494 PETROLOGICAL ABSTRACTS AND REVIEWS 



rocks and tuffs. In the western part of the area are Middle Silurian lime- 

 stones, metamorphosed to marble. Younger than the marble for it contains 

 fragments of this rock, is the polymict conglomerate. It is probably a volcanic 

 conglomerate whose cement originally was a tuff. The "gray granite" of 

 Reuss is considered a pressed granite. 



The structure of the area indicates that the metamorphism must have taken 

 place in the upper part of the earth 's crust where one-sided pressure, low tem- 

 perature, and a considerable saturation with water were factors. The rocks 

 of the inner arch are more strongly compressed than those of the outer, but 

 the materials are of approximately the same kind. 



Koto, Bundjiro. "The Great Eruption of Sakura-jima in 1914," 

 Jour. Col. Sci., Imp. Univ. Tokyo, XXXVIII (1916). Pp. 237, 

 pis. 23, map I, figs. 46. 

 Sixty-eight pages of this elaborate report are devoted to petrography. The 

 descriptions are accompanied by 61 photomicrographs on 8 photogravure 

 plates, which are beautifiilly clear and of considerable help. The author states 

 that "the characterization of the rocks is merely of prehminary qualitative 

 nature." It is to be hoped that quantitative determinations may be published 

 later. The older lavas of the volcano are hypersthene-andesites, and are dull 

 black or light brown porous and light in weight; the later lavas are pitch black, 

 slaggy, and heavy, and are hypersthene-bearing pyroxene-andesites with spor- 

 adic olivine. The lavas of 1914 are also olivine-bearing hypersthene-andesites 

 and are like those of 1779. Among the inclusions in the lava are fragments 

 of earlier segregations, among them a lava composed principally of anorthite 

 (printed anorthosite by mistake on p. 191) with interstitial orthoclase (?). 

 This rock is called microtinite but deserves a new name, since microtinite as 

 described by Lacroix was neither a pure nor nearly pure anorthite rock. No 

 quantitative data as to the relative amounts of the two feldspars are given. 

 The name ceramicite is given to porcelain-like ejectamenta which contain cor- 

 dierite as the characteristic component. The other constituents are basic 

 plagioclase and colorless glass, with subordinate hypersthene. Quartz is said 

 to be totally wanting. With 23 beautiful photograwure plates, one may over- 

 look the muddy half-tones which disfigure the text. 



Kozu, S. (i) "The Dispersion Phenomena and the Influence of 



Temperature on the Optic Axial Angle of Sanidine from the 



Eifel;" (2) " The Dispersion Phenomena of Some Monoclinic 



Feldspars," Mineralog. Mag., XVII (1916), 237-52, 253-73. 



Many valuable determinations on the optic axial angles and dispersion in 



feldspars, which would be more valuable if chemical analyses of the materials 



used were given. 



