Speight. — Petrological Notes on Eocks from the Kermadecs. 241 



Art. XXIX.— Petrological Notes on Rocks from the Kermadec Islands ; with 

 some Geological Evidence for the Existence of a Subtropical Pacific Con- 

 tinent. 



By R. Speight, M.A., B.Sc, F.G.S. 



[Read before the Philosophical Institute of Canterbury, 6th October, 1909.] 



When the scientific party visited the Kermadec Islands in the year 1907, 

 Mr. R. B. OKver, one of its members, made collections of the rocks occurring 

 there, and subsequently submitted them to me for examination. Their 

 field relations will be fully dealt with by him at a later date ; but after 

 a microscopical examination of the collection I feel justified in bringing 

 forward at once a matter which, from what he has told me, is altogether 

 apart from his own work, and may have a somewhat important bearing on 

 the biological history of New Zealand. Mr. Oliver, following Mr. Cheese- 

 man,* believes that the Kermadecs are oceanic islands ; but there is some 

 evidence that they are built up by volcanic action on the remnants of a 

 former continent which stretched south-west from Fiji and Tonga and 

 probably extended so as to join with northern New Zealand. The Ker- 

 madec Islands may be oceanic in a biological sense — viz., that their present 

 fauna and flora are derived from neighbouring lands by the various processes 

 of distribution, and are not a survival of that belonging to a continent of 

 which they once formed part ; there are facts, however, which point to a 

 close connection with a continental area, if not recently, certainly in early 

 Tertiary or Mesozoic times. 



Mr. Cheeseman's conclusions were come to after a close study of the flora 

 of the group. He maintained that the islands were populated by the trans- 

 porting agency of birds, winds, and ocean-currents, and that they received 

 the bulk of their plants from New Zealand, a smaller proportion from Poly- 

 nesia, and that five species were endemic. The occurrence of Aleurites 

 moluccana, the well-known candlenut of tropical regions, whose nuts 

 W. H. Guppy showed could not float, is one of the special peculiarities, 

 and would be very strongly suggestive of a continental connection for the 

 group were it not possible that it was introduced by man. Cheeseman, 

 however, does not mention this possibility. Apart from the flora, the 

 existence of an indigenous rat {Mus exulans) on Sunday Island, and also 

 its presence in large numbers on Macauley Island when first discovered 

 by Lieutenant Watts, is suggestive of a land connection. The rat is widely 

 distributed in Polynesia, and it is possible that it was introduced on Sunday 

 Island either intentionally or unintentionally by Natives on their long 

 sea-voyages. But Macauley Island is very inaccessible, and it is very 

 improbable that they introduced it here. It must be remembered, how- 

 ever, that this rat, which is the same as the Maori kiore, is used as an article 

 of food by the Natives of some islands even when other supplies are plenti- 

 ful, and also it is so widely distributed in Polynesia that conclusions to be 

 drawn from its distribution are perhaps ill founded,. Man has no doubt 

 been responsible for its introduction into many islands. 



*Traus. N.Z. Institute, vol. xx, 1888. 



