268 



Notes, principally Geological, on the South Mahratta country — Falls 



of Gokauk — Classification of Rocks. By Capt. Newbold, F.R.S. 



&c. Assistant Commissioner Kurnool. 



The reader has already been introduced into the South Mahratta 

 country at its eastern angle near the confluence of the Kistnah 

 and the Gutpurba.* We will now proceed westerly across it, follow- 

 ing the right bank of the Gutpurba to the Falls of Gokauk on the 

 Eastern slope of the Western Ghauts, leaving the Kolapore territory 

 to the right. 



I crossed the Kistnah about two and a half miles below the Sungum, 

 or confluence, and passed up the opposite bank towards the tongue of 

 land formed by the junction of the rivers. The apex consists of 

 silt, sand and clay, in regular layers, rising, as they recede, to the height 

 of about sixteen feet above the surface of the water. 



A section of these layers was afforded in the sides of a deep cleft 

 running down to the Gutpurba. They present a striking illustration 

 of the formation of fissures in sedimentary rocks, simply by the mass 

 contracting in consolidation, unaided by subterranean movement or 

 displacement, which we are compelled to call in to our assistance in 

 explaining the great faults and displacements, attended with scorings of 

 the faces of the fissures, and the polishings termed " slickensides," so 

 common in the coal measures, and other old sedimentary rocks of 

 Europe. Earthquakes, another cause of fissures, are unknown here. 



The fissures in these layers of silt and clay are usually vertical, and 

 widest in the more consolidated layers ; their course is often zig-zag, 

 like that of the celebrated gap in the sandstone rocks of Gundicotta 

 through which flows the Pennaur; or, like the fissures in the Regur 

 deposit : during the hot months they frequently intersect each other. 



Horizontal seams, independent of the parallel laminae of deposition, 

 have been formed, partially filled with a titaniferous iron sand, which 

 owes its arrangement, and segregation in distinct layers partly to its 

 greater relative specific gravity, and partly to the motion of the water. 

 The truth of this is easily illustrated by the simple experiment 

 of mixing intimately some common quartzose sand with a portion of the 



* See Journal, Vol, XIII. p. 1004. 



