SILVER AND GOLD, CONTINUED. 237 



younger diabase, so called, of the sub-surface dike was identical with 

 the rock elsewhere occurring on the surface and called basalt, and 

 was really a basalt, owing its holocrystalline character to its depth ; 

 and finally, the most important conclusion of all in this connec- 

 tion, although the other conclusions are among the most important 

 advances made in late years, " that the Comstock Lode occupies 

 a line of faulting in rock of Tertiary age, and cannot be con- 

 sidered as a contact vein between two different rock masses." 

 The crystalline structure of the Washoe rocks has been subse- 

 quently treated by Mr. Becker. (" The Washoe Rocks," Bull. 

 Cal. Acad. Sci., Vol. II., p. 93, January, 1887 ; "Texture of Mas- 

 sive Rocks," Amer. Jour. Sci., ii., Vol. XXXIIL, p. 50, 1887.) 

 The various structures granular, porphyritic, and glassy are re- 

 ferred more to differences in composition and fluidity than to cir- 

 cumstances of solidification. 1 



1 G. F. Becker, " Geology of the Comstock Lode and the Washoe Dis- 

 trict," Monograph III., U. S. Geol. Survey. Rec. See also Engineering 

 and Mining Journal, March 1, 1884, p. 162 ; Second Ann. Rep. Director 

 U. S. Geol. Survey. Rec. J. A. Church, The Comstock Lode : Its Forma- 

 tion and History. New York, John Wiley & Sons. Reviewed in Engi- 

 neering and Mining Journal, Feb. 21, 1880, p. 397. See also shorter papers 

 in the Engineering and Mining Journal, Dec. 28, 1878, p. 456 ; July 19, 

 1879, p. 35 ; Dec. 12, 1885, p. 397 ; Jan. 23, 1886, p. 52. " On the Changes 

 in the Comstock Vein," Engineering and Mining Journal, Dec. 18, 1886, 

 p. 434 ; " The Discovery of the Comstock Lode," Ibid., Dec. 5 and 19, 1891, 

 and other papers in 1892 by Dan Dequille. Hague and Iddings, " On the 

 Development of Crystallization in the Igneous Rocks of Washoe, Nev.," 

 etc.. Bull 17, U. S. Geol. Survey. See also Bull. 6, Cal. Acad. Sci., and 

 Engineering and Mining Journal, Dec. 11, 1886, p. 415. 



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