x ii CONTENTS. 



PAGE 



solidated Sediments, 1*72 ; Cause of Consolidation, 1*72; II. Stratified Rocks 

 have been gradually deposited, 173 ; III. Stratified Rocks were originally nearly 

 horizontal, 173; Elevated, Inclined, and Folded Strata, 174; Dip and Strike, 

 176; Anticlines and Synclines, 178; Monoclines, 178; Conformity and Uncon- 

 formity, 179; Geological Formation, 181. Cleavage Structure, 181; Cause of 

 Sharpe's Mechanical Theory, 183 ; Physical Theory, 185 ; Sorby's Theory, 185 ; 

 Tyndall's Theory, 186; Geological Application, 187. Nodular or Concretionary 

 Structure, 188; Cause, 189; Forms of Nodules, 189; Kinds of Nodules found 

 in Different Strata, 190. Fossils: Their Origin and Distribution, 190; The 

 Degrees of Preservation are very various, 191 ; Theory of Petrifaction, 192. 

 Distribution of Fossils in the Strata, 194: 1. Kind of Rock, 194 ; 2. The Coun- 

 try where found, 195 ; 3. The Age, 195 ; Geological Fauna and Era, 195. 

 Section 2. Classification of Stratified Rocks, 197; Methods: 1. Order of 

 Superposition, 197; 2. Lithological Character, 198; 3. Comparison of Fossils, 

 198; Manner of constructing a Geological Chronology, 199; Table of Main 

 Divisions, 200. 



CHAPTER III. 



Unstratified or Igneous Rocks 201-219 



Characteristics, 201 ; General Origin, 201 ; Mode of Occurrence, 201 ; Extent on 

 the Surface, 202 ; Classification of Igneous Rocks, 202. 



I. Plutonic or Massive Rocks, 203 ; General Appearance, 203 ; Principal Kinds 

 —Granite, 203 ; Syenite, 203 ; Diorite, 203 ; Diabase, 204 ; Two Sub-Groups, 

 Acidic and Basic, 204 ; Mode of Occurrence, 204 ; Intermediate Scries, 205 ; 

 Kinds, 206. 



II. Volcanic or Eruptive Rocks, 206; Texture and Appearance, 206; Phjsical 

 Conditions, 206 ; Mineral Composition and Sub-Groups, 207 ; Principal Kinds, 

 207 ; Table showing Principal Kinds of all Classes of Igneous Rocks, 208 ; Modes 

 of Eruption, 208 ; Modes of Occurrence, 209 ; Dikes, 209 ; Effect of Dikes on 

 Intersected Strata, 210; Lava-Sheets, 210; Intercalary Beds and Laccolites, 

 211 ; Age — how determined, 212. Of Certain Structures found in many Erup- 

 tive Rocks, 212; Columnar Structure, 212; Direction of the Columns, 213; 

 Cause of Columnar Structure, 214; Volcanic Conglomerate and Breccia, 214; 

 Amygdaloid, 215. Some Important General Questions connected with Igneous 

 Bocks, 215 : 1. Origin of Igneous Rocks, 215. 2. Other modes of Classification, 

 216. 3. Richthofen's Classification of Tertiary Eruptions, 218 ; Judd's Views, 218. 



CHAPTER IV. 



Met amorphic Rocks 219-226 



Origin, 219; Position, 219, Extent on the Earth-Surface, 219; Principal Kinds, 

 220; Theory of Metamorphism, 221; Effect of Water, 221; Alkali, 222; 

 Pressure, 222 ; Application, 222 ; Crushing, 223 ; Explanation of Associated 

 Phenomena, £23 ; Origin of Granite, 223. 



CHAFTER V. page 



Structure common to All Rocks 226-273 



Section 1. Joints and Fissures. — Joints, 226 ; Fissures or Fractures, 227 ; Cause, 

 228 ; Faults, 228 ; Kinds— Law of Slip, 231 ; Explanation of Direction of 

 Slip, 332. 



