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 x>laced 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 
