PLATE VIII. 
Photomicrographs of Rocks. 
A, Latite-phonolite (624 C. C.) from southern slope of Bull Cliff. Composed of soda-orthoclase, plagioclase, 
nosean, sodalite, segirine-augite, and augite. Augite shows twinning. Nosean is crowded with dark 
inclusions except at the border. Magnified 28 diameters. 
B, Same with crossed nicols. Shows flow structure. Magnified 28 diameters. 
C , Syenite (333 C. C.) from dump of Last Dollar mine. Composed of soda-orthoclase, segirine-augite, augite, 
and hornblende. Magnified 28 diameters. 
D, Trachydolerite (381 C. C.) from summit of Bull Cliff. Composed of orthoclase, analcite, augite, biotite, 
and magnetite. Magnified 28 diameters. 
