GEOGRAPHICAL DISTRIBUTION. 300 



Between Australia and New Caledonia the islands are all 

 of coral. The Australian reef extending south to the east 

 cape, in latitude 24° S., has already been described. Such 

 long reefs on the shores of continents are not common. In 

 the case of Australia, the zoophytes are not exposed to the 

 destructive agents usual on continental shores, as the land has 

 a dry climate, the shores are mostly rocky, and there are no 

 streams of any extent emptying into the ocean. The east cape 

 is the southern limit, because here the tropical current, owing 

 to the direction of the coast above, trends off to the eastward 

 of south, away from the land, while a polar current follows up 

 the shores from the south as far as this cape. South of this 

 cape there are only a few scattered coral zoophytes. 



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 Ireland, 

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



The Admiralty Islands, farther west, are enclosed 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 vol- 

 canic summits, and one of them, near New Britain, and an- 

 other, Vulcano, near longitude 145° E. t are in action. 



From the facts thus far detailed, the connection between 

 the prevalence or extent of reefs, and the various causes as- 

 signed as limiting or promoting their growth, is obvious. 



