188 DISTEIBUTION OF COEAL-EEEFS. Cii. VI. 



pearances, are still subsiding. The smallness of the 

 scale of our map should not be overlooked ; each square 

 on it containing 810,000 square miles. If we take the 

 space of ocean from near the southern end of the Low 

 Archipelago to the northern end of the Marshall Archi- 

 pelago, — a length of 4,500 miles, we see that, as far as 

 known, every island, excepting Metia, is atoll-formed. 

 The eastern and western boundaries of our map are 

 continents, and they are rising : the central areas of 

 the great Indian and Pacific Oceans, are mostly sub- 

 siding ; between them, north of Australia, lies the most 

 broken land on the globe, and there the rising parts 

 are surrounded and penetrated by areas of subsidence ; l 

 so that the prevailing movements now in progress, seem 

 to accord with the present state of the great terrestrial 

 and oceanic divisions of the world. 



The blue spaces on the map are nearly all elongated; 

 such as the great north and south line of atolls in the 

 Indian Ocean, the space between the barrier-reefs of 

 Australia and New Caledonia, the Caroline Archi- 

 pelago, &c. Whether adjoining elongated spaces, run- 

 ning in different directions, have subsided by one com- 

 mon movement, or independently of each other, we do 

 not know. In the case of the Caroline and Marshall 

 Archipelagos, situated near each other, but extending 

 in different directions, it seems probable that they have 



1 I suspect that the Arru and Timor-laut Islands present an included 

 small area of subsidence, like that of the China Sea ; hut I have not 

 ventured to colour them blue, owing to the want of sufficient informa- 

 tion. See Appendix. 



