1836.] 



Southern India. 



329 



western ghauts, the dissimilarity of the eastern range at Nakanary, and 

 the non-occurrence of the green granite in the intermediate space, are 

 circumstances indicative of a particular arrangement. 



Primitive trap or greenstone does occur in some places, as between 

 Biddadee and Muddoor to the westward of Bangalore, but it is of that 

 basaltic kind which pervades alike every formation, and is found 

 abundantly in the red granite districts: another example of this 

 detached greenstone occurs on the eastern side of Bangalore, where 

 from the height near Ooscottah a long narrow range of flat topped 

 hills may be f> seen, extending in a semi-circular sweep from the vicinity 

 of Nundidrdog to the southward of Ooscottah, near which the hills 

 pass. On examination of this ridge, the greenstone will be found, as in 

 other cases, to have the vertically tabular structure, although the flat 

 topped hills would, prima facie, lead to a contrary supposition. It is 

 difficult to say what is the difference between these hills and the basaltic 

 dykes, except that the former are on a larger scale than the latter t 

 both appear to have penetrated the strata anterior to subversion. 



In the direction of mountain ranges, although a certain order seems 

 to prevail,, yet there is not such regularity as in the direction of stratifi- 

 cation, which often continues the same, while the direction of ranges 

 may be various: both these points it is important to note in a geolo- 

 gical survey ; they might be easily registered, in the different districts,- 

 along with the meteorological phenomena. The direction of stratifica- 

 tion at Ootacamund, on all the hills near the cantonment, is W. S. W.* 

 at Trichinopoly the same, and at Nakanary not very different. The 

 lines of stratification cross the ghauts diagonally at Nakanary, or per- 

 haps more strictly speaking, the line of fracture running N. and S, 

 crosses diagonally the lines of stratification. "We see from this, that 

 there are mountain ranges having their stratification parallel with 

 their direction, and others having it oblique; it will follow also that if 

 disruption take place across lines of subverted strata, a variously com- 

 posed ridge will be the result ; whereas if the dislocation proceed paral- 

 lel with the subverted strata, there will be in consequence a continuity 

 of the same rock elevated. This is a rule that will be found to hold 

 good in most cases as applied to primitive strata, and, where secondary 

 ranges occur, the subjacent rock is more to be considered as the true 

 mountain ridge than the overlaying crust. The Gujunder Ghur hills, for 

 example, although a sandstone range, are based on granite ; owing their 



* An exception to this occurs on the north side of the cantonment where the direction 

 of a piece of gneiss or rather trap more stratified than usual runs N. and S. and has fallen 

 besides to an angle of 45°., the dip being to the westward. This fragment includes at 

 least three small hills the convexity and exfoliation of which have the usual direction 

 with regard to the horizon and are not influenced by the oblique position of the rock. 



