PETROLOGICAL ABSTRACTS AND REVIEWS 645 



ScHEURiNG, Georg. "Die mineralogische Zusammensetzung der 

 deutsch-siidwest-afrikanischen Diamantsande," Beitrdge z. 

 Geol. Erforsch. d. Deutschen Schutzgehiete, Hf. I, 1914. Pp. 49, 

 map I, fig. I. 



Describes the minerals associated with the diamond in German Southwest 

 Africa. Of petrographic interest from the description of a separating appar- 

 atus which might possibly be applied to the prehminary separation of rock 

 constituents. 



ScHLOSSMACHER, K. "Zur Erklarung der Becke'schen Linie," 

 Centralbl. f. Min. Geol., etc. (1914), 75-79, figs. 2. 

 A theoretical discussion of the Becke line. The writer shows that with 

 vertical contacts the phenomenon is to be explained by Snell's law; with 

 incUned contacts between minerals the effects are more complex, and may be 

 accounted for in part by the explanation given by Grabham. 



