CLA SSIFICA TION OF IGNEO US RO CKS 559 



Texture is considered of minor importance in classification, 

 and is taken into account after the chemical and mineral 

 composition. 



Nomenclature. — The system demands an entirely new nomen- 

 clature, and it has been sought to introduce this according to a 

 definite system, the lack of which is so painfully evident in the 

 present nomenclature. 



The nomenclature proposed consists of three parts : primarily 

 of substantive names for the magmatic units, implying the chem- 

 ical composition and the norm, or sta?idard mineral composition; 

 secondarily, two sets of adjective terms to be used to qualify the 

 magmatic names ; one set referring to the actual mineral com- 

 position, or mode, and the other to the texture of the rocks. 



The magmatic name consists of a root, derived from a geo- 

 graphical name in all cases except for the names of Classes and 

 Subclasses, and of a suffix. The suffixes are so chosen as to 

 vary in a definite way with the division of the system to which 

 the magmatic name belongs. Thus for Class, Order, Rang, and 

 Grad, the letters n, r, s, and / in alphabetical order are used 

 with the vowel a, giving in English ane, are, ase, ate. For Sub- 

 class, Suborder, etc., the vowel is changed to o, giving one, ore, 

 ose, ote. 



The roots forming the names for classes are sal and fern, 

 mnemonic of the salic and femic minerals constituting their 

 norms, and are combined with prefixes yielding the following: 

 Persalane, Dosalane, Salfemane, Dofemane, and Perfemane. 



The roots for the names of the divisions smaller than Class 

 are derived from the names of geographical localities, and as 

 far as possible from those at present in use for rock names, 

 advantage being taken of their connotations as to magmatic 

 character. 



The authors propose a nomenclature for field use based on 

 purely megascopic characters. 



The work concludes with a discussion of methods of calcu- 

 lating mineral composition from chemical composition and the 

 reverse, and presents tables to aid such calculations. 



