Smith. — Notes on the Kermadec Group. 335 



to the east of a line drawn between those places, and, therefore, 

 off the plateau. A few other soundings have been obtained along 

 this central line by other ships, and these, together with some 

 shoals and reefs lying between the Kermadec and Tonga Groups, 

 all go to prove that the plateau is probably continuous in this 

 direction. Many rocks, reefs, and shoals have been reported 

 from time to time as lying south-westerly from the Kermadec 

 Group, but there are doubts about them all. Her Majesty's 

 ships have frequently searched for them in vain ; and it is be- 

 lieved that those who reported them were deceived by the 

 colouring of the water due to the presence of Mollusca. 



Although the region under consideration may be called an 

 oceanic plateau, the depth of water on it is very great — deeper 

 probably than the height of most of our northern mountains ; 

 and, therefore, when we find little islands like the Kermadecs 

 appearing above the sea, we readily conceive them to be the tops 

 of mountains rising to great heights above their bases. We are 

 happily in possession of a most excellent survey of Sunday 

 Island and the neighbouring seas, made by Captain Denham, of 

 H.M.S. Herald, in 1854. From his chart we find that this 

 island stands on a plateau, the waters on which are of moderate 

 though uneven depth. At one mile from the shores the mean 

 depth is about 350 feet, though in one place within half-a-mile 

 of Nash Point it is as much as 1,290 feet. There can be little 

 doubt that this moderate depth — which is somewhat unexpected 

 from the abruptness of the coast-line — is due to the erosion and 

 destruction of the former extensions of the island, the materials 

 of which have been spread over the sea bottom in its vicinity. 

 In the neighbourhood of Macaulay, Curtis, and L'Esperance 

 Islands, we find from Captain Eairchild's soundings that the 

 waters are also comparatively shallow for about a mile off the 

 coasts. As, however, we pass away from the land, between 

 Sunday and Macaulay Islands, a depth of 3,120 feet and 3,780 

 feet was found by the Challenger; whilst 40 miles to the north of 

 the former the depth is 3,600 feet. Sunday Island, being 1,723 

 feet high, it follows that it is a mountain standing on a broad 

 base, with an elevation of 5,300 feet. 



The islands are all, in fact, the tops of volcanic mountains 

 appearing above the sea ; and I believe they originated in the 

 eruption of matter from the great fissure I have indicated as 

 probably extending from Ruapehu to Samoa, and which passes 

 through this group. 



With regard to the age of the islands, there is very little to 

 guide us in forming an opinion ; but bearing in mind Sir James 

 Hector's statement, to the effect that the volcanic activity which 

 caused the elevation of the central plateau of the North Island of 

 New Zealand commenced in Eocene times, we are led to infer 

 that the Kermadec volcanoes will be of about the same age. It 



