1835.] Geological Sketch of the Neilgherries . 427 



appearance) it seems to differ from the laterite of the other parts of 

 India, that I have had an opportunity of examining. The rock of 

 the Neilgherries is by no means so cavernous, and has not so many 

 tubular sinuosities as the laterite of the Carnatic, Northern Circars, 

 &c. ; it seems also to be richer in metal, and, what appears to 

 constitute a marked difference, it is entirely divested of any quartz, or 

 sandy particles, which ahound so much in the laterite of other places. 

 Besides, we are told hy Doctor Heynb, that in the laterite of the Red 

 Hills, Nellore, &c. a marl or carbonate of lime is occasionally one of 

 the ingredients ; no traces of this carbonate are found in the stone of 

 the Neilgherries*. 



That this rock of the Neilgherries is to be classed with hsematitic 

 iron ore, rather than with the true Indian laterite (an overlying rock), 

 is very probable, considering that rocks similar in appearance to it are 

 found in Europe, while the last is peculiar to Indiaf. 



It is said of the Indian laterite, that it is associated occasionally with 

 trap. On the Neilgherries, basaltic dykes are not rare, yet I never 

 saw what Voysey remarked in other parts of India, viz. the passage 

 of basalt into wacke, and into iron clay, (by this last name, meaning 

 laterite ;) another additional difference between the two rocks. 



Hitherto no organic remains have been found in this rock on the 

 Neilgherries, which appears also to have been the case with the laterite 

 of the other parts of the peninsula. 



I am not positive regarding the existence of manganese on these 

 hills : my friend Colonel Cullen says, that it is found mixed in the 

 iron ore near the lake; and I found a straggling piece of this ore in the 

 valley of Kaitf (No. 38), which I have not analysed, but which has 

 all the external characters of one. 



The lowest visible rock of the Neilgherries is of the primitive un- 

 stratifled 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 than to the 

 group itself. Besides these rocks, we find granitelle, and a rock 

 composed of four minerals, felspar, hornblende, garnets, and quartz. 



True granite, composed of felspar, quartz and mica, is not of rare 

 occurrence ; it frequently occupies the summits of the highest hills : 

 thus it is seen in some of the Kunda range, and of the Dodabetta group ; 



* Tracts. 



t If my memory serves me right, I think I saw in your museum a specimen 

 marked " black, brown, solid and perforated iron ore, from Poetz in Upper Lusatia," 

 which appears to me similar to the Neilgherries hsematitic, cavernous iron ore. 



X No. 38 is decidedly an ore of manganese. — Ed. 



