426 Geological Sketch of the Neilgherries. [Aug. 



as the masses of the iron ore shoot up ; and therefore, it is fair to 

 conclude, that the last do not overlie the former. 



I must here call the attention of the reader^to the almost imper- 

 ceptible transition of the cavernous tubular kind of ferruginous con- 

 glomerate, into the uniformly compact haematitic iron ore of this 

 hill : an appearance that I had an opportunity of observing also in 

 the Northern Circars at Pandagaram, near Samalkatah, where the 

 compact, slaty haematitic iron ore is seen passing into a conglomerate 

 very much like laterite (Nos. 33 and 34). 



Another view of the haematitic ore is obtained below the bluff rocks 

 of the summit of Dodabetta, beyond the villages of Mantu, close to 

 the road, which descends from the hollow between Kaiti rock and 

 Dodabetta. Coming towards Ootacamund, we see huge masses of ore 

 protruding through the soil (No. 35). It is scabrous and cellular, but 

 not perforated by tubular sinuosities like the laterite. It is similar to 

 some of the masses of the same ore on the declivities of the hills of 

 Scotland Valley. This vein has but a few yards' thickness, having a 

 N. and S. direction. On both sides of, and nearly in contact with 

 the blocks of ore are seen masses of sienitic porphyry, or rather 

 hornblende porphyry, containing some garnets (No. 36), which, as we 

 proceed towards the villages of Mantu, lose the garnets, and become 

 hornblende rock (No. 37). 



The two hillocks S. E., and close to the lake, and on which Cluny 

 and South Down houses are built, are chiefly composed of the same 

 iron ore. The sections in these declivities, on account of the road which 

 goes round the lake, show the ore decomposed into a red clayey 

 earth, imbedded in the lithomargic earth, resulting, as we have seen, 

 from the decomposition of the original sienitic rock. 



The same ore is seen near the summit of Dodabetta, on the hill before 

 descending into the Elephant Valley, and in other localities, which it 

 would be superfluous to describe, after having detailed the principal 

 features of those places where it most abounds. I must, however, 

 here recall to the memory of the reader what 1 have said, speaking of 

 the detritus below the vegetable earth. It is in the localities, which 

 abound with this iron ore, that the detritus is composed of ferruginous 

 rounded pebbles, occasionally cemented together into a hard con- 

 glomerate, like oolitic iron ore, by a clayey paste. 



The haematitic iron ore seems to contain some felspar, which in this 

 rock is decomposed into a yellowish clay, lining some of the cavities 

 in the rock : but I never found any quartz in it. 



Before concluding these details regarding this iron ore, I will point 

 out some particularities, in which (notwithstanding its similarity in 



