CHAPTER I.-CRYSTALS AND ROCK-FORMING MINERALS Chemical elements and compounds. Crystallography. Pseudomorphs. Rock-forming minerals. CHAPTER II-CLASSIFICATION OF ROCKS. Meaning of the word Rock. Lithological classification. Petrological classification. Historical classification. Igneous, A. Unaltered series:-Mineral composition. Differences. Classification. B. Metamorphic series :-Condi- CHAPTER IV.-Derivative OR STRATIFIED ROCKS. Origin and Composition. A. Unaltered series:-Mechani- Formation of strata. Intervals between beds. The law of vertical succession. Inter-bedding. Extension and Thinning Cause of Joints. Cuboidal jointing. Horizontal jointing. Prismatic jointing. Articulated and Spheroidal structures. CHAPTER VII.—INCLINATION and Curvature. Dip and Strike. Geological map and section. Folds and flexures:-anticlinal, synclinal, periclinal, monoclinal and iso- CHAPTER VIII.-FAULTS OR DISLOCATIONS Throw and Hade. Effects of movement along lines of fracture. Compound Faults. Effects of Faults on outcrop. CHAPTER IX.-UNCONFORMITY AND OVERLAP. Conformable and Unconformable succession. CHAPTER X.-PETROLOGY OF IGNEOUS ROCKS. 1. Contemporaneous rocks:-Extinct volcanoes; Necks; Interbedded sheets. Instances. Basaltic plateaux. 2. Intrusive rocks: A. Volcanic division:-Dykes and Veins; Intrusive sheets; Laccolites; Bosses. B. Plutonic division: -Position of Granite. Granites of Leinster, Cornwall and § 1. Structure of Metamorphic rocks:-Cleavage :-arrange- 82. Areas of Metamorphism :-Local metamorphism; Re- gional metamorphism. Metamorphic Granite. General form of Continents. Depth of Oceans compared with the height of Mountains. Evidences of compression. Age of mountain chains. Hypothesis of secular contraction. Hypothesis of columnar expansion. Conditions which determine the position of hills and valleys. Recession of escarpments. Breaching of hill ranges by rivers. ERRATA. Page 5, line 35, for Physical read Dynamical. Page 7, Part I. should have been headed "Dynamical Geology." Page 192, line 24, for navigable read habitable. Page 215, omit the two top lines. Page 313, line 10, after "Current" insert Mark. Page 317, line 6, for Cause read Origin. INTRODUCTION. DEFINITIONS are never easy, and it is especially diffi cult to frame an accurate definition of Geology, because it is not easy to limit the scope of its application. Two different definitions of the science may indeed be given; one describing it in a broad and comprehensive sense, the other dealing only with its more special and restricted meaning. 1 Regarded from the wider point of view, Geology is not so much one separate science as the application of all the physical sciences to the examination and elucidation of the structure of the earth. Mr. Jukes has well observed "that we might without impropriety regard all the physical sciences as included under two great heads, namely, astronomy and geology; the one comprehending all those sciences which teach us the constitution, the motions, the relative places, and the mutual actions of the astra, or heavenly bodies; while the other would include all the sciences which deal with the phenomena presented by the one astrum on which we live, and investigate the nature and distribution both of the inorganic matter of the globe, and of the living beings which inhabit it." The truth of this large and comprehensive view of geology is shown by the very fact of its late appearance in the world of science. The crude ideas regarding the structure and history of the earth, and the nature of fossils which were prevalent in the seventeenth and eighteenth centuries, cannot be dignified by the name of geology. "Student's Manual of Geology," p. 1. B |