CHAP. XV.] 



OCEANIC ISLANDS. 



311 



fact, taken in connection with tlie volcanic or coralline origin of 

 all of them, powerfully enforces the conclusion at which we have 

 arrived in the earlier portion of this volume, that during the 

 Yfhole period of geologic time as indicated by the fossiliferous 

 rocks, our continents and oceans have, speaking broadly, been 

 permanent features of our earth's surface. For had it been 

 otherwise — had sea and land changed place repeatedly as was 

 once supposed — had our deepest oceans been the seat of great 

 continents while the site of our present continents was occupied 

 by an oceanic abyss — is it possible to imagine that no fragments 

 of such continents would remain in the present oceans, bringing 

 down to us some of their ancient forms of life preserved with 

 but little change ? The correlative facts, that the islands of our 

 great oceans are all volcanic (or coralline built probably upon 

 degraded and submerged volcanic islands), and that their pro- 

 ductions are all more or less clearly related to the existing in- 

 habitants of the nearest continents, are hardly consistent with 

 any other theory than the permanence of our oceanic and 

 continental areas. 



We may here refer to the one apparent exception, which, 

 however, lends additional force to the argument. New Zealand 

 is sometimes classed as an oceanic island, but it is not so really ; 

 and we shall discuss its peculiarities and probable origin 

 further on. 



