62 



Ofi the Fossils of the Eastern Portion 



[July 



dependent on them, and having the same composition and direction, are 

 crossed at right angles by the Pennar, which makes its way through them, 

 like the Kistnah, by traversing narrow gorges, with perpendicular sides. 



There is not a more remarkable phenomenon in the district watered 

 j^y the Pennar than the horizontal summits of many of the ranges, and 

 the distinct manner in which the continuity of the strata can be traced 

 from one liill to another, although extensive plains intervene ; while, at 

 no great distance, the sandstone which forms the summits of these hills 

 js seen on the same level as the surrounding plains. Numerous in- 

 stances also occur in which the original continuity of the horizontal 

 summits is easily traced ; the strata on the opposite and nearly per- 

 pendicular sides of a valley being similar, but having a considerable dip, 

 the beds descend to the general level of the country. A good example 

 of this is seen, in Section 2, PI, 6,, at Chintagoouta and Gundicot- 

 tah. These anomalies were at first quite inexplicable, nothing appear- 

 ing in the valleys but a rich alluvium, nor on the summits (which are 

 reached with rmch difficulty) but a sandstone perfectly horizontal, and 

 divided into huge tables by perpendicular partings, sometimes separated 

 several feet from each other, and filled with broken pieces of the rock. 

 This jointed structure is common to the sandstone, the schistose beds 

 on which it for the most part immediately reposes, and the stratified 

 limestone into which these schists pass insensibly ; but the size of the 

 tables so formed, varies from rhombs of a few inches, in the schi-t and 

 lower part of the sandstone, to enormous masses on the summits of 

 the hills. Nowhere is this structure and the succession of strata, ©f 

 which it is characteristic, better seen than in the table land in which 

 are situated the celebrated diamond mines of Bangnapilly and others 

 now deserted. From the accompanying plate some idea will be gained of 

 one of these mines,* 



The plains at the base of the table land of Bangnapilly consist of a 

 rich black alluvium, containing fragments of basalt, jasper, and the 

 various minerals found in the hills. It rests on a fine, compact, dark 

 blue or nearly black limestone, which contains much argillaceous and 

 siliceous matter. This limestone abounds with springs, and is in some 

 places so cavernous as to afford passage to subterranean streams. Basalt 

 protrudes in a few places near Bangnapilly. On ascending the hill, the 

 limestone becomes more schistose, and is of a paler colour, gradually 

 approaching in its structure and composition to clay slate, but it is far 

 more friable. On the schist a more or less compact sandstoae rests 



• The plates will be given in our next number,— Ed. Madras Journal. 



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