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ANNALS NEW YORK ACADEMY OF SCIENCES 



The variation diagram of the series (fig. 3) indicates a rather complex 

 relationship. The pyroxenites alone, however, are responsible for the 

 sharp curves; if they be disregarded, the variation curves of the several 

 oxides will be smooth and simple. This would seem to indicate that the 

 differentiation which led to the formation of the pyroxenites was of a 



Fig. 2. Diagram of the Relations of the more important Types of the Cort- 



landt Series 



peculiar character: that either they are derived directly from some other 

 type, as the norites, or else that the primal parent magma underwent 

 great changes between the times of intrusion of the pyroxenites and the 

 other rocks. 



An effort has been made to indicate under each type, in a general way, 

 some of the more suggestive points which the map brings out. Thus the 

 granites appear to have little connection with the main body, except as 



