462 VAST AMOUNT OF SUBSIDENCE. [CHAP. xx. 



Numberless facts could be adduced to prove that upraised organic 

 remains arc common wherever there are active volcanos ; but until 

 it could be shown that in areas of subsidence, volcanos were either 

 absent or inactive, the inference, however probable in itself, that 

 their distribution depended on the rising or falling of the earth's 

 surface, would have been hazardous. But now, I think, we may 

 freely admit this important deduction. 



Taking a final view of the map, and bearing in mind the state- 

 ments made with respect to the upraised organic remains, we must 

 feel astonished at the vastness of the areas, Avhich have suffered 

 changes in level either downwards or upwards, within a period not 

 geologically remote. It would appear, also, that the elevatory and 

 subsiding movements follow nearly the same laws. Throughout 

 the spaces interspersed with atolls, where not a single peak of high 

 laud has been left above the level of the sea, the sinking must have 

 been immense in amount. The sinking, moreover, whether 

 continuotis, or recurrent with intervals sufficiently long for the 

 corals again to bring up their living edifices to the surface, must 

 necessarily have been extremely slow. This conclusion is probably 

 the most important one which can be deduced from the study of 

 coral formations ; and it is one which it is difficult to imagine how 

 otherwise could ever have been arrived at. Nor can I quite pass 

 over the probability of the former existence of large archipelagoes 

 of lofty islands, where now only rings of coral-rock scarcely break 

 the open expanse of the sea, throwing some light on the distribution 

 of the inhabitants of the other high islands, now left standing so 

 immensely remote from each other in the midst of the great oceans. 

 The reef-constructing corals have indeed reared and preserved 

 wonderful memorials of the subterranean oscillations of level ; we 

 see in each barrier-reef a proof that the land has there subsided, 

 and in each atoll a monument over an island now lost. We may 

 thus, like unto a geologist who had lived his ten thousand years 

 and kept a record of the passing changes, gain some insight into the 

 great system by which the surface of this globe has been broken up, 

 and land and water interchanged. 



