82 PETROLOGICAL ABSTRACTS AND REVIEWS 



crust, petrogenic and metallogenic elements, comagmatic regions, chemical 

 composition and rock densities, and the relations between rock densities and 

 elevations of continents. 



Washington, Henry S. "The Granites of Washington, D.C.," 

 Jour. Washington Acad. Sci., XI (192 1), 459-70, fig. i. 



Two types of granite occur as intrusives in the granite-gneiss of the District 

 of Columbia, biotite-granite and muscovite-biotite-granite. Two new analyses 

 of the mode of the former are given. The mineral composition places it in 

 226, very near 225, orthogranite, of the reviewer's system. It contains 6 per 

 cent epidote besides the essential constituents indicated in the name. Two 

 new analyses are given of the two-mica-granite, but no modal percentages. 

 Both types show cataclastic texture. Epidote is developed in the portions of 

 the biotite-granite most metamorphosed, but is absent in the two-mica-granite. 

 It is said to be apparently wholly secondary. 



Washington, Henry S. "Obsidian from Copan and Chichen 

 Itza," Jour. Washington Acad. Sci., XI (1921), 481-86, fig. i. 



Describes two Yucatan obsidians, one black, the other brown, from imple- 

 ment cores and beads. Washington thinks both types of obsidian came from 

 the vicinity where found. The black obsidian is of the usual type, the brown 

 one, however, belongs to the alcalic series. 



Washington, Henry S . " The Lavas of the Hawaiian Volcanoes, ' ' 

 Hawaiian Annual for I g22. N.p. 192 1. 

 A popular article on the various Hawaiian lavas. 



Watanabe, Mantiro. "Cortlandtite and Its Associated Rocks 

 from Nishi-Dohira, Prov. Hitachi," Science Reports (Tohoku 

 Imperial University), Ser. Ill, Vol. I (192 1), pp. 33-50, figs. 4, 

 photogravure pi. i. 



Intruded in a region of biotite-schist and biotite-gneiss is a small body, 

 possibly a laccolith. The mass is made up of various types of rocks, all parts of 

 the same intrusion. The inner core is cortlandtite. Above this is hornblendite, 

 which is succeeded successively by thin layers of quartz-bearing-gabbro and 

 quartz-diorite. The cortlandtite consists of greenish hornblende poikilitic with 

 pyroxene (hypersthene and augite) and olivine in less amount, and accessory 

 biotite, apitite, ilmenite, zircon (?), and magnetite. The hornblendite (so 

 called) is a coarse granitoid rock, chiefly of dark minerals, hornblende, less 

 augite than the cortlandtite but more biotite, and finally an unnamed plagio- 



