768 Notes, chiefly Geological, [No. 166. 



The roads through the Salem district, made under the judicious 

 directions of Mr. Orr, are the best in the Madras Presidency. 



Chrome and Magnesite Mines, — From Salem I visited the Chro- 

 mate of Iron and Magnesite mines, of which an account will be found 

 in the Journal of the Royal Asiatic Society, No. XIII, for May 1842. 

 The former are situate about four miles to the NW. of Salem, in a 

 bed of magnesian rock, analogous to serpentine, and associated with 

 talcose mica, and hornblende schists, and gneiss. 



The mineral is found in veins with the magnesite, the mines for 

 which are hard by: but the latter seems to exist in greatest abundance 

 in the hornblende schist, which is highly garnetiferous. 



The mining tract is an assemblage of low broken rocks, spreading 

 over an extensive jungly tract, at the West base of the Shevaroy moun- 

 tains. 



S anker ry-droog. The rock on which stands this old Droog, is 

 about twenty-four miles SW. from Salem. It is composed of a fine 

 porphyritic granite, which has broken up the gneiss on its flanks, and 

 rises boldly from the plain to a height (approximated by a trigono- 

 metrical observation from a paced base) of 930 feet. 



The sides are masses of bare rock, often precipitous, between which 

 not unfrequently pushes forth a vigorous vegetation. 



The porphyritic granite has invaded the hypogene rocks, and burst 

 through them in innumerable dykes on its SW. flank; the gneiss rests 

 like a mantle, with a general dip of 75°. S. 15' W. but the strata are 

 in much disorder and confusion. On the western side, the gneiss is 

 seen interstratified with layers of hornblende, actynolitic schist, 

 and garnet rock, in which is a layer of a fine crystalline limestone, 

 (marble) which from its effervescence with acid, and peculiar appear- 

 ance and weight, I should think is magnesian. Near its contact with the 

 garnet rock, its substance is starred with innumerable minute garnets, 

 both red and green. Garnets of a light brown colour, resembling cin- 

 namon stone, also occur in this limestone stratum ; the limestone is 

 seamed by a dull amber-coloured hornstone, which penetrates the 

 rock in thin seams, and stands out in relief on the surface of the more 

 rapidly weathering limestone, giving it a grooved and corrugated aspect. 



The green garnet is found in the largest crystals, in the white quartz 

 veins which intersect the hornblende schist and gneiss. The green 



