RECENT ADVANCES IN SCIENCE 219 



of the geology of Finmark, the most northern province of 

 Norway. There is a short resume in English. 



Numerous important papers on the stratigraphy of various 

 areas in the western United States have appeared recently 

 (see list in Bibliography at end of article), but as the writer 

 has not seen them it is not possible to offer any comment. 

 The reader is referred to a review by C. Schuchert (Amer. Journ. 

 Set. 1 91 9, 47, 74-9), for a discussion of the salient points in 

 this new work. 



W. G. Foye has recently made an extensive geological 

 study of the Fiji Islands, the work embracing both general 

 geology and coral-reef problems. The larger islands of Viti 

 Levu and Vanua Levu have central cores of deeply eroded 

 plutonic rocks, which are believed to be the remnants of an 

 ancient continental mass. There have been four periods of 

 volcanic activity in the islands, with the eruption first of 

 rhyolites, then two series of andesites, and finally basalts. 

 Two series of sedimentary rocks occur. One, early in the vol- 

 canic period, is believed to be of Miocene age. Later coralli- 

 ferous limestones and marls are probably post-Tertiary, and 

 are intruded by the latest basalts (" Geological Observations 

 in Fiji : Part I., Geological History of Fiji," Proc. Amer. Acad. 

 Arts & Set. 191 8, 54, 1-95). 



Petrology of Igneous Rocks. — -In a paper entitled " A Type 

 of Igneous Differentiation," F. F. Grout discusses the rocks of 

 the great Duluth gabbro mass, probably the largest mass of 

 basic igneous rock known (Journ. Geol. 191 8, 26, 626-58). The 

 rock types fall into two groups, one related to the gabbros, the 

 other to the granites, intermediate types being rare. The 

 sharpness of the separation between the two groups is shown 

 by means of variation diagrams. It is believed that none of 

 the theories of crystallisation-differentiation can fully explain 

 this separation, since they all necessitate the presence of a 

 relatively large amount of intermediate rock. The field and 

 laboratory studies strongly suggest an immiscible separation 

 of the " red rock " (granophyre) from the gabbro. The varia- 

 tions within the gabbro itself, from magnetite-gabbro to anor- 

 thosite, are believed to be due to differentiation by crystallisa- 

 tion during convection, aided by a slight amount of settling 

 of crystals. 



Many problems in the crystallisation of silicate melts are 



