APPENDIX. 213 



The depth of the great interior lake has not been ascer- 

 tained ; but Captain D'Urville appears to have entertained 

 no doubt about the possibility of taking in a frigate. The 

 reef lies no less than fourteen miles distant from the 

 northern coasts of the interior high islds., seven from their 

 western sides, and twenty from the southern ; the sea is 

 deep outside. This island is a likeness on a grand scale 

 to the Gambier group in the Low Archipelago. Of the 

 groups of low 1 islands forming the chief part of the 

 Caroline Archipelago, all those of larger size, have the true 

 atoll-structure (as may be seen in the atlas by Captain 

 Lutke), and some even of the very small ones, as 

 Macaskill and Duperrey, of which plans are given in the 

 atlas of the Coquiitts voyage. There are, however, some 

 low small islands of coral-formation, namely, Ollap, Tama- 

 tam, Bigali, Satahoual, which do not contain lagoons; 

 but it is probable that lagoons originally existed, but have 

 since filled up : Lutke (vol. ii. p. 304) seems to have 

 thought that all the low islands, with only one exception, 

 contained lagoons. From the sketches, and from the 

 manner in which the margins of these islands are engraved 

 in the atlas of the voyage of the Coquille, it might have 

 been thought that they were not low ; but by a comparison 

 with the remarks of Lutke* (vol. ii. p. 107, regarding Bigali) 

 and of Freycinet (ffydrog. Memoir EUranie Voyage, p. 188, 

 regarding Tamatam, Ollap, etc.), it will be seen that the 

 artist must have represented the land incorrectly. The 

 most southern isld. in the group, namely Piguiram, is not 

 coloured, because I have found no account of it. Nougouor, 

 or Monte Verdison, which was not visited by Lutkd, is 



1 In D'Urville and Lottin's chart, Peserare is written with capital 

 letters ; but this evidently is an error, for it is one of the low islets on 

 the reef of Namonouyto (see Lutk£'s charts), — a regular atoll. 



