n8 CORAL-REEFS. 



those much less than a hundred feet in height) by being 

 written without a capital letter ; I have detected a few 

 errors in this map, respecting the height of some of the 

 islands, which will be noticed in the Appendix, where I 

 treat of coral formations in geographical order. To the 

 Appendix, also, I must refer for a more particular account 

 of the data on which the statements on the next page 

 are grounded. I have ascertained, and chiefly from the 

 writings of Cook, Kotzebue, Bellinghausen, Duperrey, 

 Beechey, and Lutke, regarding the Pacific; and from 

 Moresby 1 with respect to the Indian Ocean, that in the 

 following cases the term "low island" strictly means 

 land of the height commonly attained by matter thrown 

 up by the winds and the waves of an open sea. 

 If we draw a line (the plan I have always adopted) 

 joining the external atolls of that part of the Low 

 Archipelago in which the islands are numerous, the 

 figure will be a pointed ellipse (reaching from Hood to 

 Lazaref Island), of which the longer axis is 840 geographical 

 miles, and the shorter 420 miles ; in this space 2 none of the 



1 See also Capt. Owen's and Lieut. Wood's papers in the Geo- 

 graphical Journal, on the Maldiva and Laccadive Archipelagoes. 

 These officers particularly refer to the lowness of the islets ; but I 

 chiefly ground my assertion respecting these two groups, and the 

 Chagos group, from information communicated to me by Capt. 

 Moresby. 



2 I find from Mr. Couthouy's pamphlet (p. 58) that Aurora Island is 

 about 200 feet in height; it consists of coral-rock, and seems to have 

 been formed by the elevation of an atoll. It lies north-east of Tahiti, 

 close without the line bounding the space coloured dark blue in the 

 map appended to this volume. Honden Island, which is situated in 

 the extreme north-west part of the Low Archipelago, according to 

 measurements made on board the Beagle, whilst sailing by, is 114 

 feet from the summit of the trees to the water's edge. This island 

 appeared to resemble the other atolls of the group. 



