1836.] SLOW SUBSIDENCE OF LAND. 473 



areas, which have suffered changes in level either down- 

 wards 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 land has been left above the level of the sea, 

 the sinking must have been immense in amount. The 

 sinking, moreover, whether continuous, 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 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 inhabi- 

 tants 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 sub- 

 terranean 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 inter- 

 changed. 



