part 1] PEOCEEDIXGS OF THE GEOLOGICAL SOCIETY. lxXXV 



greenstones and schists of the Upper Division appeared to resemble 

 Keewatin rocks of Lake Superior, such as the Ely Greenstone 

 Series (save that augite is conspicuously absent in the Mysore 

 rocks), and it had been suggested that the dark epidiorites, which 

 naturally crop out between the rocks of the Upper Division and 

 the intruding gneisses, might be merely metamorphosed portions 

 of the greenstones and chlorite-schists. This might be true in 

 some cases, but the independent existence of the dark hornblendic 

 rocks of the Lower Division was supported by the fact that they 

 do not exist in many places where the gneisses come into contact 

 with the greenstones ; that man} r of the former retain original 

 igneous structures, which would be unlikely to survive the chloriti- 

 zation and the subsequent change to epidiorite ; and, finally, that 

 the amphibolitization of the rocks of the Lower Division appears 

 to have been complete before the intrusion of the earliest of the 

 gneisses which, with its associated pegmatites and quartz-veins, 

 has developed secondary augite in the hornblendic rocks along 

 intrusive contacts. 



The Lecturer referred briefly to the autoclastic conglomerates 

 which were usually associated with intrusions of the Champion 

 Gneiss ; to the intrusive character of some of the quartzites or 

 quartz -schists; and to the evidence that the limestones were, parti}" 

 if not wholly, due to metasomatic replacement of other rocks by 

 carbonates of lime and magnesia. 



The Dharwar schists of Mysore contain a widely-extended series 

 of banded quartz-iron-ore rocks, very similar to those of the Lake- 

 Superior region, the origin of which has been the subject of much 

 discussion, and is still highly perplexing. Some of the earlier 

 American geologists considered them to be directly igneous in 

 origin ; but these views are now discredited, and replaced by an 

 interesting and ingenious theory of chemical precipitation from 

 liquids associated with subaqueous lavas. The Lecturer suggested 

 that some of these rocks might be pegmatitic intrusions of quartz 

 and magnetite, and that some might be the metamorphosed relics 

 of igneous rocks composed, in great measure, 'of highly-ferruginous 

 amphiboles (such as cummingtonite) or other chemically-allied 

 minerals. 



A short discussion followed, and the thanks of the Fellows 

 present were accorded to the Lecturer. 



Rock-specimens and microscope-sections of rocks from Mysore 

 were exhibited by Dr. W. F. Smeeth, M.A., A.R.S.M., F.G.S., in 



illustration of his Lecture. 



