552 W.CROSS, J. P. IDDINGS, L. V. PIRSSON, H. S. WASHINGTON 
are unnecessary, such as those for presodic subrangs of percalcic 
rangs, viz: Caledonose and Ouenose. 
Recently O. C. Farrington has applied the quantitative system 
to the classification of stony meteorites, and has suggested 41 new 
names in conformity with this system, most of them in Classes IV 
and V, and in subclasses characterized by prominent amounts of 
metallic minerals. In several cases in which meteorites belong to 
magmatic divisions already named for rock magmas Professor 
Farrington has given new names for meteoric magmas in order to 
distinguish the two groups of bodies.’ 
MODIFICATION OF THE FORMATION OF RANGS AND SUBRANGS IN 
CLASSES IV AND V 
Owing to the fact that the alkali-bearing femic molecules, 
NaFe(SiO,)., Na,SiO;, and K,SiO,, are not present in rocks of 
Classes IV and V in sufficient amounts to necessitate the recogni- 
tion of the femic alkalies in establishing rangs in these classes, 
although it is conceivable that rocks composed almost wholly of 
acmite may occur, it is advisable to shift the position of femic 
alkalies, Na,O’’K,0”, in the arrangement of the base-forming 
components for the formation of rangs and subrangs. Comparison 
between them should be made as follows: 
MgO+F Na.O”+K.0” 
Rangs, according to the ratio Bae = us 
MgO 
FeO+ (Na,0”+K,0”) 
Subrangs according to 
F ee FeO 
Sections of subrangs, when needed, according to Na,O”+K,0” 
Subsections of subrangs, when needed, according to Ko" 
For all rocks so far known, sections and subsections of subrangs in 
these classes are not needed and may be neglected. When notice- 
ably alkalic prefemic rocks are found, their place in the system is 
provided for. By this change the symbols for magma divisions 
in Classes IV and V are simplified in all cases so far known, by the 
‘ Farrington, O. C., Field Museum of Natural History, Chicago, Pub. 151, Geol. 
Ser., Vol. III, No. 9, tort. 
