PETROGRAPHICAL EVIDENCE IN SOUTH INDIA. 233 



bours as the results of endogenous contact action, due to the 

 absorption of lime from the calcareous rocks which have become 

 invaded ; but the field observations are of too fragmentary a nature 

 so far, to permit safe criticism of this point. And unfortunately for this 

 apparently simple conclusion the elaborate study by Professor Judd 

 of the similar rocks in Burma has led to results which rather indicate 

 that the calciphyres are the results of extreme alteration of the 

 pyroxenic rocks, the formation of the scapolite being merely a stage 

 in the process. Professor Judd is, at the same time, inclined to con- 

 sider the pyroxene-granulites, which are associated with, and possibly 

 in part changed to, the scapolitic and crystalline limestones, to be of 

 igneous origin. 1 



Although, therefore, the results obtained by Professor Judd 

 necessitate the exclusion of these scapolitic rocks and crystalline 

 limestones from the category of contact products until the field 

 relations for each particular occurrence have been studied in detail, 

 they are not antagonistic to the arguments here advanced in favour 

 of the igneous origin of charnockite series. 



The phenomena which we can safely regard as unequivocal 

 contact effects caused by intrusion of the charnockite series are 

 thus very meagre ; but it is very interesting to notice that few as they 

 are they are remarkably similar to contact phenomena produced by 

 the intrusion of pyroxenic rocks whose igneous nature is now dis- 

 puted by no one. 



In the case of the Cortlandt series, for example, the late G. H, 

 Williams has traced out the action of the norites and related diorites 

 on the associated crystalline schists. The intrusive rocks grouped 

 together in this area cover some 25 square miles, and are surrounded 

 by different crystalline rocks — gneiss on the north, limestone on the 

 west and mica schist to the south. The gneisses are not noticeably 

 affected at the contact ; but the mica schists and limestones are 

 strikingly altered, The contact phenomena are of an endogenous 

 (inverse) as well as of an exogenous (everse) kind. In the case of the 



1 " The Rubies of Burma and associated minerals, " Phil. Trans., Vol. 187 (1896), p. 151. 

 12 ( 115 ) 



