6 DESCRIPTION OF THE PLATES, 



Fig. I. — Vanikoro, situated in the western part of the South 

 Pacific ; taken from the survey by Capt. D'Urville in the 

 Astrolabej the soundings on the southern side of the 

 island, namely, from 30 to 40 fathoms, are given from 

 the voyage of the Chev. Dillon ; the other soundings are 

 laid down from the survey by D'Urville ; height of the 

 summit of the island is 3,032 feet. The principal small 

 detached reefs within the lagoon-channel have in this 

 instance been represented. The southern shore of the 

 island is narrowly fringed by a reef : if the engraver had 

 carried this reef entirely round both islands, this figure 

 would have served (by leaving out in imagination the 

 barrier-reef) as a good specimen of an abruptly-sided 

 island, surrounded by a reef of the fringing class. 



Fig. 2. — Menchikoff atoll (or lagoon-island), in the Marshall 

 Archipelago, Northern Pacific Ocean; from Krusenstern's 

 Atlas of the Pacific; originally surveyed by Capt. Hage- 

 meister; the depth within the lagoons is unknown. 



Fig. 3. — Pouynipete, or Seniavine, in the Caroline Archi- 

 pelago ; from the survey by Admiral Lutkd. 



PLATE II. 



Fig. 1. — Bolabola, in the Society Archipelago, from the 

 survey of Capt Duperrey in the Coquille : the soundings 

 in this and the following figures have been altered from 

 French feet to English fathoms ; height of highest point of 

 the island 4,026 feet. 



Fig. 2. — Keeling, or Cocos atoll (or lagoon-island), in the 

 Indian Ocean ; from the survey by Capt. Fitzroy ; the 

 lagoon south of the dotted line is very shallow, and is left 

 almost bare at low water ; the part north of the line is 

 choked up with irregular reefs. The annular reef on the 

 north-west side is broken, and blends into a shoal sand- 

 bank, on which the sea breaks. 



