I ON A PIECE OF CHALK 29 



permitted I might indefinitely increase its quantity, 

 compels you to believe that the earth, from the 

 time of the chalk to the present day, has been the 

 theatre of a series of changes as vast in their 

 amount, as they were slow in their progress. The 

 area on which we stand has been first sea and 

 then land, for at least four alternations ; and has 

 remained in each of these conditions for a period 

 of great length. 



Nor have these wonderful metamorphoses of sea 

 into land, and of land into sea, been confined to one 

 corner of England. During the chalk period, or 

 " cretaceous epoch," not one of the present great 

 physical features of the globe was in existence. 

 Our great mountain ranges, Pyrenees, Alps, 

 Himalayas, Andes, have all been upheaved since 

 the chalk was deposited, and the cretaceous sea- 

 flowed over the sites of Sinai and Ararat. All 

 this is certain, because rocks of cretaceous, or still 

 later, date have shared in the elevatory movements 

 which gave rise to these mountain chains ; and 

 rnay be found perched up, in some cases, many 

 thousand feet high upon their flanks. And evi- 

 dence of equal cogency demonstrates that, though, 

 in Norfolk, the forest-bed rests directly upon the 

 chalk, yet it does so, not because the period at 

 which the forest grew immediately followed that 

 at which the chalk was formed, but because an 

 immense lapse of time, represented elsewhere by 

 thousands of feet of rock, is not indicated at Cromer. 



