938 Notes, principally Geological, on the [No. 130. 



the sharp angles of some of the fragments, their proper locality cannot 

 be far distant. 



From Umblanur, still proceeding northerly, to within three furlongs 

 from the town of Bagwari, the route continues along the left bank of 

 the Hirri. The trap is observed in the nullah beds to undergo many 

 changes in texture and colour, even in the space of a few yards, from 

 a compact heavy basalt to a friable wacke ; from globular to schistose ; 

 from black to red and a light brownish speckled grey. The laminae of the 

 schistose variety are often intersected by transverse fissures, which 

 divide the rock into rectangular and rhomboidal prisms, similar to 

 those observed in clay slate near the line of contact with a basaltic 

 dyke. These again, by the agency of the mysterious law of crystalliz- 

 ation, which is manifested in a greater or less degree, in both ancient 

 and modern trappean rocks, from the microscopic atoms of augite and 

 hornblende to the prodigious pillars of Staffa and the Giant's Causeway, 

 often assume a pentagonal and hexagonal shape by exfoliation. By 

 process of farther exfoliation the angles are worn away, and the prisms 

 assume a globular appearance, which has led some observers to ima- 

 gine them to have been erratic boulders subjected to the rolling action 

 of water, or from their abundance, and the augite often found in them, 

 to have been showered down on the surface by volcanic agency. Near 

 Bagwari, the beds of the streams abound with hanker, indurated ferru- 

 ginous clay, fragments of red and yellow jasper, trap, amygdaloid, and 

 a few nodules of calcedony; the concave surface of the botryoidal 

 varieties of this mineral not unfrequently exhibit a succession of penta- 

 gons and hexagons. 



From Bagwari to Mangoli, the route lies over plains, the lowest 



_, , stratum of which, as seen in wells, to the depth of 



a. Mahratta country r 



from Bagwari to Bija- twenty to fifty feet below the surface and beds of 

 pore. 



nullahs, is the overlying trap. About two miles • 



N.W. from the former place, it is overlaid by a sheet of a conglomerate 

 composed of a nodular and pisiform iron ore, and fragments of ferru- 

 ginous clay imbedded in a travertine-like paste of carbonate of lime, 

 coloured of a light ochre brown by oxide of iron. The bed of a nullah 

 presented the only section (of this stratum ) ; it was here four feet thick 

 covered by a layer of black cotton soil or regur, and resting immedi- 

 ately on the concentric exfoliating trap which was penetrated by seams 



