RETROSPECT. 409 



exterminated by his agency, or reduced to a domes- 

 ticated state. Subsequently to the occupation of 

 these Islands by the aboriginal tribes, the country 

 has undergone no important physical mutations. 

 The usual effects of the atmosphere, the wasting of 

 the shores by the encroachments of the sea, the 

 erosion of the land by streams and rivers, the 

 silting up of valleys, and the formation of deltas, 

 are apparently the only terrestrial changes to 

 which England and its Islands have been sub- 

 jected during the historic ages. 



Corollary. — From this examination of the 

 geological phenomena of the south-east of Eng- 

 land, we learn that at a period incalculably 

 remote, there existed in the northern hemi- 

 sphere an extensive island or continent, pos- 

 sessing a climate of such a temperature, that its 

 surface was covered with arborescent ferns, palms, 

 cycadeae, and other coniferae ; and the ocean 

 that watered its shores, was inhabited by turtles, 

 and marine lizards of extinct genera. This 

 country suffered a partial subsidence, which was 

 effected so tranquilly, that many of the trees 

 retained their erect position, and the cycadeous 

 plants, and a considerable layer of the vegetable 

 mould in which they grew, remained undisturbed. 

 In this state an inundation of freshwater covered 



