1*8 HOLLAND: CHARN0CK1TE SERIES. 



CHAPTER III. 

 Nomenclature. 



So far as we know, the rocks described in this paper are of 

 Archaean age and have as their nearest foreign equivalents the rocks 

 known to the German petrographers as " pyroxene granulites " 

 and to the French as '* pyroxene gneisses". Although their pre- 

 dominating features are those which characterise the {C pyroxene 

 granulites, " they also show points of resemblance to certain varieties 

 of the il norites " of Scandinavia and sometimes to the " anorthosites " 

 of Canada, besides possessing peculiarities of their own. But whether 

 the rocks now under consideration ultimately prove to be the equi- 

 valents of anyone or all of the above-mentioned foreign groups is 

 at present difficult to determine : the important point for us is that 

 within the limits of Peninsular India they form a distinct and very 

 large subdivision of our old crystalline rocks, possess a very well 

 defined series of characters and present a constant relation to the 

 older gneisses; in fact, they constitute a distinct petrographical 

 province, which we propose to distinguish by a special name in our 

 literature, and, when possible, by a special colour on our maps. 



The name chamockite series, which we now commonly em- 

 ploy for these rocks in India, expresses the fact that we group to- 

 gether in one petrographical province a number of lithical types 

 genetically related to chamockite (vide infra } p, 134) and to one 

 another. Within this petrographical province there are petrical and 

 lithical forms which vary from the acid chamockite to the ultra-basic 

 pyroxenite ; but any one who has studied the group in the field would 

 readily recognise the consanguinity of the different members, and 

 indeed would often find it difficult, without the aid of the specific 

 gravity balance or the microscope, to distinguish an acid from a basic 

 variety. 



Our name chamockite series thus enables us to bring together 

 a set of genetic relatives, which, by the ordinary systems of 



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