238 Prof. A. Agassiz on the 



including Fiji and Samoa, may have been synchronous. Tt 

 may be that these islands have, like Northern Queensland, 

 been subject to an immense erosion and denudation which 

 have reduced them to their present proportions. 



The elevation may have been preceded, as in Queensland, 

 in still earlier geological times by a great period of depression, 

 during which the thick beds of coral-reef limestone may have 

 been formed. How far east this elevation extended is not 

 known ; its area probably included the Cook Islands and 

 Tahiti, and, judging from some photographs, I should feel 

 inclined to consider atolls of the Paumotus as having been 

 formed by causes similar to those which shaped those of the 

 Fijis. 



The evidence thus far collected on the Fijis shows the 

 futility of boring in this group. Any result obtained would 

 merely at some point indicate the thickness of a former 

 elevated reef — a reef formed in a period preceding our own. 

 We should obtain information which could have no bearing on 

 the main question, if I am correct in the interpretation of 

 what I have observed — information, in fact, which may be 

 obtained as one steams along without the trouble or cost of 

 boring. Should I be correct, it would be natural to look upon 

 the results of the boring at Funafuti much in the same light, 

 and to assume that the island, as well as others in the Ellice 

 group, is also in this area of elevation, and that the great 

 thickness of coral obtained was reached by boring in the base 

 of an ancient reef. So that the results obtained by Professor 

 David from the boring at Funafuti do not assist us in any 

 way in corroborating the theory of subsidence as essential to 

 the formation of atolls. 



However that may be, it only emphasizes what has been 

 said so often, that there is no general theory of the formation 

 of coral-reefs, either barrier or atolls, of universal application. 

 Each district must be examined by itself — at least such has 

 been my experience in Florida, in the Bermudas, the Ba- 

 hamas, in Cuba and the West India Islands and the Sandwich 

 Islands. The results of this trip show plainly that the theory 

 of Darwin and Dana, of the formation of atolls and of barrier 

 reefs by subsidence, is not applicable to the Fiji Islands, not- 

 withstanding the boring at Funafuti. In all the localities I 

 have visited the coral-reefs form but a thin crust upon the 

 underlying base (it is not more than 50 to 60 feet thick in 

 Florida), and the shape and slope of this base are in no way 

 due to the growth of the corals living upon it. 



This still leaves open the question of the formation of such 

 thick masses of coral-reef rock, which, though they may 



