oct. — dec. 1857.] in the District of Coimbatore. 



Gl 



specimens were obtained. The chie-f results of the examination 

 are embodied in the following notice. 



The whole surface of the district of Coimbatore as well as the 

 Mysore table land, and indeed the greater part of S. Western India 

 is composed of a vast spread of Schistose or foliated rocks, such as 

 Gneiss, Hornblende Schist, Mica Schist, &c, a class of rocks term- » 

 ed Metamorphic by Sir Chas. Lyell, (although such a term must be 

 regarded as premature until their really metamorphic nature in all 

 cases be firmly established.) The mineral characters of these rocks 

 are extremely varied, but they consist for the most part of Quartz, 

 Feldspar, Hornblende and Garnet, intermixed in various propor- 

 tions, one or more of these minerals being occasionally entirely ab- 

 sent. Mica which is one of the constituents of true Gneiss is only of 

 exceptional occurrence in the district in question. The foliation ^or 

 system of laminae) in which the constituent minerals of schistose 

 rocks are arranged, is well marked over the greater portion of the 

 Coimbatore district, but is far less distinct on the elevated plateau 

 of the Neilgherry Hills, and occasionally disappears altogether, 

 so that were it not that such non-foliated rocks pass invariably by 

 insensible degrees into others in which a foliated character is dis- 

 tinctly discernible, they might be easily mistaken for Syenite, 

 Greenstone - or some other kind of Plutonic rock, an error into 

 which previous observers have generally fallen. The foliation 

 wherever apparent conforms to a general strike in the direction 

 E. N. E., W. S. W. on the plateau of the Neilgherry Hills, and 

 such is also its direction in the vicinity of Coimbatore. In other 

 portions of the district it varies considerably and towards Bhovani \ 

 it has a North Western strike. Granite veins of small size, are 

 occasionally seen cutting through the foliated rocks, which form 

 the surface of the low country, but on the hills generally no trace 

 of Granite or any of the allied Plutonic rocks has been detected. 

 A few small dykes of Basalt being the only intruded rocks of the 

 elevated country. 



About 5 miles to the south of the Civil station of Coimbatore, 

 a low broken ridge of hills characterised by a peculiarly jagged 

 outline occurs crossing the road to Palghat and running in an E. 



