xiv CONTENTS. 



PACE 



The sources of the requisite heat, 99. Heat from 

 infall, 100. Heat from quasi-gaseous condensation of 

 the nucleus, 100. Heat from central compression, 101. 

 Heat from molecular rearrangement, 101. The hypoth- 

 etical mode of vulcanism, 102. Melting due to out- 

 ward flow of heat, 102. Selective fusion, 102. The 

 dynamics of ascension, 103. Arrested ascensions and 

 attendant heating, 104. Invasion of the fragmental 

 zone and surface explosions, 104. Volcanic action not 

 necessarily antecedent to the atmosphere, 106. 



5. The Initial Hydrospheric Stage 106 



The origin of the ocean, 106. The evolution of 

 oceanic basins and continental platforms, 107. Con- 

 trasted effects of weathering and of protection by sub- 

 mergence, 107. Areal differentiation by selective 

 action, 107. Permanent versus temporary effects, 108. 

 The progressive depression of water-covered areas, 108. 

 Configuration of basins accidental or systematic? 110. 

 Smallness of the differentiating action, 110. 



6. The Initial Life Stage Ill 



Available time, 112. When were the conditions 

 requisite for life first provided? 113. Autogenic heat 

 and light, 114. Transition to complete solar depend- 

 ence, 114. Changes in the atmosphere inaugurated by 

 the introduction of life, 115. The great factors now 

 all at work, 116. 



7. The Climax of Volcanic Action 116 



The ratio of the volcanic products to the accessions 

 and to the derivatives, 117. The Archean complex, 

 117. Diastrophism accompanying the volcanic climax, 

 117. 



8. The Great Stage of Atmospheric and Hydrospheric Domi- 



nance 118 



Synoptical view of the earth's history, 119. 



Supplementary Considerations 119 



I. The Differentiation of the Rocks during the Stages of Growth. 119 

 The average original material, 119. Volcanic differ- 

 entiation, 120. Differentiation in suboceanic versus 

 continental segments, 120. Obstacles to minute differ- 

 entiation, 121. 

 II. Deformations under the Planetesimal Hypothesis < < . . . 122 



