1XXX1V PROCEEDINGS OF THE GEOLOGICAL SOCIETY, [vol. ixxiv, 



Archaean. In 1913, Holland added a group of post-Dharwar 

 eruptive rocks, and produced a classification of the pre- Cambrian 

 rocks of India which exhibits a remarkable parallelism with that 

 given by Lawson (1913) for the pre- Cambrian of Canada. 



The work of the Mysore Geological Survey from 1899 to 1914 

 had gradually eliminated the Fundamental Gneissic Complex, and 

 shown that within the area of the Mysore State — representing 

 some 29,000 square miles of the Archaean complex — the oldest 

 rocks were the Dharwar System, which had been intruded into by 

 at least four successive granite-gneisses, namely : the Champion 

 Gneiss, the Peninsular Gneiss (forming the greater part of the 

 area), the Charnockites, and the Closepet Granite Series. If we 

 compared this succession with Holland's 1913 classification, without 

 assuming any real correlation with the Canadian rocks, but viewing 

 the Dharwar rocks as Huronian, as suggested by Holland, then his 

 post-Dharwar eruptive series (Algoman) included the whole of 

 the gneisses of Mysore, while equivalents of the Laurentian and 

 Ontarian formations were wanting. On the other hand, if the 

 Dharwar rocks were regarded as Keewatin, then the gneisses of 

 Mysore might represent Laurentian and, possibly, Algoman 

 formations, while representatives of the Huronian would be non- 

 existent. Obviously, therefore, the Mysore Archaean succession 

 was either very incomplete, or it did not fit in with the classi- 

 fications of Holland and Lawson. It was to be remembered 

 that Holland's classification dealt with a much wider area than 

 Southern India, and the essential problem appeared to be whether 

 his ' Bundelkund Gneiss' (Laurentian) and the Bengal gneisses 

 (Keewatin) were really older than, and unconformable to, the 

 Dharwar System — as represented by him — , or whether they were 

 post-Dharwar eruptives corresponding to portions of the Mysore 

 gneissic complex. In favour of the latter view it was noted that 

 observers acquainted with both have appeared to recognize the 

 Bundelkhand and Bengal types of gneisses in and around Mysore, 

 and that all of these gneisses have, until recently, been regarded 

 as forming part of the great Fundamental Gneissic Complex of 

 India. 



The Lecturer then described the map of Mysore, which, on a 

 scale of 8 miles to the inch (1 : 506,880), presented a simplified 

 summary of the work of the Mysore Geological Survey. On 

 lithological grounds the Dharwar System Avas divided into an 

 Upper and a Lower Division. The former was composed largely 

 of basic flows and sills with their schistose representatives. 

 Whether some of the chloritic schists, slates, phyllites, and argil - 

 lites were of secondary origin was still doubtful. In the series 

 as a whole, chlorite predominated, and hornblende was subordinate. 

 The presence of carbonate of lime, magnesia, and iron was a 

 strikingly prevalent feature. The Lower Division was composed 

 of dark hornblendic epidiorites and schists, which were distinguish- 

 able from the greenstones of the Upper Division by their dark 

 colour and by the practical absence of chlorite. Many of the 



