420 Notices of Memoirs — Islands and Coral Reefs of Fiji. 



resulting in such ' sunken ' banks as the Penguin Bank. By 

 ' sunken ' we do not mean in any way to refer to subsidence as 

 a factor in producing such a bank. The mass of water which is 

 poured into a lagoon on the windward face of a reef, and transforms 

 it into a gigantic pothole, is something enormous. The breakers 

 follow one another incessantly, and the hydraulic head obtained is 

 amply sufficient to account for the scouring of the lagoons after the 

 reef has once established itself as a bank, and amply sufficient to 

 wear away from the slope of the islands the platform upon which 

 the coral reef is built. The topography of this platform is naturally 

 much varied, depending upon the character of the shore line, the 

 direction of the valleys of the shore hills, and their composition. 

 A glance at the charts accompanying this Bulletin will show all 

 possible conditions of submarine erosion in the cutting down of the 

 submarine platforms of the islands of Fiji, and in the manner in. 

 which islands, islets, and rocks have been left, attesting their former 

 greater extension in the various clusters of the Archipelago. 



" When the principal openings are not on the lee side of the 

 lagoons, as is the case with Vanua Mbalavu, and the Argo Eeef or 

 Totoya, Fulanga, and a few others, there is usually a simple reason, 

 such as the lower elevation of the island once covering the area of 

 the lagoon at some point not on the lee side, or the fact that the 

 lagoon has been formed on a steep volcanic slope looking eastward 

 or northward, so that deep ravines or tongues of deep water cut into 

 the lagoons, and intercept the coral patches forming its rim on the 

 weather side, and thus leave a windward passage. It is by some 

 such erogenic condition that we must explain the existence of deep 

 soundings within atolls, — soundings which in no way indicate 

 a subsidence, as has been assumed by Darwin, and which according 

 to him were not to be explained by any other hypothesis. Such 

 deep ravines are of course also to be traced on the slopes of the 

 larger islands where we find, crossing the shallow plateaus on which 

 coral patches grow, valleys of considerable depth, which appear as 

 deep soundings within the area of an outer reef flat such as in the 

 great plateau off Viti Levu and Yanua Levu, or of Kandavu and 

 Taviuni, which according to Darwin would indicate a subsidence, 

 while, on the contrary, they are a part of the results of the elevation 

 and lifting up of that region of Fiji. 



"Nor are the great depths found close to narrow lines of corals 

 an indication that the corals have grown up as a nearly vertical 

 wall from a depth of two or three hundred fathoms or more. It 

 mei'ely indicates that the corals form a thin crust, at most 120 feet 

 in thickness, over a sharp volcanic ridge, the summits or crest of 

 which have either reached b^^ elevation the depths at which corals 

 can grow, or have been denuded by submarine erosion to form 

 a platform below the level of the sea, where corals have found 

 a footing upon them. 



" My observations in Fiji only emphasize what has been said so 

 often, that there is no general theory of the formation of coral reefs, 

 either of barrier reefs or atolls, applicable to all districts, and that 



