SUMMARY. 247 



The following points of revision suggested by recent work are 

 purely local in their effects: — (1) The magnetic iron-ore beds and 

 associated hornblendic gneisses in the southern parts of Madras are 

 probably altered representatives of the hematitic quartzites and 

 chloritic or hornblendic schists of the Dharwar system. (2) Certain 

 exposures in South India hitherto grouped with the gneisses are now 

 separated and regarded as later intrusives, old enough, nevertheless 

 to be themselves foliated in the same general directions. They are 



(a) the charnockite series, 



(b) the elaeolite-syenites and augite-syenites of Coimbatore, 



(c) the porphyritic augite-syenites and segirine-granites of 



Salem, 



(d) the central granite and the norite masses of Coorg. 



In addition to the above, the old rocks of South India are 

 traversed by intrusive rocks sufficiently young to have escaped 

 sensible deformation, namely, 



(e) the mica-bearing pegmatites of Nellore, 

 (/") the Sankaridrug and Namakal granite, 



(o) the older diabase dyke rocks generally following the folia- 

 tion lines and often slightly amphibolized. 

 Still later than these there are intrusives quite independent of 

 the foliation directions, and altogether undisturbed by mechanical 

 movements, namely, 



(h) peridotite masses, quartz bosses and quartz-barytes veins, 

 (i) olivine-norite, augite-norite and diabase (augite-diorite) 



dykes of presumably Cuddapah (older palaeozoic) age, 

 (J) olivine-norites and diabases of presumably Deccan Trap 

 age. 

 There is direct evidence in favour of regarding the charnockite 

 series as younger than the two divisions of the gneisses and of 

 the schists which are considered to be the altered equivalents of 

 some of the Dharwars. There is also proof that the charnockite 

 series is older than the groups h ) i and /, and probably older than 

 K ( 129 ) 



