1898.] Funafuti, Rotuma and Fiji. 493 



atolls, such as the Coombe, Watcrvvitch and Alexa banks and 

 in the atoll-reefs in the Lau Group of Fiji. Some atolls too 

 might have been supposed to have passed through this condition, 

 nevertheless the study of the charts of the atoll-reefs, in com- 

 parison with the barrier reefs of the Pacific, has completely failed 

 to show in them any increased regularity of outline, or any 

 approach to an annular form. The smaller atolls inside the larger 

 atolls of the Maldive Group are of a similar character to the atoll 

 shaped shoals inside the Great Barrier Reef of Fiji ; here the 

 conditions, which Dana suggests, would naturally be expected to 

 exist with a like effect to follow. However, I do not think that it 

 can be maintained that these are the effects of the debris of the 

 outer reefs at the present day, or have been in the formation of 

 the atolls of the Pacific in the past. 



The reef debris would next fill the lagoon, or, failing sufficient 

 contributions, the atoll bank would, according to Dana, lose its 

 channels into the lagoon and "become at last a small bank of 

 reef rock with a half obliterated lagoon basin." The observations 

 of Admiral Wharton are summed up on this question, when he 

 remarks 1 , "I have no hesitation in saying that a flat floor is an 

 invariable characteristic of a large atoll and I cannot find his 

 {i.e. Darwin's) ' deeply concave surface ' in any large atoll. On 

 the contrary, a flat surface is found in all these, whether the rim be 

 above, or below the surface." The study of the charts of the 

 different islands and barrier reefs of the Fiji Group show that, 

 while there may be abundant shoals, the bottom between is fairly 

 even. The fall from the reef, and then from the shoals to the 

 bottom of the lagoon, is cliff-like. The depth towards the side 

 of the lagoon gradually lessens, and in no place which I examined, 

 except where the sand bank runs off the main island of Funafuti, 

 was this cliff absent. The bottom beyond the cliff is usually 

 visible and generally covered by sand. By the reef it does not 

 show masses of debris, nor is debris being piled up and gradually 

 broadening the reefs, which are awash. There are plenty of banks 

 known in the Pacific in all conditions of submergence and all 

 seem to be of true atoll-form, none occurring with " half obliterated 

 lagoon-basins." It is possible that such constructive agencies 

 inside atoll-reefs may be in excess of the destructive, but it is 

 more probable that the widening of the reef within the lagoon 

 takes place by the growth upwards within it of shoals, formed by 

 means of coral and other lime-secreting organisms, and their 

 gradual fusion with the reef itself; this is what appeared absolutely 

 to be going on, as previously stated, inside the Great Barrier Reef 

 of Fiji and the lagoon of Funafuti. 



1 Foundations of Coral Atolls. By W. J. L. Wharton. Nature, Vol. i>v, 

 1897, p. 390. 



VOL. IX. PT. VIII. 39 



