xi THE KOROTTNI RANGE 155 



pyroxene, fine gravel, occasional tests of foraminifera ; and it often 

 contains a fair amount of carbonate of lime, in one specimen 

 tested as much as 13 per cent. The amount of lime, however, 

 varies, being in some places scanty. 



The term " conglomerate " could not be applied to the coarser 

 deposits, since the sub-angular and angular fragments always 

 predominate. They could scarcely be deemed " breccias " on 

 account of the mixture with pebbles and gravel. Their character 

 is therefore intermediate between the two. I have used the ex- 

 pression " agglomerate-tuff" because it best describes their ap- 

 pearance. A specimen of such a rock presents a curious mixture, 

 in the well-compacted mass, of angular and sub-rounded fragments 

 of palagonite up to an inch in size, small pebbles and fine gravel 

 of the same material, and detached valves of " Cardium," entire 

 and broken. One is forced to draw the inference that these 

 materials accumulated in shallow water. They are such as might 

 have been produced by the marine erosion of an emerging volcanic 

 island endeavouring to hold its own above the waves. But from 

 the occasional occurrence of blocks of a scoriaceous basaltic rock 

 it would appear that during the formation of the deposits there 

 were periods of eruption. 



At times massive and comparatively fresh-looking basaltic 

 rocks are exposed in situ on the mountain sides in the midst of 

 these submarine deposits. A specimen obtained at 1,800 feet is a 

 semi-ophitic porphyritic olivine-basalt with a specific gravity of 

 2 - 86 and showing a little interstitial glass. The mode of exposure 

 did not admit of my ascertaining the exact relation of these rocks 

 to the deposits. They are no doubt dyke- like masses representing 

 the original fissures of eruption of a submarine vent ; and during 

 the emergence they were covered up with tuffs and deposits, the 

 work of the marine erosion of the emerging land. These, however, 

 are points on which light will be thrown when we come to examine 

 other localities. 



Descending the northern slopes of the range from the summit 

 to Sealevu the general course was N.N.E. Several valleys were 

 crossed, of which that occupied by the Na Sinu river was 600 feet 

 in depth, the rivers and streams all flowing to the north-west into 

 the Ndreketi basin. Basic tuffs and agglomerates were exposed 

 at the surface all the way down to Sealevu, 400 feet above the sea. 



At the head of the Sealevu valley, about a mile or rather more 

 above the village, and a little east of the track followed in the 

 descent above described, the mountain-range terminates abruptly 



