266 THE STOEY OF THE EARTH AND MAX. 



example, in tlie somewhat celebrated " forest bed" of 

 Cromer, in Norfolk, which is regarded as Newer 

 Pliocene, we have lost all the foreign and warm- 

 climate plants of the Miocene, and find the familiar 

 Scotch firs and other plants of the Modern British 

 flora. The animals, however, retain their former 

 types ; for two species of elephant, a hippopotamus, 

 and a rhinoceros are found in connection with these 

 plants. This is another evidence, in addition to those 

 above referred to, that plants are better thermometers 

 to indicate geological and climatal change than 

 animals. This Pliocene refrigeration appears to have 

 gone on increasing into the next or Post-pliocene age, 

 and attained its maximum in the Glacial period, when, 

 as many geologists think, our continents were, even 

 in the temperate latitudes, covered with a sheet of 

 ice like that which now clothes Greenland. Then 

 occurred a very general subsidence, in which they 

 were submerged under the waters of a cold icy sea, 

 tenanted by marine animals now belonging to boreal 

 and arctic regions. After this last great plunge-bath 

 they rose to constitute the dry land of man and his 

 contemporaries. Let us close this part of the subject 

 with one striking illustration from Heer's memoir on 

 Bovey Tracey. At this place, above the great series 

 of clays and lignites containing the Miocene plants 

 already described, is a thick covering of clay, gravel, 

 and stones, evidently of much later date. This also 

 contains some plants ; but instead of the figs, and 

 cinnamons, and evergreen oaks, they are the petty 



