PACIFIC OCEAN. 
203 
three miles and a half southward of the land (which is 
represented in the drawing in the atlas of the Coquille's 
Voyage as descending abruptly to the water), shows, on the 
principle explained in the beginning of the last chapter, 
that it belongs to the barrier class. I may here mention, 
from information communicated to me by the Eev. W. 
Ellis, that on the N.E. side of Huaheine there is a bank of 
sand, about a quarter of a mile wide, extending parallel to 
the shore, and separated from it by an extensive and deep 
lagoon : this bank of sand rests on coral-rock, which un- 
doubtedly was once a living reef. North of Bolabola lieg 
the atoll of Toubai (Motou-iti of the Coquille's atlas), which 
is coloured dark blue ; all the islands which are surrounded 
by barrier-reefs are coloured pale blue : three of them are 
represented in figures 3, 4, and 5, in Plate I. There are 
three low coral-groups lying a little W. of the Society 
Archipelago, and almost forming part of it, namely, Bell- 
ingshausen, which is said by Kotzebue (Second Voyage, 
vol. ii. p. 255) to be a lagoon-island ; Mopeha, which from 
Cook’s description (Second Voyage, book iii. chap, i.) no 
doubt is an atoll ; and the Scilly Islands, which are said 
by Wallis (Voyage, chap, ix.) to form a group of low islets 
and shoals, and which, therefore, probably compose an 
atoll : the two former have been coloured blue, but not the 
latter. 
Mendana or Marquesas Group. — These islands are 
almost entirely destitute of reefs, as may be seen in 
Krusenstern’s Atlas, making a remarkable contrast with 
the adjacent group of the Society Islands. Mr. F. D. 
Bennett has given some account of this group, in the 
seventh volume of the Geograph. Journ. He informs me 
that all the islands have the same general character, and 
that the water is very deep close to their shores. He 
visited three of them, namely, Dominicana, Christiana, 
and Boapoa, their beaches are strewed with rounded masses 
