122 HOLLAND: CHARNOCKITE SERIES. 



PART I. 



PETROGRAPHY OF THE SERIES. 



CHAPTER I. 



Previous descriptions of the Series. 



Before the establishment of an organised Geological Survey of 

 India various disconnected descriptions of the rocks now included 

 in this group were published by several independent observers in the 

 South of India, such as those by Dr. P. M. Benza, 1 Captain J. 

 Allardyce 2 and Captain J. Ouchterlony. 8 



Benza referred to St. Thomas' Mount and the hills at Pallavaram 

 as composed of (t hornblende rock overlying the fundamental rock." 

 Captain Allardyce evidently recognised the similarity between what 

 he called the " primitive trap allied to sienitic granite " of Palla- 

 varam and the rocks forming the principal mass of the Nilgiris 

 (Neilgherrys) and Shevaroys, as well as those forming the Western 

 Ghats and Ceylon, He speaks of the great abundance of this rock, 

 and asserts that it " cuts off and terminates all other granites '\ 

 Benza referred to the rocks of the Nilgiris in somewhat similar terms. 

 " The lowest visible rock of the Nilgiris is," he says, "of the primi- 

 tive unstratified class, including true granite, pegmatite, sienitic 

 granite and hornblende rock ; sienitic gneiss and hornblende slate 

 are occasionally seen, but they belong more to the outskirts of the 

 hills" (loc. cit., p. 256). The same author also noticed the smoky 

 and bluish quartz which is so common in the charnockite series 



1(1 Notes' on the Geology of the Country between Madras and the Neilgherry Hills via 

 Bangalose and via Salem". Madras Journ. of Lit. and Set'., Vol. IV, pp. 1 — 27 (1836). 

 "Memoir on the Geology of the Neilgherry and Koondah Mountains". Ibid. t \o\. IV, pp. 241— 

 299 (1836). 



2 "On the Granitic Formation and direction of the Primary Mountain chains of South 

 India ". Ibid., Vol. IV, pp. 327-335 (1836). 



'"Geographical and Statistical Memoir of the Neilgherry Mountains. Ibid., Vol. XV» 

 pp. i-i-S (1848). 



( 4 ) 



