CONTENTS. 



CHAPTER I. 



SECTION I. 



The Stuucture of the Earth 1-8 



The law of the Physical Universe, 1, Definition of Litiiologv, 1, 2 ; of 

 Petrology, 2 ; and of Pktrography, 2. The former liquid condition of the 

 Earth demanded by the facts of petrography, 2. The Earth and its material in 

 a transition state, 2. Classification of llocks an index of the transition, 2. The 

 facts of petrography demand that eruptive rocks should be derived from a portion 

 of the Earth beneath the sedimentary formations, 2, 3. The assumed solidity 

 of the Earth based on hypothetical data, 3, 4. The }jroblcm of the interior 

 structure of the Earth beyond the present power of mathematics, 4. The sup- 

 posed arrangement of materials in the Earth's interioi", 4, 5. Thomson's theory 

 of the solidification of the Earth, 5 ; his mistake, 5. Experiments on the specific 

 gravity relation of hot solids and liquids, 5, 6. The geologist may adopt any view 

 of the Earth's interior consistent with geological facts, C. Early cessation of the 

 action of convection in the Earth, G. Dissipation of the Earth's heat tin-ough 

 conduction, 6. All discussions of the age of the Earth and Sun should be based 

 on the transmission of heat b}^ conduction in fluids and solids of diverse specific 

 gravities, which woidd probably give a greater age than now allowed by physi- 

 cists, G. Owing to the viscosity and higher specific gravity of the undei'lying 

 liquid, the Earth's first formed crust could not sink, as held by Thomson, 6, 7. 

 The Earth would contract as a unit, and not by the shrinking of a solid nucleus 

 away from the crust, 7. The dynamic agent causing the elevation of lavas, 7. The 

 viscidity of the interior and the irregular thickness of the crust would prev.nit 

 the connection of volcanic vents, 7, 8. Water the accident, not the cause, of a 

 volcanic eruption, 8. The view that the Earth's interior is solid, but may be 

 rcliqucficd either by increase or diminution of pressure, 8. 



SECTION 11. 



The Origin and Alteration of Uocks 8-24 



The theory of tlie Origin of Rocks taught in America, 8. 9. The aqueo-igneous 

 origin of Crystalline Rocks, 9. Rock Structure required by these theories, 9, 10. 

 Actual passage of Sedimentary llocks into Eruptive forms not proved, 10. The 



