Cretaceous Bocks. 117 



Cretaceous Rocks. 



These occupy a great part of Southern Russia, but are un- 

 known to the north of 55° of latitude. In regard to mineral 

 arrangement, there exists that sort of general parallelism 

 between the beds in Russia and those in Western Europe, 

 particularly with those of Eastern Germany, which we might 

 expect to find in strata of the same epoch, separated from 

 each other by great distances. Green sand, ironsand, chalk 

 and chalk-marl occur, in which the same groups of fossils 

 prevail as in rocks of Britain and France which occupy the 

 same relative age in geological succession ; and pure white 

 chalk, containing some characteristic organic remains, occurs 

 at intervals to the confines of Asia. In the southern steppes 

 of the Don Cossacks, on the banks of the river Donetz, chalk, 

 possessing all the characters of the English and French 

 chalk, and containing some of its characteristic fossils, oc- 

 curs of great thickness, Artesian wells having been sunk in 

 it to a depth of 630 feet, without any indications of a change 

 of rock. It contains layers of flint, and the banks of the 

 same river exhibit a section of a greensand group, seventy 

 feet thick, resting upon an equivalent of our coral rag, and 

 surmounted by white chalk. A zone of true chalk, 120 miles 

 in width, stretches through a great region about 100 miles 

 south-west of Orenburg. 



The cretaceous rocks occupy a very limited zone on the 

 eastern side of the Alleghanies, extending about 60 miles, 

 but having rarely a breadth of half-a-mile. They sweep 

 round the southern extremity of these mountains, occupyhig 

 a vast tract which stretches far westward of the Mississippi ; 

 and Mr Lyell saw a collection of chalk fossils brought by M. 

 Nicollet from the higher parts of the Missouri river. It 

 appears further, from the recent report of Captain Fremont, 

 that cretaceous rocks occur on the eastern flanks of the Rocky 

 Mountains. The series examined by Mr Lyell in the State 

 of New Jersey, consist of a lower portion of greensand and 

 green marl, and above these a pale yellow limestone with 

 corals, both however belonging, in the opinion of Mr Lyell, 

 who has carefully examined a large series of fossils, to the 



