164 DISTRIBUTION OF CORAL-REEFS. Ch. VI. 



said (for instance between lat. 16° and 13°) to form 

 part of it. Flinders l has described an atoll-formed 

 reef in lat. 10°, seven miles long and from one to three 

 broad, resembling a boot in shape, and apparently in- 

 cluding a deep lagoon. Eight miles westward of this, 

 and forming part of the barrier, lie the Murray Islands, 

 which are high and are encircled. In the Corallian sea, 

 between the two great barrier-reefs of Australia and 

 New Caledonia, there are many low islets and coral- 

 reefs, some of which are annular, or like a horse-shoe. 

 Bearing in mind the smallness of the scale of our map 

 (the lines of latitude being 900 miles apart), we see that 

 none of the larger groups of reefs and islands which are 

 coloured blue, and which are supposed to have been 

 produced by long-continued subsidence, lie near exten- 

 sive lines of coast coloured red; these latter having 

 either long remained stationary, or having been upraised 

 with new reefs re-formed on them. Where red and blue 

 circles do occur near each other, I am able, in several 

 instances, to show that there have been oscillations of 

 level ; subsidence having preceded the elevation of the 

 red spots ; and elevation having preceded the subsidence 

 of the blue spots ; and in this case the juxtaposition of 

 reefs belonging to the two great types of structure is 

 little surprising. We find, therefore, that atolls and 

 barrier-reefs, which both owe their origin to subsidence, 

 lie near together and are as a general rule separated 

 from fringing-reefs, which show that the land is sta- 

 tionary or rising ; and all this holds good to the full 

 1 Voyage to Terra Australis, vol. ii. p. 336. 



