264 CORALS AND CORAL ISLANDS. 



cape. South of this cape there are only a few scattered coral 

 zoophytes. 



The Louisiade Group is described as a region of extensive 

 reefs. 



The Salomon Islands, as far as ascertained, are but spar- 

 ingly fringed, except the two westernmost, which are said to 

 have large reefs. The peculiar character of these lands is too 

 imperfectly known to allow of our deducing the cause of so 

 restricted reefs. Off to the north of the Salomon Islands 

 there are several islands of considerable size. New Ire- 

 land, according to D'Urville, has distant reefs on part of its 

 shores. 



The Admiralty Islands, farther west, are inclosed by bar- 

 rier reefs, and beyond this group there are a few lagoon 

 islands. 



The north side of New Guinea is mostly without coral. 

 There are several islands off this coast, which are conical 

 volcanic summits, and one of them, near New Britain, and 

 another, Vulcano, near longitude 145° E., are in action. 



From the facts thus far detailed, the connection between 

 the prevalence or extent of reefs, and the various causes 

 assigned as limiting or promoting their growth, is obvious. 

 The amount of subsidence determines in some cases the dis- 

 tance of barrier reefs from shore ; but it by no means accounts 

 for the difference in their extent in different parts of a single 

 group of islands. Indeed, if this cause be considered alone, 

 every grade of extent, from no subsidence to the largest amount, 

 might in many instances be proved as having occurred on a 

 single island. Of far greater importance, as has appeared, is 

 the volcanic character of the land. At whatever time the ex- 

 isting reefs in the Pacific commenced their growth, they began 

 about those of the igneous islands whose fires had become 

 nearly or quite extinct; and as others in succession were 

 extinguished, these became, in their turn, the sites of corals, and 

 of coral reefs. Those lands whose volcanoes still burn are 

 yet without corals, or there are only limited patches on some 

 favoured spots. Zo5phytes and volcanoes are the land-making 



