202 A NATURALIST IN THE PACIFIC chap. 



to much of this rugged promontory. I crossed the mountains 

 from Loa to Waikawa. The summit was about a mile broad and 

 undulating, the level varying between 900 and 1,150 feet. At one 

 place on the top there was a deep hollow, some 300 or 400 yards 

 across, perhaps the remains of an old crater-cavity ; but the higher 

 slopes were so densely wooded that it was not possible to get a 

 clear view of my surroundings. Basic tuffs and agglomerates 

 prevailed on either side from the foot to the top of the range. 

 Specimens obtained from between 800 and 900 feet above the sea 

 are characteristic palagonitic tuffs of varying degrees of coarseness 

 containing 5 to 10 per cent, of carbonate of lime and a few tests 

 of foraminifera. At 1,100 feet I obtained a specimen which on 

 account of the large proportion of carbonate of lime (35 per cent.) 

 and the abundance of foraminiferal tests may be termed an impure 

 foraminiferal limestone belonging to the group of these rocks 

 described on page 319. The tests range up to a millimetre in 

 size, and there are also inclosed a few large fragments, 1 to 2 

 centimetres in size, of shells and crystalline limestone. The 

 residue is made of the detritus of semi-vitreous basic rocks, pala- 

 gonitic debris, fine clayey material and minerals (15 per cent), the 

 last including beside plagioclase abundant more or less perfect 

 pyroxene prisms, mostly of the rhombic type. 



Near the summit there occurred in one place blocks of a highly 

 basic blackish olivine-basalt (sp. gr. 2*99), marking evidently the 

 situation of a dyke. This rock is referred to genus 13 of the 

 olivine-class. It displays abundant phenocrysts of olivine and 

 augite with but little plagioclase. Interstitial glass is scanty, the 

 groundmass consisting of stoutish felspar-lathes ('06 mm. long), 

 abundant augite granules and prisms, and magnetite. 



The Waikawa mountains would thus seem to possess the same 

 general structure that characterises many of the ranges of the 

 island. Submarine basic tuffs and agglomerates cover their sides 

 and their summits, the deeper rocks forming the axis of the range 

 being in this case not so frequently exposed. 



On the coast between Waikawa and Navuni, rather over a 

 mile east of Fawn Harbour, basic agglomerates, palagonitic tuff- 

 sandstones, and calcareous clay-rocks containing pteropod and 

 foraminiferous tests, prevail. The tuff-sandstones and clay-rocks 

 are bedded, the stratification being often well shown in the 

 horizontal sections displayed in the shore-fiat. In one locality 

 within an area a few hundred yards across, a quaquaversal dip 

 was exhibited. At Navuni, where the hills reach the coast, the 



