1830.] 



of the Southern Mahratta Country. 



467 



Secondary Trap Rocks. — Trap rocks occur very extensively in dif- 

 ferent parts of India. They are met with in some parts of Mysore 

 and Hyderabad. They occupy a very large part of the Deccan, extend 

 from near Fort Victoria on the western coast northword beyond Bom- 

 bay, stretch thence across the country through Kandeish into Malwa ; 

 and are also met with inBundelcund and Marwar.* 



In the Darwar district they do not occur in great abundance. The 

 great formation of trap, which extends all the way from the northern 

 parts of the Deccan to the south of the Kistnah, terminates here ; and 

 the trap hills to the south and east of Bel gaum probably form its 

 boundary in that direction. It is therefore in the north-western part of 

 this district that the trap is principally met with. I must also men- 

 tion, however, that I found a compact greenstone at Sedasheghur rest- 

 ing upon granite ; but I am inclined to think that it does not belong to 

 the secondary trap which we are now considering, but to a much older 

 formation. 



The trap in the neighbourhood of Belgaum forms rounded hills, and 

 does not exhibit the appearance of steps of a stair, which characterizes 

 the trap in other places. It is also found in the form of veins tra- 

 versing granite, in some parts of the Hyderabad country. A very 

 large vein of secondary greenstone is found traversing the granite at 

 the village of Mussaputtan, near Anagoondy. It is so large as to 

 forma small range of hills, which, being nearly bare, can be recog- 

 nised at a great distance by their black colour. 



The most common rocks which occur in this extensive formation are, 

 a loose greenstone, basalt, and amygdaloid. The first, which appears to 

 be the most common, has a concentric lamellar structure, the lamellae 

 separating very easily from each other, and becoming harder towards 

 the centre, which contains a hard nucleus. Sometimes this variety has 

 a rhomboidal structure ; but, in this case, each rhomboid is found to 

 have the concentric lamellar structure in its interior. This greenstone 

 is almost always weathered to a very great depth. It is, therefore, 

 very difficult to get a fresh specimen. When weathered, it has a grey 

 colour ; when fresh, it is found to be composed of distinct grains of 

 felspar and hornblende. 



The compact varieties of greenstone are very much employed in 

 India as building stones. Most of the magnificent mosques and maus- 

 lea at Beejapore, which is situated in the midst of the trap formation, 

 are built of it. 



I found basalt at the village of Baugwarry, twelve or fifteen miles 

 east from Belgaum. It contains small vesicular cavities, which 

 appear never to have been filled with any substance. 



* Vide Mr, Fraser's paper in the first volume of the Geological Society's Transactions, 

 New Series, 



