MUSEUM OF COMPARATIVE ZOOLOGY. 181 



to a theory which is based upon the disappearance of a Pacific con- 

 tinent/ and be apparently so unwiUing to recognize the agency of more 

 natural and far simpler causes. 



Granting that during the secondary period the great East India islands 

 were connected with Asia, and that there had been in the early tertiary 

 period a great subsidence, which may have extended throughout some 

 parts of the Pacific to the time of the formation of modern coral reefs, — 

 granting even that the summits of the islands now existing indicate 

 plateaus upon which the various archipelagos of the Pacific are based, 

 and point to a former extent of land far greater than now projects above 

 the surface of the sea, and also that the islands of the Pacific mark a 

 general subsidence along a line extending from the southeast to the 

 northwest, as is urged by Dana, — yet there is nothing in all this to show 

 that the subsidence has been the main cause of the formation of atolls 

 and barrier reefs, while the existence of such a subsidence in its turn 

 derives its strongest proof, with many writers, from the existence of atolls 

 and barrier reefs. As long as we can in so many districts explain the 

 formation of atolls and of baiTier reefs by other causes, fully sufficient 

 to account for the numerous exceptions to the theory of Darwin, which 

 have been observed by so many investigators since the days of Darwin 

 and Dana, it seems unnecessary to account for their presence by a gigan- 

 tic subsidence, of which, although we may not deny it, we can yet have 

 but little positive proof. 



Dana has been led to reconsider the earlier and later observations, 

 and has given his results in the American Journal of Science.^ He most 

 distinctly rejects Darwin's hypothesis, that the slow subsidence upon 

 which he counted to form atolls and barrier reefs from fringing reefs 

 involved the whole central Pacific, besides other large areas, a Pacific 

 continent having disappeared through subsidence. 



Whether subsidence is going on now, or has ceased after the formation 

 of atolls, which he ascribes to it, seems immaterial. The point at issue 

 is, how far is it possible for atolls and barrier reefs to begin in an area 

 of limited extent without a constant alternation of elevation and sub- 

 sidence. It seems to me that the rocky islets dotting the interior of 

 Kaneohe Bay could as well be cited as proof of subsidence, as the rocky 



^ This part of the theory of Darwin, which seems a natural corollary of his 

 explanation of coral reefs, is most empliatically rejected by Dana, Am. Journ' of 

 Science, Vol. XXX. p. 90, 1885, and previously also in his Geology of the Explor- 

 ing Expedition, in 1849. 



2 Am. Journ. of Science, August, 1885, p. 89, and September, 1885, p. 169. 



