1850.] in Southern and Central India, 191 



The hills at Vellore and the big and little Mount at Madras, are 

 mostly transition trap. 



They consist of a friable mixture of hornblende, felspar, quartz, 

 and mica, with garnets and pyrope with epidote. The hornblende is 

 found in the hills in nodules in concentric layers like basalt. 



Under and among these hills, rocks of the old trap rise often in high 

 ranges with acute points. Felspar, hornblende and quartz with a small 

 proportion of mica, pyrope and epidote enter it as foreign minerals. 

 When the latter, particularly garnet, are absent the felspar is red. Of 

 this rock, the generality of the hills on this coast consist. It seems to 

 rest on granite near the seven pagodas : a rare occurrence, the appearance 

 of the granite along the coast. The granite is particularly striking here on 

 account of its freshness, whilst the former is found tarnishing and scaly. 



The hornblende which forms a constituent of our primitive trap is 

 in general shining black, and contains iron in so great a quantity as to 

 be attracted by the magnet when in small particles. It is the same in the 

 greenstone and greenstone slate on which the transition flinty slate of 

 the Pulicat hills rests. The greenstone of that part of the country ex- 

 posed to the air becomes green, although it is black, and does not con- 

 tain a particle of copper. 



The brown and hydrous copper of Dr. T. is found here and in some 

 places mica slate with large garnets. 



A compact greenstone, foliated and ringing when struck, is used for 

 lingams. Common hornblende of an olive-green is found in the Bara- 

 maul in Noorcull, in primitive trap with garnets. A remarkable rock 

 called black granite procured near Madras, is common augite rock. It 

 occurs only massive, greenish black, opake ; in small thin pieces, and 

 on the edges in large pieces, olive-green and transparent. Internal 

 lustre resinous, glistening and splendent ; fracture foliated and granular 

 and on the whole uneven. A two fold cleavage is observable, it is semi- 

 hard, rather brittle, easily frangible, Sp. Gra. 3. 20. garnets are found 

 in it and basalt. If the latter indistinct grains of a black colour, 

 foliated fracture and less hard than the augite ; the former are of a 

 ruby colour. 



Another stone found in this part of the country (Madras), I will call 

 compact hornblende, although it differs in many respects from that 

 rock. 



2 c 2 



