580 



Geological Structure. — The formations consist of granite, gneiss, 

 mica and hornblende slates, trap, argillaceous limestone, red sand- 

 stone, with diamond breccia, and tertiary freshwater strata. The 

 granite forms ap^jarently the base of the country, and the trap pene- 

 trates all the formations, including the granite and the freshwater 

 beds. In addition to these regular deposits are considerable accu- 

 mulations of travertine and kunkur, which are scattered over the 

 whole surface of the country. 



Granite. — This rock is frequently displayed in all the rivers of 

 southern India, and is occasionally visible as the substratum of the 

 other formations. In the table-land of the Mysore it attains an ele- 

 vation of 3000 feet above the sea. In the Deccan, between the 

 Kistnah and the Godavery, it is traversed by greenstone dykes, 

 sometimes porphyritic, and ranging, for the greater part, from S. by 

 E. to N. by W., a direction not very different from that of several of 

 the basaltic mountains in the northern part of the region ; but on 

 approaching the Godavery, from the south, the granite is penetrated 

 by dykes, which strike N. and S. Beyond Nagpoor the granite has 

 burst through the red sandstone, which is converted into quartz 

 rock; and, still further north, granite veins intersect the argillaceous 

 limestone, which has lost its stratified structure. Granite veins also 

 penetrate the neighbouring hills of gneiss and mica slate. 



Gneiss, Mica and Hornblende Slates. — ^These formations appear 

 to be of limited extent. Hornblende slate was noticed by the au- 

 thor only in the neighbourhood of Deemdoortee, 20 miles E. of 

 Neermul, where it contains the magnetic iron ore used in the manu- 

 facture of Damask steel. Gneiss and mica slate are mentioned only 

 at the locality alluded to above, a few miles N. of Nagpoor. 



Trap. — Mr. Malcolmson distinguishes the trap of the dykes from 

 that which constitutes the great basaltic ranges, by the absence of 

 olivine in the former, though it is common in the latter. The great 

 masses of basalt are also distinguished by being amygdaloidal and 

 more crystalline. 



"When en masse the trap overlies the granite, as well as the stra- 

 tified deposits. In the form of veins it traverses the granite, lime- 

 stone, and sandstone, and the freshwater strata are often imbedded 

 or entangled in it. 



In sinking a well near Hutnoor, (lat. 19°38'N., long. 78°30'E.) 

 seams of pure white, pulverulent limestone were found beneath 

 layers of basalt, and calcareous depositions appear to accompany the 

 formation almost universally. With respect to the minerals con- 

 tained in the amygdaloids, Mr. Malcolmson is of opinion, that they 

 have not been produced either by infiltration or sublimation, but by 

 molecular attraction, because calcareous spar is much more rare than 

 siliceous minerals, though carbonate of lime abounds throughout the 

 basalt. 



Argillaceous Limestone. — Organic remains have not been noticed 

 in this rock. It consists, in the lower part, of thin strata of compact 

 blue or white limestone, and generally, in the upper, of blue, red, 

 green and white schists, or slaty clay. Siliceous matter occurs in 



