PETROLOGICAL ABSTRACTS AND REVIEWS 477 
Wittrine, E. A. “Uber Kristallwinkel bei verschiedenen Tempera- 
turen,’’ Sitsb. Akad. Wiss. Heidelberg, 1913. A-—21. Pp. 5, 
figs. 2. 
In the determination of the changes produced in crystal angles it 
is sometimes necessary, on account of the irregular natural faces, to grind 
artificial faces. The present paper deals with the question as to the 
most advantageous angle at which they should be cut, and the con- 
clusion is reached that this is 45° with the base. If possible it is better 
to measure across the base from one pyramidal face to another, thus 
(101) to (101). 
WULFING, E. A., and OPPENHEIMER, L. “Neue Untersuchungen 
an Cordierit,” Sztzb. Akad. Wiss. Heidelberg, 1914, A-—tio. 
Ppa ken Wes. 1. 
New determinations on cordierite from eight localities. 
Witrine, E. A., and Horner, F. “Die kristallographischen 
Konstanten des Stauroliths vom St. Gotthard,” Sztzb. Akad. 
Wiss. Heidelberg, 1915, A-10. Pp. 11. 
Gives new determinations of interfacial angles and axial ratios. 
Wttrinc, E. A. “Lassen sich die kristallographischen Funda- 
mentalwinkel der Plagioklase mit der Zusammensetzung in 
gesetzmassige Beziehung bringen ?”’? Sztzb. Akad. Wiss. Heidel- 
DEV Ee OLS: A132.) Jep. 245 tgs. 0: 
New determinations of crystallographic properties make it possible 
to say with certainty that these properties follow a definite law. 
ZIEGLER, VicToR. “The Minerals of the Black Hills.” Bull. zo, 
South Dakota School Mines, 1914. Pp. 255, map 1, pls. 30, 
figs. 26, bibliography. 
In this bulletin the writer describes briefly, for the benefit of the 
miner, prospector, and student, all the minerals known to occur in the 
Black Hills. There are included three very good tables for the mega- 
scopic determination of the minerals, as well as many full-page illustra- 
tions. 
The book should be of great value to everyone working in the 
Black Hills region. 
