TABLE OF CONTENTS. XI 



Varying thickness of palaeozoic strata 50 



Relation of mountains to sedimentation 60 



Continental as opposed to local elevation 52 



Views of Buffon, Montlosier, and Constant-Prevost .... 52 



Views of Humboldt, Von Buch, and Elie de Beaumont .... 52 



Lesley on the topography of mountains 52 



Relations of mountains to synclinals and to erosion ..... 52 



Hall's views of the origin of mountains 54 



Relations of subsidence to foldings of strata 55 



Condensation consequent on the crystallizing of sediments ... 56 



The hypothesis of a solid contracting nucleus maintained ... 57 



Relation of this nucleus to water-impregnated sediments ... 57 



The softening of these produces lines of weakness in the crust ... 57 



Relation of this process to corrugations 57 



Relations of volcanic and plutonic phenomena to sedimentation . . 58 



VI. 



THE PROBABLE SEAT OF VOLCANIC ACTION (1869). 



Discussion of the views of Hopkins and Scrope on volcanoes ... 59 



Views of Lemery and Breislak, of Davy and Daubeny ... 62 



Views of Keferstein and Sir J. F. W. Herschel 62 



Exposition of the author's view 63 



Disintegration of the primitive crust ........ 63 



Hopkins on internal heat and its increase in descending ... 64 



Sorby on the relations of heat and pressure to fusion and solution . . 65 



Chemical differences in eruptive rocks 66 



APPENDIX. 



Geographical distribution of modern volcanoes 68 



Distribution of ancient eruptive rocks ; their geological relations . . 69 



VII. 



ON SOME POINTS IN DYNAMICAL GEOLOGY (1858). 



LeConte on the reconstruction of geological theory ..... 70 



His views compared with those of the author 



Hall's theory of mountains ; the criticisms of Dana, Whitney, and LeConte 73 

 Views of Hall and the author misunderstood . 



LeConte's theory of mountains considered ... 74 

 Continental elevation and erosion ; Montlosier and Jukes 



Hall on some North American mountains 75 



Origin and structure of the Appalachians ...... 75 



Their crystalline strata not palseozoic but eozic 76 



Evidences of an eastern pre palseozoic continent . . . . . 75 



Dry climate of eastern North America in palaeozoic times . 76 



Oscillations of continents; their cause 76 



