IV NAIVAKA 45 



there is exposed a hard red palagonitic tuff dipping away from 

 the summit at an angle of 40°. It is mainly composed of the 

 palagonitised debris of a vacuolar basic glass and incloses broken 

 and entire crystals of plagioclase, augite, and olivine. 



The augite crystals, which attain a length of five or six mm., 

 project from the weathered surface and are easily detached, lying 

 about in quantities on the ground in places. Although they are 

 now imbedded in evidently a submarine tuff, these pyroxene 

 crystals could only have been ejected as such from a subaerial 

 vent ; and it would therefore appear that they fell into the sea 

 around the shores of a volcanic island in a state of activity. These 

 crystals are often cracked and are as a rule not so perfect as 

 those I have gathered from the slopes of Vesuvius, Stromboli, and 

 Etna. They exhibit an unusual tabular form arising from the 

 great development of the clinopinakoid at the expense of the 

 orthopinakoid faces. 



On the whole it may be inferred that the Naivaka volcano was 

 submerged at the time of its origin, but that the eruptions continued 

 after it began to show itself above the sea. In many of its features, 

 especially in the character of the agglomerate that forms its upper 

 portion, and in the palagonitic nature of the tuffs, Naivaka differs 

 only from other elevated districts of the island, where organic 

 remains occur, in the absence of such remains. Its form bears 

 testimony to the extreme degradation we find in other districts, and 

 the occurrence of foraminiferous tuffs high up the neighbouring 

 slopes of Mount Sesaleka affords additional evidence of the original 

 submergence of this district. 



The Hill of Korolevu.^ — About three miles east of Mount 

 Naivaka there rises to a height of 800 feet, about a mile inland 

 from the shores of Wailea Bay, the singular flat-topped hill of 

 Korolevu. It displays vertical cliff-faces, with a drop often of 200 

 or 300 feet, which have become so deeply furrowed or fluted by the 

 eroding atmospheric agencies that they appear at a distance to be 

 made of columnar basalt. The hill is, however, formed in mass of 

 a compacted tuff or agglomerate tuff built up of materials of a 

 hyalomelan basic glass that has undergone partial conversion 

 into palagonite. In the upper thirds these rocks show no bedding, 

 but in the lower slopes on the seaward side they are bedded and 

 dip to the north away from the summit at an angle of 15" or 20°. 



1 This hill is figured in Wilkes' narrative under the name of Dillon's Rock 

 (vol. 3, p. 235). This, however, is not the Dillon's Rock of his chart, where 

 the name is given to a rock on the west side of the entrance to Wailea Bay. 



