Ch. VI. DISTRIBUTION OF CORAL-REEFS. 189 



subsided independently of each other; for the McAskill 

 Islands, 1 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- 

 longed by numerous reefs to a point 2,000 miles dis- 

 tant from Hawaii. The south-eastern end of this long- 

 line is one of elevation and of volcanic activity ; 

 whereas the north-western end, judging from the 

 structure of the reefs, though these are imperfectly 

 known, is one of subsidence. 2 So that here we ap- 

 parently have opposite movements in progress towards 

 the two extremities of the same long line. The com- 

 monest case seems to be a tendency to alternation 

 between the areas of subsidence and elevation, as if 

 the sinking of one had counterbalanced the rising of 

 another. 



The existence in many parts of the world of lofty 

 table-land, proves that large surfaces have been upraised 

 in mass to a great height above the level of the sea ; 

 although in almost every country the highest points 



1 Dana, Corals and Coral Islands, p. 306. 



2 Dana, Corals and Coral Islands, p. 307, 355. See also my Appendix. 



