SUBSWE^fCE IN PACIFIC CORAL REGIONS. 281 



Samoa, along by the Hervey Group. Each of these exten- 

 sions trends parallel wit Ji the gi'oups of islands. It would seem, 

 therefore, that the Society and Samoan islands were regions of 

 less change of level than the deep seas on either side of them ; 

 that therefore, instead of a uniform subsidence over the 

 subsiding area shading off toward the borders, there were 

 troughs of greater subsidence, whose courses were parallel, to 

 the ranges of islands; that, in other words, there were in the 

 ocean's bottom a few broad synclinal and anticlinal flexures, 

 having a common direction nearly parallel to the axial line 

 of the Pacific. The Marquesas and Fanning Groups lie in a 

 common line, and thus may mark the course of a great central 

 anticlinal in the oceanic basin. 



The Hawaian range has experienced its greatest subsidence 

 to the north-west, where the islands are all atolls, and show 

 some evidences of recent sinking; and this north-western 

 extremity of the range is nearer to the axis of the area of 

 subsidence, above laid down, than is the south-western. 



What is the extent of the subsidence indicated by the coral 

 reefs and islands of the Pacific ? It is very evident that the 

 sinking of the Society, Samoan, and Hawaian Islands has 

 been small compared with that required to submerge all the 

 lands on which the Paumotus and the other Pacific atolls rest. 

 One, two, or five hundred feet, could not have buried the 

 many peaks of these islands. Even the 1,200 feet of depres- 

 sion at the Gambler Group is shown to be at a distance from 

 the axis of the subsiding area. The groups of high islands 

 above mentioned contain summits from 4,000 to 14,000 feet 

 above the sea ; and can we believe it possible that throughout 

 this large area, when the two hundred islands now sunken were 

 above the waves, there were none of them equal in altitude to 

 the mean of these heights, or 9,000 feet ? That none should 

 have exceeded 9,000 feet in elevation is by no means probable. 

 Hence, however moderate our estimate, there must still be 

 allowed a sinking of many thousand feet. Moreover, whatever 

 estimate we make that is within probable bounds, we shall not 

 arrive at a more surprising change of level than our continents 



