68 FOOTE: GEOLOGY OF THE BELLARY DISTRICT 



susceptible of very high polish, and thus of furnishing stone of ex- 

 ceeding beauty for decorative purposes. The granite is in parts 

 hornblendic. 



The Adoni group measures 8 miles in length by 4 in breadth 

 at its widest just north of the town. The longer axis runs about 

 west by north : here and there, at rare intervals, the granite shows 

 a bedded structure, as to the eastward of the eastern trigonometrical 

 station just referred to, and again at the northern extremity of the great 

 northern spur descending from the summits of the Drug hill. Here 

 the quasi-bedding is strongly developed, and shows a dip of from 50 

 to 6o° E. by 5 S., the strike being in both cases N. 5 E. 



The great south scarp shows a rather striking system of jointing 

 on its face, which has to some extent affected the weather action on 

 the exposed surface, and shows up very conspicuously in a kind of 

 net-work pattern. The place is utterly inaccessible, however, and 

 the joint system cannot be determined. 



The bare face of the rock is much grooved by the direct erosive 

 Rain grooving of act ion of rain. I had been inclined to attribute 

 rocks - much of this grooving, which is a very common 



feature on bare granite rock surfaces, to inequality in the resisting 

 power of the rock connected with the quasi-banded texture so often pre- 

 vailing even in typical granites, but afterwards came to the conclusion 

 that it resulted largely from direct mechanical erosion, by rain, from 

 watching the effects of a very violent thunder shower which fell just 

 within the limit of the summit plateau. The sun was well over to the 

 westward, and lit up the storm and the face of the rock in a wonderful 

 way. The summit plateau at the point I was watching is practically a 

 bare sheet of rock ; but for a few minutes all the water which rushed 

 over the scarp in large quantity was quite turbid, but then became 

 quite limpid, and continued so to the end of the storm. The whole 

 face of the scarp was for the time swept by a violent current, which 

 only wanted volume to become immensely destructive. The utter 

 bareness of the rocks could be wondered at no longer. 



In the centre of the group the blocky form of surface does not 

 ( 68 ) 



