84 



ALBERT JOHANNSEN 



«u 



same order, though of different classes, are shown together, the 

 leucocratic rocks of Class i being represented by open circles, 

 the moderately dark rocks of Class 2 by dark circles, and the 

 dark rocks of Class 3 by triangles. The larger circles and triangles 

 indicate that a number of mode-analyses fall together at these 

 points. It will be seen that there are 32 families represented in 



Fig. 20, while in the 

 other three figures 

 there are only 24 to 

 the order, as ex- 

 plained above. 



In the following 

 list about 500 com- 

 puted rocks are ar- 

 ranged according to 

 their old names fol- 

 lowed by numbers 

 indicating their posi- 

 tions in the present 

 classification. No 

 rocks are given 

 having less than three 

 mode-analyses unless 

 of well-defined recent 

 rocks. The first fig- 

 ure in the following 

 numbers represents 

 the class, the second 

 the order, and the 

 third (or third and 

 fourth) the family. 



%t < 



Foids 



Fig. 22. — Rocks of Order 3 falling in Classes 1 to 3 



There are no orders in Families, o, 1, 6, 11, 16, 21, 26, and 31, 

 but since the rocks of these families are plotted in the double 

 triangles of Order 1, their positions may be indicated by the 

 figure 1. The figures in parentheses indicate the number of deter- 

 mined rocks which fell into that family. For example, 2123, 118, 

 422, 4210 represent respectively Class 2, Order 1, Family 23; 



