14 CRETACEOUS GROUP 



With respect to the basis on which the ferruginous 

 sand rests, I know nothing with certainty ; for although 

 the strata have been penetrated nearly one hundred feet 

 at the Chesapeake and Delaware canal, they afford no an- 

 swer to this question. But I am disposed to believe that 

 in the northern states this formation rests on primitive 

 rocks, and in the southern states, especially in Alabama, 

 on the old secondary limestone. The latter opinion has 

 recently been much corroborated by the researches of Mr. 

 Conrad. If hereafter it should be proved that the northern 

 section of our cretaceous group rests upon primitive rocks, 

 as just suggested, it will be similarly circumstanced to the 

 same formation in Sweden, where, according to Mr. 

 Nilsson, the chalk is generally incumbent on gneiss. 

 Again, in the Carpathean mountains, the chalk and gra- 

 nite are in immediate contact.* 



NEW JERSEY. 



Ferruginous Sand. In New Jersey, the tract which 

 has long been known by the name of the " marl district," 

 may be located as follows : — Draw two lines, one from 

 Amboy to Trenton, the other from Deal to Salem ; let 

 the Atlantic ocean connect the eastern, and the Delaware 

 river the western points of these lines : this irregular ob- 

 long tract incloses nearly the whole marl deposit of 

 New Jersey ; so far, at least, as it has hitherto been ex- 

 plored. There is reason, however, to suppose that it 

 occupies a much larger proportion of the peninsula, espe- 



* De la Bcche, Geol. Man. pp. 256. 



