GRANITOID AREAS. 37 



Thalur. Further west, on the higher ground between Pothakamur 



and Mullamur, where huge surfaces of rock are exposed, the bedding 



becomes apparent, and a few rather less granitoid beds are interstratified 



with the ultra-crystalline beds. No section was met with showing this 



trappoid rock in actual contact with other varieties of granitoid gneiss, 



or with the schistose rock ; but nothing was seen suggestive of want of 



conformability with the closely adjoining beds. The true character of 



the " trappoidth " rock is best seen in the Bogala 

 The Bogala Konda. L t . & . 



Konda, or "■ Charcoal hill/' so called from its 



intensely black colour. This intense blackness, added to its nearly conical 

 shape, and its supposed association with the slight earthquakes so fre- 

 quent in the region around Ongole, has given rise to the idea that it is a 

 volcanic cone. The hill itself presents, however, no signs of volcanic 

 action. The summit is divided by an irregular saddle into three unequal 

 divisions, the western being between 100 and 200 feet the higher. The 

 summit consists of a huge chaotic accumulation of blocks roughly 

 rounded at the edges by weathering, from among which spring a few 

 stunted trees of the fig tribe. The bedding of the great band of 

 hornblendic rock out of which the Bogala Konda rises can be very 

 distinctly seen from the top, and traced by the eye for several miles 

 southward. Petrologically these beds are identical in appearance with 

 the'Pothakamur beds, and they are very probably an extension of the 

 same, though the actual connection was not traced. 



On the eastern side of the Bogala Konda are considerable " screes," 

 to use a term familiar in the English lake district ; the fallen blocks 

 appear to form as it were streams down the sides of the hill. Many of 

 the blocks are so loosely perched that a very small impulse, such as the 

 slightest shock of an earthquake, would suffice to overthrow them; 

 and to the frequency of earthquakes in this region may safely be 

 ascribed the extreme confusion of the blocks on the summit, between the 

 present position of the vast majority of which and the direction of the 

 great joint planes to which they primarily owed their existence, no con- 

 nection can now be traced. This cause has probably also affected the 



( 37 ) 



