Page:A Treatise on Geology, volume 2.djvu/11

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Internal Divisions of Igneous Rocks 108
Phenomena Observed where Igneous Rocks come in contact with Stratified Masses 109
Induration of Stratified Rocks 109
Alteration of the Structure of Rocks by Heat 111
Metamorphic Rocks 125
Re-arrangement of the Particles of Rocks 126
Alteration of the Chemical Nature of Rocks 131
Dolomitic Limestone 133
Generation of New Minerals 136
Metamorphic Slates 139
Succession of Metamorphic Slates 140
Metamorphic Mica Schist, Gneiss, &c. 143
Relative Antiquity of Pyrogeuous Rocks 145
Table of the Principal Disturbances of the Stratification of the British Islands, with the Igneous Rocks observed in connection therewith 152
Class I.─Before the Deposition of Old Red Sandstone 152
Class II.─Before the Deposition of the Lias 153
Class III.─Before the Deposition of the Lower Green Sand 154
Class IV.─Since the Deposition of the Chalk 154
 
CHAP. VIII.
 
MINERAL VEINS.
 
Remarks 155
Geographical Distribution 156
Occurrence of Mineral Veins near Centres of Igneous Action 159
Relations of Veins to the Substance and Structure of the Neighbouring Rocks 163
Relation of Veins to each other 171
First Class.─Oldest Tin Veins 171
Second Class.─More recent Tin Lodes 171
Third Class.─Oldest East and West Copper Lodes 172
Fourth Class.─Contra Copper Lodes 172
Fifth Class.─Cross Courses 173
Sixth Class.─More recent Copper Lodes 173
Seventh Class.─Cross Flukans 173
Eighth Class.─Slides 173
Deposits of Metallic Veins in Cornwall 174
Theory of Mineral Veins 177
Veins are of posterior Date to the Rocks which they traverse 178
Description of Huel Peever Vein 180
Origin of Vein Fissures 188
Filling of the Fissures 192
Recapitulation 196