Petrological Abstracts and Reviews 



Edited by ALBERT JOHANNSEN 



WiNCHELL, Alexander N. Directions for Laboratory Work in 

 Optical Mineralogy. Published by the Author, Madison, Wis., 

 191 1. Pp. 36. Wrappers. 



This very useful little pamphlet for laboratory use was first published 

 for students at the University of Wisconsin. It is now reprinted with 

 the omission of the original slide numbers but with blank spaces into 

 which may be written those of any collection of thin sections. Problems 

 are given in the use of the microscope for determinations by ordinary 

 light, parallel polarized light, crossed nicols with parallel light, and 

 crossed nicols with convergent light. Throughout the book references 

 to the proper pages in the author's Optical Mineralogy are given for the 

 explanation of the phenomena observed. 



A. J. 



WiNCHELL, Alexander N. Geology of the National Mining Dis- 

 trict, Nevada. Min. and Sci. Press, 1912. Pp. 16. 

 Describes various rocks occurring in Nevada. Suggests the name 

 auganite for "a volcanic rock consisting essentially of basic plagioclase 

 and pyroxene. The plagioclase is usually labradorite, but may be more 



basic Having provided the new name for rocks ordinarily called 



augite andesite, it is possible to use the latter name for rocks which are 

 actually varieties of andesite, and consist essentially of acid plagioclase 

 and pyroxene." The reviewer believes that augite andesite, in the past, 

 has been so used by most petrographers. Auganite, therefore, appears 

 to be suggested for olivine-free basalt, the dividing line between andesite 

 and basalt being plagioclase of the composition AbiAui. 



A.J. 



WoYNO, Tadeusz Jerzy. "Petrographische Untersuchung der 

 Casannaschieter des mittleren Bagnetales (Wallis)," Neues 

 Jahrb., XXXIII (1911), 136-207. 



The Casanna schists in the central Bagnetals consist of a complex of 

 metamorphosed rocks whose chief constituents are glaucophane, epidote, 



725 



