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ERA OF THE CRETACEOUS EOEMATIOK 



The record of this period consists of a series of strata, in 

 which chalk beds make a conspicuous appearance, and 

 which is therefore called the cretaceous system or for- 

 mation. In England, a long stripe, extending from 

 Yorkshire to Kent, presents the cretaceous beds upon 

 the surface, generally lying conformably upon the oolite, 

 and in many instances I'ising into bold escarpments to- 

 wards the west. The celebrated cliffs of Dover are of 

 this formation. It extends into northern France, and 

 thence north-westward into Germany, whence it is traced 

 into Scandinavia and Russia. The same system exists in 

 North America, and probably in other parts of the earth 

 not yet geologically investigated. Being a marine de- 

 posit, it establishes that seas existed at the time of its 

 formation on the tracks occupied by it, while some of its 

 organic remains prove that, in the neighbourhood of 

 those seas, there wer-e tracts of dry land. 



The cretaceous formation in England presents beds 

 chiefly sandy in the lowest part, chiefly clayey in the 

 middle, and chiefly of chalk in the upper part, the chalk 

 beds being never absent, which some of the lower are in 

 several places. In the vale of the Mississippi, again, the 

 true chalk is wholly, or all but wholly absent. In the 

 south of England, the lower beds are (reckoning from 

 the lowest upwards): i, SJtankland or greensand, "a 



