10 



Geology of the Country, 



[July 



This consists in making several square perforations, little more than 

 an inch deep, with a hammer and a steel punch, in the rock, in a line, 

 and in the direction they wish to have it split. This done, they put 

 wedges in the holes, and strike on them with force, until the granite 

 breaks (a). In fact, many of the granitic blocks about Bangalore bear 

 the marks of this last process. 



When this gneiss exfoliates naturally (like the blocks of granite), the 

 decomposing causes act deep into its substance, detaching three or 

 more laminae at the same time. When I say that this gneiss exfoliates 

 both naturally and artificially in laminae, at an angle with the seams, I 

 do not mean to exclude the possibility, nay the probability, of its often 

 splitting in the direction of the seams. If my memory does not fail 

 .me, I think I saw this appearance in the two huge masses close to the 

 nullah, which descends from the front of the barracks south. In the 

 lower part of this nullah, going towards the bridge, the decomposition 

 of the gneiss is clearly seen, perhaps more so than in any other locality 

 about Bangalore. 



On the western end of the Esplanade there are many blocks of gra- 

 nite, intersected as usual by numerous quartz veins, in the most fantas- 

 tical way imaginable ; diagram No. 3 represents two of them. 



Going west along the road parallel with, and close to the Barracks, a 

 few hundred yards beyond them, there are some clay pits for bricks 

 and tiles ; a fine tank, and a Mussulman burying ground are close to 

 them ; the steps of the tank being constructed of gneiss, the stratifica- 

 tion of which is quite evident. 



At this place, turning to the left, we get into the road which leads to 

 the Pettah ; for a little way all the rocks, right and left of the road* 

 are granitic, split by numerous fissures both horizontally and vertically, 

 so dividing the block into cubic masses (No. 34). 



Proceeding a little farther on, in the field to the right, close to the 

 road, masses of hornblende rock are seen protruding above the soil, 

 in an uninterrupted continuation, with an east and west direction 

 (No 35). 



In this same field, flanking this bed of green-stone, are knolls and 

 clusters of granite, through which, it would seem, the green-stone in- 

 truded. The thickness of the last mentioned rock, as far as its out- 

 goings indicate, is seventy-two ordinary paces, the blocks extending, 

 with hardly any interruption, for more than three hundred paces. Like 

 many other primitive hornblende rocks, this affects the magnetic 

 needle. 



This dyke intersects the road extending a little way in the field to 

 the left j it contains very little felspar, which in some of the masses 



(a) See Buchanan's Journey, vol. I, page 133, 



