322 Notes illustrative of the Geology of Southern India. [April 



tion of the peculiarity, it might be conceived that the upraising force 

 had in the one case acted on a line to produce the range, while to 

 produce these insulated and conical hills it had been concentrated in 

 a focus or point. 



At Palleconda, a small town about 14 miles south-west of Vellore, 

 1 crossed a tract of country which has been described by Dr. Benza, 

 an observer who has added considerably to our knowledge of the 

 geology of Southern India. The plain on which the town stands is 

 sandy, and strewed over it there are many weathered masses of 

 sienite, which natural sections, afforded by the deep nullah beds, prove 

 to be the underlying rock of the whole. Traversing this there are as 

 usual dykes of trap and porphyry. The latter is of a peculiar kindy 

 the porphyriiic crystals being of felspar imbedded in a matrix of quartz. 

 Investing a portion of this quartz-porphyry, were found crystals of 

 an ore which I am inclined to believe was specular iron ore. Its 

 characteristics were highly metallic, inclining to adamantine; colour 

 dark grey, nearly black; hardness between 7 and 8; fracture splin» 

 tery ; structure laminated ; specific gravity not numerically determin- 

 ed, but high ; crystalline form a flat rhomboid. In the adjoining hills 

 felspar of the sienite was occasionally of a pink colour, and dendritic 

 on the surface. Transported masses of greenstone, basalt, mica, and 

 clay slate were found in the vicinity of the streams, though none of 

 these rocks were observed in situ. 



The country between Palleconda and Vellore, while it exhibits no 

 variety in geological structure, is interesting from the singularly wild 

 and beautiful character of its mountain scenery. On the summits of 

 the hills the tor-like masses of the sienite are grouped in the most 

 varied forms, sometimes shooting up like spires, at other times strewed 

 around hke the ruins of some extensive edifice, or again standing square 

 and solid, like the massive walls and donjon keep of some robber chief- 

 tain's tower. The valleys are covered with similar blocks piled on 

 each other in the wildest confusion, the whole seeming to tell of mighty 

 convulsions, rather than of the slow and scarcely perceptible operations 

 of the agents of disintegration and deca)'. 



A monotonous and uninteresting plain, with but little to attract the 

 attention of the geologist, extends from Vellore to Madras. The same 

 sienite which forms the distant hills underlies the whole of this plain, 

 outcropping at several points. It w^as met with immediately under 

 the sand during the progress of an artesian well sunk in the imme- 

 diate vicinity of Madras, which after passing some little distance 

 through the rock was abandoned j and indeed it is singular that, consi- 



