VIII 
CONTENTS. 
Chapter IX.—Processes of alteration—Continued. Page. 
Oxidation—Continued. 
Vein oxidation. 198 
Structure of the oxidized veins. 199 
Oxidizing processes. 199 
Influence of oxidation on gold, silver, and tellurium. 203 
Secondary sulphide enrichment. 204 
Chapter X.—The ore shoots. 205 
Dimensions and pitch of the shoots. 205 
General form of the shoots. 206 
Relation to surface. 207 
Relation to country rock. 208 
Relation to intersections. 209 
Other factors. 213 
Influence of depth. 214 
Chapter XI.—Genesis of the deposits and practical conclusions. 217 
Origin of the ores. 217 
Composition of the vein-forming waters. 217 
General statement. 217 
Silica. 217 
Fluorides. 218 
Chlorides. 219 
Sulphates. 220 
Carbonates. 221 
Hydrocarbons. 221 
Hydrogen sulphide. 222 
Iron. 222 
Calcium and magnesium. 222 
Alkali metals. 222 
Tellurium and gold. 223 
Relative quantity of sulphides. 225 
Conclusions. ' . 225 
Depth at which deposition took place. 226 
Temperature of the solutions. 226 
Time of deposition. 226 
Source of the water. 227 
Mode of deposition. 228 
Future of the district. 231 
Chapter XII.—Underground water. 233 
I ntroduction. 233 
Original water surface. 233 
Tunnel drainage. 235 
Conditions of water storage. 238 
Source of the water. 238 
Effect of drainage on water level. 239 
Future drainage. 246 
Chapter XIII.—Underground gases and temperature. 252 
Subterranean gase^. 252 
General statement. 252 
Composition of air. 252 
Distribution and mode of occurrence. 253 
Physical characteristics and composition. 254 
Physiological effects. 256 
Conditions of occurrence. 256 
