492 Mr Gardiner, The Coral Reefs of [Mar. 7, 



how much more luxuriant the growth of coral was in the lagoon 

 than on the outer reef. Study of the charts of such islands of 

 the Pacific Ocean as have been surveyed and other information, 

 collected by me, has shown me that shoals in lagoons are gener- 

 ally nearly awash, and thus a conclusive proof is afforded, if we 

 accept the theory of subsidence, that at present the whole Pacific 

 Ocean must be in a period of rest. When the barrier reef is 

 far distant to windward, the sea may have great force within 

 the lagoon, the inner reef be well formed and somewhat strewn 

 with boulders. Yet the building-up power of the coral is so 

 small here, or the subsidence has been so rapid, that nowhere 

 are there to be found secondary barrier reefs, as it were, inside 

 the primary reefs. There must be other causes inside the lagoon 

 which prevent the formation of these, or, as I fully believe, the 

 constituents of a barrier reef are radically different from those of 

 an inner reef, which has grown up as such. 



In my opinion, the effect of the waves on loose coral and shell 

 materials, of which Darwin supposes the reef to be mainly formed 

 should be noted. Dana states precisely his opinion on this point 1 . 

 It serves to " widen the reef," the windward reefs being the widest, 

 as more fragments would be heaped up by the heavier seas, the 

 growth also being probably greatest to windward. Yet the wind- 

 ward reef, including the raised islands of Funafuti, is narrower in 

 many places than the leeward reef, and the same is often the case 

 in Fiji. All the windward reefs in Fiji are of about the same 

 breadth, and indeed through the whole Pacific barrier and atoll 

 reefs to windward show a striking uniformity among themselves 

 in width. The material then is "to steepen, as a consequence of 

 the widening, the upper part of the submarine slopes." The 

 sections off the barrier of Tahiti, mentioned by Murray 2 , and 

 the sections run in 1889 by the Egeria off Sydney and Canton 

 islands in the Phoenix Group, and by the Penguin in 1896 off 

 Funafuti 3 all show a fairly even slope to about 40 fathoms at 

 about 250 yards from the edge of the reef, and then a sudden 

 precipitous fall of about 75°. My own observations off the Fijian 

 and Rotuman reefs show the same characteristic slope to about 

 40 fathoms and then a sudden fall. This steep would seem to be 

 a feature of all reefs, rather than one due to particular reefs being 

 in a condition of rest in a general area of subsidence. Where the 

 deposits from corals and shells do not exceed greatly the loss by 

 subsidence and current waste " the atoll reef should lose in 

 irregularity of outline and thus approximate towards an annular 

 form." The effect of this should be seen in the so-called "sunken" 



1 Loc. cit., p. 270. 



2 Dana, loc. cit., p. 282. 



3 Nature, Vol. lv, 1897, p. 375. 



