Editorial Comment. 51 
by adjective terms, referring to mode or actual mineral com- 
position and texture. 
The magmatic name adopted consists in each case of a root 
derived from a geographical name, except for those of classes 
and sub-classes, and of a suffix, the suffixes themselves being so 
chosen as to vary in a definite way with the division of the sys- 
tem to which the magmatic name belongs. Thus, for class, 
order, rang, and grad, the letters n, r, s, and t, in the order 
given, are used with the vowel a } giving in English the term- 
ination ane, are ase, ate. For subclass, suborder, etc., the vow- 
el is changed to 0, giving one, ore, ose, ote. 
In calculating the standard minerals, their amount and 
kinds, a method has been developed of considering first, the 
chemical composition of the rocks and from this calculating the 
standard minerals, and then considering the actual mineral 
composition, the standard mineral composition being rendered 
necessary by the fact that all igneous rocks are not holocrys- 
talline. 
The work is so concisely written that, to illustrate in detail 
the methods employed, would practically amount to an entire 
reprint. A partial attempt may, however, be here made. Thus, 
it is proposed to divide the igneous rocks into five classes, ac- 
cording to the calculated proportions of the standard mineral 
groups, which, as already stated, are designated as sal and fern 
in the formula, the prefix sal being the abbreviated form of 
silica-alumina and femoi ferric-magnesian. 
The various classes, then, would be expressed by the for- 
mulae given below, written according to the relative abundance 
of the salic and femic minerals. The class name as given fol- 
lows the formula. For the purpose of further illustration the 
reader is here referred to the table on page 52. 
~, T sal 7 .. 
Class I: 7 > — persahc. 
tern 1 r 
Class II: -, < — > — dosalic. 
fern 1 3 
Class III: -^— < — > — salfemic. 
fern 
:> d 
Class IV: ^— < — > — dofemic. 
fern 
sal 
fern 
Class V: 7 — < — perfemic. 
