226 A NATURALIST IN THE PACIFIC chap. 



island was in existence, the natives said, in the days of their great- 

 grandfathers, a statement indicating that the people of the district 

 had no reason to doubt its antiquity. A chief, who formed one of 

 the party, dived under the island. 



When I visited this lake in 1899 there were three floating 

 islands, named by the natives " Wanga levu " and " Wanga lailai," 

 that is, " Large canoe " and " Small canoe." The largest was 90 or 

 100 feet long, whilst the two smaller were about 50 feet long, the 

 breadth being less than half the length. They are composed of a 

 dense growth of reeds and sedges supporting small living trees 10 

 to 17 feet in height, swamp ferns, and other smaller vegetation, the 

 whole forming fairly solid standing-ground, and doubtless possess- 

 ing considerable thickness. 



The origin of these floating islands is probably to be found in the 

 circumstance that the dense mass of swamp-vegetation lies on a 

 rocky substratum, and that during some unusually heavy flood 

 large portions of the swampy soil-cap became detached and floated 

 up. A floating island occurs near the sea in the Lauthala district 

 on the Lower Rewa in Viti Levu. The floating island in Derwent- 

 water in the north of England is said to be " a blister of sub- 

 lacustrine turf." Those in Russia and Hungary, according to Mr. 

 Hanusz, appear to be felted masses of tree-trunks, branches, and 

 marsh-plants thinly covered with soil. 1 



I will preface my remarks on the geology of the Wainikoro and 

 Kalikoso plains by observing that this region displays three con- 

 spicuous features. In the first place, it is a region of acid rocks, 

 mostly altered tuffs, derived from quartz-porphyries, the alteration 

 consisting in the deposition of quartz often of the chalcedonic type. 

 In the second place, a silicifying process has been in operation here 

 on an extensive scale, as evidenced by the abundance of silicified 

 corals lying on the surface, especially in the district around the lake 

 and by the abundance of concretions of chalcedony, of fragments 

 of chalcedonic flints, and of portions of white chalcedonic quartz- 

 rock that in places strew the ground. In the third place, earthy 

 limonite, or bog iron ore, has been produced in quantity, par- 

 ticularly around the lake ; and in places small round concretions 

 of impure carbonate of iron cover the soil. Before referring more 

 in detail to the different parts of this region, it may be remarked 

 that the silicified corals, flints, iron-ore deposits, &c, of this and 

 other parts of the island are dealt with in Chapter XXV. 



This region of acid rocks extends about two miles to the west 

 1 Journal, Royal Geographical Society, June, 1894. 



