262 CORALS AND CORAL ISLANDS. 



Guam. This group, consequently, like the Hawaian and 

 Navigator, illustrates the influence of volcanic action on the 

 distribution of reefs. 



A short distance south-west of the Ladrones, and nearly in 

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

 large size. Yap (or Eap), Hunter's, Los Matelotas and the 

 Pelews (Palao), 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, toward 

 New Zealand, lie the large atolls Aiou, Asie, and Los 

 Guedes. 



Soidh of the equator again : — The New Hebrides consti- 

 tute 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 Caledonia. But the volcanic nature of the group, 

 and the still active fires of two vents in its opposite extremi- 

 ties, are a sufficient reason for this peculiarity. Tanna is one 

 of the largest volcanoes of the Pacific ; and nearly all the 

 islands of the New Hebrides, as far as known, indicate com- 

 paratively recent igneous action, in which respect they differ 

 decidedly from the Feejees. 



The Vanikoro Group, north of the New Hebrides, accord- 

 ing to Quoy, has large barrier reefs about the southernmost 

 island, Vanikoro ; but at the northern extremity of the range 

 there is an active volcano, Tinakoro, and no coral. Tikopia, 

 to the south-east of Vanikoro, is high and volcanic, according 

 to Quoy, though not now with active fires ; and it appears, 

 from the descriptions given, to have no reefs. Mendana, 

 north-east of Tinakoro, according to Kruesenstern, as stated 

 by Darwin, is low, with large rdefs ; Duff's Islands have bold 

 summits with wide reefs. 



New Caledonia, and the north-east coast of New Holland, 

 with the intermediate seas, constitute one of the grandest reef- 

 regions in the world. On the New Caledonia shores (p. io6), 

 the reefs are of great width, and occur not only along the 

 whole length of the western coast, a distance of 200 miles, but 



