XV NAWI TO UTHULANGA 211 



its crest for another 1 50 feet or rather more, and has a precipitous 

 face on the southern side descending far down the mountain-slope. 

 This peak, which is about 1,550 feet above the sea, when seen from 

 the opposite shores of Natewa Bay is very conspicuous and looks 

 like a thumb or a nose. The first part of the Fijian name of this 

 peak signifies a nose. 



The hamlet of Nawi, from whence the ridge begins, is built on 

 a low mound-like "rise," which is composed of a dark-grey 

 hypersthene-gabbro. Since plutonic rocks are of very rare oc- 

 currence in this island, the Nawi gabbro has a particular interest. 

 It belongs to the group of plutonic rocks described on page 250 ; 

 and is to be referred to the more basic kinds, its specific 

 gravity being 2'84. In appearance it is like a diallage-gabbro, and 

 in the slide displays monoclinic and rhombic pyroxene filling the 

 interspaces between the large plagioclase crystals and undergoing 

 respectively the diallage and bronzite stages of schillerisation. This 

 rock forms the type of the group and need not be referred to in 

 more detail here. It should be added that in the bed of the 

 neighbouring river occur blocks of a basaltic andesite (sp. gr. 2'86) 

 referred to genus i of the hypersthene-augite andesites. It is a 

 less crystalline form of the gabbro just mentioned. 



The prevailing rock exposed for the first 2 miles on the crest of 

 the ridge (by starting from Nawi) was a greenish porphyrite 

 displaying large opaque crystals of oligoclase, but showing much 

 alteration of the propylitic kind, its specific gravity being 2'5, but 

 the structure of the groundmass is much disguised. During the 

 next mile, basic agglomerates and a massive hypersthene-augite 

 andesite were exposed. The last-named is semi-vitreous, and on 

 account of the prismatic pyroxene of the groundmass is placed in 

 genus 5 of its sub-class. Its specific gravity is 27. In the last 

 and fourth mile of the ridge was exposed a dark grey doleritic 

 basalt (sp. gr. 2'85), which rings like clinkstone under the hammer, 

 and weathers in a honeycombed fashion. The felspar-lathes 

 average -3 mm. in length, the residual glass being scanty. The 

 pyroxene phenocrysts include some of rhombic pyroxene ; and the 

 rock is therefore referred to genus 4 of the hypersthene-augite 

 andesites. The actual peak of Uthulanga, as it rises abruptly 

 about 150 feet from the end of the ridge, is of agglomerate, the 

 blocks being composed of a compact grey andesite. 



The peculiar succession of rocks displayed in this mountain- 

 ridge along its length of four miles is worthy of notice. Neither 

 vesicular nor scoriaceous rocks came under observation ; and it is 



P 2 



