x THE WAISALI SADDLE 147 



In taking the path from Waisali to Narengali one soon enters 

 the hilly country where large masses of basic tuffs and basic 

 agglomerates, the last formed of blocks of a compact basaltic 

 andesite, occur on the surface up to 700 or 750 feet above the sea. 

 The rock just named has a specific gravity of 2*84, and sinee-it 

 displays rhombic pyroxene amongst its phenocrysts, it is placed in 

 genus I of the hypersthene-augite andesites. Above this elevation, 

 and as far as the top of the range, 1,800 1,900 feet above the sea, 

 porphyritic basaltic andesites, having a specific gravity of 2*8, 

 prevail at the surface. They display small porphyritic crystals of 

 plagioclase, augite, and rhombic pyroxene in a groundmass com- 

 posed of small felspar-lathes, prismatic pyroxene, and much 

 smoky glass, and are referred to genus 5 of the same pyroxene 

 andesites. It is probable, judging from one of these exposures, 

 that such rocks are dyke-like masses : but on account of the thick 

 soil-cap it is not possible to obtain a good view of them. 



In the stream-courses occur large blocks of altered basaltic 

 andesites of the propylitic type, having a specific gravity of 2-64 to 

 270, and exhibiting abundant alteration products, such as calcite, 

 viridite, &c. These propylites, I presume, constitute the deeper 

 portion of the range. It will often be necessary to distinguish 

 between the altered basaltic andesites, such as are above referred 

 to, and the relatively fresh rocks of the same type. The former 

 are light coloured (sp. gr. 2*6 to 275), and are only exposed in 

 gorges and stream-courses that deeply score the mountain-slopes. 

 The latter are blackish (sp. gr. about 2*8), and at times penetrate 

 the covering of tuffs and agglomerates. 



Descending the opposite or north-west side of the saddle-range, 

 one finds the same basic andesites, both fresh and altered, down to 

 about 1,100 feet above the sea. Then the track leads one down a 

 precipitous slope into the picturesque gorge traversed by the head- 

 waters of the Narengali River. At its lower end the gorge opens 

 out into the broad Narengali valley, and here the dense forest of 

 the higher districts gives place to the scanty vegetation of the 

 " talasinga " region. 



The rocks exposed in the sides of the gorge are basic agglome- 

 rates overlying palagonitic tuffs of mixed composition and evidently 

 sedimentary. On the bottom lie huge masses, some of them 70 or 

 80 tons in weight, of altered grey aphanitic or non-porphyritic 

 augite-andesites, penetrated in some cases by thin veins of white 

 quartz, and at times displaying a rudely columnar structure, the 

 columns being 12 to 14 inches across. Sometimes the alteration is 



L 2 



