into the underlying rock of atolls have not provided 

 satisfactory answers. The celebrated expeditions to 

 Funafuti Atoll, to the north of the Fiji Islands, resulted 

 in the sinking of a bore to a depth of over 1,000 feet. 

 According to the Darwinian theory it might be expected 

 that the core from such a boring would consist of dead 

 coral entirely, formed by upwards growth as the under- 

 lying land mass continued to sink (see Fig. 8) . The 

 theories of submarine ridges and accumulated sediments 

 would, on the contrary, lead one to expect a core of 

 silt at a depth of less than 175 feet, below which coral 

 does not grow, and below this the ancient rocks of the 

 submarine ridge. When the actual core was examined, 

 it was found to consist of coral fragments only, thus 

 supporting Darwin's theory. Objections to this were 

 raised, however, on the grounds that the bore might 

 well have traversed the outer edge or talus slope of the 

 atoll, and so missed the sedimentary and volcanic rock. 

 Although this left the question open, further borings 

 have been made recently. The results are not known in 

 detail at the time of writing, and further discussion 

 would be beyond the scope of the present brief intro- 

 duction to the fascinating problem. 



It is not the purpose of this handbook to enter into 

 a detailed appraisal of the various theories. Those who 

 would care to know more of the fascinating problem of 

 coral reef origin and the facts upon which the theories 

 are based should consult, 'The Coral Reef Problem,'' 

 by W. M. Davis. This provides the best and most 

 exhaustive of modern accounts. It is of a technical na- 

 ture however, written from the geologist's viewpoint, 

 and the general reader may prefer to read the first 

 chapter of C. M. Yonge's book, ''A Year on the Great 



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