Ch. yi. distribution of coral-reefs. 
191 
are surrounded and penetrated by areas of subsidence ; 1 
so that tbe 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 
Archipelagoes, situated near each other, but extending 
in different directions, it seems probable that they have 
subsided independently of each other ; for the McAskill 
Islands, 2 lying towards the eastern end of the Caroline 
Archipelago, are formed of upraised coral-rock; and we 
thus see that the above two areas of subsidence have 
been at one time interrupted by an area of upheaval. 
The curved line of elevation formed by the Mariana 
Islands, seems to cross a former line of subsidence pro- 
longed from the Caroline Archipelago ; for the island 
of Fais, apparently an upraised atoll, is situated nearly 
at the point of intersection of the two lines. The 
Sandwich Archipelago is 530 miles in length,, from 
Hawaii to the westernmost rocky islet, but is pro- 
1 I suspect that the Arru and Timor-laut Islands present an in- 
cluded small area of subsidence, like that of the China Sea ; but I 
have not ventured to colour them blue, owing to the want of sufficient 
information. See Appendix. 
2 Dana, Corals and Coral Islands, p. 306. 
