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122 DIAMOND MINES 



tainly not very distinct, but is sufficiently so to entitle them to be consi- 

 dered geologically as the same range. In a southern and S. W. direction, 

 they probably extend considerably beyond the Pagoda of Tripati. The 

 most southern point that has fallen under my observation is Naggery Nose, 

 a well known Sea mark on the coast of Coromandel. Travellers to Hy- 

 derabad make a considerable detour for the purpose of crossing these 

 mountains in their most accessible parts. Among the western passes on 

 the Cuddapah road are those of Bakrapet and Moorcondah on the bank 

 of the Kistna, and those of Nakrikul and Warripalli on the Ongole road 

 are among the eastern. The breadth of the range varies, but never ex* 

 ceeds 50 miles. 



The geological structure of these mountains, it is difficult to understand, 

 and it cannot be easily explained by either the Huttonian or Wernerian theo-. 

 ries. The different rocks of which they are composed, being so mixed to- 

 gether without regard to order of position, each in its turn being uppermost, 

 that it is not easy to give a name so definite as to apply in all places. 

 I once thought the term " shistose formation" would be the most simple 

 and untheoretical term, but as Clay slate is probably the most prevalent 

 rock, I have determined on giving that name to the whole, observing how- 

 ever that by " Clay slate formation'* I do not mean the Wernerian Thou- 

 sheiffer, the fourth in order, of his enumeration of primary rocks, but 

 merely a collection of rocks which I conceive to have been placed in their 

 present situation at the same period of time. 



The "Clay slate formation" then of the Nalla Malla Mountains consists 

 of Clay slate ; of every variety of slaty lime stone between pure lime stone 

 and pure slate; of Quartz rock; of Sandstone; of Sandstone Breccia ; 

 of Flinty slate ; of Hornstone slate and of a lime stone which I call Tuffa- 

 ceons for want of a better name, containing imbedded in it, rounded and 

 angular masses of all these rocks. All these vary so much in their 

 composition, and pass into each other by such insensible gradations, as? 

 well as abrupt transition, as to defy arrangement and render a particular 

 description, useless. 



