X VA-LILI 145 



In a cliff-face of the adjacent main range there are displayed 

 an agglomerate of basaltic andesite and a pitchstone-breccia, com- 

 posed of fragments of but little altered basic glass, the interstices 

 being filled up with palagonite. In the case of the Kiombo flow 

 I have endeavoured to explain the origin of a closely similar pitch- 

 stone-breccia (page 92). 



(5) The Sea-border and the Low-lying Districts at 

 THE Base of the Va-lili Range. — It may be generally re- 

 marked that palagonite-tuffs and clays, often foraminiferous, prevail 

 in these localities. Thus in the sea-border between Waiwai and 

 the mouth of the Ndreke-ni-wai basic agglomerates are displayed 

 where the mountains approach the coast ; but further west a broad 

 tract of undulating land, elevated usually 100 to 300 feet, inter- 

 venes between the range and the sea-border, and here coarse and fine 

 palagonite-tuffs predominate On the north-west the forami- 

 niferous tuffs and clays of the Ndreketi plains approach the Va-lili 

 range in the vicinity of Vuinasanga, and extend for at least 200 or 



300 feet up its sides At the east end of the range, where the 



slopes descend to the plains of the Waisali valley, a little west of 

 Mbale-mbale, there are exposed bedded palagonite-tuffs, tilted up 

 at an angle of about 20° to the south-west. They contain a little 

 [ime and display microscopic tests of foraminifera, the palagonite 

 Deing minutely vacuolar, the cavities also being filled with the 

 iltered glass. I noticed those submarine deposits at an elevation 

 Df 100 feet, but probably they reach much higher. 



The inference to be drawn from the data above given concerning 

 he Va-lili range seems clearly to be this. We have here indicated 

 ■ he emergence of a submarine mountain-ridge covered over with 

 ;)alagonite-tuffsand agglomerates, the last being uppermost. These 

 coverings have been in places stripped off by the denuding agencies 

 ;.nd the underlying massive basic rocks exposed. These rocks, 

 liowever, vary much in texture, some being vitreous, as in the case 

 (f the pitchstones, others hemi-crystalline as in the case of the 

 1 'asaltic andesites ; and it is to be gathered from this and other 

 similar indications that different submarine vents were formed 

 c long a fissure or fissures at the sea-bottom. No evidence of sub- 

 i erial eruptions came under my notice. After the vents became 

 e xtinct they were buried beneath the palagonite-tuffs and agglo- 

 r lerates. During and after the emergence the denuding agencies 

 r ishaped the surface of the range and left but little of its original 

 f )rm. 



Since it is my object to build up a theory of the origin of the 



L 



