ON A PIECE OF CHALK 83 



Thus, evidence which cannot be rebutted, and which 

 need not be strengthened, though if time 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 condi- 

 tions 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 

 may be found perched up, in some cases, many thousand 

 feet high upon their flanks. And evidence 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. 



I must ask you to believe that there is no less con- 

 clusive proof that a still more prolonged succession of 

 similar changes occurred, before the chalk was depos- 

 ited. Nor have we any reason to think that the first 

 term in the series of these changes is known. The oldest 

 sea-beds preserved to us are sands, and mud, and pebbles, 



