152 A NATURALIST IN THE PACIFIC ch. x 



sides, up to elevations of 2,000 feet and over, the valleys them- 

 selves were at one time no doubt also covered with these submarine 

 deposits, which, however, have been in great part stripped off by 

 the denuding agencies. They are still to be found, containing 

 large tests of foraminifera, between Mbale-mbale and Waisali ; 

 but the basaltic andesites, originally underlying them, are more 

 frequently exposed. One of these rocks found a little east of 

 Waisali, which has an aphanitic appearance and a specific gravity 

 of 2"82, is merely a basic glass in its early stage of crystallisation, 

 being made up of very minute crystallites -g-^nn7 of 3-" i^^ch in 

 length. On the surface in this locality there also occur basic 

 agglomerates containing scoriaceous rocks, the products of some 

 of the last stages of volcanic action in this part of the island. . . . 

 In the case of the broad part of the Vatu-kawa valley above 

 Na Salia blocks of basic rocks derived from the mountains around 

 strew the bottom in great abundance. Lower down, where the 

 valley is confined between the hills, basic agglomerates and coarse 

 tuffs are displayed in the hill-sides. 



Mention should be made here of the various hot springs 

 existing in these valleys in the low levels near the rivers and 

 stream-courses. In the Vatu-kawa valley they exist at Nukum 

 bolo, and in the Mbale-mbale valley at Natoarau, Waitunutunu 

 and other localities. These springs are described in Chapter III. 



