Coral Reefs and Islands. 145 



relations to other islands: that the subsidence indicated in- 

 volved the whole central Pacific, besides other large areas. 

 He also expressed the opinion that a Pacific continent had 

 disappeared through the subsidence. The proofs of the first 

 and the .second conclusions are partly different and should 

 not be confounded. The third is no necessary part of the 

 general theory, was not adopted in my Report, and need not 

 be further considered. 



2. Darwin did not hold that atolls were necessarily evi- 

 dence of a subsidence now in progress, but allowed that in 

 some regions they may have reached a state of rest, and may 

 perhaps have undergone an elevation since the cessation of 

 the subsidence; and also that subsidence and elevation may 

 have alternated. 



3. Darwin found what he believed to be almost certain proof 

 of subsidence in the features of the large barrier-islands and 

 atolls. He perceived in the rocky islets that dot the great 

 interior lagoon-like waters of the Gambier group, Hogoleu, 

 and other similar barrier-islands of the Pacific, and the 

 general resemblance of such islands to atolls, strong evidence, 

 11 leaving scarcely any doubt on the mind," that the islets 

 were the emerged points of sunken lands ; that such barrier- 

 islands were no less lagoon islands than Keeling atoll (the 

 atol] which he investigated); and, if evidence of subsidence, 

 the atoll was proof of further subsidence, that is, one that had 

 continued to the disappearance of the sinking peaks. 



The evidence which had satisfied him was satisfactory to 

 me when I first learned of his views in Australia (in 1839), 

 after a cruise amongst the Paumotu atolls and the Tahitian 

 and Samoan reef-regions; and more decidedly so later, when 

 I had been among the Friendly, Feejee, and other Pacific 

 islands. 



That the argument may be appreciated I here intro- 

 duce a map of the eastern half of the Feejee xlrchipelago *. 

 Several of the great barrier-reefs in this map, 10 to 20 miles 

 in length, have but one or two peaks of the sunken land re- 

 maining; Nanuku has but one little point, near its south- 

 eastern angle, a mile of peak within a barrier island 200 

 square miles in area; Bacon's Isles are the last two little 

 peaks of a still larger lagoon; and besides these and other 

 examples of disappearing lands, a dozen of the easternmost 

 islands are actual atolls — the last peak gone. 



4. To this, the chief of Darwin's arguments in his own view, 



* Reduced from the general map of the archipelago in the Atlas of 

 the Wilkes Expedition. 



Phil. Mag. S. 5. Vol. 20. No. 123. August 1885. L 



