ROOM III. GEOLOGICAL SUMMARY. 221 



found in the Purbeck beds.* Such are the general features 

 of the fauna and flora of the Wealden epoch, according to 

 the present state of our knowledge. 



GEOLOGICAL SUMMARY. From this survey of the South-East 

 of England, we learn that the present configuration of the 

 surface has resulted from a succession of physical changes which 

 took place in periods incalculably remote, and long ante- 

 cedent to the creation of the human race ; and that the 

 country is composed of sediments deposited by ancient 

 seas, rivers, and lakes, whose waters teemed with myriads 

 of beings of extinct genera and species, and of the spoils of 

 countries which enjoyed a much higher temperature than 

 any part of modern Europe, and were clothed with palms, 

 tree-ferns, cycadeous plants, and pine-forests, and inhabited 

 by gigantic reptiles, whose races have long since been swept 

 from the face of the earth. 



The phenomena we have passed in review may be referred 

 to four principal epochs ; but the period of time over which 

 each extended, cannot be conjectured with any approach to 

 probability. 



I. The Wealden Epoch. This, which is the most ancient 

 era comprehended in the present survey, comprises the 

 period during which the strata, that in the south-east of 

 England emerge from beneath the chalk, and occupy the area 

 between the north and south boundaries of that formation, 

 were deposited. The total thickness of these deposits cannot 

 be accurately determined, but amounts to upwards of 1,000 

 feet. The innumerable layers of mollusks and crustaceans, 

 and the prodigious accumulation of the bones of reptiles and 

 fishes, and of the trunks, branches, and foliage of vegetables, 

 the whole consisting of materials brought down by rivers and 

 floods of fresh water, and slowly deposited in bays, deltas, or 

 estuaries, afford unquestionable evidence of the immense 

 period of time during which the Wealden was in the progress 

 of formation. 



II. The Cretaceous Epoch. The next geological cycle 

 embraces the deposition of that extensive series of strata, 

 whose organic contents demonstrate that they were accumu- 

 lated in an ocean of vast extent, and which, probably, like the 



1 "Geological Excursions round the Isle of Wight," pp. 109, 463. 



