EUA ISLAND. 18? 



nized by its red color ; but patches of limestone occur in many places, 

 sometimes in large projecting mass, like that which forms the south summit, 

 sometimes weathered down into groups of isolated pinnacles, standing on a 

 volcanic basis." 



The outcrop of the volcanic formation is also well seen on the western 

 face of the east ridge to the north of Ohonua Village. 



On Plate XXIII,' Lister has given an approximate sketch map of the posi- 

 tion of the patches of volcanic formation of Eua." The volcanic basis 

 underlying the coralliferous limestones is exposed near the centre of the 

 eastern face, and at the shore there are dykes of intrusive rock, which 

 cut through the volcanic deposits but do not enter the overlying calcareous 

 strata. 



The present topography of Eua indicates that at one time it must have 

 been a large flat limestone plateau, originally similar to that of Tongatabu 

 and Vavau, but of greater height and less extent, pushed up by volcanic 

 outbursts on the east coast, which was little by little disintegrated according 

 to the hardness of the various terraces, and finally eroded so as to form the 

 central valley with the comparatively smooth faces of the eastern and western 

 ridges. Only a few outcrops of the coralliferous limestones are seen, here and 

 there, in the valley, — remnants of the harder terraces, such as the 

 fourth terrace, a long line of which is left on the northern part of the west 

 slope of the central valley. On looking back on Eua on our way to Tonga- 

 tabu one can see, perhaps better than on the island itself, extending for a 

 great part of its length, the deep central valley of erosion, which has given 

 to Eua its characteristic topography, and certainly there is nothing less like 

 a lagoon than this inner valley or sink of erosion of Eua.^ 



1 Loc. cit., Geol. nf the Tonga Islands. 



2 See Harker, Volcanic Rocks of Eiia, Geol. Map;-, June, 1891. 



8 CoiiiinanikT Oldham of the H. M. S. " Egeria" has given in " Nature " of May 22, 1890, p. 85, an 

 interesting sketch of Kiia, corresponding in the main with Lister's account. In a note to the above Pro- 

 fessor Judd speaks of the limestones as made up of Foraminifera and water-worn Nullipores. As re- 

 gards the volcanic rocks he thinks their composition lends support to the view that all oceanic islands 

 are of volcanic origin. 



