GEOGRAPHICAL DISTRIBUTION. 59 



plained (p. 46), the schistose rocks form a scarp with its ghats leading 

 from a gneissic upland of from 1,000 to 1,500 feet down to the Gangetic 

 alluvial plain, and the schist belt is consequently a region- of erosion. 

 In Nellore, on the other hand, the schists with their included pegmatites 

 are found in the low-lying plain, forming the area on which the Penner 

 and Swarnamukhi rivers, running eastwards from the Veligonda ridge, 

 made by the Cuddapah quartzites, deposit their alluvium. Much of 

 the mica deposits of Nellore are consequently concealed by sub- 

 recent and recent formations and will never probably be detected 

 although it seems likely, from the mica already raised, that the peg- 

 matites are more valuable than those of Bengal. Mining too, on 

 account of the flat surface, is generally more expensive than that per- 

 mitted though little practised, in the hilly ground of the Bengal mica 

 belt. An account of the methods pursued will be found in Chapter VI. 



The mica mines of this district have been worked for very little 

 more than a decade, and before the development of the industry the 

 country had been only cursorily examined. The general geological 

 features were mapped and described in outline by the late Dr. W. King 

 in 1880. 1 Dr. H. Warth examined the mines being worked in 1891 

 and described the workings at Inikurti (Podalakur, 1^22' ; 79°48') 

 and Utkur (14 14' ; 79°48') in a special report to the Madras Govern- 

 ment. 2 The industry has, however, considerably developed since that 

 date, the mines now being worked numbering over 30. In 1898 the 

 writer, accompanied by Dr. Walker, made a tour through the 

 mining area, and the latter has since made a detailed examina- 

 tion of its geological features of which the following is a sum- 

 mary. 



Geology. — The region specially examined by Dr. Walker extends 

 from the fourteenth to the fifteenth parallel of north latitude, and from 

 about the longitude of Nellore west to the Veligondas, a width of thirty 



1 Mem. Geol. Surv. Ind., Vol. XVI, part 2. 



2 Proceedings of the Board of Revenue {Madras), No. 279, dated 10th June 

 1892. 



E ( 49" ) 



