1 80 On the Granite formation 



black specks of hornblende increase, the rock takes a 

 speckled appearance, the quantity of the black nearly equa- 

 lizing the quantity of the other true ingredients, it is then 

 a syenite;* and when the hornblende is in still greater 

 quantity, so as to give a black or very dark grey appearance, 

 it becomes hornblende rock, the common black granite of 

 India, of which all the Hindoo idols are made. 



The difficulty of a definition of granite is very great, and 

 while writers on geology have failed, it is not to be expected 

 that I should be able to supply the deficiency ; and the 

 best way both to save time and further attempts of explana- 

 tion, is to refer to published descriptions. The granite of 

 Cornwall, as described by Dr. Boase, appears to be more 

 felspathic than that of this district, containing much earthy 

 felspar or eurite, and it resembles therefore in some measure 

 the Pallicondah granite. I have been unable to identify 

 any granite in Dr. McCulloch's works ; but by his definition 

 of syenite, (Western Isles, vol. i. page 371,) and the points 

 in which it resembles granite, it would seem that no such 

 granite, forming hills or extensive formations, occurs in 

 this district; but that such a rock as he seems to allude 

 to occurs frequently in beds and insulated masses among 

 the schistous series, and is a loosely aggregated collection of 

 grains of different minerals, without any of that mutual 

 penetration or interference which appears to give the cha- 

 racteristic solidity to granite. 



I shall therefore, with Dr. Christie and most other writers 

 on India, consider the rock as a true granite, and reserve the 

 term gneiss as applicable to any lamillar or schistous va- 

 riety,-^ or to what McCulloch would term granitic gneiss ; 



* The aggregation or structure becoming at the same time no longer 

 confused, but distinct and separate. 



t As Bakewell has done, (Geology, p. 93,) where he distinctly defines 

 gneiss as a "schistose granite," independent of the arrangement of its 

 component parts. 



