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Granitic Formation of 



[Oct. 



countries patches of limited extent, but surrounds and intersects the 

 whole peninsula ; it seems to have its regular place among the granitic 

 strata, with which it is confluent at the line of junction, passing gra- 

 dually from green to red and white felspar rocks : it generally cuts off 

 and terminates all the other granites : possessing this character it may 

 be considered the oldest rock here unfolded in the granitic series ; for 

 if the primitive mountains are the subverted fragments of a formerly 

 horizontal crust, which all observation and experience tend to prove, 

 then according to the laws of subversion that prevail in the more recent 

 formations, the stratum found encompassing the others will be that 

 which was earliest formed and originally undermost in the series. 



The primitive trap together with its associate the small grained 

 sienitic granite is by far the most extensive and continuous of the 

 Indian rocks.* On the western coast it seems to extend uninterrupt- 

 edly from Surat to Cape Comorin, or rather to Ceylon, for the moun- 

 tains there appear to be of the same character as the western ghauts, 

 and are besides nearly on the same line. From Ootacamund to the 

 N. E. at least as far as Madras, this rock extends in full character, but 

 does not constitute the mass of the eastern ghauts at Nakanary, which 

 in this respect differs from the western chain. The mountains of the 

 Northern Circars are said to form a very continuous and well-defined 

 range of trap hills, but elsewhere in the line of eastern ghauts or 

 between Salem and the Kistnah, the strata appear to be of various 

 kinds. Connecting the western ghauts at Surat with the eastern at 

 Balasore or Ramghur, is the Vyndiah range also of this trap: so 

 that the trap or green felspar rock appears to surround the penin- 

 sula on every side. Numerous similar and smaller chains cross the 

 interior, generally in a direction S. W. and N. E. Travelling west- 

 ward from Palaveram where green felspar prevails, we do not again 

 meet with the same rock until reaching the western ghauts on the 

 opposite coast. The identity of the Palaveram rock with that of the 



called also primitive greenstone, hornblende rock, and gneiss when distinctly stratified. 

 The composition is, in most cases, at least two thirds felspar, of a bottle green colour, or 

 usually some shade of green, which changes to a light sandstone hue in decomposition j 

 mica, quartz, garnet, hornblende and schorl also occur but in minor proportions, the es- 

 sential ingredient being felspar. In the western ghauts near Goa this trap consists of a 

 paste of bluish grey felspar with scarcely any other ingredient, perhaps the distinguishing 

 mark of trap that will apply most generally is its difference in texture from granite, the 

 one being a compact vitrious paste, the other a more freely granulated compound— in th!s 

 sense the term is here used, for any definition founded on origin or manner of eruption 

 will not hold good with regard to the primitive traps. 



* If sienitic granites are to be distinguished by the presence of hornblende it will be 

 found that, according to the present unlimited application of the word, there is scarcely a 

 granite in this part of India that might not be included as sienitic : but, if we regard them 

 simply as intermediate between granite and trap, it is better at present, for the sake of 

 perspicuity, to drop the dubious term sienitic granite, and pass on to the trap, which will 

 include the granite* next to it having a close texture and vitrious aspect. 



