XVI CONTENTS. 



PAGE 



Computed Pressures, Densities, and Temperatures within the 



Earth Based on Laplace's Law 564 



Recombination of material, 568. Compariscn cf the 

 hypotheses, 568. 

 Observed Temperatures in Excavations 569 



Explanations of varying increment, 570. The permeation 

 and circulation of water, 570. Chemical action, 570. Differ- 

 ences in the conductivity of rock, 571. Compression, 571. 

 Gradients projected, 571. The amount of loss of heat, 572. 

 The amount of shrinkage from loss of heat, 572. 



Other Sources of Deformation 574 



Transfer of internal heat, 574. Denser aggregation 6f 

 matter, 574. Extravasation • of lavas, 574. Change in the 

 rate of rotation, 575. Distribution of rigidity, 578. 



Sphericity as a Factor in Deformation 580 



The influence of the domed form of the surface, 581. 

 Theoretical strength of domes of earth-dimensions, 581. 

 Stress-accumulation independent of sphericity, 583. The 

 actual configuration of the surface, 584. Concave tracts, 584. 

 General conclusion, 588. 



CHAPTER X. 

 THE EXTRUSIVE PROCESSES. 



Outward movements, 590. '"'^ 



VULCANISM. 590 



Phases of vulcanism, 591. 



1. Intrusions. 591 



The heating action, 592. 



2. Extrusions 592 



Fissure eruptions, 593. Volcanic eruptions, 594. Inter- 

 mediate phenomena, 596. Lunar craters, 598. 



Volcanoes .• 599 



Number of, 599. 



Distribution of Volcanoes 599 



In time, 599. Relative to land and sea, 599. Relative 

 to crustal deformations, 601. In 'atitude, 603. In curved 

 lines, 603. 

 Relations of Volcanoes 604 



