r76 NEW YORK STATE MUSEUM 



perthite, the ratio of eoda to potash will remain substantially a» 

 it is in the syenites. 



The gabbro'S and anoTthosites are quite normal representatiyes 

 of these groups. But in the transition rocks between theee and 

 the syenices we find low magnesia, low ratio of lime and mag- 

 nesia to alkalis, and approximately equal amounts of soda and 

 potash^ and these characters continue to the end of the series. 

 The soda-potash ratio is a slow'ly changing one, the potash being 

 at first below, but eventually overhauling and passing the soda 

 in the more acid rocks. In these respects the syenites, and prob- 

 ably the grandtes, depart somewhat from the corresponding rocks 

 of the Ekersund-Soggendal area in Xorway, w^hich also accom- 

 pany anorthosite and gabbro, and which Kolderup has so exhaust- 

 ively described. In general the Adirondack syenitic rocks run 

 higher in the alkalis and lower in lime and magnesia than the 

 corresponding Norwegian rocks. These differences are but slight, 

 and the general agreement between the two series is very close, 

 but they point to a slight original difference in the character of 

 the parent magma of the two districts. The appended analyses 

 bring this out clearly. 



1 2 :j 4 5 6 



Si02 57 57.11 63-45 64.35 68.5 70.33 



AI2O3'. 16.01 17 18.38 15.46 14.69 15.59 



FesOs ^ .42^ 1.34 1.4 



> 10.3 12.48 > 7.5 



FeO J 3.56J 3.25 1.54 



MgO 1.62 1.78 .35 .5 .26 1.3 



CaO 6.2 3.99 3.06 3.58 2.2 3.05 



Na20 4.35 3.96 5.06 3.28 3.5 4.5 



K2O 3.53 2.59 5.15 3.54 5.9 1.29 



H2O 15 3 4 



Ti02 '. 1-59 .07 1.63 85 



Zr02 MnO.l .24 



BaO .13 05 



Total 99.16 100.5 99.73 99.84 100.22 100.09 



1 Basic syenite from Natural Bridge; 7 of previous table. 



2 Monzonite from Fuldland near Farsund. Description and analysis by 



C. F. Kolderup. Die labradorfelse (les westlichen Norweg.ens, Be'rgens 

 museums aarbog. 1896. p. 129. 



3 Augite syenite from Loon lake; 11 of previous table. 



