120 A NATURALIST IN THE PACIFIC chap. 



highly vesicular, that had been thrown up in a submarine eruption 

 off Vulcano in the Lipari Islands. 



(4) The Upper Valleys of the Ndrawa River. — The 

 two valleys of Liwa-liwa and Ndrawa meet at Ravuka, where their 

 two streams unite to form the main Ndrawa River. The former is 

 the largest ; and its large impetuous stream, during its descent of 

 about two miles from Liwa-liwa past Lutu-kina to Ravuka, which 

 is between 2(Xi and 250 feet above the sea, has a drop of 300 or 350 

 feet. The main stream flows with a gentle gradient to the coast 

 about ten miles away. I did not descend its course for more than 

 two miles below Ravuka, where some hot springs well up through 

 the gravel on the left bank (see page 31.) 



This is a region of palagonite-tuffs which like those of the 

 Nganga-turuturu cliffs are mainly derived from vitreous and semi- 

 vitreous aphanitic augite-andesites. They do not effervesce with 

 an acid, and neither foraminiferous tests nor other organic remains 

 occur. The palagonitic material is usually vacuolar, the vacuoles 

 being filled with palagonitic glass or with a zeolite as in the more 

 altered rocks. Where bedding is shown, the beds are generally 

 horizontal. These tuffs are extensively displayed in the sides and 

 beds of the rivers from Liwa-liwa and Ndrawa to Ravuka and as 

 far as I went down the main river, namely to the hot springs. 

 They are associated with agglomerates, formed of the aphanitic 

 augite-andesites, below Ravuka and in the Ndrawa valley. 



(5) The Vicinity of Ndrawa.— The village of Ndrawa, 

 which is not elevated more than 300 feet above the sea, is situated 

 in the heart of the island in a deep valley more or less hemmed in 

 by the mountains. This is one of the wettest localities in Vanua 

 Levu, and probably, as in the case of that of Ndriti in the Seatura 

 basin, the rainfall is not far under 300 inches in the year. In the 

 river-gorge descending westward to Ravuka are displayed horizon- 

 tally bedded palagonite-tuffs and agglomerates above referred to in 

 the description of the Ravuka district, and the same rocks are 

 exposed on the mountain-slopes to the south of the village.^ 



Immediately to the north lies a broken hilly country, about 800 

 feet above the sea, which has to be crossed on the way to Mbatiri 

 and is much cut up by streams descending from the vicinity of Na 

 Raro to join the Ndrawa River below Ravuka. The prevailing 

 rocks are tuff-breccias and agglomerates. The first are made up 

 chiefly of angular fragments, less than an inch in size, of aphanitic 



1 The blocks of the agglomerate in this last locality are from one to three 

 feet across. 



