164 On the Granite formation 



chanical separation, but by a soft portion having been washed 

 or fallen out, and the end of the fissures generally end in 

 a rounded-shape. 



In the vicinity of these fissures the granite on the sides 

 may often be seen to be somewhat loose and friable in aggre- 

 gation ; but I have never had an opportunity of observing a 

 graduation between such portions and the kaolin. 



It would seem from Bakewell's remarks, (Geology,) that a 

 similar structure is found in granite hills in Europe, for he 

 remarks : " where hard and soft granite are intermixed in the 

 same mountain, the softer granite is disintegrated and falls 

 away, and the harder blocks remain piled in confusion on 

 each other, like an immense mass of ruins." 



Composition and Varieties. 



The composition of the granite of this district is the 

 same as that which appears to prevail over all South India, 

 being formed of a crystalline aggregation of quartz, felspar, 

 and hornblende. Micaceous granite is found sometimes, 

 but not often. Talcose and schorlaceous granites I have 

 never met with. 



Accurate definitions of the composition of granite are not 

 common in authors, but Phillips (Encyclopedia Metropo- 

 litana, art. Geology 759,) has given the following as the 

 probable composition : — 



20 parts of felspar. 

 5 parts of quartz. 

 2 parts of mica. 



I have had no means of ascertaining the probable pro- 

 portions of the composition of the granite of this district ; 

 but I should be inclined to think, that it contained a great 

 deal more quartz than the above. I have found* that it is easily 

 fusible by the heat of a powerful wind furnace; but on 

 breaking the fused mass, it appears as if the greatest portion 

 was composed of quartz, which had been divided into 

 minute crystalline portions, which were agglutinated by a 



