APPENDIX. 191 



(which is represented in the drawing in the atlas of the 

 Ccquille'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 Rev. 

 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, and un- 

 doubtedly was originally a living reef. North of Bolabola 

 lies the atoll of Toubai (Motou-iti of the Coquille's Atlas), 

 which is coloured dark blue ; the other islands, surrounded 

 by barrier-reefs, are pale blue : three of them are represented 

 in Figs. 1 and 4 in Plate II., and Fig. 5 in Plate III. There 

 are three low coral-groups lying a little E. of the Society 

 Arch., and almost forming part of it, namely, Bellinghausen, 

 which is said by Kotzebue {^Second Voyage, vol. ii. p. 255) 

 to be a lagoon island ; Mophea, which, from Cook's descrip- 

 tion (Second Voyage, book iii. chap, i.), no doubt is an atoll ; 

 and the Sally Islands, which are said by Wallis (Voyage, 

 chap, ix.) to form a group of low islets and shoals, and, 

 therefore, probably, they compose an atoll : the two former 

 have been coloured blue, but not the latter. 



Mendana or Marquesas Group. — These islands are 

 entirely without 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, Domini- 

 eana, Christiana, and Roapoa; their beaches are strewed with 

 rounded masses of coral, and although no regular reefs 



