78 A NATURALIST IN THE PACIFIC CHAP. 



which denudation has stripped off nearly everything that could 

 guide us in speculating as to its past. Although the hills of Koro- 

 i-rea and Koro-tolutolu doubtless represent old volcanic necks, the 

 relation of Ulu-i-matua to the very differently composed northern 

 part of the same range, as described on page 73, is extremely 

 puzzling. Then again in the opposite sides of Solevu Bay we see 

 exposed the remains of lava-flows that bear no relation to the 

 present configuration of the surface. We may suspect, however, 

 that most of the volcanic energy was displayed under the sea. 



NANDI BAY. Lying north of Solevu Bay, this bay is situated 

 between spurs, descending to the coast from the mountainous 

 interior. The valley extends a long distance inland without 

 much change of level, the elevation i J miles from the coast being 

 not over 100 feet above the sea. At its head is the Nandi Gorge, 

 which leads into the Ndriti Basin, the great crateral cavity of 

 Seatura. There are some remarkable lofty, isolated hills in this 

 valley that would be well worth examining. 



That the bay represents the site of an old volcanic centre is indi- 

 cated by the occurrence on the shore of two basaltic dykes, one on 

 either side of the village of Na Savu and 300 to 400 yards apart. The 

 eastern dyke is perhaps 30 feet thick, whilst that to the west is 

 scarcely half this thickness. They exhibit an imperfect columnar 

 structure, the columns, which are 6 to 12 inches across, being inclined 

 at an angle of 1 5 or 20 from the vertical in such a way that it may be 

 inferred that the molten material was ejected from some subter- 

 ranean focus lying to the northward (or inland) at an angle of 1 5 

 or 20 above the horizon. The basalt is a compact bluish-black 

 rock with specific gravity 2'95~2'99. It contains abundant olivine 

 but no other phenocrysts and very scanty interstitial glass, whilst 

 the felspar-lathes average 'I mm. in length. It is referred to genus 

 1 6 of the olivine basalts, and is remarkable for the flow arrange- 

 ment not only of the felspar-lathes but also of the smaller olivine 

 crystals. 



Blackish basaltic rocks of the prevailing type are exposed on 

 the surface of the broad spur, not over 500 feet in height, that 

 divides the Nandi and Nasawana valleys and descends to the coast 

 between the two bays thus named. They belong to genus 37 of 

 the olivine-basalts and display a few small plagioclase phenocrysts. 

 The felspar-lathes average '2 mm in length, and there is a little 

 interstitial glass. Entering Nasawana Bay we find ourselves on 

 the southern slopes of Seatura, of which the high Na Suva range 

 that backs the bay is the southern extension. 



