476 PETROLOGICAL ABSTRACTS AND REVIEWS 
WRIGHT, FRED. EUGENE. ‘The Accurate Measurement of the 
Refractive Indices of Minute Crystal Grains under the Petro- 
graphic Microscope,” Jour. Wash. Acad. Sci., V (1915), 101-7. 
Considers the conditions necessary for the exact measurement of 
refractive indices of minute crystal particles by the immersion method. 
WRIGHT, FRED. EUGENE. ‘‘A New Crystal-Grinding Goniometer,” 
Jour. Wash. Acad. Sci., V (1915), 35-41. 
Describes the precision goniometer used in the Geophysical Labora- 
tory, which is capable of grinding a plate to within 1’ of the required 
position. 
Wricxt, FreD. EUGENE. ‘Obsidian from Hrafntinnuhrygghur, 
Iceland. Its lithophysae and Surface Markings,” Bull. Geol. 
Soc. Amer., XXVI (1915), 255-86, figs. 12. 
The writer cee the formation of spherulitic, lithophysal, and 
pumiceous structures in the obsidians of Iceland, as well as certain mark- 
ings produced by the etching effect of hot volcanic gases. 
WRIGHT, FRED. EUGENE. “The Position of the Vibration Plane 
of the Polarizer in the Petrographic Microscope,” Jour. 
Wash. Acad. Sci., V (1915), 641-44. 
The writer concludes that there is a slight practical advantage in 
having the plane of vibration parallel to the vertical cross-hair. 
WRIGHT, FRED. EUGENE. ‘“‘A Simple Device for the Graphical 
Solution of the Equation A=B.C,” Jour. Wash. Acad. Scz., 
VI (1916), 1-5. 
Describes a device by means of which certain formulae may be solved 
by the use of a series of scales. 
WRIGHT, FRED. EuGENE. ‘‘A Geological Protractor,”’ Jour. 
Wash. Acad. Sci., V1 (1916), 5-7. 
A device for solving various problems, such as the slope of any bed, 
in the field. 
Witrine, E. A., and Becut, K. ‘‘ Uber neue Turmalinanalysen,” 
Sitsb. Akad. Wiss. Heidelberg, 1913. A-—20. Pp. io, analyses. 
