CONTENTS. 



VOLUME II. 



CHAPTER I. 

 THE ORIGIN OF THE EARTH. 



PAGE 



Hypotheses of the Earth's Origin 3 



I. The Laplacian or " Nebular " Hypothesis 4 



The postulated nebula, 4. Formation of rings, 4. For- 

 mation of gaseous spheroids, 5. The earth-moon ring, 5. 

 Darwin's modification of Laplacian hypothesis, 6. Supposed 

 passage of the earth from the gaseous to the present condi- 

 tion, 6. The supposed crust, 7. Astronomical argument for 

 solidity of earth, 7. Supposed solidification of earth from .the 

 center outward, 8. Supposed middle molten zone, 8. Hy- 

 pothetical gaseous center of earth, 9. Part played in geologic 

 doctrines, 9. Supporting phenomena, 9. Objections to the 

 Laplacian hypothesis, 10. Unfavorable testimony of existing 

 nebulae as to the Laplacian hypothesis, 12. 



II. The Metcoritic Hypothesis of the Earth's Origin 13 



A simple but untenable form, 13. The hypothesis of 

 Lockyer and Darwin, 13. Is some other form of the meteor- 

 itic hypothesis tenable? 15. The two general conceptions of 

 the origin of the meteoritic state, 15. 



1. Assemblage from a Primitive State of Dispersion 16 



Conditions affecting the initiation of a meteoritic 

 swarm, 16. The velocities of meteorites, 16. The pos- 

 sibilities of parallel movement, 18. The danger of dis- 

 persion, IS. The sparseness of distribution and its bear- 

 ing, 19. The time factor, - 20. 



2. Derivation from Previous Aggregates. . 21 



(a) Dispersion by explosion, 21. (6) Dispersion 

 by collision, 21. (c) Dispersion by tidal disruption, 

 22. 



