102 ON CORA.L REEFS AND ISLANDS. 



west of Kauai, are represented as coral reefs, excepting the rocks 

 Necker and Bird Island; the line stretches on to 28° 30' N.* 

 the northern limit of the coral seas. 



The Ladronos, like the Sandwich Group, constitute a line or 

 linear series of islands, one end of which has been long free from 

 volcanic action, while the other has still its smoking cones. 

 While the appearances of recent igneous action increase there- 

 fore as we go northward, the extent of the coral reefs increase as 

 we go southward ; no reefs occur about the northernmost islands, 

 while they are quite extensive on the shores of Guam. This 

 group consequently, like the Hawaiian and Samoa, illustrates the 

 influence of volcanic action on the distribution of reefs. 



A short distance southwest of the Ladrones, and nearly in the 

 same line, lie extensive reefs. Mackenzie's is an atoll of large 

 size. Yap, Hunter, Los Matelotas and the Pelews are high 

 islands, with large reefs. In the last mentioned, the reef-grounds 

 cover at least six times the area occupied by the high land. Still 

 farther south, towards New Zealand, lie the large atolls Aiou, 

 Asie, and Los Guedes. 



South of the equator again : — The New Hebrides constitute a 

 long group of high islands, remarkable for the absence of coral 

 reefs of any extent, though situated between two of the most 

 extensive coral regions in the world, — the Feejees and New Cal- 

 edonia. But the volcanic nature of the group, and the still 

 active fires of two vents in opposite extremities are a sufficient 

 reason for this peculiarity. Tanna is one of the largest volca- 

 noes of the Pacific; and nearly all the islands of the New Heb- 

 rides, as far as known, indicate comparatively recent igneous ac- 

 tion, in which respect they differ decidedly from the Feejees. 



The Vanikoro Group, north of the New Hebrides, according 

 to Q,uoy, has large barrier reefs about the southernmost island, 

 Vanikoro; but at the northern extremity of the ramie there is an 

 active volcano Tinakoro, and no coral. Tikopia, to the south- 

 east of Vanikoro, is hi^h and volcanic, according to Q,uoy, though 

 not now with active fires; and it appears from the descriptions 

 given to have no reefs. Mendaua, northeast of Tinakoro. ac- 

 cording to Kruesenstern, as stated by Darwin, is low with large 

 reefs; Duffs Islands have bold summits with wide reefs. 



New Caledonia and the northeast coast of New Holland, with 

 the intermediate s«-as. constitute one of the grandest reef regions 

 in the world. On the. New Caledonia shores the reefs are of 

 great width, and not only occur along the whole length of the 

 western coast, a distance of 200 miles, but extend to the south 

 beyond the main land 50 miles, and north 150 miles, making in 



* For an account of some of these islands, see Lisiansky's Voyage, 1803-6, in 

 the Neva, 4to., London, 1814, pp. 254, 257 ; also Hawaiian Spectator, vol. i. 



