1837.] 



through the Northern Circars. 



51 



Having reached a nullah, which ran down from the north declivity of 

 the hillock, we dismounted, directing our horses to be taken a mile 

 or two further on. 



In the bed of the dry nullahs, as well as along the road, were seen 

 blocks of limestone, some of them loose, and others implanted in the 

 soil of the declivity of the hillock. This rock has a white colour, and a 

 fracture semi-chonchoidal and glimmering, on account of the numerous 

 crystals of carbonate of lime, into which all the fossil shells are con- 

 verted. The height of the hillock may be three or four hundred feet 

 above the plain, and the slope of the northern side is gentle and gradual. 

 Its form is oblong ; the ridge having a north and south direction. 



The north declivity is covered with blocks and large pieces of basalt, 

 scattered and intermixed with those of the limestone. Some of the 

 masses of the last mentioned rock were entirely composed of shells, 

 converted into brilliant and sparry crystals of carbonate of lime. It 

 seems, that they must have undergone violent compression, since they 

 are fractured, and many of them crushed into comminuted fragments. 

 This limestone is very compact, and differs from that a few yards higher, 

 in not containing sparry particles (No. 19). Ascending still, the basaltic 

 masses became more numerous, both loose and fixed ; many of them 

 decomposing in concentric layers, and passing into wacke (No. 20). 

 Although this trap appears tough and of a firm compact texture, yet 

 when looked at through a lens, it is observed full of microscopic cavi- 

 ties, some of them lined with a yellow powder (No. 21). 



The top of this hill, which forms a kind of table-land, is capped with 

 basalt, apparently extending a few miles eastwardly, and decomposing 

 in concentric layers, which are clearly seen in the dry beds of brooks, 

 having their line of separation well defined. This wacke contains no 

 shells of any sort (No. 22). Many of the masses of basalt, on the 

 summit of the hill, are vesicular, sometimes approaching- amygdaloid, 

 not only on the surface, but also in the substance of the stone. Not 

 rarely, large isolated nests of this amygdaloid occur in the compact 

 basalt, the cavities being, in both cases, lined or filled with calcspar 

 (No. 23). 



Descending a little way to the right (N. E.) we came to a thick bed 

 of limestone projecting in a little ridge, a foot or two raised above the 

 side of the declivity, running some hundred yards east and west, and 

 cutting the hill in a direction parallel to its base ; it appeared to be 

 vertically situated. The outgoings of this bed are tufaceous, as well as 

 the surface of the implanted blocks all around it, and in which the fossil 

 shells were clearly distinguishable, such as oysters, limas, small 

 melaniee, &c. (No. 24). Notwithstanding the tufaceous structure of the 

 outgoings of this bed, the limestone, when fractured deep, exhibits a 

 texture similar to that of the loose blocks on the declivity of the hill, 



