vni TAVIA RANGES 121 



augite-andesites, some of them being more or less vitreous and in 

 different stages of palagonitisation, whilst the finer material derived 

 from the same rocks contains some carbonate of lime. The 

 agglomerates are composed of the same type of these augite- 

 andesites, with however but little interstitial glass. It should be 

 added that pebbles of a kind of jasper or iron-flint occur in the 

 stream-beds in this locality. (The microscopical characters are 

 described on page 355.) 



By following up the valley that extends to the east from 

 Ndrawa, one enters after about a mile into the region of Na Raro> 

 which is described on page 123. 



THE TAVIA RANGES. 



North of Vatu Kaisia the elevated Nandronadranu district 

 divides into two ranges, one of which stretches eastward to the 

 south of Na Raro as far as the gap of that name, whilst the other 

 extends southward on the east side of the Yanawai valley. Near 

 the angle of bifurcation is situated Mount Tavia, a remarkable 

 pyramidal peak marked 2,210 feet in the Admiralty chart and lying 

 ij miles north-east (N33E) of Vatu Kaisia. It is shown in the 

 view facing page 108. All this region is densely wooded, and I had 

 chiefly to rely on " course-and-distance," and on my aneroid, to 

 determine the surface-configuration. 



(1) RANGE ON THE EAST SIDE OF THE YANAWAI VALLEY. 

 No ascent of these hills was made. They vary from 1,500 to 1,800 

 feet in height, and judging from the loose blocks and gravel in the 

 bed of the Yanawai River below Vatu Kaisia they would seem to 

 be mainly formed of basaltic rocks, acid andesites being also 

 represented. However, I crossed the southern end of the range, 

 where it is 500 to 600 feet in height, to the north of Ndawara, and 

 found basaltic andesites prevailing at the surface. 



(2) RANGE EXTENDING EASTWARD FROM MOUNT TAVIA ON 

 THE SOUTH SIDE OF NA RARO. Mount Tavia, which has the 

 appearance of a dacitic peak, was not ascended ; but the range was 

 crossed in two places in going from Ndrawa to Vatu-vono and 

 from Valeni to Nareilangi, its usual height varying between 1,200 

 and 1,500 feet, the extreme height being about 1,700 feet. 



In making the traverse from Ndrawa to Vatu-vono, one first 

 passes through a part of the hornblende-andesite region of Na 

 Raro, which is described in a later page. Afterwards while ascend- 



