1842.] Bijapore to Bcllary via Kannighirri. 943 



S., joints horizontal. At the quarries of Bijapore, the fissures took a 

 direction N. 20 E., joints dipping 5° to E. 20 S. Calc spar occurs in 

 thin discoloured seams, lining the fissures. A number of empty- 

 vesicular cavities pervade the rock, which appear never to have contain- 

 ed any mineral substance, and probably were occasioned by the evo- 

 lution of gases while the rock was in a liquid state. Their direction is 

 not uniform, but it will be found generally south-westerly, conforming 

 to the axis of the trap's direction. 



The petrographical structure varies often in the space of a few feet, 

 Petrowraphical struc- fr° m a compact greyish black basalt, having a 

 ture of rocks. granular structure and conchoidal fracture, with 



streak of ash grey, to a soft wacke speckled with brownish decaying 

 crystals of augite and amphibole. The trap in this vicinity has a blush of 

 red traceable in the darker portions, and becoming stronger in the 

 wacke and amygdaloid ; the latter has for its basis, a fine red clay. The 

 dark compact variety melts into a black glass, and is faintly translucent 

 at its edges, exhibiting a dull green ; the rest are opaque, and melt with 

 difficulty into a greenish black glass. Some varieties, which appear to 

 contain much silicious matter, are infusible. The less compact trap 

 has an uneven fracture. When reduced to a coarse powder, a few of 

 the fragments are taken up by the magnet ; the fine powder is of dull 

 greenish grey. It does not gelatinize when treated with acids. Its 

 specific gravity I found to be 3.35. 



The variety used in building the splendid palaces, mosques, and 

 mausoleums of Bijapore is of a deep reddish brown opaque, and of a 

 granular fracture, approaching earthy. This rich colour adds much to 

 the appearance of the ruins. The rock is by no means uniform in 

 texture, being more or less vesicular, amygdaloidal, or clayey, and sub- 

 ject to exfoliation : consequently, when the stone has not been carefully 

 selected, it gives way under the superincumbent pressure ; many of the 

 structures are rapidly falling into decay on this account. The variable 

 nature of the trap is perhaps most strikingly seen in making the circuit 

 of the city walls, which are built upon the rocks from which their ma- 

 terials have been quarried. Not only is the disintegration seen in the 

 walls themselves, but wherever they rest on an amygdaloidal founda- 

 tion ; which, exfoliating, splitting, and giving way, causes whole masses 

 of masonry to be precipitated piece-meal into the fosse. Vertical 



