Darwin *s Theory of Coral Reefs. 187 



step farther, and to deduce the effect of subsidence in produc- 

 ing an embayed shore line on a dissected island. He must 

 surely have read Dana's paragraph on this point. Indeed, in 

 describing the Marquesas Islands, he says : " Dana infers . . . 

 from their steepness and deeply indented outline, that they 

 have subsided "; * but the general principle here involved did 

 not engage his attention. Even the explicit reference to Gam- 

 bier Island, a western member of the Paumotu group, in 

 Dana's reportf as exhibiting forms that are indicative of sub- 

 sidence, independent of the occurrence of its well-developed 

 barrier reef, seems entirely to have escaped his notice. How 

 regrettable it is that the great naturalist lost the pleasure of 

 appreciating the value which this evidence possesses in giving 

 independent confirmation to his theory ! 



In recent years several students of coral islands have, espe- 

 cially in Australasia, given to the evidence afforded by drowned 

 valleys the importance that it deserves. The latest of these is 

 Marshall, of Otago, New Zealand, who writes as follows in his 

 recent essay entitled " Oceania," in the " Handbiicher der 

 Regionalen Geologie " : " The deep inlets that intersect the 

 coast line of . . . [several islands of the Society group] are 

 clearly due to stream erosion. Prolonged marine action would 

 have shallowed or filled them up or at least would have built 

 up bars of coastal debris across the entrances. The author is 

 therefore strongly of opinion that the absence of cliffs at the 

 termination of the radiating spurs, the presence of deep water 

 in the lagoon, and of far-reaching inlets prove that marine ero- 

 sion has not had any influence on the form of these islands at 

 the present sea level . . . Finally the deep inlets appear to be 

 drowned stream valleys and their nature strongly supports the 

 belief that the islands have been subjected to an important 

 movement of subsidence."^: His conclusion is : " The author's 

 observations on the islands of the Cook and Society groups cause 

 him to support Darwin's theory as perfectly full and sufficient 

 to account for the reef phenomena in those islands. "§ " Dar- 

 win's theory still holds good in the majority if not in all coral 

 areas."| This direct testimony from an observer in the anti- 

 podes is most welcome. It reaches me through a friend since the 

 writing of this article was begun, and is most apposite in provid- 

 ing precisely that impartial revision of the problem by an open- 

 minded investigator which was pointed out above as desirable 

 before any final conclusion should be adopted. In view of the 

 result of this expert and first-hand investigation, further delay 



* Coral Eeefs, 2d ed., London, 1874, 201 ; also, 163. 

 f Geology, U. S. Explor. Exped., 1849, 131. 

 jVol. vi, Sec. 2, No. 9, 1911, p. 13. 

 § Ibid, p. 7. || Ibid, p. 30. 



