CONTENTS. XXV 



PAGE 



Auvergne, the Paris basin, and south-east of England one region of earth- 

 quakes during the Eocene period Why the central parts of the London and 

 Hampshire basins rise nearly as high as the denudation of the Weald 

 Effects of protruding force counteracted by the levelling operations of water 

 Thickness of masses removed from the central ridge of the Weald Great 

 escarpment of the chalk having a direction north-east and south-west 

 Curved and vertical strata in the Isle of Wight These were convulsed after 

 the deposition of the fresh-water beds of Headen Hill Elevations of land 

 posterior to the crag Why no Eocene alluviums recognizable Concluding 

 remarks on the intermittent operations of earthquakes in the south-east of 

 England, and the gradual formation of valleys Recapitulation . 303 



CHAPTER XXIII. 



Secondary formations Brief enumeration of the principal groups No 

 species common to the secondary and tertiary rocks Chasm between the 

 Eocene and Maestricht beds Duration of secondary periods Former con- 

 tinents placed where it is now sea Secondary fresh-water deposits why rare 

 Persistency of mineral composition why apparently greatest in older rocks 

 Supposed universality of red marl formations Secondary rocks why more 

 consolidated Why more fractured and disturbed Secondary volcanic rocks 

 of many different ages . . . 324 



CHAPTER XXIV. 



On the relative antiquity of different mountain-chains Theory of M. Elie 

 de Beaumont His opinions controverted His method of proving that dif- 

 ferent chains were raised at distinct periods His proof that others were 

 contemporaneous His reasoning why not conclusive His doctrine of the 

 parallelism of contemporaneous lines of elevation Objections Theory of 

 parallelism at variance with geological phenomena as exhibited in Great 

 Britain Objections of Mr. Conybeare How far anticlinal lines formed at 

 the same period are parallel Difficulties in the way of determining the 

 relative age of mountains ...... 337 



CHAPTER XXV. 



On the rocks usually termed { Primary ' Their relation to volcanic and 

 sedimentary formations The { primary ' class divisible into stratified and 

 unstratified Unstratified rocks called Plutonic Granite veins Their vari- 

 ous forms and mineral composition Proofs of their igneous origin Granites 

 of the same character produced at successive eras Some of these newer than 

 certain fossiliferous strata Difficulty of determining the age of particular 

 granites Distinction between the volcanic and the plutonic rocks Trappean 

 rocks not separable from the volcanic Passage from trap into granite 

 Theory of the origin of granite at every period from the earliest to the most 

 recent . 352 



