INDIAN GEOLOGY. 129 



gneissic rocks ; and to this series he gave the name of 

 "Dharwar". 1 It forms long bands, or rows of elliptical 

 patches, which run from N.N.W. to S.S.E. ; and eco- 

 nomically it is of great importance, for all the quartz 

 reefs which bear gold in paying quantities occur within it. 

 Since quartz reefs are equally abundant in the gneiss, it is 

 most natural to suppose that the gold lay originally in the 

 Dharwar rocks and has since collected by some process of 

 " lateral secretion " in the reefs which now traverse them. 

 And since the Dharwars consist largely of lava-flows, we 

 may presume that the gold was brought up from below in 

 those flows. 



The Dharwar rocks invariably overlie the gneiss and 

 are evidently newer than the greater part of it ; but the rela- 

 tions of the two are not quite simple. Often near their borders 

 the Dharwar bands are penetrated by masses and veins of 

 gneissic rock ; and this alone is sufficient to suggest that 

 some parts of the gneissic system are eruptive and newer 

 than the rest. Subsequent researches have tended to con- 

 firm this view, and the matter awaits further investigation. 2 

 It is unfortunate that there are no detailed petrological ob- 

 servations on the gneiss of India except those of Lacroix, 3 

 which were based on collections made many years ago in 

 the Salem district. One of the most remarkable peculiari- 

 ties, which has been noticed by several observers in various 

 parts of India, is the abundance of hypersthene in these 

 rocks. 



In the Peninsula the oneisses and Dharwars are sue- 

 ceeded by a great thickness of unfossiliferous rocks, and no 

 remains of life appear in any beds older than the Gond- 

 wanas (Carboniferous- Jurassic), but in the Punjab an un- 



1 See especially R. B. Foote. " The Dharwar System, the chief auriferous 

 rock series in South India". Rec. Geo/. Surv. India, vol. xxi. (1888), p. 

 40; vol. xxii. (1889), p. 17. 



2 Referred to in Rec. Geo/. Surv. India, xxvi. (1893), p. 172; xxvii. 



(1894), p. 7. 



s "Contributions a l'etude des gneiss a pyroxene et des roches a werne- 

 rite." .Bu/l. Soc. Franc. Miti., 1889. Translated, so far as it relates to India, 

 in Rec. Geo/. Surv. India, xxiv. (1891), p. 155. 



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