1840.] Notes, principally Geological, an Southern India. 135 



to them, are frequently found in the vicinity of these dykes. The 

 deep vertical fissures, we often see cleaving from summit to base whole 

 hills of granite, divide also the basaltic veins. At what period these 

 fi'isures and dislocations have occurred — whether from foreign disrup- 

 tive causes, or from that spontaneous separation, to which it is well 

 known granite is subject, is difficult to determine. It seems certain that 

 they are posterior to the irruption of the basalt. 



The rock of Nundidroog rises to the alleged height of 1,700 feet 

 above the surface of the plain, at the southern termination of two 

 ranges of hills. The western range has a N. W. direction, the eastern 

 proceeds nearly due north, until it approaches Purniah Chatram, 

 whence it bends its course to the N. N. E. to Worralconda. From 

 Worralconda it extends northerly toSondoo; thence sweeping to the 

 N. W. it enters the Ceded Districts. A range is observed some miles 

 to the east of Purniah Chatram, which has hitherto a N. E. direction, 

 but here bends towards the west. The valleys, as in the Nundidroog 

 range, appear to cross the line of direction, their course being nearly 

 east and west. A hill called Chinna-raya-conda, a little north of 

 Nundidroog, and the next in the range, was pointed out to me as the 

 site of the sources of the rivers Pennaui and Palaur. The former takes 

 hence a northerly course, and Mis into the Bay of Bengal, near Nellore. 

 The latter pursuing a southerly course to the east of Bangalore, adds 

 its waters to the ocean near Sadras. This fact, if it does not prove 

 this to be the highest part of the table land of Mysore, demonstrates 

 the descent of the land hence to the north and south. 



The hill of Nundidroog is a mass of granite, on the sides of which 

 rest blocks of the same rock, and dislocated masses precipitated from 

 the summit. Among them are occasionally seen globular and angular 

 blocks of trap, indicating the vicinity of a dyke. At the base granitoidal 

 gneiss is seen near the summit, impending cliffs of granite and 

 sienitic granite rise to the apparent perpendicular height of 60 or 70 

 feet above the rest of the rocks, cleft by vertical fissures, and without 

 the slightest appearance of stratification : this rock contains both a 

 brownish and white felspar : a small grained sienitic variety with a 

 light green chloritic hornblende also occurs. But the variety which 

 predominates has crystals both of a translucent (albite) and opaque 

 whitish felspar ; the latter projecting on the surface give the rock a 

 peculiar white mottled appearance. Porphyritic veins imbedding large 

 crystals of foliated felspar, with plates of a dark green mica, intersect 

 this last rock. 



