Chap. IV. 2.] metamorphic rocks. 95 



yards east of the Bangalore road, wliere the south edg-e of the southern 



area of magnesian rocks is crossed by a large nullah.''^ 



Of rocks not commonly occurring throughout the metamorphic 



region and evidently connected with the ultra- 

 Associated rocks. 



metamorphic agencies observable in this region, 



we have to notice two kinds — 



Istly. — The earthy-reddish or reddish-brown mass, bearing some re- 

 semblance to an impure serpentine traversed by the magnesite veins 

 already alluded to, which occurs very largely towards the eastern end of 

 the south or Mancoopum area, and which predominates all over the northern 

 or Carupoor area. Whether the earthy character of this rock belongs to it 

 throughout, or is only the result of superficial weathering, there was no 

 means of ascertaining in the absence of fresh and deep sections. The 

 section afforded by the railway cutting shows a rather compact and 

 apparently unaltered pale drab quartzo-felspathic rock traversed by 

 small veins of magnesite ' hading' at various and sometimes rather low 

 angles. This spot, however, is so near the extreme western end of the 

 system of magesite veins, that this rock, which is not found elsewhere, 

 and does not aj)pear there as weathering to an earthy texture, cannot 

 be regarded as any thing but a local variety of the gneissic series, which 

 in this part of the country shows chiefly its hornblendic varieties. 



2ndly. — We find at the southern and eastern extremities of the 

 great Carupoor area a peculiar black porphyritic rock, highly decomposed, 

 OAving its porphyritic character to the presence of numerous not very 

 perfect crystals of a black mineral. This occurs in some quantity 

 between the north-east flank of the Nagra INIullay and the foot of the 

 Shevaroys, but more especially in the stream valley to the south of the site 



* Subsequently to my visits to the Chalk Hills, I was informed that compact talc or 

 pot-stone is largely dug in pits at Carupoor village, to be manufactured into bowls and other 

 vessels. I did not happen to come across these pits, though I passed through and complete- 

 ly round the village.— R. B, F. 



(317) 



