CONTENTS. x iii 



PAGE 



Section 2. Mineral Veins, 234 ; Kinds, 234 ; Characteristics of Fissure-Yeins, 

 235 ; Metalliferous Veins, 235 ; Contents, 235 ; Eibboned Structure, 236 ; Ir- 

 regularities, 237 ; Age, 238 ; Surface-Changes, 238 ; Cupriferous Veins, 239 ; 

 Plmnbiferous Veins, 240 ; Auriferous Quartz-Veins, 240 ; Placer-Mines, 240. 

 Some Important Laws affecting the Occurrence and the Richness of Metalliferous 

 Veins, 241. Theory of Metalliferous Veins, 243 ; Outline of the Most Probable 

 Theory, 243 ; Vein-Stuffs explained, 243 ; Metallic Ores, 245 ; Auriferous Veins 

 of California, 247 ; Illustrations of the Law of Circulation, 249. 



Section 3. Mountains : Their Origin and Structure, 250 ; Definition of Terms 

 — Mountain-System — Mountain-Range — Ridge — Peak. Mountain Origin, 251 ; 

 Mountain- Structure, 252 ; Proof of Lateral Pressure : 1. By Folded Structure, 

 254 ; 2. By Slaty Cleavage, 255 ; Modifications of the Ideal : 1. By Fracture 

 and Slipping, 256 ; 2. By Metamorphism ; 3. By Erosion Mountains are Lines 

 of Thick Sediments, 257 ; Mountain-Ranges were Marginal Sea-Bottoms, 258. 

 Illustrated by — 1. Appalachian, 2. Sierra, 259 ; 3. Coast Range ; 4. Wahsatch; 

 5. Alps, 260 ; Why along Lines of Thick Sediments, History of a Mountain- 

 Range, 261 ; Slowness of Mountain-Growth, 261 ; Age of Mountains, 261 ; Other 

 Associated Phenomena explained, 262. 1. Fissures, Dikes, Lava-Floods ; 2. 

 Volcanoes, 263 ; 3. Mineral Veins; 4. Faults and Earthquakes. Cause of Lat- 

 eral Pressure ; Most Probable View, 264 ; Another Type of Mountains, Mono- 

 clinals, many Mountains combine the Two Modes, 265, e. g., Sierra, Wahsatch ; 

 Origin of Basin-Structure, 266 ; Mountain- Sculpture, 266 ; Amount of Erosion, 

 267 ; Sculptural Forms : 1. In Horizontal Strata ; 2. In Gently Undulating 

 Strata, 268 ; Synclinal Ridges how formed ; 3. Strongly Folded and Highly In- 

 clined Strata, 269; Hog-backs; 4. Gently Inclined Strata, 270; Tables and 

 Cliffs, 271 ; Migration of Divides, 272 ; 5. Metamorphic and Granitic Rocks ; 6. 

 Kind of Agent — Ice vs. Water. 



CHAPTER VI. 



Denudation, or General Erosion 273-279 



Agents of Denudation, 273 ; Amount of Denudation, 274 ; Average Erosion, 275 ; 

 Estimate of Geological Times, 276. 



PART III. 



HISTORICAL GEOLOGY; THE HISTORY OF THE EVOLUTION OF 

 EARTH-STRUCTURE AXD OF THE ORGAXIC KIXGLOM. 



CHAPTER I. 

 General Principles 279-285 



General Laws of Evolution, 279 ; Great Divisions and Subdivisions of Time — Eras, 

 2S1 ; Ages, 282 ; Subdivisions, 283 ; Order of Discussion, 283 ; Prehistoric Eras, 



285. 



CHAPTER II. 

 Latjrentian System of Rocks and Archaean Era . . . 285-289 

 General Description, 285 ; Rocks, 286 ; Area in North America, 287 ; Physical Ge- 

 ography of Archaean Times, 287 ; Time represented, 288 ; Evidences of Life, 288. 



