ARCHAEAN. 



43 



If this observation were confirmed, it would of course settle the 

 question of the sedimentary origin of the limestone, and consider- 

 ably strengthen the argument in favour of the organic origin of the 

 graphite ; but I am informed by Mr. Hayden, whose report on this 

 tract has not been published, that he is not convinced that the 

 conglomerate was actually in situ at the base of the limestone, 

 and that what he saw was piobably a superficial boulder deposit, 

 cemented by calcareous matter ; and as I know, from my own 

 experience, that such superficial deposits of what is to all appear- 

 ance a hard and ancient conglomerate are not uncommonly to be 

 met with in the stream beds, especially along the western edge of 

 the Shan plateau ; and that, in some cases, the detection of their 

 real character, and of the fact that they are not interbedded with 

 the older rocks, is not easy, I think it would be unwise to lay too 

 much stress upon the observation quoted by Mr. Griesbach, without 

 further investigation of the facts. 



Regarding the age of these ancient crystalline rocks, it seems 



Age of the gneiss to me that we ma F be dealing with two 

 and crystalline lime- systems belonging to very different periods. 

 stones ' The similarity between the complex of crys- 



talline limestones, pyroxene and scapolite gneisses, and granulites 

 of the Ruby Mines with some of the developments of the Dharwar 

 system of the Indian Peninsula is very marked. I have already 

 alluded to Dr. Fermor's account of the crystalline limestones occur- 

 ring in the Dharwars of the Chhindwara district in the Central 

 Provinces, 1 and a perusal of his paper will show that the char- 

 acters and relations of the rocks in the two areas are almost 

 identical. In both districts we have a series of crystalline lime- 

 stones closely associated with quartz pyroxene gneisses and calci- 

 phyres, forming lenticular bands imbedded in biotite gneisses, which 

 latter, in Chhindwara, Dr. Fermor looks upon as being the most 

 ancient rocks of the area. The parallel is completed by the fact 

 that in both areas the rocks are intersected in every direction by 

 veins of graphic granite or pegmatite. It seems probable, therefore, 

 that the biotite gneisses should be referred to one of the lower 

 divisions of the Archaean group, while the limestones and associated 

 pyroxene gneisses, etc., may be considered to belong to the 

 Huronian system, with which the Dharwars of the Indian peninsula 



1 Records, Geol. Surv. Ind., Vol. XXX1I1, Pt. 3, p. 159. 



