TRACHYTE ON THE ISLAND OF HAWAII 



521 



brings out the fundamental chemical relations of these varied rocks 

 and their positions in the Quantitative System of Classification. The 

 current names assigned to these rocks are those of the authorities 

 quoted. 



The nordmarkose-umptekose rock of Hawaii is shown by the 

 table to be nearly akin in its chemical characters to other rocks of 

 varying occurrence and texture in widely separated parts of the 

 world. The textural differences and those due to the distinguishing 

 roles played by quantitatively subordinate constituents have led to a 

 variety of names, obscuring the fundamental similarity of the magmas. 



Considering the trachyte of Puu Waawaa as a possible differen- 

 tiate of an underlying parent magma, it is interesting to note that the 

 associations of the chemically similar rocks of the table are widely 

 different. Several of the rocks compared belong in the grorudite- 

 tinguaite series described by Brogger from the Christiania region of 

 Norway.' Others are from the similar petrographic province of 



NORMS OF ROCKS COMPARED WITH THE HAVi^AIIAN TRACHYTE. 



I Die Eruptivgesteine des Kristianiagehietes, "Die Gesteine der Grorudit-Tin- 

 guait-Serie" (Kristiania, 1894). 



