THE GNEISSIC SERIES. 17 



PART II. 



CHAPTER III.— THE GNEISSIC SEEIES. 



Generally over Southern India, the gneiss is rather a crystalline 



The Nellore gneisses aggregate of minerals than a foliated or schistose 

 aregenerallyfoliated. ^ . &nd gQ manifegt ig tMg abgence of foliatio ^ 



that the rock is still more usually spoken of as granite. However, there 



is perhaps in this part of the Carnatic a greater display of the more 



schistose varieties of the rock, or even the more evident laminated results 



of sedimentation, than in many other parts of the Madras Presidency. 



While many classifications or groupings of the different gneisses are 



The massive and schis- possible, looking at their differences of constitution, 



ose gneisses. structure, and modes of occurrence, there is one 



very broad distinction apparent in Southern India in the massive and 



the schistose gneisses, the latter being necessarily foliated, while the 



former are only partially so ; a very important and extensive section being 



scarcely distinguishable as a foliated rock at all, it being only admissible 



into the great family of gneisses on account of its banded or apparently 



bedded character displayed over very large areas, in contradistinction 1 



to the intrusive or exotic condition attached to the recognition of granites. 



1 In the present immature condition of the survey of the crystallines in South India, 

 a geographical classification of the gneisses is not without its advantages if only as a means 

 of separating and recognising the many gneisses already included under such general 

 groups as granitic, syenitoid, or hornblendic, and in this view I have long held that the 

 massive granitoid red gneiss might be distinguished as the Bellary or Mysore, or better as 

 the Bala Ghat gneiss, since it is remarkably prevalent in the upland of Southern India, its 

 eastern confines from the Palar to the Kistna being almost continuous with the edge of the 

 ghats. It is typically developed, as far as my own knowledge goes, in the western parts of 

 North Areot, in the Cuddapah sub-division, in the eastern part of the Bellary district, in 

 the Kurnool district, and thence all over the eastern portion of the Hyderabad Territory 

 up to the higher reaches of the Godavari river. In the same way, such a term as the 

 Carnatic gneiss might be a convenient synonym for the schistose gneisses of South India, 

 and a further term of Nilgiri or mountain gneiss for a very typical intermediate and less 

 foliated rock composing the higher ranges of the Peninsula and Ceylon. There are, of 

 course, grave objections to such a classification, but it is put forward as a convenient one, 

 and in any case the fact still remains that there are such marked guciss groups, and that 

 they are geographically separable. 



b ( 125 ) 



