EDITORIAL. 
With this number of the JourNAL there appears the first sec- 
tion of a series of articles of more than ordinary moment to 
petrographers. The initial article by Mr. Cross is the first 
installment of a historical review of the various systems of 
classification of igneous rocks developed in the nineteenth 
century. This essay is the result of a conscientious and critical 
study of petrographical classifications in their historical aspects, 
and presents an admirable synopsis of this complicated sub- 
ject. Quite by itself it will certainly be found of great service 
to students of petrography in furnishing them with a perspect- 
ive view of the growth of our present unsatisfactory system. 
The second part will appear in the next number of the JOURNAL. 
Aside from its inherent interest, a special value lies in its 
introductory relations to a still more important essay on “A 
Classification and Nomenclature of Igneous Rocks,” which will 
occupy the whole of the sixth number of the Journat. The 
system proposed in this article is the outcome of some years of 
collaboration by Messrs. Cross, Iddings, Pirsson, and Wash- 
ington, and represents the united judgment of these experi- 
enced petrographers. The system is radically different from 
those in present use, and the nomenclature is new. The self- 
abnegation shown by these four petrographers in merging their 
individual views and preferences in a common effort to produce 
a working system in advance of the present unsatisfactory one 
is a pleasant token of the healthful relations of petrographic 
workers. 
DCG. 
