482 PETROLOGICAL ABSTRACTS AND REVIEWS 



the freshness of the other constituents present, the analcite is probably 

 primary. However no such an argument applies to the analcite of the 

 Rathjordan basalt as the rock is much altered. The author suggests that 

 possibly this rock was originally a leucite basalt and that the leucites have 

 been subsequently altered to analcite. 



Clarence W. Russell 



Ransome, F. L., Emmons, W. H., and Garrey, G. H. "Geology 

 and Ore Deposits of the Bullfrog District, Nevada," Bull. U.S. 

 Geol. Survey, No. 40^, 1910. Pp. 130. Figs. 20, PI. 13. 



Two areas of pre-Tertiary crystalline rocks are described. The first 

 consists of quartzite, quartz-biotite and quartz schist, grading through 

 calcite schist into nearly pure marble. A few pegmatite veins and a larger 

 number of quartz veins cut the schists. The schists are overlain by lime- 

 stone presumed to be Silurian. 



In the second area the crystalline complex consists chiefly of quartz- 

 biotite injection schist, pegmatite, and augen gneiss. A "sheared diorite" 

 is thought to be a dike which cut the sedimentaries previous to their meta- 

 morphism. A quartz diorite dike cuts the schists and pegmatite and 

 with them is cut by a subsequent diorite dike. 



The Tertiary volcanic rocks are described as consisting of sixteen 

 rhyolite flows, five basalt flows, one flow of quartz latite and one of quartz 

 basalt, two sedimentary tuffs, an intrusive rhyolite porphyry, dikes of 

 plagioclase basalt and an intrusive leucite basanite. This rock falls into 

 a subrang of the quantitative classification which has not been previously 

 represented by an analysis from the United States. Five analyses of Ter- 

 tiary igneous rocks of the region are included in the report. 



The Introduction and the Economic Geology section are by Ransome; 

 the General Geology section by Emmons and Garrey. 



Albert D. Brokaw 



Travis, C. "On the Behavior of Crystals in Light Parallel to an 

 Optic Axis," Am. Jour. Sci., 4th ser., 1910, XXIX, 427-34. 

 Figs. 2. 



A mathematical explanation of the fact that a section of a biaxial 

 crystal cut normal to an optic axis appears uniformly illuminated in parallel 

 light between crossed nicols. The author concludes: (i) Interior conical 

 refraction, in a strict sense, plays no part whatever as a cause of the phe- 

 nomenon; (2) The cause is to be found in the fact that so-called parallel 



