A FORM OF MULTIPLE ROCK DIAGRAMS 623 
of interest to try’ first an arrangement in the order of increasing 
albite, and then in the order of increasing anorthite, and so on. 
The sequence and the exceptional rocks are noted in the process of 
arrangement even more readily than in the photographs. 
Attention may be called to certain significant points shown by 
the diagrams (Figs. 1, 2, and 3). Norms were selected at random 
Fic. 1.—A multiple diagram of a series of rocks from the Alaskose subrang in 
the quantitative classification. The predominance of quartz and alkali feldspars is 
clear. 
in the subrangs in the quantitative system. The contrast in the 
three pictures is evident; so also is the relative uniformity in the 
norms of a single picture. A further remark is to be made in this 
regard, however. ‘The uniformity is clear in the first two but not 
so clear in the third. This group of rocks is from the class of 
salfemanes; that is, salic and femic minerals are present in about 
equal amounts. Salfemanes are grouped according to the relations 
