632 CROSS, IDDINGS, P IRS SON, WASHINGTON 



Examples. — To illustrate the methods proposed, the follow- 

 ing examples may be given, especial stress being laid on the 

 possibility of expressing the exact amount of knowledge which 

 is at hand or is to be conveyed. 



1. The typical monzonite of Brogger, from Monzoni — an 

 evenly granular, phaneric rock, composed, as seen in the field, 

 of dominant feldspars, with only traces of quartz, considerable 

 pyroxene, hornblende, and less biotite, with insignificant amounts 

 of magnetite and apatite. 



From the analysis by V. Schmelck 1 the following norm is 

 calculated : 



Orthoclase - - - - - 26.1 ) 



Albite 26.2 I 68. 1 



Anorthite 15.8) 



Diopside ------ 18.4 ) "] 



Hypersthene - - - - 3 . 3 >- 24 . 5 j 



Olivine 2.8) I 



Magnetite - - - 5.3 / g i [ 3I \ 9 



Ilmenite - - - - - 0.8 \ 



Apatite 1.3 1.3 J 



100. o 



The rock belongs, therefore, to Class II, the dosalanes, with 

 salic minerals dominant over femic, and this is evident even in 

 the field. 



Since, among the dominant salic minerals, neither quartz nor 

 feldspathoids (lenads) are present, it belongs to the fifth Order, 

 and is consequently, gcrmanare. This, likewise, can be deter- 

 mined from the megascopic examination. 



On referring to the analysis it is seen that the alkalies are to 

 lime in normative anorthite as the ratio 0.097: 0.057= 1.70. The 

 rock, therefore, belongs to the second Rang, the domalkalic, to 

 which we have given the name of 7nonzo?iase. This, and the fol- 

 lowing points, could not be determined in the field. 



As K 2 0' : Na 2 0' :: 0.047: 0.050, the two are in nearly equal 

 amount, and the Subrang is thus the third, sodipotassic, which 

 we have called mo?izonose . 



We have thus characterized the rock completely, as far as 

 the dominant minerals are concerned. Taking up the subordi- 



1 W. C. Brogger, Eruptivgest. Kristianiageb. Vol. II, p. 24, 1895. 



