XH 



GENERAL CONTENTS. 



CHAPTER XVII. THE HISTORY OF VOLCANIC ROCKS. 



PAOE 



Method of study . . . .252 

 Colours of minerals in polarised 



light 253 



Texture of igneous rocks , . . 254 



Propylite 255 



Quartz propylite . . . .257 



Andesites 258 



Dacite 263 



Trachyte 264 



Phonolite 

 Rhyolite 

 Augite andesite 

 Basalt . 

 Leucite basalt 

 Nepheline basalt 

 Peridotite . 

 Serpentine . 



PAGE 



268 

 269 

 274 

 277 

 283 



2^5 



286 

 288 



CHAPTER XVIII. THE HISTORY OF VOLCANIC ACTIVITY IN BRITAIN. 



Evidence of former existence of 

 volcanoes 290 



Pre-Cambrian volcanoes : St. Da- 

 vid's, Wrekin, &c. . . .291 



Cambrian volcanoes . . . 293 



Devonian and Old Red Sandstone 

 volcanoes 297 



Carboniferous volcanoes 

 Permian volcanoes 

 Serpentine . 

 Secondary volcanic rocks 

 Tertiary volcanic rocks 



303 

 3ii 

 312 



313 



CHAPTER XIX. CONCOMITANTS AND RESULTS OF VOLCANIC ENERGY. 



Earthquakes . . . .321 



Changes of level in land . . 325 



Disturbances of the strata . . 330 



Fractures and dislocations of strata 333 



Dykes 334 



Breaks in succession of the British 



strata 340 



Table of disturbances in the British 

 area 



Table of disturbances in the Euro- 

 pean area 



Collateral effects of upheaval and 

 depression .... 



Mountain ranges .... 



343 

 345 



349 

 351 



CHAPTER XX. METAMORPHISM. 



Effects of internal heat . .356 

 Metamorphism of rocks . -357 

 Mineral constituents of metamor- 

 phic rocks . . . .361 



Gneiss . 

 Mica schist . 

 Quartz rock . 

 Crystalline limestone 



370 

 374 

 376 

 377 



CHAPTER XXI. DISTRIBUTION OF GNEISS AND MICA SCHIST. 



In England 379 



In Anglesey . . . .381 



In the Hebrides, &c. . . . 382 



Along the Grampians . . . 383 



In the North-Western Highlands 385 



Scenery of gneiss and mica schist 387 



Scenery of quartz rock . . 388 



Crystalline limestone in Scotland 

 Metamorphic rocks of Ireland 

 Of the Pyrenees .... 

 Of Central France 

 Fossil-bearing schists of Norway . 

 Metamorphic rocks of America . 



CHAPTER XXII. MINERAL VEINS. 



Mineral veins now forming . 

 Source of metals . 

 Daubree on the origin of ores 

 Modes of occurrence of metals 

 Structure of a lode 

 Classification of veins . 

 Stock works 



397 

 398 

 399 

 400 

 401 

 403 

 405 



389 

 39i 

 392 

 393 

 394 

 395 



Intersection of veins . . . 407 

 Directions of mineral veins . . 408 

 Relation of metals to rocks . .410 

 Werner's systems . . -413 

 Relation of mineral veins to local 

 igneous action .... 414 



