PETROLOGICAL ABSTRACTS AND REVIEWS 285 



texture, age, metamorphism, and classification. Three additions of 

 moment are noted. These are discussions of (1) gases, based principally 

 on the work of Gautier without reference to that of R. T. Chamberlin; 

 (2) the relation of size of grain to the temperature in a cooling intrusive 

 mass, based on Professor Lane's paper; (3) applicability of the phase 

 rule to the complex hydrous and gaseous solutions of more or less dis- 

 sociated material of the magma which is not an arbitrary mixture but 

 such that when computed water free contains 184 molecules. 



The systematic description of the igneous rocks divides them into 

 three major groups — deep-seated, dike, and effusive — as formerly. The 

 groups, in turn, are divided into 10 families, three subgroups, and 14 

 families respectively. Each family is described with respect to its 

 mineral and chemical composition, texture, subdivision, geological 

 occurrence, and distribution. 



The discussion of deep-seated rocks shows careful revision and the 

 incorporation of many of the results of the recent investigations. 

 The systematic treatment is conspicuously modified by placing the dis- 

 cussion of the Peridotites last and by the expansion of the chapter on 

 Ijolite and Missourite into two chapters entitled "Missourite and 

 Fergusite" and "Ijolite and Bekinkinite." Less conspicuously there is 

 introduced the far more fundamental conception of the division of the 

 deep-seated rocks into three great series by the elevation of the Charnock- 

 ite-Maugerite-Anorthosite series to equal rank with the better known 

 alkali and alkali-lime series. The new series is characterized as follows: 



Charnockite-Anorthosite Series. — The rock series based upon gradations 

 in composition and association in the field passing from Granite through 

 Syenite and Diorite to Gabbro — the lime-alkali series — and that from alkali 

 granite through alkali syenites to Essexites, the alkali analogue of the gabbro — 

 the alkali series — have been well recognized. There have, however, in these 

 series been certain members lacking, e.g., the alkali analogue of the Diorite 

 and the lime-alkali analogue of the Nephelite syenite. 



Each of the series has its own areas of occurrence and the different members 

 of a series are usually intimately related in occurrence while members of the 

 alkali series never occur in regions of lime-alkali rocks. 



We find now among the Plutonic rocks, a type whose mineral composition 

 is of the same sort as the gabbro — the anorthorite and labrador fels — which, 

 notwithstanding its chemical character and association, varies throughout 

 from the gabbro. This anorthorite type we find in association with the 

 hypersthene granite or charnockite, and here, moreover, the silica-rich char- 

 nockite is connected by a number of intermediates with the silica-poor anortho- 

 sites, so that we may speak of a charnockite-anorthosite series which even has 

 peridotite or pyroxenic end members 



The number of occurrences of rocks of the charnockite series is, on the 



