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these islands are surrounded by ocean exceeding 1000 fathoms in 

 depth. Another important island also, isolated by sea exceeding 

 1000 fathoms in depth, is New Caledonia, where both palseozoic and 

 mesozoic fossiliferous beds are met with *. This, however, is a pre- 

 cisely similar case to that of New Zealand. The Auckland and 

 Campbell Isles f south of New Zealand are said to be separated 

 from it by a sea more than 1000 fathoms deep, but contain ancient 

 sedimentary rocks. The sedimentary deposits of the Fiji Islands, 

 formerly supposed to be ancient, have been shown by Mr. Brady ij: 

 to be of subrecent formation. 



The occurrence of granitic and gneissic formations in islands 

 differs from that of sedimentary beds in this respect, that the former 

 may have consolidated at some depth below the bottom of the ocean. 

 But such rocks, when in place, cannot have formed parts of ordinary 

 submarine volcanic accumulations. A granitic or gneissic island 

 must be part of an ancient land tract, for the rocks could only have 

 been exposed after a long period of denudation. The most important 

 instance of granitic or gneissic rocks occurring in oceanic islands is in 

 the Seychelles §, and these are probably a continuation of the main 

 Madagascar range, which is of similar formation ; they are separated 

 from Madagascar and from all other land areas by sea of consider- 

 able depth. It should also not be forgotten tbat granite and schist 

 are said by von Buch to have been thrown out from the volcano of 

 Caldera (I. de Palma) in the Canary Islands ||, that similar rocks 

 have been ejected from the Cape Yerde volcanoes^, and that horn- 

 blendic granite was found by Darwin amongst the fragments thrown 

 out at Ascension **. Granite and gneiss are also said to occur ft on 

 the Marquesas Islands in the Pacific ; but there appears to be some 

 uncertainty about this. If confirmed, however, this occurrence 

 would beof the greatest importance. 



* Heurteau, 'Ann. Mines' (7), ix. p. 232(1876). 



t Tchihatcheff, ' Considerations sur les lies Oceaniques,' p. 34. 



t Q. J. G. S. xliv. p. 1. 



§ By some mistake, Wallace, in his recent work, ' Darwinism,' p. 342, lias 

 stated that the Seychelles are formed of coral rocks. There is, however, no 

 doubt about their geological conformation, as may be seen by referring to the 

 following writers : Velain, Bull. Soc. Geol. France, 1879, ser. 3, vii. p. 278 ; 

 Perceval Wright, Brit. Assoc. Eeports, 1868, sect. p. 143 ; E. Newton, Ibis, 1867, 

 p. 335. This list of references could easily be increased considerably. 



II Von Buch, Phys. Beschr. d. Can. Inseln, p. 289. 



% Dolter, Die Vuikane der Capverden mid ihre Producte (Graz, 1882), p. 159. 



^* Darwin, Vole. Islands, p. 40. 



ft Jules Marcou, Expl. 2 ed. Carte Geol. de la terre, p. 185. 



