Table Lands of South India. 319 



thickness occur also in the lamination, and irregular veins 

 also run through the mass. 



It occurs frequently in hills formed of piled globular masses, 

 associated with granite, and forming indeed a part of the same 

 granite hill, the interstices between the round masses being 

 filled with a sort of imperfectly granular and friable wacke. 

 It must be considered, therefore, as one of the rocks of the 

 granite series or formation. 



Sienite. 



Dr. MacCulloch first pointed out the impropriety of apply- 

 ing this term to hornblendic granite ; but as even by those 

 who have admitted the correctness of his remarks, the term 

 has still been fancifully applied to a rock of the same mineral 

 composition as the granite, and considered as associated with 

 trap and porphyries, no definite idea can be attached to the 

 term, and it is impossible to discover from the published 

 descriptions of authors, with any certainty, whether the sienite 

 of Malvern, &c. is a granite or not. Without altering the 

 application of the term, we may, however, be able to use it 

 with perspicuity as applied to Indian rocks, by strictly defin- 

 ing the characters usually given of this rock. 



It is composed of granular or crystalline hornblende, in 

 aggregation with felspar. 



It differs from greenstone in containing less hornblende, 

 and in having always a speckled appearance, which greenstone 

 never has. 



In the greenstone, the felspar and hornblende are partially 

 mingled together ; but in sienite, the crystals of both are entire- 

 ly distinct, and in no way confused together. In greenstone the 

 felspar has a rusty red colour ; in sienite the felspar is quite 

 white and resplendent, or sometimes is slightly red: but 

 never dull in lustre. In small hand specimens, it does very 

 closely resemble hornblendic granite; but in mass, it can 

 easily be seen that it has no cleavage, and that it has not the 

 solidity and firmness or aggregation of granite. 



