ORIGIN OF ATOLLS 565 



thus substantiated, it may be regarded as giving the best explanation of 

 atolls as well as of barrier reefs and unconformable fringing reefs, par- 

 ticularly if the atolls are near barrier-reef islands, as in examples that I 

 have described in Fiji (1916, h). But it is well to recognize that, as far 

 as isolated atolls are concerned, this proof of their origin is indirect and 

 not compulsory. There are no means of making the proof more direct, 

 apart from expensive borings, such as those on Funafuti, in the Pacific, 

 and Bermuda, in the Atlantic, the results of which may be briefly re- 

 viewed. 



THE FUNAFUTI BORING 



In 1898 the Eoyal Society of London sent an expedition to Funafuti, 

 an atoll of about 7 miles diameter, in the Ellice group of the equatorial 

 Pacific, and a boring made the year before in the reef to a depth of 698 

 feet, under the direction of Professor David, of Sydney, New South 

 Wales, was continued to a total depth of 1,114 feet. As the boring was 

 in the reef rim of the atoll, and as the depth reached was only about one- 

 thirtieth of the atoll diameter, or about one-twelfth of the neighboring 

 ocean depths, it is not surprising that no volcanic rock was reached. The 

 limestone core was minutely studied by specialists ; but as their published 

 reports (1904) were limited to matters of fact, the principal object of 

 the expedition, namely, a determination of the origin of the atoll, on 

 which these specialists must inevitably have formed well based opinions, 

 was left to the readers of the report for settlement by such inferences as 

 they might be able to draw. Many readers, recognizing that they could 

 not possibly acquaint themselves with the facts of the case as thoroughly 

 as the specialists had done, did not attempt to make a thorough analysis 

 of the report ; and the origin of atolls Avas therefore much less illuminated 

 by this expedition than it would have been if the investigating specialists 

 had been permitted to state their conclusions. 



It is only in other publications that the conclusions legitimately de- 

 rived from the Funafuti borings have been announced by the investi- 

 gators; for example, by Sollas in his general work on "The Age of the 

 Earth" (19 — , 121-132). An excellent summary of the permissible con- 

 clusions has lately been presented by Skeats, who introduces them with 

 the following statement : "The significance of the evidence made available 

 by the publication of the very detailed and exhaustive examination of the 

 Funafuti bores appears to have escaped many workers on coral-reef prob- 

 lems or to liave been misunderstood. This no doubt is partly to be attrib- 

 uted to the circumstance tliat the committee responsible for the work 

 consisted of adherents of diverse views on atoll formation, and decided 



