118 



Geology of Bangalore, and of 



[Jan. 



act5'nolite, quartz aiKl other minerals, forming either a conglomerate or 

 breccia, is found connected with semi-opal, ferruginous opal, or jasper 

 opal. The soil where it is found is bia;k, well contrasted with some 

 high ground near it, which is red, and most likely ferruginous and not 

 calcareous. Much magnetic iron ore on the. surface in some places, and 

 sometimes attached to the semi-opal. In a most interesting spot, point- 

 ed out to me by Mr. Gilchrist, a low, ragged, and peculiar looking rock, 

 juts out only a foot or so from the ground; it is of a brown shining- 

 aspect externaUy, and I think deserves the name of jasper opal or fer- 

 ruginous opal, and passes into semi-opal, chalcedony and a coarse kind of 

 jasper. Near this there is found a chloritic talc slate, which graduates 

 into a sort of potstone. The jungly hills to the westward are of granite 

 towards the top, with trap at the bottom; magnesite is found in the 

 neighbourhood. 



The road towards Periapatam is for some miles jungly, and then is very 

 flat — much kunkar in small nodules on the surface, trap dykes passing 

 across the road, chiefly of hornblende with crystals of olivine. In several 

 phices, found jasper opal, as at Hoonsoor. In a ditch near Periapatam de- 

 composing gneiss, with vertical veins of a tufaceous limestone, and above 

 the gneiss, large masses of nodular basalt, decomposing into a yellow earth 

 v.dth black soil on the surface. In the ditch or nullah, were large masses of 

 basaltic hornblende, ringing on being struck, with a peculiar squeezed ap- 

 pearance, like half WTought images. I have observed this frequently in the 

 basaltic hornblende— is it the result of igneous action under great pres- 

 sure ? A very flat country around Periapatam, with much water and 

 much kunkar in the soil. The country, all the wa)'- to Fraserpett or 

 Cushelnugger, is jungly and hilly, with small villages and patches of 

 cultivation here and there. Soil generally black—all the hills appear 

 to be of trap — in one place where a section was afforded, the soil on the 

 surface was black, but reddish below. Near a village about half way, 

 found specimens of a very coarse jasper opal, approaching upon and 

 running into quartz ; and a white calcareous like substance, with horn- 

 blende slate, decomposing in horizontal strata. 



The Coorg mountains are part of the Western Ghauts, and consist of horn 

 blende rock andsienitic granite.The geological formation resembles much 

 that on the Neilgherries— only the hills are smaller, more generally round- 

 ed, and show a more perfect state of decomposition into lithomargic earth. 

 Quartz veins and iron ores are not abundant, indeed of the last I saw 

 none ; and nothing answering to Benza's hasraatitic iron ore; but it is 



