334 



Granitic Formation of 



[Oct. 



probability of concretion in the present position of strata. It has cer- 

 tainly been suggested that vertical structure may be the effect of crystal- 

 lization on a large scale, but this hypothesis is unsupported by analogy 

 oh the smaller scale, and is quite at variance with existing appearances 

 in the rocks themselves. 



It is in the larger masses that the grain or direction of structure can 

 be most correctly taken : the smaller fragments are often irregularly 

 disposed and they are liable besides to be confounded with the superin- 

 cumbent schists. The relation of the newer schists to the subjacent strata 

 has never been fully explained, but they are certainly two distinct forma- 

 tions, and of different date. They may be seen to good advantage on the 

 island of Seringapatam, where the older strata, having a red felspar, are 

 easily distinguished from the schists, which have invariably a white or 

 grey felspar. 



"With regard to dislocation as the general cause of inequalities, the 

 eastern ghauts may be considered a fair example : this range seems to 

 be solely owing to a cross fracture of the strata. The observer, look- 

 ing along the hills at Nakanary, will at once perceive that they are of 

 a different character from the southern or Cauvery chain, bounding the 

 table-land on the extreme south, and afterwards stretching into the 

 plain. The trap hills, extending from the Neelgherries eastward, which 

 for the sake of distinction may be called the Cauvery chain, are in 

 many places four thousand feet high, while the Nakanary ridge is 

 scarcely more than half that height : the latter, although so low, is far 

 more rugged than any part of the western ghauts ; while the hills are 

 more numerous, and widely extended into the plain. On examination of 

 the granite it will be found of that kind which usually forms the area, 

 and not the boundary, of the Mysore district: the same variety of white 

 granite continues from Sautghur to a considerable distance above the 

 Nakanary pass, no change being perceptible at the ghaut. The point, at 

 which this white granite ridge appears to commence, is near Salem, but 

 the exact course of the different ranges here requires to be more cor- 

 rectly ascertained. In maps of the peninsula the eastern ghauts are 

 always formally laid down, probably as being the boundary between 

 the two levels, but the high mountains, extending by Salem and Gingee 

 to Madras, are comparatively unnoticed. 



Geologically viewing these chains in conjunction with the table- 

 land, it appears that the surface, nearly as far to the eastward as Salem, 

 has been forced to a considerable height, with the Cauvery ranges for its 

 boundary ; but beyond this it breaks short of the trap ranges, and the 

 dislocation runs north, through the interior of the basin or compart- 

 ment, towards Nakanary. The fracture, in this instance, departs from 

 its usual course, and excludes the northern part of the Carnatic from 

 the level of the table-land. The eastern ghauts preserve nearly the 



