1810.] 



of the Great Basaltic District of India. 



17 



the basins of the Pennar and Kistnah ; and higher up the stream, a fine 

 white quartzose sandstone, having a few imbedded fragments of quartz, 

 is found in situ. It dips at a slight angle to the south-west*. The sur- 

 rounding country is covered by a deep basaltic soil, so that the rock on 

 which it rests could not be discovered ; but the argillaceous limestone, 

 passing, in its upper strata, into a greenish or red schist, is traversed by 

 a stream a few miles to the north. Short ranges of trap hills, some of 

 them at nearly right angles to the Sichel mountains, occur to the 

 north-east ; and beyond them, an extensive tract of sandstone has been 

 traced for a great distance along the Wurdah. 



At Zynad, argillaceous limestone appears on the surface for several 

 miles, and agrees in every particular with ihe compact marbles of the 

 diamond districts of the Pennar and Kistnah. The strata sometimes dip 

 at an angle of 40 degrees, but they are in general nearly horizontal, the 

 edges of the laye; s being disposed in steps on the slopes of gently-rising 

 grounds. Rock crystal and calcareous spar are distributed in thin seams 

 between the strata, as well as through the substance of the rock ; and 

 along the vertical partings of the strata, there are rows of circular cavi- 

 ties, which are generally empty, but are sometimes tilled with calcareous 

 concretions. In a few instances, these hollows occur out of the line of 

 fissure, and entirely penetrate the stratum, being connected below with 

 horizontal channels of the same kind. On the surface, calc-tuff (Kun- 

 kur) is very abundant, often adhering to the strata, or investing frag- 

 ments of the rock. 



The same appearances are seen near the diamond mines of Chinoor on 

 the Pennar, where the strata are much disturbed, and basaltic pebbles 

 cover the banks. The only explanation which can be offered of the 

 phenomena in both those distant localities is, tliat the extrication of 

 gaseous fluids and water from below, had taken place in the lines of fis- 

 sure, and had dissolved a portion of the limestone, which was again de- 

 posited in the great accumulation of tuff and conglomerate so remarkable 

 in these places. That they at all indicate the " argillaceous limestone'* 

 to be of freshwater origin, could never be imagined by any who had seen 

 the rock in question, which, wherever it occurs in the south of India, is 

 entirely devoid of fossilsf. This supposition is confirmed by the pheno- 



♦ Minute undulations, resembling those formed by the ripple of running water, were 

 observed on this sandstone, in a seam not quite parallel to the line of stratification. 



+ This assertion may, in the progress of knowledge, be found to be erroneous ; but 

 having carefully looked for fossils during extensive journeys through districts princi- 

 pally composed of this rock, I doubt whether such will be the case. Fossil plants have 

 been repoi ted to be found near Gundycottah ; but these I ascertained to be mere dentri- 

 tic markings on the suiface of the strata. 



