TABLE OF CONTENTS. 



PAGE. 



Introductory 1 



The Natural System of Volcanic Rocks 5 



Order First : Rhyolite 12 



Order Second : Trachyte 17 



Order Third : Propylite 20 



Order Fourth : Andesite 25 



Order Fifth : Basalt 26 



Correlation of the Five Orders of Volcanic Rocks 28 



Laws Relative to the Age of Massive Eruptions 29 



Laws regarding the Mutual Relations of Massive Eruptions and Volcanic Activity 32 



Relation of Volcanic Rocks to Ancient Eruptive Rocks 35 



Correlation of Age and Texture 39 



Correlation of Age and Composition 41 



Correlation of Eruptive Rocks in regard to their Geographical Distribution 43 



On the Origin of Volcanic Rocks 46 



1. Origin of Massive Eruptions 47 



2. Origin of Volcanic Action 60 



3. Other Tfieories regarding the Origin of Volcanic Rocks 68 



Relation of the Distribution of Volcanic Rocks to the Configuration of the Surface 



of the Globe 78 



(133) 



