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APPENDIX. 
ing again to it : all these islands have been coloured red.— 
A chart of Rose Island, at the extreme [east] end of the 
group, is given by Freycinet, from which I should have 
thought that it had been an atoll ; 1 but according to Mr. 
Couthouy (Remarks, p. 43) it consists of a reef, only a 
league in circuit, surmounted by a very few low islets ; the 
lagoon is very shallow, and is strewed with numerous large 
boulders of volcanic rock. This island, therefore, probably 
consists of a bank of rock, afewfeet submerged, with the outer 
margin fringed with reefs ; hence it cannot be properly 
classed with atolls, in which, as we have reason to believe, 
the foundations always lie at a depth greater than that at 
which the reef- constructing polypifers can live ; not coloured. 
Beveridge Reef, 20° S., 167° W., is described in the 
Naut. Mag. (May 1833, p. 442) as ten miles long in a N. 
and S. line, and eight wide ; ‘ in the inside of the reef, there 
appears deep water ; ’ there is a passage near the S.W. 
corner : this therefore seems to be a submerged atoll, and 
is coloured blue. 
Savage Island, 19° S., 170° W., has been described by 
Cook and Forster. The younger Forster (vol. ii. p. 163) 
says it is about 40 feet high : he suspects that it contains 
a low plain, which formerly was the lagoon. The Rev. J. 
Williams gives 100 feet as its height, and he informs me 
that the reef fringing its shores resembles that round 
Mangaia ; coloured red. 
Friendly Archipelago. — Pylstaart Island : judging 
from the chart in Freycinet’ s Atlas I should have supposed 
that it had been regularly fringed ; but as nothing is said in 
the Hydrog. Memoir (or in the Voyage of Tasman, the dis- 
1 [It is an atoll. — Capt. Wharton. Eose Island has a lagoon six 
to twelve fathoms deep and an entrance to it of four fathoms. 
Except two small banks, one supporting a group of trees, it is under 
water at high tide. — Letter from Prof. Dana to Mr. Darwin, July 21, 
1874.] 
