1835.] Geological Sketch of the Neilgherries. 429 



places the garnets, instead of being either amorphous, or in angular 

 crystallized pieces, assume the granular form, resembling colophonite ; 

 in which case, the rock containing it assumes a stratified appearance 

 (No. 41). 



The colophonite is composed of granular garnets, greenish horn- 

 blende, a little felspar, and less quartz. I have seen in your museum a 

 specimen sent by Struvb from Norway, very much like the specimen I 

 now send. The geological position of this rock, which I have found 

 in one or two localities only, is the following." It is to be seen clear- 

 ly in the ravine just above the high road going to Kunur, and close 

 to the public bungalow of Kaitf. Two huge masses of a black-looking 

 unstratified rock are seen overlying three strata of a different rock. 

 The upper and unstratified mass is a hornblende porphyry, which 

 passes into sienitic granite. It is very nearly similar to the rock of the 

 same composition I have mentioned as flanking the hsematitic iron 

 ore, behind Mantu village (No. 42). I have found precisely the same 

 rock overlying the sienitic porphyry of the Garabunda pass, in the 

 Northern Circars. Its hornblende is shining and lamellar, and is the 

 most abundant of the component minerals ; the garnets appear to be 

 surrounded by a white powdery opaque felspar, they themselves half 

 decomposed. Below this half-rounded mass is a stratum of a felspar 

 rock, with a very little quartz and hornblende decomposing (No. 43). 

 The thickness of this stratum, which is uniform, does not exceed a 

 few inches; another, but thicker stratum of a granitic rock, lies under, 

 and conformable to the above, being composed of reddish felspar, some 

 garnets, little quartz, and mica ; the passage from one rock to the other 

 is sudden, decided, and well marked. Under this, and conformable 

 to it, is a stratum of a rock almost entirely composed of hornblende 

 and granular garnets : this is the lowest of the rocks seen ; it be- 

 comes harder as it descends, when it assumes the appearance of colo- 

 phonitic hornblende rock. 



This lower rock appears stratified, and besides the seams of strati- 

 fication, it has some fissures, perpendicular to them ; so dividing 

 the stone into prismatic portions. On account of the thick stratum 

 of soil at the foot of the rock, I could not ascertain whether the 

 last-mentioned was the lowermost rock. I must here remark, that 

 the appearance of the two rocks immediately under the hornblende 

 porphyry was that of a decomposing stoue, as if from the action of 

 fire. 



The rock which prevails in the Kaiti range, as well as in other 

 places, is the one which abounds both with hornblende and amor- 

 phous garnets. These last sometimes are of a large size, and not 

 3 K 



