probably been ascertained. The extreme 
depth in one of the harbours within the reef is 33 fathoms 
(see charts in Atlas of Coquille's Voyage), and outside at 
half a mile distance from the reef, no bottom was obtained 
with 250 fathoms. The reef is surmounted by many 
islets, and the lagoon-like channel within is mostly shallow, 
