446 PROCEEDINGS OF SECTION E. 



rocks is as Jensen argues cannot be settled by the evidence offered 

 in this region. However, it has been mentioned that the supposed 

 ■association of Ath\ntic coast and such rocks is strikingly denied by 

 actual occurrences in New Zealand. It appears somewhat heroic to 

 regard such isolated islands as Rarotonga and Tahiti as fragments of 

 a fractured and shattered continent. 



It is impossible here to enter into a full discussion of the matter, 

 but it may be remarked that the frequent association of alkaline and 

 highly basic lavas is suggestive. Such association may be a result of 

 magmatic differentiation. Such I believe to have been the case at 

 Dunedin. The union of groups of Pacific islands into festoons and 

 chains seems largely fanciful. That there was shallow water or land 

 connection between New Zealand and New Caledonia in Triassic times 

 is shown to be true by the identification of similar Triassic fossils 

 in the two lands. The subsequent folding was probably effected at 

 the same time, and in both countries the rocks have been penetrated 

 by the ultra basic magmas. These facts coupled with the shallow 

 water between the lands are, perhaps, sufficient to prove that they 

 form portions, now isolated, of a common earth structure. 



The similarity between Tonga and the north-east of the North 

 Island of New Zealand again establishes a close relationship, and the 

 idea is supported by the occurrence of a shallow water ridge between 

 them — a ridge which extends thi'ough Fiji to the New Hebrides — and 

 these islands, show a similarity of structure, so far as later geological 

 deposits are concerned, such as the association of andesites with raised 

 limestones. There appears to be more reason to regard this ridge 

 as a continuous structural feature than any other that has been 

 mentioned in this part of the Pacific. 



I can find no further support for the supposed existence of the 

 South Pacific chain mentioned by Gregory than the fact that some 

 groups of islands have an arrangement that is more or less linear. 

 Soundings, however, show that these islands are, so far as known, 

 isolated volcanic movmtains towering high above an ocean floor 

 which is remarkably level. The idea of Savaii lying at the junction 

 of two lines of earth weakness does not appear to me to have any 

 support from actual facts. Nor is such an explanation necessaiy to 

 account for the extravasation of lava which, during the present 

 eruption, has not been gi'eater than in hundreds of other areas 

 where volcanic action has been in progress. 



EiLEVATION AND DePEESSION. 



In the enumeration of elevated areas many of the Pacific islands 

 were mentioned, and it is possible that a large portion of the floor 

 of the Pacific has been undergoing slow upward movement in late 

 geological times. 



On the other hand coral structures, such as atolls and barrier 

 reefs, indicate the opposite. Darwin's theory of the origin of atolls 

 has received such strong support from the Funafuti borings that in 

 the absence of other evidence it is now reasonable to regard the 

 occurrence of atolls as proof of subsidence within the area in which 

 they are found. Now such atolls are found in the Fiji group and in 

 the Tonga group ; and barrier I'eiefs are also present in the Fiji group, 



