NILGHIRI HILLS. 219 



Gneissose character, and in no case do they form igneous veins, or 

 present any appearance of intrusion. It is principally in the elevated 

 country that they exhibit a granitoid appearance ; in the plains generally, 

 the foliation is extremely well marked, a fact which, hereafter, may prove 

 of some theoretical interest. 



The minerals principally entering into the composition of the foliated 

 rocks are Quartz, Hornblende, Felspar and Garnet? 



Mineral Composition. ^^^ ^-^^^^ ^^^^^ ^^ ^-^^ ^^^^ ^^^^^^ relative propor- 

 tions, one or more of them being frequently absent. Mica occurs 

 but rarely throughout the hills, and indeed appears to be an exceptional 

 mineral in this part of India generally. Besides the above there are some 

 few minerals of local occurrence, viz : — Magnetic 



Accidental Minerals. j^.^^^^ Hsematite, Specular Iron, and Graphite, and 



as the results of decomposition, the various earthy forms of the 

 Hydrated Peroxide of Iron, such as Ochre and Laterite ; and 

 Kaolin. 



Of the minerals of occasional occurrence, the Oxides of Iron are the 

 most abundant. They occur forming short irre- 

 Hmmatites. gular bands or masses in the Gneiss, such bands 



generally running nearly in the direction of the foliation. Haematite and 

 Specular Iron are far more common on the surface than Magnetic Iron, 

 but froni their massive structure and mode of occurrence, they are pro- 

 bably Magnetic Iron peroxidized by atmospheric agency. The most 

 important masses of Iron ore occur above the village of Karrachola, a mile 

 and a half West, of Kotergherry, and on a small spur of Dodabetta, over- 

 looking the Dbobi's village. Dr. Burrell informs me that from the same 

 locality, he has a piece of Magnetic Iron which is 

 agnetio ron. sufBcieutly magnetic to carry a bodkin eighteen 



grains in weight. Another rich deposit of a similar nature occurs about 

 three miles east of Jackatalla, where the Hasmatite is iuterfoliated with 

 the gneiss, in broad strings of the pure mineral, 



Q 



