GENERAL INDEX 



(To facilitate the use of the geological map, Atlas-sheet IV., the positions of the 

 in the text are indicated in thn index by letters and numbers attached in parenthej 

 rospondint; series of letters and numbers answering to each minute of surface.] 



e noteworthy localities mentioned 

 The map is provided with a cor- 



Alteration of minerals in sitii, von Richthofen on 20 



Amalgamation, barrel 6 



pan - 6 



Amazon (D. 7), analj'sisof raetaraorphiodioritHfrom the, 



table following page 151 

 analyRisofmetamorphic diorite from the. 155 



metamorphic diorite of the 43, 106, 196,406 



American Flat (B. 5), analysis of augite-andesite from 



t-able following page 151 

 analysis of quartz-porphyry from, 



table following page 151 



Analyses, table of follows page 151 



Andesite 374 



LSee Augite-andesite and Homblende-andeeite.) 



and propylite, Zitkel on 27 



assays of 155 



occurrence of 382 



Apatite. {See illustrations.) 



brown, in augite-andesite 64 



brown, in earlier homblende-andesite 56 



brown, in eruptive diorite 40 



Ascension theory, applicability to the Comstock, von 



Richthofen on 19 



Assays of Comstock rocks 154, 223 



of rocks, results of 224 



Attwood, G., analysis by .. . 153 



Augite. (See illustrations.) 



conditions of crystallization of 63 



formation of chlorite from 211 



formation of pyrite from 210 



orientation of obliquely cut twins of 113 



with black borders 123 



with contorted twin lamellae 129 



with pinacoidal cleavage in homblende-andesite. 55 

 Augite-andesite. (See illustrations.) 



analysis of table following page 151 



description of slides of 126 



feldspars of 407 



independence of eruption of 202 



lithological description of. 62 



occurrence and age of 201 



occurrence of ore in 202 



peculiar weathering of. 65 



Bag, advantages of, as terminal 356 



Baltimore^ granite of the 34, 190 



Page. 



Barus, Carl, computations by 245 



his experiments on koolinization 236,397 



on the electrical activity of ore bodies. 290, 400 



Basalt, description of slides of 134 



lithological description erf 70 



occurrence and age of the 205, 373, 383 



Basalt Hill (B. 6), augite-andesite of 71, 201 



metamorphic diorite, 3, 000 feet SE. of 107 



Belcher, assay of slate from the 155 



cross-section through the 277 



fault at the 278 



later diabase of the 33,152 



ore on the 3,000-foot level of the 278 



quartz-porphyry of the 196 



slates in the 191 



Belts, mineral, west of the Rocky Mountains 2 



Berkshire Canon, propylite from 143 



Bisilicates, course of the decomposition ofthe 214 



Black border of hornblende. (,Sec illustrations.) 

 Black dike. (See Diabase, later.) 



occurrence and age 109 



Blake, "W. P., on mineral belts west of the Rocky Mount- 

 ains 2 



Boiler (kaolinization), description of 292 



Bonanza, definition of 268 



of the Consolidated Virginia and Oalifomia 

 mines 270 



of the Consolidated Virginia and California, 



comb- structure in the 270 



of the Consolidated Virginia and California^ 



origin of the opening occupied by the 274 



of the Consolidated Virginia and Cali/omia, 



rock fragments in the 270 



Bonanzas. {See Ore.) 



character of openings occupied by 395 



occurrence of, on the Comstock 21« 



proportions of gold and silver in yield from, by 



groups 9 



Virginia group of 274, 275 



Bristol, K. S., analysis by 152 



Bullion. {See Gold, Silver, product.) 



BtiUion, quartz ofthe 17 



V. Richthofen on the prospectn of the 23 



Bullion Ravine (C. 3), assays of granular diorite from the 154 



diorite of 39,41,93,150,406 



(413) 



